About the article

Car-Stereo LED Power (VU) Meter

Car-Stereo LED Power (VU) Meter
This circuit senses AC audio voltage supplied to the car-radio loudspeakers and displays it as power using a LED bar graph, achieving at the same time an attractive visual effect. It is designed to cover common car-radio output power ranges, but can easily be modified to suit different needs. It is supplied from the 12 V car electrical system and is suitable for classical CC (Capacitor-coupled) as well as BTL (Bridge Tied Load) types of amplifier with no changes to the circuitry or connections at all. In fact, only the meaning of the LEDs changes — with BTL, the LED increments equal four times the CC value on the same load.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component list
R1,R5 = 22k?
R2,R6 = 10k?
R3,R7 = 820?
R4,R8 = 470?
C1-C4 = 470nF, lead pitch 5mm
C5,C6,C7 = 10µF 63V radial
D1 = 1N4001
D2-D21 = LED, 3mm dia. or rectangular-face
IC1,IC2 = LM3915N-1 (National Semiconductor)
IC3 = 7805
Heatsink for IC3 (10 K/W)
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