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Possible to use LM3914 with bicolor LED?



Jan 1, 1970
I'm doing a serious cosmetic tweak on the front of my PC and I wanted a
visual display of sound output. (It'll be on the 5.25" faceplate with
temp sensor and fan RPM)

I wanted to use a bicolor LED and hook it to an LM3914 dot/bar display
driver (in bar mode). Since there are only 2 leads per bicolor LED, no
common anode or cathode so I'm going to use a hex inverter like 7404 or
4049 so it'd always be red or green. (see for example) The
question is can the LM3914 drive an inverter?

My plan was to hook the display driver to the sound output (one for each
left and right audio) and have the display indicate 0v to 1v (all green
on 0v, 1 red bar on bottom & rest on green on 0.1v, 2 red bars on bottom
and rest green on 0.2v, all red on 1v, etc.) I'm assuming the line out
is 1v max (not speaker out, unamplified line out for powered speaker or

If LM3914 can't drive that, then what can? I could try building one
using individual op amps and/or resistor network but I don't want big
circuit, just something small and simple.

I have tried googling for sound display but all I found were single
color only.

Rich Grise

Jan 1, 1970
Yes, an LM3914 can drive inverters, if you put a pullup on each of
its outputs. Then, you'd go to kind of a bridge arrangement -
each output goes to the inputs of two inverters. Use HCMOS inverters,
like 74HC04 - they can source current for the "other" LEDs.
Then the output of one inverter goes to one end of one of the
led/resistor sets, the output of the second inverter goes to
the input of a third inverter, whose output goes to the other
end of the led/resistor set. You can do 2 LED's worth with one
hex inverter.

Have Fun!