LED Bar Graph Volt Meter
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Schematic of LED Bar Graph Volt Meter
This is a simple volt meter based on a 3916 VU meter display driver chip. I used this in my transistor throttle. There are only 5 components. The circuit is powered by 12V at pin 3 with ground at pin 4. The measured voltage is applied to pin 5. The 100k variable resistor provides trim adjustment. Just put your DMM on the input and adjust it to show max scale at the desired voltage. The mode switch changes the display from a single LED at a time to a bar graph display. When used as a bar graph the chip has to disipate a lot of heat when all the LEDs are lit. The LED module is available from Radio Shack (276-081).