Sonoff is an ESP8266 based on/off switch that will let you control electrical devices around your home. Out of the box it can be only managed by the eWeLink app which is running on Chinese servers. If you want to take full control of the device you can flash the firmware and access it inside your local network.
Fast Fourier transform (FFT) is an analysis method that let's you dissect complex waveforms and determine out of which frequencies they were composed. This function is often present on an oscilloscope and in this blog I will show a basic application of it.
Electrolytic capacitors are known for their terrible accuracy. Just by reading the value on the package is often not enough to know their true capacitance. In this blog I will show how to measure the real value by using a scope.
In addition to the WeMos battery powered temperature server, it would be nice to know what the remaining level of the battery is, so we can recharge it in time. This is easily done using a voltage divider circuit and the analog input on the WeMos D1 mini module.