Prototyping a monitor circuit for GaN RF power amplifier devices. This is indicating drain current and heat sink temperature, and can be expanded to other measurements as needed. What started as a ‘simple’ project became an entire side quest. This uses an Arduino Pro Mini, an INA169 current sensor, and a thermistor. Could be done more simply with a PIC but this is what I had. The cheap OLED display self destructed not long after this photo, as I fed it 12v instead of Vcc.