Do you want to test batteries or solar panels? You need a load resistor. With this electronic load resistor project, you can not only simulate a load, but also implement useful additional functions.  

As a model airplane enthusiast who only has electrically powered models, you have a lot to do with batteries that you want to test or just discharge. But also in many DIY electronics projects, such as power supplies, the question of performance often arises. Does the power source reach the targeted maximum current without a voltage drop? These and similar tasks or questions can be answered with fixed resistors, but you quickly realize that a whole lot of them are needed. Also, a reasonable structure of a load resistor is essential, especially at higher powers, to ensure safe use.

While searching for an elegant solution, I came across a suggestion on the Internet that seemed to solve part of the problem. However, only the heart of the circuit is documented; a power supply and even...