Circuit Lake

The dummyload project simulates loads from zero to 1000 mA to help characterize new power supply designs. This design can present a single load to the supply, or it can toggle between two loads with a selectable period and duty cycle. The project is built around microcontroller AVR ATmega169.

The load circuit consists of a DAC, op-amp circuit, power transistor and a power resistor. The current from the power supply under test flows through the transistor and resistor and is controlled by a voltage presented to the non-inverting input of the op-amp. The LTC1669 DAC is controlled by the ATmega169 using its I2C bus interface. Various parameters can be set using the LCD and joystick interface, including minimum load, maximum load, period and duty cycle. The dummy load project is designed by Kenneth Lumia.