# Controling a regular residential 110V/15A circuit switch (or relay) from a PC

I am a software engineer by trade and also a rather skilled and well rounded (residential) builder with a special interest in wiring. I have rewired my entire two-unit house, panels included and seen it all.

In the course of home remodelling, I was wishing to be able to control every single electric control on every circuit in my house remotely using an Android app. To make that possible, I would need every single switch/thermostat to be upgraded into a relay and have cat5 cable run alongside every Romex cable to each control on one side and into a PC (or some other cheaper form of a CPU hosting device with a modem) which has a static IP online, on the other side.

Of course, that is a huge project, whose biggest parts would be making relays that can be controlled from a PC and writing software to control it all, web services, mobile app etc. So the first step in R&D would be to actually make something like that -- unless, of course, it exists already.

Is it possible to buy a relay that, on one side controls a regular 110V residential circuit, and on the other can be flipped using a PC?

A residential feature like this could be used to, e.g. report and control temperature at home remotely, turn the heat on 30 min before arriving home etc. You could even mount a web cam and watch your pets remotely.

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Is it possible to buy a relay .....flipped using a PC? YES Is it feasible, practical, reliable? NO , Not without enormous effort and fail-safe Normally ON relays not to mention humungous internal rewire job –  Tony Stewart Nov 28 '12 at 3:02
of course, i am aware of the level of undertaking. i just think that wiring all residential controls and making them available online is the future of residential construction –  amphibient Nov 28 '12 at 3:07
Why cat5 cables? There are different possibly cheaper cables intended for that application. You can buy all the stuff as a whole product, but it's usually pretty expensive (as a top class product). –  Al Kepp Nov 28 '12 at 3:16
cat5 came to mind because it is data cable. you probably don't need 8 wires for this –  amphibient Nov 28 '12 at 3:26
You can find relays inexpensive here, but low voltage coils need >10x the current avail to most logic level outputs, so additional drivers or a custom card. digikey.com/product-search/en/relays/power-relays-over-2-amps/… –  Tony Stewart Nov 28 '12 at 3:28

There are a number of home automation solutions that may meet your needs. Current technologies include both PowerLine Communication (PLC) and RF.

They typically consist of a relay or Triac-based controller that mounts in the place of a traditional light switch. There are appliance modules that plug between outlets and appliances (and some that replace the actual receptacle themselves).

There are also PC-based systems that interface via USB and transmit/receive the necessary PLC/RF to support full-duplex communication with each of the individual switch modules.

These systems are nice because all of the modules that touch line voltage are ETL recognized (superset of UL). This mitigates the safety and insurance liability aspects of a homebrew solution, though you should still have a qualified electrician install them.

I believe there are also thermostat modules in the same line, though I have no experience with them.

They're sold under the brand names X-10 and Insteon to name a couple, though there are others.

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yep -- X10. thanks –  amphibient Nov 28 '12 at 3:25