Have you ever taken something out of the oven to the table and forgotten to turn off the oven? Or, taken something off the stove when the phone rings and forgotten to turn the burner off? I developed this sensor to keep an eye on electrical appliances and let me know if they have been left on. Our home has a heater in the bathroom to make it cozy after a bath or shower which we occasionally forget to turn off when we’re done.

This sensor monitors the current usage for up to four circuits, sending a message when the appliance is first turned on, again when it is turned off, and of course it always sends a status message once an hour. The desktop application can then be configured to send you a message to let you know if any of the appliances have been on too long.

This module uses simple clip-on split coil Current Transformers (CTs) that clip around the insulated wire that supplies power to your appliance. I have found the simplest access is at the supply panel (circuit breaker box). Just identify which breaker controls the appliance you want to monitor and clip the CT sensor around the wire leading from that circuit breaker. The sensor module is approximately two inches square and one inch deep. It easily attaches to the wall adjacent to your breaker box with the included Velcro adhesive pads.

Warning

The voltages in your home can be lethal, if you are not knowledgeable and comfortable working around high voltage electrical circuits, have someone you know who dose or a licensed electrician attach the clip on transformers for you. Be Safe.

How it works:

The Sensor module's firmware checks each CT sensor every 15 seconds to see if the circuit is in use.
Most heating appliances turn their power on and off frequently to maintain a given temperature. In some cases the off cycle can last for several minutes. The sensor’s firmware allows for this by applying a trailing edge hysteresis, waiting for five minutes to make sure the current stays off before sending the off signal. You can then configure the desktop app to let you know if the power has been on too long. The delay will be different for different types of appliances.

About the sensor

Because the sensor must run frequently, and the algorithms for measuring the AC current are lengthy, prototype testing demonstrated that the battery runs down too quickly (within a few months). Therefore this sensor is powered by a five (5) volt wall wart. The CT sensors are pretty sensitive and can react to switching on a single light bulb (incandescent).

Note: To date, I have tested with the EChun Split Core Current Transformer ECS1030-L72 (30 amp), the YHDC SCT013 (30 amp) and the YHDC SCT016 (120 amp). All three work well but have different transfer ratios. This is easily handled via the scalar term in the settings control of the desktop application:

• ESC1030 - .01
• SCT-013 - .0143
• SCT-016 - .01475

Like the rest of the Sensible Living sensor family it wakes up once per hour (default setting) to send it’s status. The Sensible Living Receiver and Desktop application are designed to work with the Quad Current Monitor. The Desktop Application can send you a warning message if the appliance has been on too long.

Also available on this site:

• Receiver
• Mini-Plant Sensor
• Mini-Temperature Monitor
• Mini-Water leak detector
• Mini-Tilt Sensor
• Mini-Light Sensor
• Mini-General Purpose Sensor
• Temperature and Humidity Monitor
• Refrigerator/freezer temperature monitor
• Quad AC Current monitor (monitors up to four circuits simultaneously)
• Wireless MQ2 Combustible Gas sensor
• General Purpose Sensor board
• Motion Sensor
• Range Extender
• USB to Serial Adapter

Why did you make it?

We have occasionally forgotten to turn off an appliance (stove, oven, space heater etc.). Not only is this a waste of electricity and money it can be a potential fire hazard. This is even more of a concern for our older relatives and friends. All of these sensors were built to address specific needs around our home and for our extended family.

Arduino ® enthusiasts

If you are interested in playing with wireless sensors and know the Arduino environment, you can use this board and sketch as the starting point of your own unique power monitoring device. The Arduino sketch is freely available as a starting point.