1. RFID Introduction

Having the Right Mindset for RFID technology.

RFID is known as Radio Frequency IDentification. The technology is able to wireless-ly picking up information from a RFID tag which can be embedded onto most object. Fast and reliable. RFID has helped to rise up our productivity.

The process starts with the RFID reader transmitting power and command wireless-ly. The RFID tag intecept the energy to power up itself. It starts to decode the request commanded and transmit the result back to the RFID reader. All these happen instantly with microseconds.

Many of the old technologies (bar-code, magnetic stripe, smart card) can be replaced by RFID system, but rate of adoption rate is slow. Examples of applications that the RFID have completely taken over are, security door access system and transportation payment card. Comparing RFID over the old technologies, it is perceive to be more expensive. The technology do has its advantages and disadvantages, which is why not all applications use RFID.

People likes to compare RFID to a bar-code system which is a cheaper alternative. The fact is, RFID tag will never be as cheap as a printed bar-code. It is more complex than bar-code. No matter how big the production volume will be, it will not be cheaper than the bar-code. Using a RFID to perform barcode application is analogy to hiring an engineer to do simple office cleaning work. No company would be in the right set of mind to invest in a expnsive solution to replace what a cheaper solution would solved.

People also think of RFID technology as a solution. RFID unique and good, but it can only solve part of the problem that we are facing in our life. You can analogy it to a very good engineer that you have hired. He/she has all the skills and know-how to design a quality system that no one else can, but there are no proper tools and equipments provided. Only a broom and a dustpan is provided. The engineer will be as good as a cleaner. RFID is designed to solve certain problem very efficiently. By itself, it cannot do any much. It has to work hand in hand with another good technology.

RFID has its own unique properties that no other technology is able replace it completely. Applying RFID technology to its advantage, to the right application will be the key to success adoption. If you want RFID system to be successful, you cannot think using a bar-code brain.

This site is dedicated to understand more about the properties of RFID technology, hence allowing us to apply its unique leading edge where no other technologies can replace. The focus will be mainly in the RFID for ISO/IEC14443 (HF 13.56MHz RFID system) which has a near perfect characteristic for interaction between humans and object; and also information on ISO/IEC18092 (NFC protocol implementation) which is the new trend on applying RFID technology. With the growing number of NFC mobile phones being launch, we can clearly see that the industry is committed in making our life more productive.

Let us start by a simple overview of various technologies that is related to RFID. We can easily see the advantages/disadvantages that the RFID can have in the application of tagging and identification.

Comparison chart of tagging/identification technologies

Description				Form factor can be like like a thicker credit card
Technology name	LF RFID (LF Passive)	HF RFID (HF Passive)	UHF RFID (UHF Passive)	Active RFID Tag (UHF Active)	2D Barcode	Barcode	Smart Card	Magnetic Stripe	Light	Sound
small in size
conceal easily
contain more information
attach to odd shaped object
attach to object with metal surface or liquid content
store information
durable
passive (no need battery)
contactless
no need to be line of sight
retrieve data fast
secured communication
low cost
far reading distance
simple to manufacture
frequency	<135KHz	13.56MHz	868-950MHz	433-5.8GHz
read distance	low 0-15cm	low-medium 0-1.5m 0-15cm (NFC)	far up to 10m	very far more than 10m to km
data rate	4-8kbps	6.7-848kbps

 Selecting guide your RFID technologies. Click here -> rfid-guide.pdf

2. RFID Tags

HF RFID tag 125KHz / 13.56MHz	UHF RFID tag 860 – 960 MHz / 2.4Ghz

Click to enlarge the picture.

Basic RFID Tag

RFID tag, is also known as RFID Transponders. The tag is make up of three basic components. An IC chip, an antenna or coil, and a substrate that holds the chip and antenna/coil together.

The picture on the left shows two typical tag design. The one on the left is a coil design. It is mean for LF/HF RFID tag (low/high frequency) that operates in a low frequency range. The tag uses induction method as a means for power and communication. The UHF RFID tag (ultra high frequency) on the right uses a dipole antenna design. The tag uses RF transmission (radio frequency operating at a much higher frequency) method to obtain its power and achieve communication.

Higher frequency tag is able to transmit information faster, and need less energy to receive/transmit information compare to a tag that uses lower frequency; lower frequency takes more time. Antenna helps to transmit the signal can be smaller at higher frequency. With the signal transmitting out of the antenna, tag can be read at a further distance away.

At this stage in time, you may think that a UHF tag is better than a HF tag. You can be right and wrong. A tag that can be read at a far away distance can be good. The same property will not be good if you need to get hold of a specify tag but end up with all the rest of the tag nearby. There is little value in defining the good and bad. What is more important, is understanding the property of what it can or cannot do, and apply its properties to its advantage. This depends mainly on the application.

For the application of tagging an object, I have valued HF tags more than the other alternative technologies. Passive RFID tag using HF or NFC has a higher potential in solving problems relating to interraction betweeen living things and physical object. This which will be further presented as another topic in another site.

This is a finger that I have downloaded from the internet. Notice the black square dot on the middle of the finger. That is the RFID transponder IC chip which can be found on a RFID tag. You can hardly see it.

IC chip for RFID tag

The IC chip on the RFID tag is very very small; not much bigger than a gain of sand (see photo on the left). This makes the tag small enough for a lot of purpose. This IC contains memory which can store information. The cost of the chip is proportional to the memory size and functional it has. The IC chip needs power to operate. It will get its power from its antenna. The tag’s antenna will capture the energy transmitted by the RFID reader. The RFID reader will generate the RF energy from its own antenna when a read command is initiated.

There is a limit distance in which the antenna can effectively capture the RF energy for powering up the tag. This distance will depends on the transmitting power from the RFID reader, as well as the size of the tag’s coil. The bigger the coil on the tag, the further the distance. As a rule of thumb, a bigger tag is expected to achieve a further read distance than a smaller tag..

**pic of transmitting energy from induction stove, RFID reader. Coil with LED. big tag further distance. higher power further distance

When the tag received enough power to operate, the IC will immediately power up, and response to the command from the RFID reader. The tag will usually read the binary information contains in its memory and send them back to the reader. The basic form of read information will be the tag identification number. If the tag contains additional user data, the reader can issue command to read them all. All these process happens within micro seconds.

RFID tag is essentially similar to a memory card. Similar to the flash memory card that we have been using for our digital camera, the RFID tag is using wireless power/communication, and has much less memory. The memory available can be as little as a few bytes to store the tag ID, to about 8Kbyte to store other user’s data. Each alphabet letter takes about 1byte of space, so a 8Kbyte memory can store about 8000 characters. The higher memory capacity tag will usually cost a bit more.

The LF RFID tags that I have seen can only be read. HF tags can be read/write. It is also possible to protect the tag from data writing. Some IC chip is able to kill the tag, therefore prevent a read from the tag, rendering the tag useless.

Depending on the chip, tags can be pre-programmed during the manufacturing to contain the same or unique ID no. (identification number). An unique ID no. for each tags will enable the reader to differential the multiple tags read.

LF and HF tags uses induction method and has a short reading distance <10cm. UHF tags can go as far as 10m. The distance will varies with varies RFID reader’s transmitting power and antenna/coil size. A bigger size antenna will usually have a longer read distance.

	Ferrite raw material in powder form
	Ferrite bead commonly used for EMI on cable.
	Ferrite sheet is form like a rubber mat and can be cut and place behind the RFID tag to improve readibility.

Fig 1. Magnetic field pattern of a typical RFID operation.
Fig 2. Magnetic field interference when RFID tag is stick close to a metal surface.
Fig 3. Improve magnetic field operation with a ferrite sheet between the tag and metal surface.

Fig 4. Cross section of the magnetic field detected

RFID operation with metalic or liquid objects

RFID has difficulty operating near metalic, liquid object (water bottle/ human body). Induction field around the tags will be collapse by these object. A minimum gap away from such object is required for proper operation. Metal surface can block/reflect RF signal, causing distortion to the signal, making it difficult to read the tag. There are special anti-metal tags (RFID Metal Pad) that allows RFID to operate under such tough condition. These tags are padded with a sheet of ferrite material behind the tag. The sheet actually forms the gap between the tag and the metal surface, allowing the tag to be read through the RF. The ferrite is itself a RF friendly material which permits the RF & field to sustain. With this padding, the tag readability can be improve slightly.

Ferrite sheet is available from:

TDK, FLEXIELD material

MARUWA, FLEX-u sheet

Active RFID tag

Active RFID tag with sensor attached

Active RFID tag with built-in sensor

Active RFID tag (sef powered, usually a battery) operates like a typically electronic transceiver device. Reading distance is a lot further than a passive RFID tag (not self power). The operations is similar to a passive tag where the reader will be able to retrieve the tag information when it is near enough. Some call the tag a signal beacon, where the tag keeps sending signal out. The tag can be read at a much further distance. This is because it has its own power source and do not need to harvest from the reader.

There are active tags that have built in sensor. The temperature/humidity sensor for example, will be operated by the RFID tag and send back the temperature read back to the reader. The battery usually last quite sometime, but it will definately need replacement one day.

Buy your NFC Tag Now at the PIC-store

Three typical standard among RFID tags
– LF tag (Low Frequency 125KHz) ISO11784 / ISO11785
– HF or NFC tag (High Frequency 13.56MHz) ISO/IEC 14443
– UHF tag (Ultra High Frequency EPC Class 1 Gen2)

Good RFID tag reference information, http://www.gorferay.com

RFID tag IC chip and standard

When dealing with RFID tags or reader, we will often come across various ISO standards. These ISO defines a common standard for the hardware or software to interact with one another.

The LF RFID (125Khz), ISO11784/ISO11785 is a common standard.

For UHF RFID, it is EPC Gen2 or EPCglobal UHF Class 1 Generation 2

For HF there are standard ISO15693, ISO14443 and ISO18092 (NFC). For NFC, we will focus on ISO14443 and ISO18092.

Some notes regarding NFC standards or ISO18092 (from website http://users.skynet.be/marc.sel/index-MTC.html)

In transport applications, cards suffer from daily use, for which reason contactless cards are preferred. Contact cards are more prone to hardware wear-out, hence contactless cards are better suited in the transport sector. This led to the creation of the RFID standard, ISO 14443, composed of 4 parts. It operates in the non-licensed 13.56 Mhz band. As there were two main “competitors”, there are two substandards:

• ISO 14443 type A (origine: NXP)
• ISO 14443 type B (origine: RATP)

Later under impetus from Sony, the NFC standard was established as ISO 18092. It’s a backward compatible extension to RFID, mainly aiming at use in mobile phones. It’s was actually proposed as ISO 14443 type C by Sony, based on FeliCa. It’s used e.g. in the Hong Kong Octopus and Singapore EZ-link systems. It did not make it to the 14443 standard, but came back as NFC.

Article for ISO/IEC 14443

• ISO/IEC 14443-1:2000 Part 1: Physical characteristics
• ISO/IEC 14443-2:2001 Part 2: Radio frequency power and signal interface
• ISO/IEC 14443-3:2001 Part 3: Initialization and anticollision
• ISO/IEC 14443-4:2001 Part 4: Transmission protocol

Mifare Tag ID issues (tag ID unqiue?)

Mifare name comes from the “MIkron FARE Collection System”. Mikron was aquired by Philips (NXP) in 1998. Given the Mifare Classic tag ID of 4 bytes, will the tag ID run out of unique ID?

• Mifare RFID Tags, an FAQ on ID Issues.pdf
• AN10927, MIFARE and handling of UIDs.pdf
• Mifare RFID tag & reader IC comparison chart.pdf

RFID tag/transponder IC manufacturer

	NXP Semiconductors, Mifare RFID transponder IC manufacturer
	Alien Technology, has many UHF tags
	ST microelectronic
	EM Microelectronic
	Texas Instruments
	Legic
	Inside Contactless
	Atmel
	Siemens (infineon)
	Innovation Research & Technology
	ISSI

Common RFID tag packaging

**Packaging (find chinese terms)
– inlay (wet/dry)

Reference:
http://www.skyrfid.com/RFID_Tag_Inlays.php

Inlay (dry)

Dry inlay is the fundenmental building block for RFID tag. They are usually be further packaged into RFID tag products. The term “dry” means that it does not have adhesive on it’s tag surface. The inlay can comes in roll or sheet form.

Common size:
35x35mm
43x26mm
50x30mm
85.5x54mm

Inlay layer and thickness
	Layer: IC:75um-150um Al(TOP)30um PET:38um AL(Bottom):10um

Layer within a RFID card
	Different layer of a package RFID card. The RFID inlay is sandwiched between the PVC (Polyvinyl chloride) and next with printed PET/PVC (polyethylene terephthalate) finishing.

Inlay (wet)

Wet inlay means that the inlay has adhesive on one of its side. The tag will be attached to a pressure sensitive liner base.

– sticker label

IDCard/Badge

These are hard PVC card about 1mm thickness. The card printing can be customised. There is also a special printer that prints on these plain tags.

– PVC/Plastic card
– glossy, matt paper

ezlink using CEPAS card

FlashPay using CEPAS card

Visa Paywave

www.octopus.com.hk

Payment Card (Singapore)

Ezlink, based on the Sony FeliCa smartcard technology

Flash Pay

payWave

CEPAS = ISO/IEC 14443-4 + ISO/IEC 7816-4: 2005

– Singapore Standard, specification for contactless e-purse application

Octopus card, based on the Sony FeliCa smartcard technology

base on MIFARE DESFire EV1 card

RFID Tag manufacturer

	HID
	Intermec
	Avery Dennison
	Alien Technology, has many UHF tags

4. RFID Reader

RFID reader is getting more and more common. Nowsaday Windows & mobile phone OS has built in driver treating RFID reader as a standard device.

USB RFID reader kit

RFID Reader manufacturer

	HID
	Intermec
	Alien Technology, has many UHF tags
	Motorola

5. NFC

NFC (Near Field Communication)

NFC phone to phone,

Phone to RFID tag

NFC currently use for Payment, transportation payment.

Instantly access to webpage,

Instant bluetooth/WiFi connectivity.

Reference:

– NFC Tags A technical introduction, applications and products, R_10014

– Understanding the Requirements of ISO IEC 14443

– MIFARE Ultralight as Type 2 Tag, AN1303

– NFC Type MIFARE Classic Tag Operation, AN1304

– MIFARE Classic as NFC Type MIFARE Classic Tag, AN1305

– MIFARE Type Identification Procedure, AN10833

6. Card Reader IC

13.56MHz RFID card reader IC

Getting to understand RFID was quite a confussing experience, with so many technical jargon. This was the reason why this website is setup; to sort out all the technical stuff into bits and pieces.

Card Reader is another interest topic to looking. A card reader helps to read out the information in a tag. An RFID reader is not a different device to understand, but not the card reader.

What is the difference between an RFID reader and a card reader? The RFID reader reads RFID tag. There are many variety of RFID standards in the industry. This means that there are also many type of RFID reader to read each type of card. (The type of cards was already presented above).

The variety of reader is going to make things complicated for developer who are developing application. This call for an universal solution known as ISO 7816. This is a standard defined for interfacing application with all smart card devices.

From what I read in the internet, this standard goes way back to the smart card technology. The smart card unlike RFID card is using wired communication to read the information on the card. You can identify it by the contact pins as shown in the following pic.

It is possible that a card has both the smart card as well as RFID card.

With the introduction of new form of card like RFID, the ISO 7816 evolve over time. ISO 7816 defines a standard interface for the card reader. The communication standard to a card reader device becomes a standard.

Article for ISO 7816 (specification for interfacing with card reader)

– AN4029, The DS8007 and Smart Card Interface Fundamentals

PCSC Personal Computer Smart Card is a standard framework for Smart Card access on Windows Platforms. This will make the job easier for application developers to interface to a card reader. To the developer, all card reader seems to work the same way.

The window operating system will automatically detects.

Interoperability Specification for ICCs and Personal Computer Systems

– PCSC_Part1, Introduction and Architecture Overview.pdf.pdf
– PCSC_Part2, Interface Requirements for Compatible IC Cards and
Readers.pdf
– PCSC_Part3, Requirements for PC-Connected Interface Devices.pdf
– PCSC_Part4, IFD Design Considerations and Reference Design
Information.pdf
– PCSC_Part5, ICC Resource Manager Definition.pdf
– PCSC_Part6, ICC Service Provider Interface Definition.pdf
– PCSC_Part7, Application Domain and Developer Design
Considerations.pdf
– PCSC_Part8, Recommendations for ICC Security and Privacy
Devices.pdf

My card reader

ACR122 NFC card reader from ACS.

Documentation
– PPE_ACR122, presentation.pdf
– API_ACR122U, Application Programming Interface.pdf
– TSP_ACR122U_v2.5, Technical Specification.pdf

Win7 64bits driver
– DIG_ACR122, Driver Installation Guide.pdf
– ACR122U_MSI_Winx64_1120_P

This is the first NFC card reader that I have brought. I have purchased this reader without any development kit, and was struck wondering how I can read a RFID tag without any software.

After understand about ISO 7816 and PCSC, I managed to find a number of free software that can communication with this NFC card reader. They are designed to work with PCSC compliants card reader.

– SCardToolSet, Smart Card ToolSet PRO v3.4
– sq2075-ba, SpringCard PCSC Diag
– online PCSC card reader program

The software are able to detect my card reader immediately. When my RFID tagis placed on the reader, the software detects it and display the tag information.

The very first unqiue string that was captured when I read the RFID tag is this string call ATR (Answer To Reset). It is a very weird name, because I was thinking that this should be the unqiue ID of the RFID tag. No it is not. This ATR string (as defined in ISO 7816) is telling us how we can communicate with the current tag found on the card reader.

This is the ATR string that I read when the tag (picture on the left) is on the reader

ATR = 3B 8F 80 01 80 4F 0C A0 00 00 03 06 03 00 03 00 00 00 00 68

So what does this hexidecimal string of number means?

With this ATR string provided by my card reader, I will know more about the RFID tag that I am actually dealing with. The RFID tag that I have place is using the Mifare Ultralight tag’s IC chip. ISO14443A is use for communication between the reader and the tag. The rest of the information seems not so useful to me.

To communicate with the card reader we will have to send a string of bytes to the card reader. The data format to communicate with the reader is known as APDU (Application Protocol Data Unit).

I have refered to the API (Application Programming Interface) datasheet provided by the card reader manufacturer. The first command to try is the command “Get Data”. The command will fetch the unique ID of the tag.

data send -> FF CA 00 00 04
where CA is the <Get Data> command.

The following response bytes are received.

data received <- 04 06 CD E2 90 00
where “90 00” is the response code (The operation completed sucessfully)
” 04 06 CD E2″ is the unique tag ID.

Next I tried to get the card reader firmware version.

data send -> FF 00 48 00 00
data received <- 41 43 52 31 32 32 55 32 31 30

The data received is “ACR122U210” in ascii format

Another Mifare Ultralight tag1 was read for its ATR and tag ID

ATR = 3B 8F 80 01 80 4F 0C A0 00 00 03 06 03 00 03 00 00 00 00 68
APDU send -> FF CA 00 00 04 (read tag ID)
APDU received <- 04 AA 2C 79 90 00

Another Mifare Ultralight tag2 was read for its ATR and tag ID

ATR = 3B 8F 80 01 80 4F 0C A0 00 00 03 06 03 00 03 00 00 00 00 68
APDU send -> FF CA 00 00 04 (read tag ID)
APDU received <- 04 2D 44 79 90 00

Reading Singapore Ezlink card (CEPAS card)

Next I tried another RFID tag. Our Singapore Ezlink card, which stores transportation logs in CEPAS format.

ATR = 3B 8C 80 01 50 72 23 AA 5E 1C 2D 94 11 F7 71 85 4F

When the tag is removed and placed on the reader again, the ATR string changes. This is unlike the previous tag where the ATR will remains the same for the same tag.

ATR = 3B 8C 80 01 50 21 0A 96 CF 1C 2D 94 11 F7 71 85 98
ATR = 3B 8C 80 01 50 B5 AE 55 A7 1C 2D 94 11 F7 71 85 03
ATR = 3B 8C 80 01 50 6D 83 67 F0 1C 2D 94 11 F7 71 85 93

The ATR tells us that it uses the application identifier 0x50. I don’t know what it means.

Next I proceed to send read tag ID command.

ATR = 3B 8C 80 01 50 5D 83 48 22 1C 2D 94 11 F7 71 85 5E
APDU send -> FF CA 00 00 04 (read tag ID)
APDU received <- 5D 83 48 22 90 00

ATR = 3B 8C 80 01 50 FE 15 0F A4 1C 2D 94 11 F7 71 85 AA
APDU send -> FF CA 00 00 04 (read tag ID)
APDU received <- FE 15 0F A4 90 00

The tag ID changes with the ATR string. A closer look review that the tag ID is the same data as the substring in the ATR.

A DESFire EV1 card ATR string is unexpectedly short.

ATR = 3B 81 80 01 80 80

The ATR string remains the same when the tag is

APDU send -> 90 0A 00 00 01 00 00
APDU received <- 84 D9 62 65 A2 3C A7 C8 91 AF

APDU send -> 90 0A 00 00 01 00 00
APDU received <- 91 CA

APDU send -> 90 0A 00 00 01 00 00
APDU received <- F3 A2 3C CC 2A 89 6E 51 91 AF

APDU send -> 90 0A 00 00 01 00 00
APDU received <- 91 CA

APDU send -> 90 0A 00 00 01 00 00
APDU received <- EB F4 A2 15 88 41 0C 3C 91 AF

APDU send -> 90 0A 00 00 01 00 00
APDU received <- 91 CA

APDU send -> 90 0A 00 00 01 00 00
APDU received <- FF 15 CD 6C 73 F0 28 D5 91 AF

APDU send -> 90 0A 00 00 01 00 00
APDU received <- 91 CA

APDU send -> 90 0A 00 00 01 00 00
APDU received <- BA B1 7A 2A 9C 23 C8 B7 91 AF

APDU send -> 90 0A 00 00 01 00 00
APDU received <- 91 CA

Load
APDU send -> FF 82 00 00 06 FF FF FF FF FF FF
APDU received <- 90 00 (90 00 means ok)

Read binary Page 0x04, 4 bytes
APDU send -> FF B0 00 04 04
APDU received <- 31 39 30 39 90 00

Read binary Page 0x04, 16 bytes
APDU send -> FF B0 00 04 10
APDU received <- 31 39 30 39 2D 2D 53 49 4F 4E 47 20 42 4F 4F 4E 90 00 (each page consist of 4 bytes)

Read binary Page 0x00, 256 bytes
APDU send -> FF B0 00 00 FF
APDU received <- 63 00 (no information given)

Read binary Page 0x01, 256 bytes
APDU send -> FF B0 00 01 FF
APDU received <- 63 00 (no information given)

Read binary Page 0x00, 16 bytes
APDU send -> FF B0 00 00 10
APDU received <- 04 06 CD 47 E2 87 28 81 CC 48 00 00 00 00 00 00 90 00

Read binary Page 0x01, 16 bytes
APDU send -> FF B0 00 01 10
APDU received <- E2 87 28 81 CC 48 00 00 00 00 00 00 31 39 30 39 90 00

Read binary Page 0x04, 16 bytes
APDU send -> FF B0 00 04 10
APDU received <- 31 39 30 39 2D 2D 53 49 4F 4E 47 20 42 4F 4F 4E 90 00

Read binary Page 0x08, 16 bytes
APDU send -> FF B0 00 08 10
APDU received <- 20 4C 49 4D 00 00 00 00 00 00 00 00 00 00 00 00 90 00

Read binary Page 0x0C, 16 bytes
APDU send -> FF B0 00 0C 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00

Read binary Page 0x10, 16 bytes
APDU send -> FF B0 00 10 10
APDU received <- 63 00 (no information given)

Read binary Page 0x10, 1 bytes
APDU send -> FF B0 00 10 01
APDU received <- 63 00 (no information given, memory bank stop at page 0x0F)

Read binary Page 0x0F, 1 bytes
APDU send -> FF B0 00 0F 01
APDU received <- 00 90 00

Read binary Page 0x0F, 16 bytes
APDU send -> FF B0 00 0F 10
APDU received <- 00 00 00 00 04 06 CD 47 E2 87 28 81 CC 48 00 00 90 00 (16 bytes of data can be read from the last page 0x0F. There is no page 0x10, the data is actually from page 0x00)

Mifare tag memory data from page 0x01 to 0x0F read:

04 06 CD 47 E2 87 28 81 CC 48 00 00 00 00 00 00
31 39 30 39 2D 2D 53 49 4F 4E 47 20 42 4F 4F 4E20 4C 49 4D 00 00 00 00 00 00 00 00 00 00 00 0000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Total memory is 64 bytes.

Ascii message contains “1909–SIONG BOON LIM”

This tag is a Mifare Ultralight tag with memory of 64 bytes

byte 00 SN0 (serial number)
byte 01 SN1 (serial number)
byte 02 SN2 (serial number)
byte 03 BCC0
byte 04 SN3 (serial number)
byte 05 SN4 (serial number)
byte 06 SN5 (serial number)
byte 07 SN6 (serial number)
byte 08 BCC1
byte 09 Internal
byte 10 Lock0
byte 11 Lock1
byte 12 OPT0
byte 13 OPT1
byte 14 OPT2
byte 15 OPT3
byte 16 Data0
….
….
byte 64 Data47

Reading the tag ID full 7 byte serial number
APDU send -> FF CA 00 00 07 (read full tag ID 7 byte)
APDU received <- 04 06 CD E2 87 28 81 90 00

Actual Tag ID is in the following sequence (high address, high byte),
SN6 SN5 SN4 SN3 SN2 SN1 SN0
 81  28  87  E2  CD  06  04

Try read tag ID 8 byte, not a correct read
APDU send -> FF CA 00 00 08
APDU received <- 04 06 CD E2 87 28 81 90 90 00
Able to read a 0x90 data for the last byte but this data cannot be found within the tag’s memory.

Read binary Page 0x29, 4 bytes
APDU send -> FF B0 00 29 04
APDU received <- 00 00 00 00 90 00 (ok)

Read binary Page 0x2A, 4 bytes
APDU send -> FF B0 00 2A 04
APDU received <- 63 00 (not ok)

Total available page is 42 from 0x00 to 0x29.
Total memory is 42 pg x 4 bytes = 168 bytes

Read binary Page 0x2B, 4 bytes
APDU send -> FF B0 00 2B 04
APDU received <- 00 00 00 00 90 00 (ok)

Read binary Page 0x2C, 4 bytes
APDU send -> FF B0 00 2C 04
APDU received <- 63 00 (not ok)

Total available page is 44 from 0x00 to 0x2B.
Total memory is 44 pg x 4 bytes = 176 bytes

Reading tag ID
APDU send -> FF CA 00 00 04 (read tag ID, 4 bytes)
APDU received <- 2B 2C 1E 95 90 00

APDU send -> FF CA 00 00 07 (read full tag ID, 7 bytes)
APDU received <- 2B 2C 1E 95 07 00 00 90 00

APDU send -> FF CA 00 00 08 (try read incorrect tag ID length)
APDU received <- 2B 2C 1E 95 07 00 00 90 90 00

Read from block 0x04, 16ytes
APDU send -> FF B0 00 04 10
APDU received <- 63 00
Reading from location fails

Authentication with a type A (0x60), key number 0x00 for memmory block 0x04
APDU send -> FF 86 00 00 05 01 00 04 60 00
APDU received <- 90 00

Read from block 0x04, 16ytes
APDU send -> FF B0 00 04 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read ok.

Read from block 0x04, 16ytes
APDU send -> FF B0 00 04 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read again ok.

Card is removed and place back on the reader.
Read from block 0x04, 16ytes
APDU send -> FF B0 00 04 10
APDU received <- 63 00
Reading from location fails. The card will need to go through authentication again.

Authentication with a type A (0x60), key number 0x00 for memmory block 0x04
APDU send -> FF 86 00 00 05 01 00 04 60 00
APDU received <- 90 00

Read from block 0x04, 16ytes
APDU send -> FF B0 00 04 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read ok.

Read from block 0x05, 16ytes
APDU send -> FF B0 00 05 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read ok.

Read from block 0x06, 16ytes
APDU send -> FF B0 00 06 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read ok.

Read from block 0x07, 16ytes
APDU send -> FF B0 00 07 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read ok.

Read from block 0x08, 16ytes
APDU send -> FF B0 00 08 10
APDU received <- 63 00
Reading not ok.

Read from block 0x03, 16ytes
APDU send -> FF B0 00 03 10
APDU received <- 63 00
Reading not ok.

Authentication on block 0x04 can only allows reading of data for block 0x04 to 0x07 (which is on the same sector 1) for as many times without the tag leaving the card reader. Memory block 0x03, 0x08 cannot be read.

Mifare 1K tag memory block
Sector 00, Block 0x00 – 0x03 (16 bytes/block)
Sector 01, Block 0x04 – 0x07
….
….
Sector 14, Block 0x38 – 0x3B
Sector 15, Block 0x3C – 0x3F

Authentication with a type A (0x60), key number 0x00 for memmory block 0x3F
APDU send -> FF 86 00 00 05 01 00 3F 60 00
APDU received <- 90 00
Ok, reading the last block.

Read from block 0x3F, 16ytes
APDU send -> FF B0 00 3F 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00
Read ok.

Authentication with a type A (0x60), key number 0x00 for memmory block 0x40
APDU send -> FF 86 00 00 05 01 00 40 60 00
APDU received <- 63 00
Not ok. (out of the 1K zone)

Reading Mifare 4K is the same as Mifare 1K. Only the memory map is different.

Read binary Page 0x00, 16 bytes
APDU send -> FF B0 00 00 10
APDU received <- 04 AA 2C 0A 79 62 02 80 99 48 00 00 00 00 00 00 90 00 (ok)

Read binary Page 0x04, 16 bytes
APDU send -> FF B0 00 04 10
APDU received <- FF FF FF FF 00 00 00 00 00 00 00 00 00 00 00 00 90 00 (ok)

Read binary Page 0x08, 16 bytes
APDU send -> FF B0 00 08 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00 (ok)

Read binary Page 0x0C, 16 bytes
APDU send -> FF B0 00 0C 10
APDU received <- 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 90 00 (ok)

Read binary Page 0x10, 16 bytes
APDU send -> FF B0 00 10 10
APDU received <- 63 00 (not ok)

Data Memory in the tag
04 AA 2C 0A 79 62 02 80 99 48 00 00 00 00 00 00
FF FF FF FF 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Seems like no NFC data inside.

Any material can influence magnetic, it is a matter of the intensity.

Strong Magnetic Materials (Ferromagnetic materials)
– Iron
– Nickel
– Cobalt

Not Strong (Paramagnetic materials)
– Aluminum
– Magnesium
– Platinum

Weak (Diamagnetic materials)
– Copper
– Lead
– Sliver

KRF-DTR401 FM Transceiver

After working successfully on my first transceiver, I started souring for other transceiver for research purpose. It is at that time, I have noticed that some of the transceiver have similar specification. The circuit layout is compared and found very similar in various area. After further investigation, the IC chip they used in the PCB is the key to building this transceiver.

The circuit is simple and is mainly operated by the IC on the PCB board. It is actually originated from nRF401 IC from Nordic Semiconductor ASA.

The testing of the RF module couldn’t have taken place without the development of my own dc-dc converter. Commercial module is available but cost is high. Voltage regulator is necessary for most electronics circuits project. Therefore learning to build a dc-dc circuit from discrete components is worth the effort.

Schematic for Data Encoder MC145026, Decoder MC145027.

2006-03-xx: There is a problem that was found during the attempt to use this design on my robot. The wire link from the transceiver and the decoder IC cannot be too far apart. Data error rate seems to be very high, and reception is very poor. It could be due to the weak signal strength, which should be resolve by using a digital buffer. The signal is digital from the output of the transceiver. If it is a transmission issue, then it will be quite difficult to troubleshoot without proper equipment.

433Mhz AM Transceiver

433Mhz Transmitter

433Mhz Receiver

Dated: 2012-05-18

There are many RF transceiver module in the market. When the transmitting distance is a concern, my preference will be transceiver in the range of 80 ~ 500Mhz. Wireless module in the gigahertz range can achieve higher data transmission rate but transmission distance will be shorter, especially when deployed indoor.

433Mhz is a good choice for distance communication. These pair of wireless module form a one way communication. You can get these from PIC-STORE. Working in this frequency range, the antenna may be slightly long. The antenna can be just a simple wire. The interfacing can be easy as what is presented in this experiment, but in order to transmit useful information, data modulation will be recommended. Data modulation is a process which changes the physical signal to another format so that it is less prone to noise/error and is easier to decode.

The data rate for such a wireless setup is quite low, about 1~4Khz, but it is enough for most of the simple applications.

I have managed to setup a simple transmitter and receiver circuit. The schematic is attached below. The objective is to understand how the signal looks like. This will allows us to understand and make use of these raw transmitter/receiver for sending useful data. It is not so direct using these raw module. Pre-processing will be required in order to send information.

The picture shows two portion of the circuit. The left side is the 433Mhz transmitter, and a push switch (black). The right portion is the receiver which consist of the 433Mhz receiver and a LED indicator.

This is the schematic details of the simple setup. When the button is not pressed, the transmitter will send out logic 0. When the button is pressed, it will transmit logic 1.

The receiver will have a LED indicator which allows me to see the response when the button is pressed. When the receiver’s data output is low, the LED will light up. When it is high, the LED will be off.

I have attached a video of how the response is when the button is pressed.

– Video of this setup. MVI_0275.AVI

In the video, you will be able to see that when the switch is not pressed (logic 0), the LED will blink continuously. When the button is pressed (logic 1) the LED will constantly light up (low output).

How the actual signal looks like? I managed to probe the data in of the transmitter, and data out of the receiver with my digital oscilloscope. They are presented in the following section.

Signal 1 (Transmitter, TTL input logic 0), Signal 2 (Receiver, TTL output pulsing signal)

The yellow line at the top is the signal input to the transmitter module (Signal 1). The blue line below is the signal output from the receiver module (Signal 2). The left scope display is the zoom out view, while the right is the zoom in view.

The transmitter is transmitting a logic 0. The output shows the periodic pulses indicating logic 0 or no transmission detected. This is the reason why the LED indicator keeps blinking. The receiver output is pulsing on and off.

The running pulse width is not consistent, ranging from 20ms to 30ms. The pulse period of 80ms is rather constant when I measure the falling edge.

Signal 1 (Transmitter, TTL input logic 1), Signal 2 (Receiver, TTL output signal pull down to 0.8V)

Now the transmitter is transmitting logic 1. The output signal is now constantly pull to 0.8V (I will consider it as logic 0). The logic 0 output will drive the LED constantly on, which is what we have observed earlier.

Signal 1 (Transmitter, transition from logic 0 to 1), Signal 2 (Receiver, output signal response)

This is how the transition looks like when the transmitter transmits from logic 0 to logic 1.

The response is pretty simple and within my expectation.

Signal 1 (Transmitter, transition from logic 1 to 0), Signal 2 (Receiver, output signal response)

This is how the transition looks like when the transmitter transmits from logic 1 to logic 0.

The response is a bit tricky. The receiver took some time to pulse it’s output periodically. There is a consistent delay between the first pulse and the subsequent pulse. First pulse width is able 50ms, followed by a 150ms delay, before the periodic pulses return.

The pulsing period of 80ms (12.5Hz) is going to cause some issue when decoding the transmitting data. It will be very slow differentiating logic 0 and 1 from the transmitter.

2012-05-19

The setup is further tested. The transmitter and receiver module is now 2m apart using separate power supply.

The experiment fails. The receiver did not response. Even when both circuit is place very near each other (10cm apart), the receiver fails to response. The pulsing signal is more random than the experiment above.

The antenna was then pulled very near the receiver module, the receiver starts to function properly as before.

I have came to read a relating article online. The symptom is very similar to what I have describe. The issue is due to improper tuning of the receiver. The module should works after proper tuning. I may have to verify this for my next experiment.

During my work in Teleradio Engineering, I am task to research in the area of magnetic field. Eventually some ideas were came up with to test out on radiated electromagnetic field. Electromagnetic field is simply the energy form by magnetic and electric field. The theory details on electromagnetic field is very mathematically intensive as what I had go through during my diploma and degree courses. However the concept is actually quite simple. Mathematics is simply one of our human language which can accurately be used to describe the physical property of electromagnetic. The deriving of the mathematics has gone through a lot of work. Eventually electromagnetic can be accurately predicted by the famous Maxwell Equations.

Wow, you may think, four simple equation and they have describe almost over 90% of electrical and magnetic phenomenon. These four equation are headache to study.

Electromagnetic theory is a form of geometry mathematics. If you can understand the concept of volume, area and vector in school, you have the potential to master this subject. It is not as difficult as it seem to be. You will have to apply some imagination and interpret the electromagnetic concept because these thing is physically not visible.

A book that have great influence in my understanding in electromagnetic is “Electromagnetism for Engineers (An Introductory Course) 3rd Edition by by P.Hammond (University of Southampton, Southampton UK)“. This book is fully recommended for beginners like me, as it has minimum mathematics which is very easy to read and understand. Most importantly, the book is thin and have sufficient pictures illustration.

Electromagnetic theory is a very useful in practice. The learning experience is applicable to a lot of engineering problem. I had manage to apply the knowledge to resolve lightings issue during my research work in Teleradio Engineering. It all started when I was confronted with my first commercial system (UV3, Under Vehicle Surveillance System) that I build for the company. A new chassis design were already in place before I join the company. After a test run, it is found to have lighting problem. The lighting positioning is wrong, resulting in dark images captured. We have to resolve this immediately because the delivery date to our oversea buyer is near. I am confronted by a problem which I was not trained to resolve in school. Number of simple reflector were made for testing but it does not seems to work well. I decided calm down and rethink the problem all over again. All our office’s fluorescence lighting were switch off. The bulb is being switched on, as I observed the bulb glow, the radiation pattern of the bulb. Within the next few moment, electromagnetic concept surface in front of my mind. I had come up with a simple custom reflector design base solely on the radiation pattern and managed to resolve the lighting issue for delivery. Although the concept of reflector is quite simple, it took me over a year to be able to understand and explain the lighting’s intensity distribution from all the various reflectors I have designed. I have spent much of my time in Teleradio doing reflector design and lightings research for camera vision.

The illustration of the light radiation from a bulb is very much similar in a way to electromagnetic theory.

LM7805, TO220 package

SD-50A-5

  SDM-30

PMA8811SF

UT70A

Various type of voltage regulator design

a) Zener diode voltage regulator.

Suitable only for very low power application.

For Vcc 24V
– Zener (Vout) = 12V 240mW, Iout(max) = 20mA, Rreg = 600ohm 240mW
– Zener (Vout) = 12V 120mW, Iout(max) = 10mA, Rreg = 1200ohm 120mW
– Zener (Vout) = 5V 100mW, Iout(max) = 20mA, Rreg = 950ohm 380mW

For Vcc 12V
– Zener (Vout) = 5V 100mW, Iout(max) = 20mA, Rreg = 350ohm 140mW
– Zener (Vout) = 3.3V 66mW, Iout(max) = 20mA, Rreg = 435ohm 174mW

Refer to the following website to compute zener, resistor value for a required Vout/Iout.
http://www.reuk.co.uk/Zener-Diode-Voltage-Regulator.htm

b) 3 rectifier diodes as voltage regulator.

Suitable only for very low power application.

c) Using voltage reference TL431 as a voltage regulator.

This is a very simple and useful adjustable voltage regulator. If the load is <100mA, this is a very attractive solution. For 5V output, R1=R2=10Kohm. TL431 datasheet.

d) Linear voltage regulator.

Suitable for application that requires low noise.

e) Switching voltage regulator.

Suitable for application that requires high power.

Circuit diagram taken from,

A dc-dc regulator/converter or another name known as buck regulator or switching regulator, provides stable regulated output voltage to supply electronic circuits. Schematic, PCB layout and component list are available on this page.

LM2576 circuits perform same function as the commonly known voltage regulator LM7805 from National Semiconductor. The 7805 voltage regulator dissipates a lot heat. The higher input voltage, the more heat is generated. The extra input energy is converted to heat, keeping the output voltage regulated at 5V.

LM78XX series is available to regulate 5, 6, 8, 9, 12, 15, 18, 24V. If you want the output voltage adjustable, there is also a adj model. For -negative voltage supply, you can use LM79xx series. These regulator is able to support up to a maximum of 1A current rating.

LM7805 IC requires input voltage to be higher than output in order to regulate the output voltage. Input voltage needs to be at least 7V (up to a maximum of 20V) in order for LM7805 to regulate at an output of 5V. It is advisable to supply a voltage input range from 7.5V to 10V. Any higher input voltage is consider inefficiency, generating a lot of  heat.

A switching mode power supply such as LM2576 dc-dc converter, uses switching control to reduce the input dc voltage on average. This is equivalent to a lower input voltage resulting in minimum heat dissipated. The control results in better regulated output, less energy wasted through heat and the use for high current application. Nowadays dc-dc converter are getting smaller and comes in the TO-220 package too. You can simply change your LM7805 to dc-dc converter without any change in your design.

The first commerical module I tried is the SD-50A-5 from Meanwell rated at 5V 10A. It is very good and easy to use. However it is very big and bulky. If size is a constraint, you might consider the model SDM-30. It is able to handle up to 5V 5A and is a lot smaller than SD-50A-5. However it generates a lot of heat through its metal casing.

The best dc-dc I have tried before is PMA8811SF from Ericsson. It is by far the most compact (smaller than SDM-30) and most efficient dc-dc. Heat is also dissipated through it ceramic package, however it does not scalded your finger as much as SDM-30 do.  The IC package is surface mount however soldering is relatively easy because the IC leads are quite broad. It is rated at output 5Vdc 16A and generate far less heat. Each pieces cost about S$60, a lot more than the other converter model.

Through some research, I get to learn about commercial standard dc-dc IC that perform with only a few external components. The following article discuss on LM2576 IC with rating up to 5V 3A. LM2576 is one of the dc-dc IC product range from National Semiconductor. There are also various brand of dc-dc regulator IC available.

The interfacing of most dc-dc IC requires the use of inductor. This is the case for LM2576 too. Try sourcing your local electronics shop for one if possible. I am not stopping you to make your own inductor. Just that making your own inductor takes up time and it is very likely to cost you more than what a shop might be selling.

If you are interested in making your own coil, you might interested in this website, http://www.skylab.org/~chugga/mpegbox/coil/. The aurthor Jeff Mucha had demonstrated a simple and creative way to make inductive. One Long screw, 2 board flat washer, 2 nut, 1 ring spacer, glue, and XXX is all the tools that is require to make your own air core inductor. It is really interesting.

More article: home brew your own inductors

Jens Moller has contributed a program which generate a table of information for building air core inductor. Simply input the inductance value you need, the program will display a table containing the wire coil height radius and number of turns required. You need not have to understand formula to make your own inductor. Take a look at the following website, http://www.colomar.com/Shavano/inductor_info.html

A greenhorn when I first attempt to use inductor. It is a tough job building circuits using inductor. I do not have proper equipment to measure the inductor on hand. Never able to find out the inductance value I have. Fortunately, there is this inductance measurement product selling at an affordable price. UT70A from Uni-Trend Technology. It also function as a multi-meter, and can be used to measure voltage, current, etc… . Even with an inductance meter, it is not a easy task to measure inductance accurately.

Other reference:

The practical basic of building a power supply.

– The Power Supply.pdf

http://www.talkingelectronics.com/

projects/ThePowerSupply/Page79PowerSupplyP1.html

2009-09-13 dc-dc step up, LED driver using 1.5V alkaline battery

The simplest DC-DC step up converter I have done. Typical LED requires about 2V to operate. This ciruict is able to drive the LED from a 1.5V battery. The transistor forms the oscillating circuit generating pulsing output. Although the output is pulsing, we can’t actually see it on the LED, as the switching is quite fast.

Click the picture to enlarge.

The voltage output is about 3Vpeak oscillating at about 33kHz.

Schematic

Photos of DC-DC circuit built

This is the 1st successful DC-DC circuit I built.

There a variety of capacitors out there in the market. Capacitance, voltage rating, dielectric material, etc… . Choose a suitable voltage rating across the capacitor. The circuits deals with high current, therefore it will be better to choose a low ESR (equivalent series resistance) Aluminum electrolytic capacitor. As a general guide, a higher voltage rating has lower ESR rating.

The inductor coil use should be able to handle the current passing through the inductor coil. If the wire is too thin, the coil may be burn or just fail. My previous circuit uses small wattage inductor (package like a big resistor). The circuit couldn’t work and was later found to be IC problem. I have not yet do a test to check on the possibility of the inductor contributing to the failure.

Using a inductor meter to measure the inductance will be easier. Inductance value can be observe immediately for any modification to the coil of wire. The inductance value can also be calculated, depend on the coil size, number of turns, wire size used, dielectric of the core etc… .

The 1N5822 is a high current, high speed, schottky diode and is suitable for this digital switching circuit. Schottky diode (Schottky Barrier Rectifier), means that the forward voltage drop is low. For this application, a low forward voltage diode is necessary.

Schematics

PCB Bottom Layer (PCB trace)

Component Layout (Silkscreen)

Bill of Material (BOM) for LM2576 circuit

Failure, my first prototype circuit to test out the performance of LM2575, LM2576.

Some of the various sizes of inductor tested and seems to be working with LM2576.

Initially I thought that I had use the wrong type of inductor, resulting in the circuit malfunction. Initially I had used a smaller type of inductor (looks like a resistor). Realizing that this circuit drive high current load, I should use a thicker inductor coil. That’s why I modified the circuit with an inductor (enamelled wire, wound around the ferrite core).

Still it doesn’t work. I guess that both IC LM2575, LM2576 must have been damage by my previous attempt. The capacitor used is suspected because the datasheet call for low ESR capacitor. It is very difficult to find these in the local shops, therefore I use a normal capacitor instead.

One day, I visited a shop selling ready made inductors and brought LM2576 at the same time. The circuit was rebuild and it finally works. My deduction at that time was either the inductor or the capacitor is giving me the problem. After further testing, I find out that ordinary capacitor works as well. There is hardly any difference in performance. Various type of inductor were tested (except the resistor like type). All inductor works too, big or small. Quite weird actually, and I couldn’t figure it out the actual problem I had in my previous attempt.

The mystery is resolve finally. One fine day I went back to the shop where I first purchase my LM2576 and brought 2 additional LM2576 for more testing. A new circuit was build and the familiar failure was observed. The output voltage of 5V cannot be sustain and eventually drop when more than 1A of current is draw by the load. The lab power supply display a current loading limit warning. IC becomes very hot. The datasheet specify that LM2576 should be able to supply 3A without any  problem. Both brand new IC are tested to have the same problem.

This is weird, as the same inductor and capacitor previously tested do not result in this same old problem. However the circuit shows the same failure symptom. The next thing that comes to mind, is the IC. The IC LM2576 from the previous working circuit is then transfer over the new circuit board for testing. Everything works fine. It is then clear that the problem comes from the IC itself.

Checking up on the previous IC, I notice that they are from the same manufacturing batch number and believe that they are already damage in some way.

Sample of the 5Ω 50W aluminum house resistor used for testing 1A current performance.

General tester for LM series dc-dc IC chip.

Some of the newly fabricated board built to support other prototype projects. It has been tested to support a RF transceiver operating at 5V without any issue observed.

Home fabricated circuit board

It has been some time since I learn to use LM2576. The circuitry is able to handle a higher current at 3A 5V output. This translate to a higher cost and circuit size, since all component must be able to handle that high power capacity. These component include the LM2576, inductor and the diode. Since most electronics kit requires less than 1A power supply, it is wise learning how to apply a low power dc-dc regulator like LM2575. Cost can be reduce by 50%.

There is one day that I happen to come across this IC LM2575 while searching high and low for LM2576. LM2576 is actually quite difficult to find. There is only 2 shop I know of, but I have rule out one shop because they are selling a faulty batch of LM2576 IC. LM2575 seems very common from shops around and I decided to find out more about this chip. Indeed it is what I have been looking for, a low power regulator. So I purchase the IC and its component to try it out. When I started writing this acticle, only did I realize that I have actually tried it about 6 months ago. The experiment was forgotten after a series of failure.

The following experiment is done during the 1st test on LM2575 circuit. The experiment compare between the performance of using different inductor. One using a wire coil inductor, and the other smaller one inductor that looks like a resistor with it’s color bands..

The photos on the left column shows the LM2575 circuit using the correct inductance value at 330uH but the inductor is low power rated. It is small and looks like a color coded resistor.

A few second after the left circuit is powered up, the small inductor turns very hot. The waveform observed at the output of the dc-dc regulator, contains a high amount of noise/ripple energy.

The photo on the right column shows the same circuit using a slightly higher inductance at 480uH but the coil is thicker and bigger in size.

The circuit using a high power rating inductor on the right shows a cleaner DC supply, although the inductance value is different from the design. There is still ripple at it’s output but I guess it will be minimum using an inductance value of 330uH with higher power rating. Too bad, I do not have the right inductor to experiment further. It is either coil one myself or buy one from shop.

12 June 2006, Lim Siong Boon

I have found this article regarding about the property of inductor Isat (current saturation) and Irms (continuous current). They are usually one of the important specification to take note while selecting inductor from datasheet.

Current saturation means the amount of current required that flow through the inductor, in order to reduce the inductance of the component.

Continuous current means the amount of current required to heat up the inductor to a certain temperature. If the amount current continue to flow through the inductor, the inductor is basically becoming a heater. The temperature depends on the amount of current flowing through it.

The following contains information that I learn from.

Isat_Irms explain.pdf

02 Dec 2008, Lim Siong Boon

LM2575 Schematic taken from National Semiconductor LM2575 datasheet

Bill of Material (BOM) for LM2575 circuit

I happen to see this very good website, teaching about handling noise. There are many illustration which are easy to understand.

http://www.williamson-labs.com/480_byp.htm

04 Oct 2011, Lim Siong Boon

Switching Power IC

LM2575, LM2576, LM2596, LM2678

The following table provides a quick reference for power supply circuit. The circuit schematic and component list are selected from the manufacturer’s datasheet.

For exact component value design, you need to the datasheet. The following component value is design for typical input voltage of 12Vdc or 24Vdc drawing power at 75% of the current rating.

LM2575 (1A)

DC to DC step down voltage regulator.

Wide input voltage 8Vdc to 40Vdc.

Part number:

– LM2575-3.3 (3.3Vdc output)

– LM2575-5.0 (5Vdc output)

– LM2575-12 (12Vdc output)

– LM2575-15 (15Vdc output)

– LM2575-ADJ (1.23Vdc to 37Vdc output)

Alternative:

NJM2367

Package: TO-220(T)

LM2575 datasheet

Click for LM2575-adj circuit

Component list

please refer to the table for resistors in parallel for more resistance design options.

    Vout, R1 & R2 design selection calculator

    Design calculator might not work on some web browser.

LM2825 (1A)

DC to DC step down voltage regulator.

Wide input voltage up to 40Vdc.

Part number:

– LM2825-3.3 (3.3Vdc output)

– LM2825-5.0 (5Vdc output)

– LM2825-12 (12Vdc output)

– LM2825-ADJ (1.23Vdc to 37Vdc output)

Package: MDIP24

LM2825 datasheet

no external component required

LM2576 (3A)

DC to DC step down voltage regulator.

Wide input voltage 8Vdc to 40Vdc.

Part number:

– LM2576-3.3 (3.3Vdc output)

– LM2576-5.0 (5Vdc output)

– LM2576-12 (12Vdc output)

– LM2576-15 (15Vdc output)

– LM2576-ADJ (1.23Vdc to 37Vdc output)

Alternative:

NJM2367

Package: TO-220(T)

tested working on 2007-06-26

tested working on 2007-06-26

LM2576 datasheet

Click for LM2576-5.0 layout

Click for LM2576-adj circuit

Click for LM2576-adj layout

Reference:

– AN-946, lm2576 as a charger

Component list

Resistor value for Adj (adjustable version). Voltage reference is 1.23V

    please refer to the table for resistors in parallel for more resistance design options.

    please refer to above for design calculator for resistance value selective

LM2594 (0.5A)

DC to DC step down voltage regulator.

Wide input voltage 8Vdc to 37Vdc (up to 60V for HV version).

Part number:

– LM2594-3.3 (3.3Vdc output)

– LM2594-5.0 (5Vdc output)

– LM2594-12 (12Vdc output)

– LM2594-ADJ (1.23Vdc to 37Vdc output) (57V for HV version)

Package: SOIC8, DIP8

LM2594 datasheet

Component list

LM2596 (3A)

DC to DC step down voltage regulator.

Wide input voltage 8Vdc to 40Vdc.

Part number:

– LM2596-3.3 (3.3Vdc output)

– LM2596-5.0 (5Vdc output)

– LM2596-12 (12Vdc output)

– LM2596-ADJ (1.23Vdc to 37Vdc output)

Package: TO-220 (T)

LM2596 datasheet

Component list

LM2678 (5A)

DC to DC step down voltage regulator.

Wide input voltage 8Vdc to 40Vdc.

Part number:

– LM2678-3.3 (3.3Vdc output)

– LM2678-5.0 (5Vdc output)

– LM2678-12 (12Vdc output)

– LM2678-ADJ (1.2Vdc to 37Vdc output)

Package: TO-220

LM2678 datasheet

Component list

LM2574 (0.5A)

DC to DC step down voltage regulator.

Wide input voltage 4.5Vdc to 42Vdc.

Part number:

– LM2574-5.0 (5Vdc output)

– LM2574-ADJ (1.2Vdc to Vin output)

Alternative:

NJM2369A, NJM2374A

Package: Wide-SOIC14

LM22674 (0.5A)

DC to DC step down voltage regulator.

Wide input voltage 4.5Vdc to 42Vdc.

Part number:

– LM22674-5.0 (5Vdc output)

– LM22674-ADJ (1.2Vdc to Vin output)

Package: PSOP8

LM22674 datasheet

Component list

LM22675 (1A)

DC to DC step down voltage regulator.

Wide input voltage 4.5Vdc to 42Vdc.

Part number:

– LM22675-5.0 (5Vdc output)

– LM22675-ADJ (1.285Vdc to Vin output)

Package: PSOP8

LM22675 datasheet

Component list

LM22676 (3A)

DC to DC step down voltage regulator.

Wide input voltage 4.5Vdc to 42Vdc.

Part number:

– LM22676-5.0 (5Vdc output)

– LM22676-ADJ (1.285Vdc to Vin output)

Package: PSOP8

TO-263 thin (7 pin)

LM22676 datasheet

Component list

LM22678 (5A)

DC to DC step down voltage regulator.

Wide input voltage 4.5Vdc to 42Vdc.

Part number:

– LM22678-5.0 (5Vdc output)

– LM22678-ADJ (1.285Vdc to Vin output)

Package: TO-263 thin (7 pins)

LM22678 datasheet

Component list

MC34063 (1.5A)

DC to DC step down/up.invert voltage regulator.

Wide input voltage 3.0Vdc to 40Vdc.

Part number:

– MC34063A, MC33063A

– SC34063A, SC33063A

– NCV33063A

Package: SOIC-8, PDIP-8, DFN8 (8 pins)

Load regulation performance measured seems poor. Ideally, this is a 5V 0.5A voltage regulator.

1) Vin=10V, Vout=4.92Vdc, Load=opened circuit (0A)

R2=10kΩ, R1=3.3kΩ, Rsc=0.33Ω 0.5W, L=330uH

2) Vin=10V, Vout=4.10Vdc, Load=15Ω (0.27A)

3) Vin=10V, Vout=3.00Vdc, Load=10Ω (0.3A)

Seems that the circuit can only handle 0.1-0.2A load. The voltage regulation is quite poor. According to the document, it is ok for the inductance to be higher. Could it be that my R1 & R2 value being too high? I need to check it up.

Circuit 1: Step down dc-dc 25Vin -> 5Vout (0.5A)

Current rating can be boost by using external transistor to drive the load.

Adjustable Vout computation (very similar to LM2576, LM2575) with Vref = 1.25V

Vout = 1.25 [1+(R2/R1)]

R2 = R1 [(Vout/1.25)-1)]

<For 3.3Vout> R1=3.3kΩ, R2=5.6kΩ
<For 5.0Vout> R1=3.3kΩ, R2=10kΩ

<For 0.5A Iout> Rsc = 0.3 / (2*Iout) = 0.3 / (2*0.5A) = 0.3Ω (0.075W), please note that Iout < 1.5A using internal driver.

Circuit 2: Step up dc-dc 12Vin -> 28Vout (0.175A)

Circuit 3: Step up inverting dc-dc 4.5-6Vin -> -12Vout (0.1A)

MC34063A-D datasheet

MC34063 project example.pdf

MC34063 AN10360, Schottky rectifiers for DCDC converters.pdf

MC34063 AN920-D, Theory and Applications.pdf

MC34063 slva252b, Application Switching Regulator.pdf

NCP3063 (1.5A)

DC to DC step down/up.invert voltage regulator.

Wide input voltage up to 40Vdc. Almost similar to MC34063 dc-dc ic.

Part number:

– NCP3063, NCP3063B, NCV3063

Package: SOIC-8, PDIP-8, DFN8 (8 pins)

.

NCP3063 is very similar to MC34063. Please refer to MC34063 for some handy information.

NCP3063 datasheet

LMZ14203 (3A)

DC to DC step down voltage regulator.

Wide input voltage 6Vdc to 42Vdc.
 

Part number:

– LMZ14203TZ-ADJ (0.8Vdc to 6Vdc output)

Package: TO-PMOD (7 pins)

LMZ14201 (1A)

DC to DC step down voltage regulator.

Wide input voltage 6Vdc to 42Vdc.
 

Part number:

– LMZ14201H (5Vdc to 30Vdc output)

Package: TO-PMOD (7 pin)

LMZ14201H datasheet

LMZ12003 (3A)

DC to DC step down voltage regulator.

Wide input voltage 4.5Vdc to 20Vdc.

Part number:

LM3102 (2.5A)

DC to DC step down voltage regulator.

Wide input voltage 4.5Vdc to 42Vdc.

Part number:

– LM3102MH

Package: TSSOP (20 pin)

LM3102 datasheet

LM2577 (3A)

DC to DC step up voltage regulator.

Wide input voltage 3.5Vdc to 40Vdc.

Part number:

– LM2577-12 (12Vdc output)

– LM2577-15 (15Vdc output)

– LM2577-ADJ (1.23Vdc to 37Vdc output)

Package: TO-220 (T)

tested working on 2006

tested working on 2007-06-21

tested working on 2007-06-21

LM2577 datasheet

Click for LM2577-adj circuit

Click for LM2577-adj layout

Component list

DC to DC step up voltage regulator.

Low input voltage 0.7-5.0Vdc

to output voltage 2.5-5.5Vdc

Suitable for battery powered circuit.

Part number:

– MAX1708EEE

Package: QSOP16

Front (tested with current up to 0.05A. Perheps the inductor used is not correct.)

QSOP IC mounted at the back of PCB.

MAX1708 datasheet

Click for MAX1708 circuit

DC to DC step up voltage regulator.

Low input voltage from 0.8Vdc

to output voltage 1.9-5.5Vdc

Suitable for battery powered circuit.

Package: SOT23-5

Not tested.

DC to DC step up voltage regulator.

Low input voltage from 0.35Vdc

to output voltage 2.0-5.5Vdc

Suitable for battery powered circuit.

Package: SOT23-6, DFN

Not tested.

Output 3.3V from a 1.2V alkaline battery using MCP1640

Output 5.0V from a 3.2V LI-ION battery using MCP1640

MCP1640.pdf

DC to DC step up voltage regulator.

Low input voltage from 2.7-14Vdc

to output voltage up to 20Vdc

Suitable for battery powered circuit.

Li-Ion, Li-Po

NOTE!!! (!SHDN pin does not shutdown the output. When shutdown pin is activated, Vout=Vin-0.2V. Vout will be close to Vin instead of pumping up to a higher voltage when shutdown pin is pull to low.)

Package: SOT23-5

5V output version

This board uses inductor from BOURNS SDR0403-6R8ML (RMS Current (Irms): 1.41A, Saturation Current (Isat): 2.1A )

12V output version

LM2731.pdf

Note: The size of the inductor plays an important part in determine the load’s max current.(applies to all switching regulators)

DC to DC step up voltage regulator.

Low input voltage from 2.97Vdc

to output voltage up to 40Vdc

Package: SOIC-8, VSSOP-8

DC to DC step up voltage regulator.

Low input voltage from 1Vdc

to output voltage up to 3.3V 0.3A, 5.0Vdc 1A)

Suitable for battery powered circuit.

Li-Ion, Li-Po, NiCd

Package: SOIC-8

LT1308.pdf

DC to DC step up voltage regulator.

Low input voltage from 1.8Vdc

to output voltage 5V or 12Vdc 120mA

Suitable for battery powered circuit.

Li-Ion, Li-Po

Package: SOIC-8

LT1301.pdf

Package: SOT23-5

SN6501.pdf

Transformer 760390015.pdf

MAX662A 4.5-5.5V to 12V (30mA), no need inductor

MAX734 4.75V – 12V to 12V (120mA)

MAX761 2-16.5V to 12V (150mA)

MAX732 4V – 9.3V to 12V (200mA)

MAX762 2-16.5V to 15V/Adj (150mA)

Singapore Customized, custom made Electronics Circuits & Kits

Schottky diode (1A)

1N5817, 1N5818, 1N5819, MBR120P, MBR130P, MBR140P, MBR150, MBR160, SR102, SR103, SR104, SR105, SR106, 11DQ03, 11DQ04, 11DQ05, 11DQ06

(smd alternative to 1N5819) MBRS140T3G, SS12, SS13, SS14, SK12, SK13, SK14

Schottky diode (3A)

1N5820, 1N5821, 1N5822, MBR320, MBR330, MBR340, MBR350, MBR360, SR302, SR303, SR304, SR305, SR306, 31DQ03, 31DQ04, 31DQ05, 31DQ06

(smd alternative to 1N5820, 1N5821, 1N5822) MBRS320T3, MBRS330T3, MBRS340T3, SS32, SS33, SS34, SK32, SK33, SK34

Schottky diode (4A-6A)

1N5823, 1N5824, 1N5825, 50WQ03, 50WQ04, 50WQ05, 50WR06, 50SQ060, MBR340

Diode references from Diotec     

– diotec diode cross reference list.pdf

– diotec diode case reference.pdf

– diotec diode smd selection.pdf

– diotec transistors-diodes zener selection.pdf

– diotec diode bridges selection.pdf

– diotec smdbridges.pdf

– diotec diode axial.pdf

– diotec hv-diac.pdf

– diotec arrays-special.pdf

Resistor Colour Codes

Images taken Farnell.

for EIA codes for SMD resistors,

please check out this link.

EIA marking code

W series- Vitreous enamelled wirewound resistors offering high power, high stability and reliability. Suit for use in harsh environment.

WH series- Aluminium clad resistors for applications where high power dissipation in a small space is required.

MFR series- High stability metal film resistors offering higher performance than carbon film with very low noise levels and high reliablility.

RC series- Very high stability metal film resistors offering very high reliability and tight tolerances.

WCR series- Surface mount resistors suitable for automatic placement. Features include nickel barriers, wide ohmic range and high reliability.

The DC-DC converter design for the adjustable IC version, you may need the following resistor standard EIA decade resistor values for references. Long time ago, when technology is not so advance, resistor manufacturing is not unable to produce precise resistor value, as in today. Due to its large variation in tolerance, the resolution of the range of standard resistor value is limited. Example is E3 series having tolerance of 50%, which have only resistors in decade of 100, 220, 470. There is not much point to define or differential between 100Ω and 101Ω, having a tolerance of 50%. With such high tolerance, there is hardly any difference between 100Ω and 101Ω. They should both belongs to the same class of 100Ω

The standard EIA decade resistor value is group into different series. Each is grouped according to their tolerance level. The higher the tolerance, the higher the resistor value resolution will be. The common resistor value range would be the E24 (tolerance 5%) and E96 (tolerance 1%) series.

To find the range of resistor value that is available in the industrial, multiply the normalise standard found in the table in terms of 100, 1000

– Example: E24 series referring to normalise value 1.0

   It means that under E24 series, you should be able to find these Ω range 100Ω, 1000Ω, 1kΩ, 10kΩ, 100kΩ, 1MΩ, 10MΩ, 100MΩ. Other resistor value under E24 can be determine from the rest of the normalised value in the table below. Lower Ω are not available in the series as they should be in resistor package for higher wattage

Standard EIA Decade Resistor Values

E24 (preferred standard resistor values with 5% tolerance)

E96 (preferred standard resistor values with 1% tolerance)

Tolerance Codes

B=0.1%, C=0.25%, D=0.5%, F=1%, G=2%, J=5%, K=10%, M=20%

website references:

– http://sound.westhost.com/miscc.htm

– http://www.logwell.com/tech/components/resistor_values.html

Most common resistance stock available:
0, 1, 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 75, 82, 100, 120, 150, 180, 200 ,220 ,270, 330, 390, 470, 560, 680, 750, 820, 1k, 1.1k, 1.2k, 1.3k, 1.5k, 1.8k, 2k, 2.2k, 2.7k, 3.3k, 3.9k, 4.7k, 5.6k, 6.8k, 7.5k, 8.2k, 10k, 11k, 12k, 13k, 15k

Second common resistance stock available:
0.1, 0.15, 0.22, 0.33, 0.47, 0.68, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2, 11, 20, 49.9, 51, 62, 110, 124, 160, 240, 249, 300, 360, 392, 430, 475, 499, 510, 620, 681, 910, 1.02k, 1.24k, 1.33k, 1.62k, 1.82k, 2.21k, 2.4k, 2.49k, 2.74k, 3k, 3.01k, 3.24k, 3.32k, 3.6k, 3.92k, 4.02k, 4.22k, 4.3k, 4.75k, 4.87k, 4.99k, 5.1k, 5.11k, 5.62k, 5.76k, 5.9k, 6.04k, 6.19k, 6.2k, 6.34k, 6.49k, 6.65k, 6.81k, 7.32k, 8.06k, 8.25k, 9.1k, 9.53k, 10.2k

Commercial Stock Availiability Statistics from element14 24 Oct 2013, for resistor value >40 types availability.

Table for resistor in parallel

This resistor table is interesting. While dealing with circuits prototype, I often need to use resistor value that may not be common. To keep sufficient stock for all resistor range is a bit too much to manage. A larger and better storage system will be needed. I find it difficult to manage the wide range of resistor. This brings me the idea of forming the required resistance from two commonly stocked resistor connecting in parallel. This means that I can keep fewer resistance range and easily stock larger quantity for each value.

On the following table, the 1st row and column represents the common resistor value that I normally keep stock. The rest of the cells present the various possible resistance I can obtain by having the resistance in parallel from the respective row and column. The computation is done in the microsoft excel sheet. formula: “=($A2*B$1)/($A2+B$1)”. Those value highlighted in yellow are quite useful when designing my adjustable DC-DC circuit when I do not have the stock for the resistor that is not commonly in use.

Typical aluminum electrolytic capacitor size – Capacitor Vishay datasheet – Capacitor selection (Panasonic) – Capacitor selection( Rubycon)
Type of capacitors, advantages and disadvantages explain.

Standard Capacitor Size

Panasonic/Vishay
(Rubycon) -> capcitor dia to lead pitch relationship (dia, lead dia, pitch) (5, 0.5, 2), (6.3, 0.5, 2.5), (8, 0.6, 3.5), (10, 0.6, 5.0), (12.5, 0.6, 5.0), (16, 0.8, 7.5), (18, 0.8, 7.5) -< confirm standard same as Panasonic/Vishay as well.

size dia x L in mm

hover to get the case code pin size, pitch

Standard size:

Ultra-Miniature High Voltage Power Supplies

Q Series

Q01-5 (5Vdc to 100Vdc)

Inductor Introduction

Typical symbol of the inductance.

Inductor is simply a piece of wire coil. A striaght wire do not have inductance. A slight bend in the wire will starts to introduce inductance on the wire. I have been working on electronics for quite some time, but have not understand the practical aspect of inductance on a circuit.

An inductor makes no impact on a DC (direct current) Voltage or Current. Like a capacitor, it affects the AC (alternative current) components. Inductor allows DC or lower frequency components to flow through it while it block AC or higher frequency components. For this reason, inductor is often used in line with a wire carrying power supply, to block any noise on the supply line.

The inductance of a inductor is affected by the following parameters,
– the area size of the coil
– the number of turns to make up the coil
– the diameter size of the wire or the length of the coil

Formula for inductance, L = (r x o x N x N x A) / L

where,
r – normalised permeability (/o)
o – magnetic constant (4π 10−7 H/m)

Normalised Permeability (r),
of Air is about 1.0
of Ferrite is about 640

Reference:
Coil Inductance Calculator, http://www.eeweb.com/toolbox/coil-inductance
Air Cored Inductor Calculator, http://www.m0ukd.com/Calculators/air_core_inductor_calculator/

The reference table above computes the inductance of a wire coil for each change in the parameters. An increase in the number of turns increases the magnetic field through the coil, hence increases in inductance value by quite a lot. An increase in the coil (D) increases the coil circumference, hence more surface area contributing to the field within the coil resulting in an increase of the inductance. Inserting a high permeability material into the coil provides a lower resistance for the magnetic field which helps to increase the inductance.

??????
The increase in the wire (d) while all parameters remains, reduces the resistance, however reduces the inductances. This also means that if the wire is a perfect conductor (0Ω or no resistance), there will be no inductance. Inductance needs resistance to exists. This is something that I need to understand.
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Inductor impedance formula

XL = 2π x f x L

XL -> Inductance Reactance
π -> 3.14159
f -> frequency
L -> Inductance

Capacitive reactance Xc = 1 / (2 π f C)
Resonant frequency f0 = 1 / (2 π √(L C))

Some good must have features in a power supply,

– able to support high current and wattage.

– current and voltage meter.

– current limiting function.

Of course there are more high tech advance features, but these are the 3 most important function that I cannot live without.

With a higher current/voltage or wattage rating, you can power up wider range electronics devices.

Before connecting any load to the power supply, it is a good practice to adjust the current limit to a range which you think the load consume. When connecting to any unknown load or load that you suspected may have problem, it is a must to set a current limit, to prevent over drawing of current from the power supply. If there are short circuits in the load, current limiting can prevent huge current from flowing through and therefore reducing the chance of burning the whole circuit down. With proper limit, a short circuit wire could be warm rather than burning with red hot fire. A lot of the problem can be detected by observing the amount of current being drawn.

KIKUSUI ELECTRONICS CORP

Regulated DC Power Supply

Model: PAD 35-10L 0~35V 10A

Voltage range:

0Vdc – 35Vdc

Current range:

0A to 10A

Function

<1> adjustable current limit

To limit the current up to a value. If the current drawn is greater than the value set. The power supply will seize further current supply, such that the current supplied will not exceed the limit. With some voltage adjusted, press current limit button <5>, and turn, <1> to the required current limit.

<2> adjustable voltage

Adjusting the open terminal voltage to the requirement. This also sets the voltage limit of the power supply.

<3> over current indicator (C.C)

LED lights up if current drawn is greater than the limit set.

<4> over voltage indicator (C.V)

LED lights up if voltage at the terminal is greater or equal than the voltage setting. With open terminal (not connecting any load/circuit), the C.V LED should be lighted up. When loaded, the C.V LED should be off.

<5> current/Voltage limit button

Press the button to see the current limit being set.

<6> OVP function (over voltage protection)

Adjust a limit to the voltage, such that if the system’s voltage exceed the setting, the own power supply equipment will be shut down, and OVP LED will be lighted up. A reset (Off/On) will be required to reset the power supply to normal working conditions. This is a safety feature in case the voltage at the terminal is greater than expected unintentionally.

<7> voltage meter zeroing

see voltage calibration

<8> current meter zeroing

see current calibration

<9> V.FS (voltage full scale)

see voltage calibration

<10> A.FS (current full scale)

see current calibration

<11> V.OS (voltage offSet)

see voltage calibration

<12> I.OS (current offset)

see current calibration

<13> Voltage display

see voltage calibration

<14> Current display

see current calibration

Setting up the power supply for use:

1) Always turn current/voltage knob to minimum (anti-clockwise) before switching on the power supply.

2) Switch ON the power supply.

3) Adjust the voltage knob to the voltage required. It is important to verify the voltage using a multi-meter. Do not rely solely on the voltage reading on the power supply equipment.

4) Press the current limit button <5>, and turn the current limit knob to the maximum current allowed. Always keep the current limit as low as possible to prevent over driving faulty circuit, which may result in burning/fire.

5) Switch OFF the power supply.

6) Connect up your circuits.

7) Switch ON the power supply.

8) If the voltage and current when switched on is not of expected, switched off the equipment and think over what is happening.

Calibrating the voltage display <13>:

1) Make sure the power supply is switch OFF.

2) Adjust the OVP <6> to maximum, to prevent the protection mode from activating.

3) Adjust the voltage knob to minimum (anti-clockwise).

4) Switch ON the power supply..

5) Insert a digital VOLTAGE-meter and it should read 0V across the +ve -ve terminal.

6) If it does not read zero volt, adjust V.OS <11> until the digital multi-meter reads 0V. adjustment should be small and slow as the reading needs about a minute to be stable.

7) After the digital multi-meter reads 0V, it means that the output voltage at 0V has been tuned. Check the power supply voltage display 0V too. If the display does not show 0V, adjust the voltage meter zeroing <7> to 0V reading on the power supply equipment.

8) Adjust to increase the voltage to exactly 30V shown on the multi-meter. The voltage display on the power supply may not shows the 30V. Adjust V.FS <9> to adjust the voltage display to show the 30V on the equipment. Note that adjusting V.FS do not change the voltage output from the power supply equipment.

9) The equipment should be calibrated. Adjust to varies voltage to check if the voltage display tally the reading shown on your multi-meter.

Calibrating the current reading <14>:

1) Make sure the power supply is switch OFF.

2) Adjust the voltage/current knob to minimum (anti-clockwise).

3) Insert a digital CURRENT-meter and it should read 0V across the +ve -ve terminal. Make sure the priority is correct or else your meter will be damaged. +ve probe connected to the +ve terminal, while the -ve probe to the negative. This forms a short circuit across the power supply terminal as a amp-meter is 0 ohm.

4) Switch ON the power supply. The C.C <3> indicator will light up to indicate over current. This is because the current limit knob is turn minimum, limiting the current.

5) Increase the current knob by a bit. This should turn off the C.C indicator.

6) Increase the voltage knob by a bit. The C.C indicator could be lighted up, with a current reading on the display <14>. The display reading should reads the same as your digital CURRENT-meter. Adjust to varies current limit to check if they are of the correct reading.

7) If the reading is incorrect, A.FS <10> and I.OS <12> will need to be adjusted as it is done for the voltage calibration. The procedure will be slightly more complicated as current measurement is not as direct as voltage measurement, however the priciple is still the same. Tuning the offset first followed by the meter zeroing, and lastly the full scale tuning.