“An inexpensive, adjustable lab power supply. Requires an external DC power supply with a voltage somewhere between 12-30V to function. I use an old laptop-charger. Based on a XL4015 DC-DC buck converter from ebay (link in BOM section). This provides an adjustable output-voltage from about 1.4V, up to the input voltage (nearly). Current limit can be set from 0mA, up to about 5A. The converter is rated for 75W, but if you plan to use this much power over longer periods, you will probably need extra cooling. The converter module has thermal shutdown and short circuit protection built in. Approximate total cost of parts (excluding printed parts and external PSU): 16$. Dimensions: 14cm x 6cm x 5cm”