Thread: motion sensor killswitch?

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greetings,
for the past couple years i've been doing a spook house for the local kids. last year i started using motion sensors and it really added a lot. this year i want to have a room where the lights are initially on but will turn off while the kids are inside. is there a way to make a standard motion sensor act as a killswitch rather than an on switch? i know i could wire a kill switch to a floor plate (as i've done with an on switch) but i want the lights to stay off for a bit longer than that. i don't have any helpful minions that i can employ to just turn them off manually. nor can i put them on a timer since it's nearly impossible to run the kids through in perfect time.

so once again can a motion sensor be rigged as a killswitch or does someone have an alternate idea?

thank you

It is possible. What type of motion sensor are you using?

actually, i've just been using ones that you would attach to a porch or floodlight. i'm not sure of the brand but they come from wal-mart. the ones i have used are sold as just the sensor (like if you needed to replace the one on your unit). instead of hooking them up to the house's power supply i splice them right into the cord of the light. works like a charm and only costs about 12 bucks.

they look something like this
http://www.castlewholesalers.com/media/249SL5407

Get a relay with a 120VAC coil:

125VAC/10A DPDT Plug-In Relay - RadioShack.com

hook it up like this:

AC Power ---> Motion Sensor -----> Relay ----> Electrical Outlet ----> Lights

Hook up to the NC (normally Closed) contacts on the relay, this will allow the lights to be on when the motion sensor is inactive, and then when the motion sensor activates the connection will be broken.

excellent, thanks! MacGyver would be proud

The only caveat is that the relay contacts are only rated at 10 Amps, that equals 1200 Watts.

that is quite a bit, so you should be ok with most lighting.

Originally Posted by bradbaum

The only caveat is that the relay contacts are only rated at 10 Amps, that equals 1200 Watts.

that is quite a bit, so you should be ok with most lighting.

You could always just go with a larger relay like this 15 amp R145A15120. Put like Bradbaum said 10 amp should be more than plenty for simple lighting, just watch the amount of watts you're actually lighting with.

what's the difference between a SPDT and DPDT relay? this place has much lower prices but the 15 amp is an SPDT.
BGMicro Hobby Electronics and Parts - Product Search - Criteria: relay

Here's a 40 amp AC coil relay for cheap:

120 VAC, 40 AMP RELAY | AllElectronics.com

See if you need anything else that you can order from A-E - it'll help offset the $7.00 shipping charge.

Originally Posted by thebeingwithin

what's the difference between a SPDT and DPDT relay? this place has much lower prices but the 15 amp is an SPDT.
BGMicro Hobby Electronics and Parts - Product Search - Criteria: relay

Single Pole, Double Throw = one switch with a NC and NO

Double Pole, Double Throw = two switches with NC and NO

with the single you can only switch one source on/off
with a double you can switch two sources on/off at the same time.

There is also a 3PDT, 4PDT, SPST, DPST, etc.....

The NC stands for Normally Closed meaning the item you are switching is on while the Relay is off. When power is supplied to the relay, then the NC connection opens up and the NO (Normally Open) then closes, thus what was off turns on.

Hope this helps.