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Hello. I am an experienced Windows programmer. However I have not written any drivers and I have little electronics experience (beyond a hobby).

My problem is I want to have a series of 50 "switches". I want to make them as low tech as possibe. So I want a simple contact in a circuit to send a single to some kind of "master" IC or whatever when the switch is fliped. Then I want each switch signal to some how send a number like "45" or "50" to a PC via a USB or whatever I can get that is as modern as possible. I have looked at 1-Wire but it looks like it may be over kill for what I am wanting to do. I just dont know how to wire this up so I dont blow up my PC.

Thanks for any help.

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Have you considered using your paralel port(IEEE 1284) for that aplication.By converting the output lines(wich are bidirectional) to input lines you'll have 8 input lines. There are 4 aditional input line that you can use as "sensors" by grounding them.
You can program the IEEE 1284 interface to sense when one or more inputs ar grounded...So,your "master IC" would be the printer port controller :).
Well,50 switches is :o .You could multiplexe the inputs or get a dedicated IC for that(if someone knows one,he/she could suggest it)
Concerning the data transfer(sending numbers) I can't be of much help as i'm new at it.
I hope i was helpful(even a little bit).I'll post some schematics for you ASAP.
Good luck with your project!!!

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I do have a couple web pages I have found that describe using the parrell port. If I can get away with ONE port with some kind of IC that will read just the signal I want then that would work also. But then again there are thousands of ICs ..which do I need? And what software driver do I need to talk to the parrell port? Or is it just something I should use the Windows API for?

Thanks again.

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One way to do this if you will only use one switch at a time would be to trigger comparators with the switches, then feed this voltage into a A/D. Will you only use one switch at a time? If you want to get different combinations of the switches, then you will be better off using a microcontroller to sort it out. 50 combinations are a lot. What will this be used for?

MP

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heres an idea
a circuit like this

|--/--| |--/--| |--/--|
----/\/\/-------/\/\/---------/\/\/-------
the swithces are connected i parrallel with a risistor and connected to an analog Microprocessor (parralax stap) when a button is pressed the value of the chips pin changes and sends a value to the pc containing the pin and value to the pc.

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I want to have 50 keys with 50 locks and I want to be able to tell from the PC which keys are in the lock position and which are not (no key). I assumed that I will make the lock create the contact to close a circuit on an individual wire going from the lock to a circuit board from there I dont know what to plug into the circuit board to make it so that my software can talk to the circuit board and get a true or false for an individual wire (lock/key).

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heres an idea
a circuit like this

|--/--| |--/--| |--/--|
----/\/\/-------/\/\/---------/\/\/-------
the swithces are connected i parrallel with a risistor and connected to an analog Microprocessor (parralax stap) when a button is pressed the value of the chips pin changes and sends a value to the pc containing the pin and value to the pc.


This sounds alot like what I am trying to do. So how do I send a quest to the external circuit board and then get back a true false...i.e. I send a "45" to the microprocessor and it returns a true or false???

Thanks again for any help.
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Hi. Ok I might be right off track on what you're trying to do. What about using a keyboard hack as I have for an arcade machine. And a keyboard splitter that would give you over 100 individual contacts. You may need to amplify the signal from the keyboard if you need a considerable distance. If this is at all useful I can help out with the keyboard splitter and the matrix mapping for the keyboard.

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