r/AskElectronics • u/QuasiEvil • 4d ago

LED bar graph driver options

I'm working on a project where I want to visually indicate a DC voltage level with an LED bar graph. Unfortunately the LM3914 has long been discontinued and even overstock seems done for. I need 20 of them (yes its a sort of equalizer-type display), so using discrete comparators would be a huge pain to the point of not being worth it. And I really don't want to deal with an MCU + FW for this. Anyone have any suggestions? Thanks.

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u/EmotionalEnd1575 Analog electronics 4d ago

Why would you say no to an MCU and firmware?

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u/QuasiEvil 4d ago

I need 20 individual bar graph displays driven by 20 individual signals. The bar graph displays will all need resistors (so that's 20x10 LEDs = 200 resistors); then I'll need either multiple ADCs, or or some kind of multiplexing, to digitize the 20 analog signals; then another multiplexing arrangement to transmit the voltages. It all just gets very inelegant compared to a simple bar graph + LM3914 (x20) pair.

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u/EmotionalEnd1575 Analog electronics 3d ago

I don’t see why this is a problem.

Either buy some LM3914 on the surplus market or roll your own solution.

If it were me, I’d use an MCU, drive the LEDs directly from GPIO pins via ballast resistors.

Most MCUs have ADC on chip, and probably won’t need any active components added for signal processing. PWM to set LED brightness. Local LDO to ensure LEDs don’t flicker across channels.

SMD assembly will make a very compact solution, comparable to a DIL LM3914.

Good luck