Designing a Multimeter for Power Supply Unit

Overview

The project aims to develop a multimeter that can be used to measure the output voltage and current in a PSU wherein at the negative rail, the current sense shunt resistor is connected in series with the load.

Details

The main PSU can be acquired with only a single supply voltage while being able to control an electric fan used for the main heatsink to be cooled, which is an additional feature. A One Touch Button Setup is used to adjust the power threshold at which the fan switches ON. All the functions of the multimeter are handled by a single Atmel ATmega8 microcontroller as the multimeter can be used as panel meter due to the compact construction.

The multimeter can interact well with HD44780 controller based standard LCD as the system uses a single-sided PCB. The voltage measurement resolution stands at 10mV since it can measure 10mA current measure resolution a 10mV voltage measure resolution. The LCD connector is used to deliver the programming signals and the programming cable can be made using an old PC HDD cable. The circuit must be supplied with 5V during the programming of multimeter circuit.