Voltmeter Ammeter

  
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This Voltmeter Ammeter was designed to measure output voltage of 0-70V / 0-500V with 100mV resolution and 0-10A or more current with 10mA resolution. It is a perfect addition to any DIY laboratory power supply, battery chargers and other electronic projects where voltage and current consumption must be monitored. Thanks to added calibration via SE
Voltmeter Ammeter - schematic

TUP, UP & DOWN buttons it is now possible to calibrate the meter to measure voltage that is higher than 70V and current that is greater than 10A. The heart of the Voltmeter Ammeter is PIC16F876A microcontroller with built-in analog to digital converters (ADC) and 2x16 green / blue backlighted LCD display. Voltmeter Ammeter uses very few external components making it possible to fit this handy meter on a small PCB. The meter provides exeptionally accurate readings due to buit-in software based calibration and the use of 1% metal film resistors. It needs only one supply voltage that can be acquired directly from the main power supply. Entire voltmeter consumes only 10mA with LCD backlight turned on and 3mA with the backlight tuned off. LCD backlight can be turned off by disconnecting 10 Ohm resistor from the LCD display. Current sense 0. 47 Ohm shunt resistor is connected in series with load at the negative voltage rail and is passed to microcontroller chip through 100K resistor. Additionally the Voltmeter Ammeter can be easlily calibrated by temporaily connecting three (SETUP, UP & DOWN) tactile buttons or even a piece of wire to C1, C2 and C3 PIC16F876 microcontroller ports. To enter the calibration setup mode make sure the meter is powered off. Press and hold the SETUP button for two seconds while powering the meter until "Setup Mode" message is displayed on LCD display. After "Setup Mode" message disappears we will be...



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