I am wanting an at a glance indicator of what voltage level is being supplied by a DC generator (think pedal power). My general thought is a series of LEDs that light up in sequence as the input level increases, but I am having trouble coming up with a workable circuit. My voltage level can range from 0-24VDC, and I am looking for something that will indicate the current level in ~3V increments. The generator is the only power source I have, so comparators that need an external reference voltage or power source are out. I don’t need precise switching on the LEDs, they can gradually get brighter, but I would like something that only allows one at a time to be “partially” lit. I think I remember building such a circuit in one of my early electronics classes, but it has been many years, and the details elude me.
So basically the goal is 8 LEDs:
0-3V – LED 1 goes from off to fully on
3-6V – LED 1 is on, LED 2 goes from off to fully on
6-9V – LED 1 & 2 are on, LED 3 goes from off to fully on
etc.
I am thinking this should be possible with a zener/resistor/LED network, but every layout I have toyed with would push too much current through the lower level branches as I move up towards max power. So far my google skills are failing me in terms of finding a workable solution.
Best Answer
Try the LM3914. It runs from a supply as low as 3V and drives up to 10 LEDs. The display is linear with input voltage too. Max supply voltage is 15V so some form of low drop-out regulator is required to limit it from seeing the full 24V.