Electronics: Swingy Meter

Electronics: Swingy Meter

The Akiniscope has a swingy meter. The meter is an old meter from Ebay, that looks about right, but I have no idea what it was originally used for. It’s an ac meter, going up to 1V max. After playing with it for a bit, I’m guessing that’s 1V RMS. I’ve found it doesn’t really care what frequency is input, having tried 1kHz, and 50Hz sine waves.

The Raspberry Pi doesn’t have a digital to analogue converter (DAC), but one can be attached via I2C, but it would take quite a bit of processing power to generate a waveform, and control it’s amplitude. So, I decided to ofload the processing to something else, which was a Adafruit QT Py – SAMD21. This little device has a 10 bit DAC, and is small and cheap, so is ideal. The code generated a triangular wave, and alters the amplitude randomly. Added in is a digital input from the Raspberry Pi, which goes high when the camera is operating, when that happens, the meter bounces round at the full range.