Digital Egg Timer
A good friend in my other life is retiring soon and needs a suitable home made present. She is passionate and putting some thought into gifts so I decided to build something electronics based and home made. A digital egg timer.
The device would be based around two electronics IC. The 555 and the 4017 counter. I asked her how long she likes to boil an egg (much to her confusion) and then configured the 555 up to trigger a signal 1/10th this time to the 4017. This then increments the pink lights until the final light shines blue. The timer then restarts. Whilst the 555 is not particularly precise in counting beyond 30 minutes, the accuracy on this 3 minute 11 second timer was pretty much spot on.
The circuit would be USB powered and use a capacitor reset circuit built on to the 4017 to inhibit random start times should the device be unplugged and plugged back in. This ensures it always starts timing from zero.
The device is built on three easily available small through-hole PCB’s which are drilled and bolted together in the corners. Resistor coded coloured wires cable each light sequentially from the 4017.
The device needed a mould and much to everyone’s amusement I chose a long thin tube which started life as a container for bubble fluid. The tube was cut and the circuit carefully held in on a clamp. This was then filled with high quality two part epoxy.
A test run on a separate tube caused the tube to distort due to the heat when hardening, so on this project the epoxy was added in stages.
After hardening a suitable base was made (also from epoxy) and lettered with more epoxy and the usb cable run out the back.
The finished product.
