20 & 30 Segment LED Voltmeters

  
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So you could easily set it for 20 or even 200 Volts Full Scale, Using a Suitable Potentiometer on the Input. DO NOT EXCEED 30 VOLTS to PIN 5 of the LM3914`s. The 20 K resistor Shown across the LED is required to null out the #10 LED, when higer LED`s are lit up in Dot Mode. Leaving this resistor off will cause #10 (Also #20 on the 30 LED one) to l
20 & 30 Segment LED Voltmeters - schematic

ight Faintly when LED`s above #10 are lit. This 20 K resistor is soldered to the Copper Side, due to space limitations! I designed The 20 LED unit to operate from any Voltage Supply beween 5 to 12 volts MAXIMUM. It runs with about 10 mA per LED and Exceeding 12 Volts Supply Voltage in Bar Mode WILL cause Overheating of the LM3914. In Dot Mode you can Safely operate this circuit up to a 20 Volt supply. This NEW, Three LM3914 Version (Shown Below) has a Minimum 3. 75 Volts for full Scale. It is Programmed for around 8 mA per LED, so it can operate from Voltages Up to 15 Volts in BAR Mode, without damaging the LM3914`s.



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