Next steps for my dummy load prototype based on IRF830 N-Channel MOSFET, and a LM328 plus a multi turn pot. Currently in tests, but the initial measurements look good. My intention is to build a µC – controlled dummy load.
Dummy Load Prototype – breadboard closeup, view from above; detail: the thermal sink, the small fan and the temperature sensor; IRF830 is attached to the sink;
I have added a small 12Vcc fan, to test various cooling options. The thermal sink reach 88C at 1.5A load, which is a bit too much without active cooling. Initial tests with a small 20mm fan cools the fan to a controlled 50C. With a larger one, results will be better.
The temperature sensor shows in the image to the left, attached with a crocodile. The thermal sink, the small fan and the temperature sensor. IRF830 is attached to the sink;The 1R power resistor has very poor tolerance. It is actually 1.32R measured. Accordingly, there is a mismatch between the measured voltage drop across and the actual current that passes thru.
More to come.
Leave a Reply