Mobile Passive IR Home Security (PIR) for <$100

Home SecurityI came up with this idea while visiting my uncle in Steamboat Springs, CO.  With the heavy drought that year, the bears had been coming into town for food and were tearing apart hot tub covers and other items outside homes.  I was working for Lutron at the time and had a sample of our appliance module with wireless occupancy sensor.  We attached the module to a small radio and lamp on the trail the bears use.  When the passive infrared occupancy sensor saw the heat signature of the bear, it turned on the light and the radio thereby scaring off the bear.

Although this application stretches the design limits, a little ingenuity goes a long way. Considerations should be made to waterproofing and camouflaging the sensor since it is not intended for exterior use, however, it does have a variety of applications. I am testing one outside right now to see how long it lasts in the variety of weather conditions we get in California.

The system is very simple. An appliance module has an RF receiver built into it that operates at 434 mhz. The appliance module is basically an extension cord with a wireless relay built into it.  This frequency allows it to receive an encrypted signal through 30 feet of re-bar and concrete (or 60 feet line of sight) from a passive infrared sensor. Up to 10 sensors can be paired with an appliance module according to the documentation attached. In open conditions, I have demonstrated its range at over 300 feet. Battery life on the sensor under normal interior conditions is 10 years.

When the PIR sensor senses thermal movement, it sends a signal to the appliance module and the relay is triggered. This can turn on a desk lamp, sound an alarm, or activate another device in the house to alert you. At my house, I use it to turn on/off an interior light that signals movement outdoors. The appliance module is inside the house and the sensor is outside the house.

The sensor has a variety of sensitivity and time duration presets. I would not expect the manufacturer to support this application but I will let your imagination work through the possibilities it represents.

Anytime you are working with electricity, please remember safety first. Consulting an electrician is always less expensive than a trip to the hospital. GFCI outlets are a must and in wet environments this may not be a good solution. Neither nor our staff can predict all the possible dangers you may face and attempting this application is at your own risk.

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