Motion Sensor Power Consumption?

[DigitalMind]

After months of research I have bought batteries, Solar Panels, and inverter for my sisters off-grid home.   Just enough to give her a few hours of lights every day. (Which for her is better than only having candles as an option)

My question, before I go on and on about what I have, is, How much power does a Motion Sensing light use when "looking" for motion to sense?  

I Got a really small set-up for them : 30 watts of panels, and 225AH of batteries.  Seems to me a motion-sensing light would probably waste power 24/7 looking for motion.  Anyone have any idea HOW MUCH it actually takes??  I told my sister we'd probably have to replace that fixture because phantom loads = bad, but I figured I'd check with the Alt. energy gods here first...  The Light fixture is the typical 120 volt with 2 light sockets and 1 motion sensor at the bottom.  

This is a picture of the batteries I picked up for them at a local supplier here in Montreal...  

http://www.telinpho.com/pictures/Christmas%202007/slides/PICT0230.html

I'll take lots of pictures when I install this in a couple weeks !

Other pictures on my blog at www.techienation.com ...

Thanks Guys !

[Flux]

Don't take this as accurate but I think the sensor unit alone uses very little power but it is normally powered by what is probably an inefficient circuit from the high voltage supply to the lamp. Even allowing for this crude power supply I suspect the power used is small and far less than an inverter used on no load to supply it.

If you took a standard unit to bits and powered it direct from low voltage its consumption would be very little. You may be able to obtain special units for direct connection to low voltage. I believe it is just a pyrosensor and a clever low frequency audio amplifier and should only need a few mA.

Flux

[DigitalMind]

I hope you're right Flux that is only uses a few mA !  I'm just using a small, OLD, 300 Watt inverter that we had lying around.  I'm hoping because it's such a small inverter the losses will also be really small ,although i'm worried that because it's so old (10 years old almost) that it may have too many losses.. (I just don't know! )  

I'd love to re-wire her shack for 12 volt lights only and by-pass the inverter, but she would love to keep all their light fixtures and such. (The city forced them to install the lights and fixtures and electrical outlets, even though they weren't planning on having any Grid-Power installed)  

Thanks for the info Flux !

[wdyasq]

Phantom loads will kill a small system.The idle load on your light system may not be enough to trigger the inverter. I don't think that CFL lamps do well on motion sensing devices, I may be wrong there.

IF a motion sensor light is required you may want to find one of the solar powered units that have small panel, battery and light. It may also be possible to rewire one of those to operate on 'system' (assuming 12V) voltage.

Ron

[Gordy]

Hi,

As Flux said I don't know about the 120v. But the local Menard's sells battery operated motion sensor lites, for closets, bath rooms, ect. Their not flood lites but will let you find your way. I didn't look that close at them (volts, ect) but being battery operated the idle power consumption must be low. You may be able to do some thing with them.

These lites are mixed in with the night lites at Menard's. I seem to remember seeing a solar powered motion sensor lite some where, where the out door solar lites were displayed. I'll have to look for them again.

Gordy

[vawtman]

Not sure how this fits in here,but remote motion sensors for alarm systems can go 3plus years on 2-3v paralelled camera batteries.

[jonas302]

I really don't think you would want a motion light on your small batts as flux said the inverter alone will be draining them down but when a cat walks by your lights will come on not good the city code made her install the lights but they don't have to be on after inspection I know your budjet is limited but harbor freight makes a stand alone solar shed light

Otherwise if you really want to know I would be glad to go measure the draw on a motion sensor and maybe one of my old inverters

[DigitalMind]

Hmmm you guys may have a point.  Maybe best to replace the fixture with some sort of specialty low powered one that will run right off the 12 volts.  Kind of a pain though to replace the wiring in this new (small) house though for these 2 outside lights.  Would be nice to have a fixture that only the sensor part runs on AA solar re-charged batteries and the light itself off inverter power.  

I guess i'll just hook up my meter direct to this light fixture and test it out when I install the mini system. That'll show if it's an issue or not.  I'll let y'all know if you're interested how much currrent it draws when the light is off but the motion sensor on.  

Thanks for the info guys !

[DigitalMind]

Yeah I know what you're saying Jonas.  If it's not too much trouble for you to check it out it would be AMAZING to know, i'm really curious and don't have any motion sensors here.  Don't go nuts though, I can always wait the few weeks until I go install it and measure myself.  

Thanks!

[fungus]

have a look at this;

http://thebackshed.com/Windmill/articles/12vSensorLight.asp

[Norm]

A motion detector can be adjusted to detect things

larger than a cat works on change of the

ambient lighting....or so it says in my handy-

dandy Electronics Lab for Beginners, couple of

rechargeable AA batteries can operate it, which

could be recharged with a small solar cell.

  Just a matter of opinion 'tho if it was me I

wouldn't be overly concerned, mileage may vary

depending on the individual.

   Back to my 101 electronics projects kit.

[jonas302]

ok it was no problem to check one it is a typical $12 menards light

 it took .027 amps x 120 volts 3.24 watts  off 2.4 amps with both huge bulbs on the bad news is it refused to work on a 400 watt colman chepo inverter i did test it was working with a drill i will try it on another inverter later

on side note this inverter drew .425 amps idle my batt voltage 12.25 so 5.10 watts. more than my panels are bringing in right now

hope that helps out some Have you got any of it set up for her yet?

[coldspot]

Yes,

Like the link to the back shed showed,

I found a bunch a few years back on sites that had people converting the 120 VAC units to 12 VDC for trail cameras.

 I bought a cheap-o for about $8.00 and just used the sensor part and not the dual lights.

Rewiring the home for 12 VDC isn't required.

Adding wiring for 12 VDC would be.

$0.02

[ghurd]

That is the best idea, I think.

The solar motion light kits are 6V.  I reworked some to 12V to run on 12V systems.

A 7806 in the battery space, and a 6V relay instead of the 6V bulb.  The relay operated a 12V bulb.

G-

[hydrosun]

A few years ago i found motion sensors that work off 9 volt batteries that then screwed into regular 120 volt sockets to turn on lites screwed into this unit. I found them in a local hardware store. You may want to look for them. they allowed the inverter to be in sleep mode until the lite was turned on by this motion detector.

Chris

[independent]

First post! Hello all from New Zealand, been lurking for awhile really enjoy the quality info!

Anyway, you can now get let pir motion sensors which have small sensors.

Trademe_auction"

Should be easy to find on ebay or your preferred auction site. Saves hooking into your home system. Home-brewing one shouldn't be too difficult either with a bit of know-how.

[Gordy]

I found a couple solar powered one's here http://www.health-boundaries-bite.com/Solar.html it' another option.

Gordy

[Gordy]

Sorry there about half way down the page. http://www.health-boundaries-bite.com/Solar.html

Gordy