Finally assembling the electronic load modules for some basic testing of minimum voltage at different current levels, and heatsink thermal capacity.
Before designing the microprocessor controlled analog board, I wanted to test the capabilities with the modules mounted in an enclosure, under semi-real world conditions.
I used a variant of my original analog test board that set the current level using a potentiometer for each channel. It is capable of driving the L2 Linear MOSFET’s at up to 10 volts
The 60mm fan has it’s own dedicated 12 volt power supply and can pull up to 1.4 amps. The fan is a Delta Electronics PFC0612DE-F00 and is capable of 67 CFM (1.2 M3/Min) of airflow at zero static pressure. It’s speed can be controlled by a PWM signal from a starting speed of 30% to 100%. It is a real screamer at 100%.
The control board has its own separate 12 volt power supply.
I am using two 15 AWG wires per channel to reduce the voltage drop from the input terminals to the board. Ribbon cables connect the modules to the control board.
So far everything is working as expected. I may end up increasing the current sensor gain from 50 to 100, to get some additional current capability from the modules at lower voltages and control the maximum wattage in software.
By strategically placing the inlet air holes I was able to achieve some additional cooling of the module heat-sinks and MOSFET hold down clamps. The Wakefield-Vette heat-sinks have additional fins on the component side, and by directing incoming air directly at these fins there is a significant increase in module cooling vs using the fan alone in my initial testing. The rear MOSFET in each module still runs hotter by around 5 degrees F under heavy loads though.
As it sits, the Dual-channel L2 MOSFET DC-load works well for general load testing. I still would like to add a graphical LCD display and microprocessor control, but currently that is not a priority.
Eagle CAD 7.7 board and schematic files for L2 MOSFET board