MightyWatt turns your Arduino Uno R3, Arduino Zero (M0/M0 Pro) or Arduino Due into an electronic load capable of dissipating 70 Watts in a very small form factor. Ideal for testing power supplies, batteries, fuel cells or power amplifiers. MightyWatt is for hobbyists and DIYers but I have used it for research in academia too. Revision 1 featured on Hackaday. This is the very much improved revision 2, currently in even more evolved version 2.5 (see blogpost), (latest revision).
Some assembly required
MightyWatt comes either as a kit (see photo) with a free 3.5g tube of Arctic Silver thermal grease or as a fully assembled unit. You will thus get everything you need except the Arduino. The kit includes board with all components soldered except pin headers. Next, there is the fan, pre-drilled heatsink and all the screws, washers and nuts you need. For best results, it is good to do some calibration. For that, you will need an adjustable voltage power supply and one multimeter.
So you will have to:
It should take about 1 hour altogether.
Please, observe the correct connection to Arduino:
How does it work
MightyWatt uses a special FET in linear mode to act as a variable resistor. User values are set via DAC that is controlled with Arduino. Current and voltage are measured and the load can switch between a constant-current or constant-voltage mode in hardware. In addition, constant-power and constant-resistance can be maintained via software control loop.
Firmware, as an Arduino sketch, is provided. A Windows software (written in C#) is also available so you can control everything with a few mouse clicks. Everything is open-hardware and open source and I am open to your questions.
Specifications and highlights
Optional test cables:
Optional acrylic case:
Optional booster pack (read the guide):
Firmware and software
MightyWatt uses two kinds of Arduino sketches as its firmware. First, the regular sketch that runs in order to control the load. Then, a second sketch is for calibration. You only need to calibrate it once. Windows software uses the virtual serial port of Arduino to send commands and receive data from the load. It can set constant current, voltage, power and resistance. Monitor temperature, log data and create scripts that include constant values and ramps. It also has watchdog to disconnect load in case value drops below or rises above a user-set threshold. You can also switch between 2-terminal and 4-terminal measurement. All the firmware and software are open source and fully functional right away but you are more than welcome to tinker with it!
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I am 30-year old and have a PhD in inorganic technology (specialized in electrochemistry). I create hardware that is often inspired by electrolysis and fuel cell research.