Guest
This is my entry for the Flashing Light Prize 2017 contest, using 19th century technology - a reminder of how we did things before the age of semiconductors. The vertical device is the innards of a cheap submersible aquarium heater, mounted upside-down. Essentially, it is a mechanical thermostat based on a bimetallic strip. The lightbulb is soldered at the top in place of the resistive element. How it works: Bulb heats bimetallic strip; circuit opens; strip cools down; circuit closes; and so on. A small square permanent magnet near the contacts provides hysteresis for clean on/off switching. Other thermostat designs use bistable spring arrangements. The fan helps reduce the cooling time, to achieve the required blinking frequency of about 1 Hz. The main difficulty was shooting close-up video of the flashing bulb at constant exposure. I used 1000 W worth of ambient lighting and had to wear welding goggles. Safety considerations:
