ICL7107 Digital LED Voltmeter

This circuit is a digital voltmeter with LED display. It's ideal to use for measuring the output voltage of your DC power supply. It includes a 3.5-digit LED display with a negative voltage indicator. It measures DC voltages from 0 to 199.9V with a resolution of 0.1V. The voltmeter is based on single ICL7107 chip and may be fitted on a small 3cm x 7cm printed circuit board. The circuit should be supplied with a 5V voltage supply and consumes only around 25mA.



The use of 7805 5V voltage regulator is highly recommended to prevent the damage of ICL7107, 555 ICs and to extend the operating voltages.


Parts list of The Digital LED Voltmeter:

• R1 = 8K2 R1 = 8K2
• R2 = 47K / 470K R2 = 47k / 470K
• R3 = 100K R3 = 100K
• R4 = 2K R4 = 2K
• R5, R6 = 47K R5, R6 = 47k
• R7 = 0R / 4K7 R7 = 0R / 4K7
• R8 = 560R R8 = 560R
• C1,C5, C6, C8, C9 = 100n C1, C5, C6, C8, C9 = 100n
• C2 = 470n / 47n C2 = 470n / 47n
• C3 = 220n C3 = 220n
• C4 = 100p C4 = 100p
• C7 = 10-22u C7 = 10-22U
• D1, D2 = 1N4148 D1, D2 = 1N4148
• IC1 = ICL7107 IC1 = ICL7107
• IC2 = NE555 IC2 = NE555
• OPTO = CA 10 pin FTA = CA 10 pin

The digital LED voltmeter can also be configured to measure different voltage ranges and display higher voltage resolution.