
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
Eagle CAD 7.7 board and schematic files for DC Load Analog 2ch board
Hi there any chance you can supply the schematic of the MOSFET board and driver board ? I’ve been looking around to build an E Load for a while and your design looks good .….
thank you
Graham
Hi Graham,
I have added the Eagle CAD board and schematic files for the Dual L2 MOSFET board to the bottom of the DC Load — Part 2 post.
The driver board was developed for my testing purposes, and will be incorporated into a finished project, so it is not available for release yet.
Greg (Barbouri)
Hi Greg,
I am looking at your board and schematic. I cannot find any R5, R6 and R7 on the board as well as C3, C4 and C5. Do you have a newer board or .…?
Thanks
Alex
Hi Alex,
Those 6 components are clustered mostly around the MAX44284 IC and just above the current sense resistor.
Greg (Barbouri)
OK, I see. I do not have these components on my brd file. I have just downloaded a fresh copy of your file and now I can see them. Thank you for pointing it out.
You are driving it with 0–10V control board based on MAX6225 (2.5V) voltage reference (2ppm/C tempco)? How do you find it drifting so far/influencing your DC load ? My personal experience so far with multiple Vrefs without going into LTZ1000/LM399 ultra high precision territory was that the lowest low long term drift was LTC6655 in LS8 package (hermitically sealed).
Alex
Hi Alex,
I didn’t see any appreciable drift, and only used the MAX6225 vref, because I had some excess stock.
I was only shooting for a stability of 1 mA on the analog control board for testing purposes, before moving the design to full digital control.
Greg (Barbouri)
I am interested in building this design.
Is the schematics for the analogue board available please.
Thanks
Brian
Hi Brian,
I have updated the post to include the 2ch analog board.
Greg(Barbouri)
Thank you Greg