How to drive a LED bar graph with w/o a micro?

Other Hardware General Electronics
1

Hi all,

I've wondering what's the most reasonable approach in driving an LED bar graph without using a micro controller.

Let's say, I have a resistive sensors that I use as a voltage divider. Now I'm trying to light up some LEDs based on the out voltage. 1 LED up to 1V, 2 LEDs up to 2V, etc.

I've been thinking about using op amps to get the difference between Vout (from the sensor) and the reference voltage for each LED. Feels like, I'd need a whole bunch of op amps for this. (About twice the number of the LEDs)

My other idea is to use diodes to drop the voltage under some threshold for each LED, but I don't think this would have enough control. What if the needed drop is not the multiple of the diodes' forward voltage? How to amplify the remainder to the level required by the LED?

What are some better/simpler approaches to this?

2

Hi try LM3915 or LM3916, one has linear response, the other VU for audio applications.

Tom.... :slight_smile:

3

I think you will find it is the LM3914 that is a linear display - the 3915 and 3916 are logarithmic for VU meters.

4

Yes, the 3915 is logarithmic, the LM3916 is optimized to match a VU display.

Best solution I can think of outside of using a microcontroller. I've built a fair number of projects using them. Even a crude 10x10 LED oscilloscope.