Internet PLC Forum

     Ok I reverse engineered the circuit board. I love doing that, I was having so much fun I got a nose bleed.  Well I discovered that the #1 and #2 0-1v inputs go to a LM324N Quad Op-Amp.

http://www.alliedelec.com/Images/Products/Datasheets/BM/ON_SEMICONDUCTOR/On-Semiconductor_Actives-and-Passives_5684630.pdf

     I set to 1k pot to 1v and traced it to pin 5 and pin 10. I read 1v on each but I read 0v on pins 7 and 8. Must be a bad op amp? Well I will get another tomorrow and hopefully that will work. Any insight on why this would be bad or possibly something I did? I always do an inspection to ensure everything is connected properly before turning the plc on after adding or changing the wiring. Although it has been 8 years since I worked with a plc and it was a 6502 programmed in assembly code. The I/O?s were UART 16550A with 16 byte FIFO, man what a dinosaur.

-Samson

I did monitor it with a DMM and could see the voltage going from 0vdc to 4.82vdc

I also tried this program for all ADC inputs (I have a 4x20 LCD)


       1st Scan                               1  FN_#1
---------||--------------------------------{dCusF}



        Clk 0.5s                               2  FN_#2
---------||--------------------------------{dCusF}

FN_#1
setLCD 1,1,"   Watch Dog 100"
setLCD 2,1,"Deviation     :"
setLCD 3,1,"Amperage    :"
setLCD 4,1,"Temperature:"

FN_#2
setLCD 1,15,CHR$(ADC(1))
setLCD 2,15,CHR$(ADC(2))
setLCD 3,15,CHR$(ADC(3))
setLCD 4,15,CHR$(ADC(4))


All I got on the screen is

4092
4092
4092
4092

I tried to ground all without result and tried the pot on all and nothing. It is very bizare. Is there a chip on the board that has just the ADC? Or is the ADC in the main CPU?

-Samson