Giant Bulb VU Meter


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.


20 thoughts on “Giant Bulb VU Meter

  1. Obviously the light bulb filiments are slower than leds, but it appears that they have it set to dot graph instead of bar graph. The green ones should remain bright while the yellow and red are coming on.

  2. SSR’s can indeed be hellishly expensive if purchased retail, but I have always had good luck finding boxes of new ssr’s left over from industrial surplus. Nice thing is they are usually only 3-10 bucks each and can usually be found in reasonable to even large numbers of matching units.

    There is no end of mayhem that can be accomplished with the careful abuse of a few of these!

  3. Agreed i’ve seen circuits for this sort of thing in the past and they were always triac based. why use SSR if they are so expensive ?
    Imagine the price of trying to put together a proper VU set of say 10 strips all tuned to different frequencies.
    it could cost you a small fortune

  4. i also question the author’s comment on not using mechanical relays because they broke in a couple of days… he obviously did not use the appropriate relay for the task. in many cases, relays can be more rugged than solid state equivalents. mechanical relays also have lower contact resistance and capacitance, allowing them to better switch high current or high frequency circuits.

    point being, mechanical relays still have a place in modern designs and won’t be going away any time soon. good article here:

  5. Agree with agent420. I did something like this using triacs back when i was in college (long time ago). Cool project though. Nothing beats a VU meter using line powered high wattage bulbs :)

  6. When it comes to dressing up the display, a cabinet with rectangular, would be one way to go. For something different a cabinet constructed in an arc with segments rather than rectangular ones, to simulate an analog meter would be far out. mechanical relays would be reminiscent of tagging along with mom to the telco office to pay the bill, and hearing all that clicking coming from the back of the building. Yea I’m a grey beard.

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