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Help me with a reader system of Wiegand protocol

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digitalpowers

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So I have seen this topic covered several times before but no one really seems to finish with a lot of information. Let me give you some background on what I am trying to do and see if someone can help me.

I am cheep, so I would love to build my own access control system using HID Card readers that output in Wiegand, they are easy to find on ebay for cheep. Now the problem comes into when you look into the Wiegand protocol adn realize that it uses 50 micro second pulses to encode the data. Now that is too fast for my paralell port to read even in an infinite loop (not pritty code). So I got smart (i wish) and decided to buy a daq card (NIDAQ 6520). I got it cheep as well (thank you ebay). Unfortunately what I didnt see was that that card reads 12v pulses as high not 5v pulses as high. Unfortunately my reader outputs 5v for high. So now I have come to the point of either starting from scratch, ie comeing up with a new system to read wiegand, or figuring out how to pull the data lines high enough without pulling the low up to high. I tried a transistor amplifier but that pulls the low data signal up above the 4v it has to stay below to be considered a low pulse.

Anyways, I am not exactly sure what I want to do about this but if anyone has any ideas that would be great. And remember cheeper is better.

Thanks.
 

Re: Wiegand Protocol

Could U bring an schematic of the circuit U are using. May be there is a biassing problem.
 

Re: Wiegand Protocol

Well I have tried a few things, the transistor amp looked like the first attachment. The resistors are all low like in the 10ohm range. Although I tried all sorts of options. I noticed two things with this circuit that didnt work well. First the transistor got very hot, second while I could get 12v when the input goes low we get around 10v when it goes high, I need high to be above 11v and low to be below 4v.

Before that I tried an opamp but while it does pull the values up above 12v and keep the lows low, it switches to slowly and I only get about half of the data. The opamp I tried is LM324N and there is nothing additional to the curcuit, just the opamp hooked up to the HID reader and the DAQ card.

Thanks
 

Re: Wiegand Protocol

Regarding you ckt, use base resistor 2k2 to 2k7 and collector resistor 100 to 220 ohms. This shoul work.

Regarding WIEGAND, it uses to data output lines, one outputs a pulse when bit=1 and the other when data bit is 0. ( never both lines get active at the same time )

You can transform it to a data and clock signal conecting D0 and D1 to the inputs of a XOR gate. At the output you will get CLK ( clock ) so use this signal to seen when you have a bit available. Then only read D0 or D1 and you get the data. I used this a long time ago and worked !!!
 

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