Hello,
I am in need of a schematic for a 2 digit 7-segment LED digital resistance meter....
I had a simple home-made wire mapper, it used rj11 plugs with resistors from 10k to 200k connected between pins 4 and 5, which read as 1 - 20 on the meter, the meter was housed in a small plastic project enclosure and used what I believe was a 7107 chip 2 - 7 segment LED's and a few resistors and caps. The PCB was a homemade 1 sided board. I found this a couple of years ago at a business auction in the bottom of a toolbox, it was slightly corroded but it worked. Curious as I am, I opened it up and looked at it only once about 2 years ago, I should have probably payed more attention then, anyway, about a year ago, it got lost, or, may have gotten into the hands of another curious tech who may have forgot to return it....
Anyway, I have been trying unsuccessfully to build another one, for the past month or so.
I believe I could use a maxim max139cpl, max140cpl or icl7107cpl chip to do the ADC and drive a 2 digit 7-segment LED. It only needs to read
10k - 200k in whole numbers, 10k incraments, 10-19.999k would be 1, 20
-29.999k would be 2.... I believe the original design was based on 10k incraments to allow for various wire lengths and gauges. It was originally powered by 4 AA batteries, but I thought 1 9v might be better.
I have a scematic that I am currently working on here:
Thanks