Working Principle

The ATtiny814 controls the electronic dummy load with its internal digital to analog converter (DAC). All of its 5 internal reference voltages are being used in order to get the maximum accuracy and resolution of the DAC. The DAC is connected to an OpAmp which acts as a unity gain amplifier controlling the resistance of the MOSFET. Voltage and current are measured via a high side 8 mOhm shunt resistor connected to an INA219 with a resolution of 4mV/1mA. A second INA219 is connected to another 8 mOhm shunt resistor between the PWR-IN and PWR-OUT terminal. The Power Analyzer is connected via USB to a PC or a RaspberryPi. Commands to the Analyzer can be sent via a serial monitor or by the GUI-based Python skript. The Analyzer has different built-in automatic test algorithms. The collected data is sent back via the serial interface/USB to the PC/RaspberryPi. The ATtiny814 constantly measures power and temperature of the heatsink. It controls the fan and cuts off the load when the temperature gets too hot.


Test Algorithms

Load Test


Voltage Regulation Test


Efficiency Test


Battery Discharge Test


Long-Term Multimeter


Commands for Direct Control

"i"transmits indentification string ("Power Analyzer")
"v"transmits firmware version number
"x"terminate current test program
"s loadcurrent[mA]"set load to a constant current of loadcurrent
"r"reset the load to minimum
"t"read current and voltage of both sensors and transmit them