Monitor an outlet to see when power switches on and off

Question

My washing machine doesn't have any bells/whistles/buzzers to let me know when it's done. I just got my first Raspberry Pi and am thinking wiring it up so it texts me when a load of clothes is finished would make a good first project. First thing I need to get started is a way to monitor the current going to the washer. (There is nothing digital on the washer so when it's not running there is no current moving.)

I can think of three options:

1. Wire the Raspberry Pi directly to the washer cord to monitor changes.
2. Use something that go between the washer cord and the wall that can signal the Raspberry Pi.
3. Use something that will monitor current going through the cord externally.

I would much prefer to do option 2 or 3 since I'm new to this. Is there something like a SmartThings SmartPower Outlet that can talk to a Raspberry Pi?

Answer 1

You could make a tweet a watt (option2). Alternatively, you could use a clamp on current sensor - as discussed on the Raspberry Pi forums (option 3)

There are a couple of alternatives that you may not have thought about:

• If the washer has an LED you can monitor that,
• depending on how loud the ambient noise level is you could use a microphone,
• you could attach a piezo disk/vibration sensor, or
• simplest of all set the Pi up as a timer that you set when starting the washer.

Answer 2

• You could use a waterproof wireless pedometer inside the drum to detect start and end of centrifugation.
• You could use a small floatation device in the drain or a simple electrical circuit in the drain pipe to detect when the machine is emptying.
• If SmartThings uses some open standard wireless protocol, you can definitely use that, but it might need some reverse engineering. Also maybe have a look at http://www.thesmartcord.com/