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What Type Of Resistor Is Needed?
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lettuce:
Well i took my multi-meter to the credit board and checked the coin pulse terminal when i inserted a coin, it was sitting at about 1.5 volts, and the drops slightly when inserting a credit, so i guess im ok without a resistor/zener diode
rockin_rick:

--- Quote from: BobA on July 15, 2007, 09:54:49 am ---You need to invert the signal as well as isolate 12V from 5V.  The ipac needs a ground to indicate a contact closure.

Use an NPN transistor and a 1000 ohm 1/4 watt resistor to make the following.



--- End quote ---

It doesn't sound as if you are going this direction, but for reference (perhaps someone else is remembering this circuit for some use), the circuit from BobA needs another resistor to limit the base current into that transistor.  So the 12V in would go through a current limiting resistor (say 10K ohms, 1/4W) then to the base of the transistor.  Connecting the 12V input directly to the transistor will allow the transistor to draw too much current, thus damaging it. 

Rick
BobA:
Thanks for pointing that out rockin_rick.   I had just used an opto isolator circuit then figured you didn't need the LED part of it and forgot to put the resistor into the base.   For isolation the opto is probably the best because there is not direct connection even with component breakdown.

I think I would still advise Lettuce to use the zener on the input to the ipac as Andy recommended.  1.5V falling to ground when tripped does not like a proper output for a credit board.

lettuce:
But if the voltage on the Coin pulse terminal doesnt exceed 5 volts do i really need to?, i would probably worry if it was near 5 volts but its not even half that. I had to set the multi-meter to 2000m on the DCV setting for it to even register a voltage, before that i had it set at 20 and didnt think the credit board was working as there was no reading.

The last credit board i had (Shefras Green Board) i used on an I-PAC for over 2 years without a problem, i think that was a really old credit board as is this one i think, so maybe its the older credit boards that drop down voltage on a coin insert?
AndyWarne:
It sounds like you have an open-collector signal which has no pull-up. So this is fine to connect to the I-PAC directly, and the internal pull-up resistor in the I-PAC will pull it to 5 volts with no coin.
Andy
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