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Digital I-O Board - Inputs Not Working — Parallax Forums

Digital I-O Board - Inputs Not Working

T-townT-town Posts: 17
edited 2014-05-20 18:02 in General Discussion
Hi everyone.
So, I got my digital I-O board (27113) and I had a friend who has a background in soldering assemble it (you wouldn’t want to see it if I did it!). He is an ex-Navy avionics electronics technician and it turned out great.

I’m using a 12 volt power supply for the board power and to power the inputs. The outputs are working fine, but the inputs are not.

When the input side of the 4N25’s are low, the output pin gives me 5 volts; when the input side of the 4N25’s are high, the output pin only drops to 2.3 volts (two drop to 2.2 volts). The 2.3v is above the 1.4v that the stamp is looking for to assign a Zero. The input LED’s do light up, but not very bright.

The JP1 jumper does not reverse the logic. Pin’s one/two, two/three or out completely seems to make no difference.

Full disclosure: my friend did a great job on the board except he initially put in all the LED's (except the Logic Power light) backwards. I discovered this while checking out the board for the first time (so I did apply power with them in wrong). Would having the LED’s in backwards hurt the 4N25’s or the 74HC165????

So, the question on the floor is: What would keep the 4N25 from pulling its output down to zero??? I have been troubleshooting the board for some time and I even hit up an EE friend of mine for advice, but to no avail.

I’m not sure where to go next with this. Does anyone have any ideas on what I should be looking at?

Thanks,
Joe

Comments

  • LeonLeon Posts: 7,620
    edited 2014-05-17 07:23
    Schematic?
  • PublisonPublison Posts: 12,366
    edited 2014-05-17 07:27
    Here you go Leon,

    http://www.parallax.com/sites/default/files/downloads/27113-Dig-IO-Brd-Schem.pdf
  • PublisonPublison Posts: 12,366
    edited 2014-05-17 07:27
    And the docs:

    http://www.parallax.com/sites/default/files/downloads/27113-Digital-IO-Board-Documentation-v1.1.pdf
  • Mike GMike G Posts: 2,702
    edited 2014-05-17 07:41
    I believe Leon is answering the op's question by referring to the schematic for troubleshooting.

    I'd assume the board is assembled incorrectly. Without pictures, it's pretty hard to troubleshoot over the forum.
  • PublisonPublison Posts: 12,366
    edited 2014-05-17 08:10
    Mike G wrote: »
    I believe Leon is answering the op's question by referring to the schematic for troubleshooting.

    I'd assume the board is assembled incorrectly. Without pictures, it's pretty hard to troubleshoot over the forum.

    Mike,

    I my past experience with Leon, he asks for schematics so he and others can understand the product. Not everyone will relate the number 27113 to a Parallax product.

    I agree, without photos, there is little help.

    Jim
  • kwinnkwinn Posts: 8,697
    edited 2014-05-17 09:32
    Try removing one of the leds from the input circuit if that is possible and see if that makes a difference. If it does you have your answer.
  • T-townT-town Posts: 17
    edited 2014-05-20 18:02
    Hi Jim,
    After reading the second sentence in the instructions "Inputs can be a voltage from 5-30 VDC" I mentally blew past the section in the directions on setting the input voltage range by changing out the LED resister. I was using 12 volts so I thought I was good.
    Thanks for your consideration.
    Joe
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