resistors value comfermed by LED light????

Thread Starter


Joined Nov 19, 2005
I am trying to make circuit for testing 14 different resistors values will be marked 1,2,3,4.....If I connect to open circuit resistor with value 1, first or only one LED light should light up. If I connect resistor value 5, the fifth or whole 5 led lights should lit. Any idea from where to start. I was thinking using zener diodes but as my knowledge is not the highest, still strugling. Any IC I can use. Thanks
Boban Klasnikov


Joined Sep 20, 2005
What is the resistors range? I would use fourteen comparators and measure the voltage on the test resistors.


Joined May 16, 2005
If the values are evenly spaced, you could sense the voltage drop accross the test resistor and use that to drive a dot/bargraph driver. If they're not evenly spaced, something else would have to be done.


Joined Jun 30, 2006
Examine the 4 level voltage detector here.

I think you could set that up with 14 comparators (yipe!)
Replacing RV with a circuit and contacts you can plug your resistors in would be needed.

You could replace all those ICs with one IC and a 14 position (ick) switch that would switch in and out various resistances until the single LED lights up. :) A 14 position switch can be a stripped and tinned wire and 14 brass tacks. :p

It's a tough question and I'd like to see a schematic when you have it.

Thread Starter


Joined Nov 19, 2005
My simpliest tought was like this: In front of each resistor, I set the other one so combined it should make voltage from last resistor point to ground cetain value. Put zener diode to that value so current can go through iv value is right. Lot of holes, but based on my knowledge it looks the simpliest way.. something like this. If you guys come to any solution, I would appreciate it. These are resistor values: 2.-523 ohms, 3.-681, 4.-887, 5.-1130, 6.-1470, 7.-1870. 8.-2370, 9.-3010, 10.-3740, 11.-4750, 12.-6040, 13.-7500, 14.-9530, 15.-11801 . NUmber 1 is skipped. It actually exists but is not used. Aplication is for GM VATS keys reading ( I am automotive locksmith).


Joined Apr 20, 2004

Why not get a DVM to read the values directly? Most meters take a bananna plug where the leads attach. Get a couple of clip leads and bananna plugs. Take the alligator clip off one end of each clip lead and attach a bananna plug. Then you can just grip the resistor leads with the alligators and see what the resistance is on the meter readout. You also get a DVM to use for other purposes.