I started this project a while ago but did not post it back then because of the lack of time. The point of this project was a simple variable load to test power supply’s. As an extra I put in a voltage, current and temperature measurement circuit.
The power is converted in to heat via 8 2N3055 transistors. Each transistor has his own driver and current feedback. This way I can read then individually in the pic and therefore can check if they are all still in a working state.
There are 2 fans mounted next to the heat sink. The fans suck air to the slots of the heat sink. The temperature is measured with a LM35 which is connected to the pic, so if it gets to hot the pic can shut it all down.
Circuit pic print:
The power supply I used came from an old hub. (From witch I also recycled this enclosure)
The displays are the same as from my safety transformers V2 and V3. I started this project earlier and copied the design to those two projects
Front panel ready:
The voltage and current measurement works at the moment. The current measurement is a bit of a problem. The MAX186 seems not to work (or I’m doing something wrong :p). I didn’t have time yet to fix it. The code will be posted as the project is complete.