sensor to detect appliance state

Other Hardware Sensors
1

hello,

I have searched and I cannot find something suitable. Now wondering if it's possible. I want to build something simple that tells me if my refrigerator is running or not. A amperage and or voltage output is not needed, and something that doesn't require splicing wires would be optimal. With a clamp, you need to get to the hot or it won't output. Is there something that I can put between the refrigerator's plug and the outlet socket? Would a hall effect sensor work?

Thank you

2

Wouldn't the simplest solution be to use a temperature sensor?

3

Sorry, my inquiry is poorly worded. So, my fridge is plugged in all the time, but it doesn't run all the time. I just want to know reliably how many times a day it is drawing current. I'd also like to be able to move this to something like a lamp. So if I'm away, I will know if the lamp is on or not. I don't necessarily want to be able to switch it, just know whether or not it is drawing current.

Thank you

4

A current transformer will work, but it needs to surround either the hot or neutral (not earth ground) lead. For that, you usually have to temporarily remove the plug to separate the two wires. http://openenergymonitor.org/emon/buildingblocks/how-to-build-an-arduino-energy-monitor-measuring-current-only

5

Thanks Charlie and jremington.

I saw that as well, was wondering if there was any other way. Is there something (or can I build something) to place between the plug of the device and the wall outlet that would work for this application? There are compatible switches for this purpose, but I'm not looking to switch it on or off, just know when it is drawing current.

thanks

6

Google "appliance power monitor" for commercial offerings.

7

You can build an outlet box with a current transformer on the hot lead and plug the box into the outlet on the wall and plug your fridge into the box. The two leads from the CT can go to an amplifier circuit that outputs a dc voltage to a Pro-Mini inside the box.
The Pro-Mini can run off a small 9V wall wart with the leads going into the box connected to the Vin pin and GND.