# assistance needed in RFID

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#### hahawahaha

##### New Member
hi ... i would like to build a tag and a reader for RFID stock check/management.
it could be a simple one that needs around like 1-5cm of distance to detect it.
i don't know where or how to start with it. i would love to get advices on circuitry, chips to use and so on as im totally lost.

thank you !!

#### tresca

##### Member
building one from scratch is probably going to be alot harder than you might expect.
Your best bet is to get a reader from somewhere else, and then use its compatible cards/tags/fobs watever...

depending on the type of hardware you buy..you can connect it to your pc directly, or if its portable then to a microcontroller etc...

but if you are attempting to build this from scratch, and you already dont know where to start or what to do, then i would advice against it because it will be beyond you. I go to school for this kind of stuff and its above me too.

#### hahawahaha

##### New Member
hrmmm ... if thats the case what sort of hardware should i be buying?
im doing this for a project in school and i would probably think that they need us to build it ... if building it from scratch isnt sensible for a student, what do you reckon?

please let me know what sort of hardware i should be looking for ... the reader and the tag ... also what sort of software i should be using ... if possible where could i find it ...

now i have with me a few circuits where i dun even know wat they are for ... i've checked this site

Final Design Project - RFID Proximity Security System
but im not sure it is useful or not ...

#### dougy83

piece of cake! Well the card reader is anyway. You can also buy ready-made tags for less than $1 each. The reader is just a 125kHz (usually) oscillator feeding a series LC circuit. The LC junction point is fed into a peak detector (diode and RC) and this is AC-coupled into a comparator or bit-slicer. Output is then fed into a controller or PC. Or you can just buy one. Try google. #### Mr RB ##### Well-Known Member Here's a complete reader module for$24;

RFid Reader Extra Development Board | mikroElektronika

They have MikroC source code available and they have cards for $1.50 too. #### hahawahaha ##### New Member hi dougy ... thanks for sharing ... so from what you're saying ... i just need to find out how each of those circuits that u said works? for example how an oscillator feeding a series LC circuit looks like and the right values ... then look for peak detector which contains diode and RC and so on .... look for these circuits and then build them up from there?? do you have any references that i could refer them to ??? i just need to compare whether those circuits that i found and combined together would look the same as how the actual one looks like thanks alot for your information ... sounds very useful to me piece of cake! Well the card reader is anyway. You can also buy ready-made tags for less than$1 each.

The reader is just a 125kHz (usually) oscillator feeding a series LC circuit. The LC junction point is fed into a peak detector (diode and RC) and this is AC-coupled into a comparator or bit-slicer. Output is then fed into a controller or PC.

#### hahawahaha

##### New Member
hey mr rb,

thanks for the info, but i would need to build the reader from scratch ... but i might need to buy the tag from somewhere ... any advice on building the reader ??

thank you

Here's a complete reader module for $24; RFid Reader Extra Development Board | mikroElektronika They have MikroC source code available and they have cards for$1.50 too.

#### dougy83

##### Well-Known Member
... i just need to find out how each of those circuits that u said works? .... look for these circuits and then build them up from there??
Sure. None of the building blocks are difficult to understand (the microcontroller or PC used to decode the signal might need a bit of work).

Just have a look around for the circuit blocks you think you might need.
An example oscillator is at Circuit - CMOS INVERTER 125KHz LC OSCILLATOR - Circuits designed by David A. Johnson, P.E.
There's some RFID design info at https://www.electro-tech-online.com/custompdfs/2009/11/51115F.pdf (don't need to read the whole thing tho) including some reference designs. I would suggest using ASK tags and reader instead of FSK or PSK as they may be easier to understand and decode.

#### hahawahaha

##### New Member
hey dougy ...

ermm ... when you say decode, what do you mean ?? you mean decode what my tag is right ?? if that is so, what sort of program or software do i use ? i will have to create a program that does all these interfacing ?? or what ??

im really really bad in programming, pardon me for asking foolish questions if it seems so to you ...

apart from that, what sort of microcontroller should i be using?

thanks

Sure. None of the building blocks are difficult to understand (the microcontroller or PC used to decode the signal might need a bit of work).

Just have a look around for the circuit blocks you think you might need.
An example oscillator is at Circuit - CMOS INVERTER 125KHz LC OSCILLATOR - Circuits designed by David A. Johnson, P.E.
There's some RFID design info at https://www.electro-tech-online.com/custompdfs/2009/11/51115F-1.pdf (don't need to read the whole thing tho) including some reference designs. I would suggest using ASK tags and reader instead of FSK or PSK as they may be easier to understand and decode.

#### hahawahaha

##### New Member
hey dougy ..
so how do i do the programming?

#### dougy83

##### Well-Known Member
hahawahaha said:
what i would like my RFID project to do is, a reader ... from the DOOR of the room (store room) then detects how many tags are there left in the store for certain items. its fine if i could detect only ONE item instead of various for start up. then i guess i would have to send those code to the computer through whatever methods to keep track of how many tags are gone (lesser stocks) and indicates that its time to stock up. so probably yes, a sending those data to a spreadsheet.

Programming for the microcontroller: choose a microcontroller. I might suggest a PIC; for this project it doesn't really matter - maybe a PIC12F509 or a PIC16F628 or one of the 18F series. Choose a language: Basic & C are very popular. Get a compiler; you can get demos for free that will be abl to do what you want. Get/make programming hardware. Ask someone for a tutorial on how to do this.

Or if you buy a prebuilt reader with serial output the only programming you'll need to do is for the PC - you can use one of the programming languages from Visual Studio [express] for this (or many others).

#### hahawahaha

##### New Member
hey ... sorry for leaving this thread unattended for the past few weeks. was really busy with the project. now that i've decided to BUY a reader instead of making one, could you recommend any simulation softwares that has got to do with my stock checking rfid that has a rfid device attached to it.

as in the simulation software is only for the use of a certain device that is in the market. so i can try out the simulation software, and then go straight ahead to buy the device if i know how to use the simulator.

thanks

#### genius.split

##### New Member

Is there a way to read RFID labels in stack and know their order as well(position of each tag in stock). If someone offers me solution there is reward for that person!

Thank you.

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