Electronic Load and Power Supply
E-Load and PSU
2020
This started as a simple and quick project for an electronic load, which I needed for testing some CR18650 projects and some other power supplies, I was way too cheap to pay $7 for a commercial one. I ended up finding some pretty nice, paired, NPN and PNP transistors I salvaged from an old receiver I took apart about a year prior. I really wanted to use up and recycle some parts, so even though these were meant for audio amplification, they were very high power and pretty much perfect for this application.
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I had extra paired transistors so I decided to just make this project into a "Current Sink/Source Unit", which is just my quick easy way of describing what the electronic load and lab power supply combo is.
I have no idea what the current limit is of the E-Load is, but it is theoretically upwards of 20A. I am far too scared to go that high though because I feel like something will blow up. The PSU is just a 30V supply regulated with a few LM317's, as this is a dual channel supply.
There is also a somewhat useable current limiting feature in this PSU, which I did with PWM, a MOSFET, a shunt resistor, and a differential amplifier. I didn't know the LM317 had a designated circuit for this nor did I know that a MOSFET and PWM is not the ideal combo for current limiting in this respect, but I got this a lot more right in my next revisions of PSU's. MOSFET's are not great for current limiting as all their values change with a variety of other factors.
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This project ended up turning into an Arduino Nano controlled electronic load (0-20A) and dual channel power supply (~2-25V). The Nano essentially just read the voltages and currents and displayed them on an LCD over I2C.