Knowing how to wire and solder will be needed here:
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If you cannot get the same PTs and IREDs as I did you have to start testing the PT's resistors. Going from paper to real life the circuit didn't work as I expected, so you may have to experiment a little bit as I did. I suggest that you take a look at the IC's requirements to represent a "0" and a "1".
What you must know is that every ICís input you donít use has to be connected to ground. The IC outputs you do not use, you will leave without connections. You'll also need to take a look at the IC's data sheets of each IC to know which pins feeds the IC with + (VDD) and - (VSS), if you don't connect these, your circuit won't work.
You have to think which optoisolator fits the circuit and your mobo. The only thing you must know is that you can only get 8mA at the 4081's output, if you draw more than 8mA you'll burn the 4081. You might need to use a resistor to limit the current as it's shown in the schematic. Come to the Forums and see if others have found an optoisolator that matches your mobo.
Mounting the Reading Circuit
Get a piece of wood, a little bit bigger than your coded card. Drill the holes for your PTs and IREDs as shown in the picture.
After youíve drilled the holes, cut the piece of wood at the middle, as you can see Iíve marked it with a green line. This is where the card is going to be inserted, so separate both pieces of wood just a little bit more than the cardís thickness.
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Make sure both pieces of wood are aligned, put something between to separate them and then use screws or nails to secure both pieces. You may also use the screws or nails as the cardís rail, if so, put them as close to the cardís width as possible. Put the PTs and IREDs in their places and use glue or some kind of epoxy to secure them to the piece of wood. Don't put them too deep into the piece of wood, just half way.
Be careful! If you put the PTs and IREDs too close any PT might work with the IRED that is supposed to work with the PT that is at its side, remember, they work with light.
Here you have the little slit I've done on the plastic project box, the piece of wood containing the glued PTs (only 3 because my circuit only had 15 possible combinations). The IREDs are on the other piece of wood that is at the bottom of the project box.
Now you can see the 2 pieces of wood. The black thing that hangs is a relay, this has been supplanted by the optoisolator.