Coin Domino

When I first saw the assignment, I thought about three ways of making a switch that doesn’t require the use of hands:

  1. Ride a bicycle over two metal panels on the ground and press them together.
  2. Make light-weighted, conductive material touch by blowing wind to them.
  3. Flip a coin, make it spin, and when it stopped use it as a conductor between two wires.

I never really tried the first idea primarily because I don’t have a bike. Then it would also be hard trying to find spare, large metal panels. Blowing wind to conductive material seemed more feasible, and I brought my wallet with some coins in it to the lab. I tried with flipping coins and had a lot of fun aiming them at a certain target. But my coins are hardly controllable once they left my hand… oops, does flipping a coin means the use of hand? I realised the third idea doesn’t meet the criteria of the assignment. After some thought, I decided to combine the second and third project by blowing to a Domino set of coins, making them touch to serve as a switch.

So first I set up the Redboard and breadboard, added a red and a yellow LEDs, and cut off two pieces of wires. Then I soldered one end of a wire to a potentiometer and placed them on the breadboard like this:



The most difficult part was connecting another wire. I first tried to solder the wire with a coin. However, due to the high melting point of the coin, I couldn’t solder them together tight. Then I tried to solder with another small, light object that I randomly found in the lab. It still didn’t work well.




After spending much time on soldering and not nailing it, I decided to simply go with tapes. I taped the end of the other wire to the first coin in my Domino and arranged all four coins.



Finally I experimented a few times blowing wind to the first coin and making all four collapse. They seemed to touch alright, but not always fell to the right place and light up the LEDs. Playing with my coin domino was kind of fun though. Here’s one of the videos I made when the coins did the right job.

Coin Domino

There are definitely many ways of making this coin domino switch look and function better. Adding more coins and rearranging them, refining the connection of wire and coin, as well as using stuff other than the potentiometer could all help.

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