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I put together this Voltage Unit (VU) meter using LEDs on a breadboard the other day. It only has 4 LEDs, but can easily be expanded to more

It’s basically a simple display for showing a value. It’s originally for showing signal level in audio circuits, but there’s no reason you can’t use it to show temperature, rain intensity, light level, or whatever other value you are measuring.

In the video above, I added a potentiometer as a voltage divider between 9V and 0V, so that the output would be somewhere in between. This way I could easily test the VU meter.

If you want it to show audio level or any other signal with very low voltage, replace the potentiometer with an amplifier.”

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