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Project Help and Ideas » Relay help

August 03, 2009
by kcen
kcen's Avatar

TLDR version; I need a link to a cheap relay(actually a contactor) that can switch a few amps at 120VAC.

Long version: I have a family friend that was an a car accident a couple years ago and is now confined to a wheel chair. With my nerdkit (+an couple of old rc cars that operate on the same frequency and various other electronics) I am trying to build a remote so that he can turn off various electric devices in his house(lights, thermostat, etc.). The issue is IDK what to use to switch the wall current on or off. I've been looking around for some cheap contactors but all that are large enough seem to be in the $50+ range. Is there a reasonable option or am I going to have to hack a clapper at $20 a piece?

August 04, 2009
by Capt
Capt's Avatar


Is it possilbe to find a contactor with 12v coil and is leagle to switch 120VAC?

When you pay for a contactor, you pay for security and durability.

I know thers some small contactors for controll sircuits. Don't think they are en the expensive range. And they should be able to switch some amps. If not, connect them in paralle.

Somthing like this is what i think of:

Abb-SST15891-2 (Don't have any price list available)

note: please don't use car relays, they are not ment for such loads.

August 04, 2009
by mrobbins
(NerdKits Staff)

mrobbins's Avatar

Hi there,

As for relays, I don't have any specific favorites, but I would begin my search here.

Just a reminder -- please be very very careful with 120VAC. If you are willing to be safer at the cost of some more complexity, consider wiring up a lightswitch and a small servo so there's true mechanical isolation. :-) There are some intermediate levels of safety, like using optocouplers for isolation, but a loose wire or unintentional connection will still lead to a bad day. Also make sure that whatever you do, all 120VAC connections are done inside a grounded metal box. Hope that helps!


August 10, 2009
by BobaMosfet
BobaMosfet's Avatar

Some advice. Be very careful about making things that plug into someone else's house-current. If their house burns down, and it is traced to your device- you are liable. I would not take mrobbins statement as any kind of approval of, condonement of, or suggestion that you do so. I certainly didn't interpret it that way. For legal reasons, I'm sure neither NerdKits nor anyone else here can accept any liability for your actions.

Think very carefully about the possible consequences of something going wrong, before embarking, and how you might safely and legally mitigate such risks by working with a local electrician willing to help you.

August 16, 2009
by Nerdful_com
Nerdful_com's Avatar

For home automation, I use controllers for AC plugs and light sockets. All certified safe and you do not have to mess around with bare wires (someone who has had an accident does not need another from AC current). IR Remote controlled, RF control or PC controlled, programmable, control over the internet and many more features. I even ahve a phone dialer controller that allows me to call home and enter codes to run macros!

I just bought a basic starter kit and then bought modules (motion sensors, light/night detector, power mods, etc) for x10 from ebay (search for x10) for much cheaper.


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