# Motion activated amperage?



## Quadzilla1977 (Oct 4, 2012)

Just curious as to how many amps you guys and gals think standard light motion activated sensor contacts can handle. Meaning how many wiper motors could you hook up to one sensor. If they can't do but one I thought of using a contactor (with 120 volt coil) that the sensor will pull a set of contacts in because those contacts can support alot of amps.


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## The Watcher (Sep 13, 2008)

Each sensor controls 1 relay, unless you are using a programed board. Then they can be programed in a series. But the relay it's self carries the voltage. I am sure some of the smarter guys can better explain it.


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## Quadzilla1977 (Oct 4, 2012)

Hey thanks for the response. Yea I knew the sensor controls one relay but what I was curious about was how many amps is the relay contacts rated for, meaning could I plug two wiper motors into where the two lights were (using 2 screw in receptical of course) Thanks again


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## corey872 (Jan 10, 2010)

Quite a bit unknown to give a good answer. Sounds like you're using an off-the-shelf motion sensing light. So we'll assume when it sees motion, it sends 120VAC power to the light sockets. That would probably cause a wiper motor to explode. 

Are you planning to hack the circuit in the fixture to send 12VDC out of the sockets? Or are you planning to have the sockets run the usual 120VAC, then step that down to 12VDC afterward? Does your fixture have a maximum wattage rating for the light bulbs?


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## BillyVanpire (Apr 22, 2015)

if you have a 120vac motion sensor with the lightbulb sockets you can control dc wiper motors using 12vdc power supplies (laptops or even a desktop power supply will work)

motion sensor activates ..sending 120vac to the light sockets (plug adapted), which turns on the laptop power supply, which converts the 120vac to 12vdc required for the wiper motors.

you can probably connect 2 wiper motors to a single laptop 12vdc supply, but i've never tried it myself.


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## dstading (Aug 6, 2014)

Most fixtures will have a max. wattage rating for the bulb(s) you can use. If the rating is for a 100W floodlight, the relay will need to switch about 0.9A. Wiper motor wall warts are usually 5A and up, and the inrush current (when the motor starts) can pull a bit more than 5A. If the manufacturer went with the lowest acceptable relay rating (probably not more than 2-3A for a two-bulb fixture) you *might* have a problem. I have read about folks using these successfully for switching wiper props, so YMMV.


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## Quadzilla1977 (Oct 4, 2012)

Yea I was stepping the 120 volts down to 5 volts DC with the power supply from fright props. I have seen people on here using a standard off the shelf light motion detector for wiper motor props but being you can add two screw in recepticals on most of these motion sensor my question was how many amps would the relay contacts be able to handle. I figured instead of having a motion sensor for each prop I could use it to control two props. If I can't do that then I will use the relay in the motion sensor to pull in a more heavy duty contactor and run different props off the contactor contacts that can def handle more amps.


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## stagehand1975 (Feb 22, 2010)

Cheaper ones are typically 300 to 600 watts. so 2.5 to 5 amps. Its typical rating house hold dimmers and switches


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## corey872 (Jan 10, 2010)

If you're stepping the power down after the light fixture, then one benefit is the transformer ratio. ie: An outdoor flood light fixture (?) could likely handle a 150W bulb. A 12V power supply at 150 watts would 'theoretically' yield 12.5 amps. In the real world, you'll loose some in the transformation and rectification. As an example - looking at the SMPS brick on my computer, it shows 100-240V / 1.5A input, 19V 3.4A output. So assuming the rated amperage is at the lowest voltage, that is 150W input, 64W output, so about 42% overall efficient. That actually seems low, but still double the amps out as going in. 

Overall, I suspect you'd be fine on amps to run a wiper motor...unless it's lugging something really heavy. Though you did mention a '5V' power supply...I'm not sure that would run a 12V wiper motor?


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## BillyVanpire (Apr 22, 2015)

you can run a 12v wiper motor on 5v, it just runs much slower.
torque might be an issue, depending on the motor. (might not lift as much weight)

keep in mind that the ground (negative) wire on most wiper motors is the motor casing itself.
i have seen them wired incorrectly but still work, just with very little torque.


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