Archive → May, 2011
Many months ago, I watched the EEVBlog posting on building a constant current dummy load. It seemed like a very useful device to have around, and I planned on building my own, but only got around to it recently.
My version is pretty faithful to the original. I made a few changes, mainly to decrease cost. For instance, in place of the panel meter, I just put a couple holes where you can insert the leads from a cheap multimeter. I also replaced the pricy multiturn potentiometer with a couple cheap single turn versions which provide a coarse and fine adjustment. (I know Dave hates those!) I think the only performance related change I made was to replace the LM324 op amp with a MCP6004, which has better rail to rail performance.
Here’s a little video of the board, and the schematic and BOM. I have a few PCBs and kit of parts available if you want to build your own. The kit includes PCB and all parts except the 9V battery. Shipping is a flat $5.20 using USPS small priority mail box. I can only ship to customers in the USA with this method.