RGB LED Voltage indicator for 15 - 10 volts

I would like to make a one RGB LED DC voltage indicator, 15 – 10 volts in half volt changes.  At first I thought I would use a bunch of zener diodes, but it seems a bit more complicated than that as on my chart how I want the colors indicated.  Any ideas how I can accomplish the circuit?  There are probably new fancy things I could use but am not aware of since it’s been a very long time since I’ve made a circuit.  I am currently just using an analog panel meter.  It would be nice have a colored light indicator.  If it could be done.

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comcc3 years ago

I don't know how this turned out for you, but you could use 2 or 3 LM3914s to do what you want... drive each color of the RGB LED from one LM3914 in dot mode, connecting to the pins that would be needed for each color combination. This would also allow you to adjust the brightness of each color for the best possible result. I would probably isolate the individual driver outputs with a diode on each one, but that might not be needed.

I looked at the idea of using logic gates to do this, but it would most likely use more power and more components. The datasheet for the National Semiconductor LM3914 (NOT the TI datasheet) has example circuits showing ways to make the LEDs blink without too many additional components as well:


There is also a pretty good practical video for making a circuit using this IC here:

Wish you the best

comcc comcc3 years ago

I forgot to mention... I would imagine the most difficult part would be calibrating the LM3914s to all step at the same time, but if you can live with that, it might work for you.

K00kie (author) 3 years ago

Actually, I looked it up... and... I got an arduino. Looks like fun. They used to be SO expensive. Not bad. Looking forward to playing with it. Still want to make a discrete circuit, but at least I can see if the LED indicator colors will make sense.

K00kie (author) 3 years ago

Yes I was afraid someone would say something like that. I have no experience with microcontrollers or their expense. Sounds expensive. I will look it up. I've seen mention of arduino on here before, but did not know what it is. I was thinking of using a LM3914 IC, but I have to have 2 or 3 states on in certain conditions. It would make for a complicated circuit. I wish I remembered all my logic circuit work from many years ago. Still very complicated for a simple task, kind of.

The LM3914:


By far the easiest method is to use a microcontroller like the arduino.