The latest Inventgeek project is a 12 outlet control box. They decided to demo it using a giant bulb based VU meter. The control box has 12 individual outlets hooked up to two layers of six solid state relays. [Jared] notes that SSRs can be very expensive, but he purchased his on eBay for ~$10 each. Wiring and installation on this project is incredibly clean and they plan on using the control box for future how-tos. The simple audio circuit used for the VU is based on the LM3915. You’ll find full plans on the site or you can watch the overview video embedded below.

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So here’s the situation: you have an audio device, maybe a boombox, perhaps one you built yourself, but it has no VU meter. No problem; building a VU meter is easy with these instructions from [Joe].

You’ll need either an LM3915 or LM3916 chip, a couple of bread boards, two audio jacks, ten LEDs, and a few other components. Wire them all together per the schematic, then plug an audio source into the input jack. You can plug your speakers or output device into the output jack, and you’re done. Keep in mind that LM3916s switch negative, so positive to positive wiring from LEDs to the bread board will be necessary. The wiring on [Joe]‘s version is a bit convoluted, but it can be cleaned up on yours if you take the time. Video embedded below.

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