Friday, July 6, 2012

Washing Machine Monitor

Introduction

About a year ago we bought a new washing machine which seems to work nice, but it lacks a very important feature: it doesn't notify me when the washing is done. I usually start a new load in the morning and, even though the programs usually finish in about an hour, I tend to forget it and hang the cloths only in the evening.

The finished board - just add a washing machine and it's ready to roll! :)

After this happened a few times, I decided that as soon as the warranty period is over I would install a small circuit inside the washing machine and let it beep once the program is finished. (The circuit would be very simple as I don't have to dig deeply in the private parts of the washing machine - I noticed that when a washing program is over all three status LEDs on it blink at the same time.)

However, as time has passed, I forgot the wet clothes in the machine for longer and longer periods and it became clear I needed a solution for this as soon as possible.

I had the following criteria for any solution to be acceptable:
  • Since there is no power outlet in our bathroom (apparently, when our house was built installing power sockets in a bathroom was illegal or at least frowned upon...) it must be operated without a separate power inlet.
  • It should not void warranty of the washing machine (for obvious reasons...)
  • It should be very simple, easy to use, preferably no user interface on it at all. It should do only one thing, but it should do it well.
  • It should be cheap, easy to make using commonly available parts.
  • +1: it should be compatible with not only our current washing machine but with any other as well.
Probably, a simple timer would suffice (although different programs take different amount of time to finish), but I wanted to make something special (or geeky, one might say...) as well.