I blew the serial port on my BX-24 already. I started using them more than 6 months ago, and should have known better than to cavalierly plug it in without making sure everything was grounded. Always keep receipts – it’s too late for me.
For this week, I wanted to experiment with piezo buzzers. The idea was to vary the pitch by configuring a 3-pronged potentiometer into a voltage divider – using the voltage change to create a pitch change. Unfortunately piezos don’t work this way. The crystals resonate at a fixed pitch. Crystals are interesting in that you can put mechanical strain on them to create a voltage difference, or you can apply a voltage difference and get a mechanical movement.
There seems to be a lot of reciprocity on. I’ve been reading about Stirling engines, which use a heat source to provide mechanical movement. By enclosing a gas in something like a tube, the Stirling engine heats one side of the gas. The hot gas exerts pressure onto a lever, which moves, opening a valve that lets the hot gas enter a cooling chamber. Once cooled, the gas contracts again and the lever returns to its starting position. By shuffling around the hot and cold gas between the heating and cooling chambers, the lever is cranked like in a gas engine, but without the noxious fumes. The heat source is irrelevant – it could be dung, fermenting beer, your sweaty palms, my mom’s breath, etc.
On a different note about reciprocity, a simple DC motor can be used backwards to let spinning motion generate electricity instead of vice-versa – something I experimented with in a windmill sculpture, but never got enough current.