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Digital Voltmeter

Digital Voltmeter Using ICL7107

This digital voltmeter circuit provides a precise voltage measurement using the ICL7107 analog-to-digital converter. The display shows the measured voltage on a 3½ digit LCD or LED display. The measurement range can be adjusted by changing resistor R3, and calibration is performed using potentiometer P1.

Key Components

  • ICL7107: A precision A/D converter designed for direct driving of LCD/LED displays.
  • R3: Determines the measurement scale; changing its value alters the full-scale voltage range.
  • P1: Potentiometer used to calibrate the voltmeter for accurate readings.
  • Capacitors and resistors: Set reference voltage, integration timing, and filtering for stable display.
  • LCD or LED display: Displays measured voltage digitally.

Circuit Operation

  • The input voltage is applied to the ICL7107 through a voltage divider and protection resistors.
  • The ICL7107 integrates the input signal and converts it to a digital value displayed directly on the LCD/LED.
  • Changing the value of R3 scales the input voltage range, allowing the meter to measure different voltage ranges.
  • Potentiometer P1 allows fine calibration to ensure the display matches the true voltage accurately.
  • Capacitors provide filtering and stability to avoid flicker or erroneous readings on the display.

Key Features

  • Digital voltage display with 3½ digits resolution
  • Adjustable measurement range via resistor R3
  • Precision calibration with potentiometer P1
  • Stable and low-noise readings using proper filtering
  • Can drive LCD or LED displays directly without additional driver circuits
  • Suitable for battery, laboratory, or general-purpose voltage measurement

Construction Notes

  • Ensure proper layout to minimize noise pickup, especially around the analog input.
  • Use a stable reference voltage for accurate readings.
  • Adjust P1 carefully during calibration to match a known reference voltage.
  • Choose R3 according to the desired full-scale voltage for your application.
  • If using an LED display, ensure current-limiting resistors are included to prevent damage.
  • Keep analog input wiring short and use shielded cables if possible for best accuracy.

ICL7107 datasheet

Digital volmeter with ILC7107

Components

  • R1 = 180k
  • R2 = 22k
  • R3 = 12k (see note)
  • R4 = 1M
  • R5 = 470k
  • R6 = 560
  • C1 = 100pF
  • C2 = 100nF
  • C3 = 47nF
  • C4 = 10nF
  • C5 = 220nF
  • P1 = 20k Trimpot
  • U1 = ICL 7107
  • LD1,2,3,4 = 7 segment Display comon An

Note- R3 ( voltmeter scale)

  • 0-20 V ….R3 = 1.2K
  • 0-200 V …R3 = 12K
  • 0-2000 V ..R3 = 120K

Voltmeter PCB

volmeter pcb