I want to run a 12 v motor (power window) from my 120v house curr

moparnutFebruary 2, 2009

how can i power a 12 volt power window motor from a car to run on 120 volt house current.I'm using them for various outdoor projects.I want to build a rotating light for my 10' lighthouse and power lift for my spa cover

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you will need a 12v power supply. and not some little dinky wall wort either, you need a 12A-20A supply, depending on the size of the motor. this will run you soemwhere around 100.00 for teh supply.

or you can use a car battery and just use a charger to recharge it after use.

    Bookmark   February 2, 2009 at 11:14AM
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I would be careful using the motor for any continuous purpose like your lighthouse project (really? A lighthouse?) because power window motors are designed for heavy loads in short bursts. I suspect prolonged use will overheat them and make them fail. In theory your spa cover should be ok except it'll be a lot heavier than a car window, you may need additional gearing.

As for the supply, Davidandkasie is/are right, you'll need something fairly heavy duty. A deep cycle battery would work well, and you could even charge it with a solar panel.

    Bookmark   February 2, 2009 at 12:22PM
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OK thanks that helps .What kind of motor would you use for my lighthouse ,I have 120 near the lighthouse

    Bookmark   February 2, 2009 at 1:43PM
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Look for a 120v rotating beacon light. You may even be able to use as is with colored lense removed. To slow it down more add a motor speed control.

Here is a link that might be useful: beacon

    Bookmark   February 2, 2009 at 2:46PM
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thanks for the help

    Bookmark   February 2, 2009 at 4:05PM
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I think a barbeque spit motor would be perfect for that application.

    Bookmark   February 2, 2009 at 4:50PM
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Windshield wiper motor from the junk yard.

    Bookmark   February 2, 2009 at 4:53PM
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use a old PC power supply to get the 12Vdc for the motor..
cheap and easy.

    Bookmark   February 3, 2009 at 8:05AM
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PC power supply might not supply enough power for a window motor.

    Bookmark   February 3, 2009 at 8:26AM
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Great help thanks ,going to look in to these idea's

    Bookmark   February 3, 2009 at 8:31AM
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How about an A/C gear motor? Then you eliminate the whole voltage conversion problem.

    Bookmark   February 3, 2009 at 11:36AM
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I was just thinking the same as mike, I was thinking of a humidifier motor, if the load isn't too heavy. I don't know how they'd like being driven in a vertical position (made to run horizontal) but some gearing would fix that. They usually do one or two rpm.

I assume this 'lighthouse' is decorative?

Downside to a/c power is I suppose the fact it's outside so there will be more requirements for electrical code etc.

Another option would be to use a dc hobby motor, you can buy them cheaply and they often have gearboxes you can fit with various options for speed etc.

The whole original point at least in my opinion is window motors will overheat because they are not rated for continuous duty, they're like starter motors.

Upon reflection I doubt they'd be strong enough for the hot tub cover, what would be ideal would be a garage door opener motor. Don't know if they're ac or dc

An enterprising individual could join Freecycle (freecycle.org) and ask for non-working garage door openers (say, a Sears one, when you look at the garage forums ;) which may well still have a working motor. You would also score some gearing etc that would help, I think a garage door opener would be the ideal mechanism for the hot tub cover, and it'll have limit switches etc too.

Here is a link that might be useful: Freecycle

    Bookmark   February 3, 2009 at 2:19PM
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A word of caution about using PC power supplies : some PC power supplies are of a type which does not have galvanic isolation between then outputs and the mains input. If one of these power supplies develops the wrong type of fault (its rare, but it is possible and does happen occasionally) you can end up with mains voltages on the outputs. It hardly needs to be said that this could create a potentially-hazardous situation!

    Bookmark   February 3, 2009 at 2:34PM
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of course they would have to find one that outputs enough current. I have some the output upto 20amp on 12V..should run a window motor..check the cars fuse rating..

the rare output main to output problem...mains ciruit breaker and or the little fuse in the power supply..most have the fuse..a main to output short sure would be ugly even in a PC.

if 12V was too fast they'd still have +5 or +3.3 to try with building anything..if that doesn't work they need to build a PWM controller to slow the motor down.

    Bookmark   February 3, 2009 at 6:20PM
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I don't think a pc power supply would be the best choice for this application and I very much doubt it would cope with peak loads etc. If not an ac motor, then this - transformer goes to what is called a bridge rectifier - easily obtained from electronic supply houses, transformer connects to tildes/wavy lines ~ ~ which denote a/c then attach two wires to the other poles, one will be positive, one negative, attach a polarised dc electrolytic capacitor to that, say 500 to 1000 microfarads or more (more might be better, a surplus store might have them on for a good deal, rated at least double the final voltage to allow some headroom, add a fuse to the positive, then attach the load (motor) to that. When you're powering a motor you don't really want a switchmode type power supply that's all regulated etc because they don't cope as well with peak loads. A plain rectified and somewhat filtered supply is probably better. Or a deep cycle battery.

    Bookmark   February 3, 2009 at 7:52PM
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Do note my "bench" power supply. It is an ATX computer power supply.

NO PC power supply provides "full" isolation, as the DC ground outputs are connected to the AC power cord's ground pin. However, +300VDC (or more) internally is isolated from the output by the switching transformer . . .

current ratings of roughly 8A are common for the +12V line of PC power supplies. I've seen a few that were higher. You may be very surprised by your "12A to 20A" motors, as, with small loads like you're proposing, they're unlikely to pull that much current. I'm betting a PC power supply will work well.

Some PC power supplies have a "minimum load" - an amount of current that must be pulled on one of the lines (usually +5V) in order to achieve accurate regulation. In this application, regulation is irrelevant, so you ought not have to worry about the minimum load. Most of the time with these, if you don't meet the minimum on +5, your +12 output will be low.

Aim for an older-style "AT" power supply, one whose motherboard connectors consist of two six-pin plugs. These have a mechanical latching power switch and don't require any clever tricks to turn them on. If you do have to use an ATX supply, having a 20-pin motherboard connector, you will need to connect the GREEN wire to one of the BLACK ones next to it.

No matter which power supply you use, one of the 4-pin drive power connectors will have the wires you want: black is -, yellow is +12. If you choose to use 5V instead, black is still -, but red is +5.

My day just got a dite more irritating so I'm gonna cut this post short.

Good luck.

    Bookmark   February 3, 2009 at 9:28PM
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You people are awesome,never thought I would get such a response.The reason I posted was to get ideas and you all came through. I like to tinker with things and the wife wanted a lighthouse so I built one then had the idea to make it better and I had a few 12v window motors tried to use them but could not get the right rpm.Don't have much spare cash so trying to use what I had on hand.Great help!! Thanks I'll try to post a pic

    Bookmark   February 4, 2009 at 10:32AM
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did you try a lower voltage..lower than 12v feeding the motor..since its DC it will run slower

    Bookmark   February 4, 2009 at 4:53PM
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Beacon : Use a rotating beacon like what construction vehicles use and put a resistor or rheostat in line with the power on the motor so you can slow it down for realism. I would use a low voltage photo cell and possibly replace the bulb with LED's from a place like superbrightleds.com. They should have a compatible led light that will go in the plug or have the things needed to make your own setup.
Power: I think a lead acid lawn mower battery (U1L the old bigger battery not a motorcycle style) series and trickle charger would be adequate for the beacon and the lift. IF you go with the LED setup you could charge it via solar panel.
Lift : I think a window motor could be adapted and work well or the early to mid 90's rangers and F series trucks had electronic shift on the transfer case for 4x4. It was a starter style motor with gear reduction and stop switches for different ranges and best of all they are fairly well sealed. If you check some of the motorcycle shops you might be able to get a starter from there that has a planetary gear reduction (high torque) that just needs taking apart and given some TLC for little or no money. This would be a pretty compact and rather quiet option.

I see both projects as being really cool ideas but the lift might be better to just buy a lift designed for such use and adapting it further for your setup. I would check ebay.

OH wait umm what voltage did the old monster satellite dish rotators run off of? That would be by far the easiest to adapt. Either lift or rotate could be used.

I like the solar charge with photo cell and LED light idea the best with wire run over to the adapted satellite dish rotator spa cover lift the best!

    Bookmark   February 4, 2009 at 11:24PM
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Consider an old-fashioned sewing machine external motor. Most are 80-140W, all are 120v AC/DC universal motors rated for continuous use, have cases and built-in cooling fans and are fully serviceable with parts that will be around for a long time. Because they are universal motors, they can be used with both dimmer-type AC, and PWM DC motor speed controls.

    Bookmark   March 20, 2011 at 5:27PM
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From my days of tinkering with PC power supplies back in the late 1980s and early 1990s, I think I recall that many or most of them wouldn't provide any 12v power unless you also drew some current from the 5v output. So to use one of those for 12v, you might have to waste some energy running a light or something.

I'd recommend against using a battery. A small 12v battery will set you back at least $30 or so, and figure another $20 for the charger. Then that charger will overcharge and ruin the battery in a year or two unless you unplug it when the battery is fully charged. Trickle chargers and most battery maintainers usually do more harm than good.

But to me the 12v deal sounds like too much hassle. I like the idea of using a barbecue spit motor for your lighthouse. You should be able to find one at a garage sale or the like for a buck or two.

Another idea would be a geared clock motor. Link below (not an endorsement or recommendation). The $4 16rpm timing motor looks like a possibility, if it has enough torque to handle the load you propose.

I'll bet you can make the power window motor work for your hot tub cover, if you want to mess around with the 12v. My old GE Elec-Trak electric lawn tractor uses a 70s vintage Buick power window motor to raise and lower the dozer blade, which probably weighs a good 60-75lb. It's geared down though. The gear drives a windlass with a nylon strap on it.

But yeah, power window motors are designed for intermittent operation. I wouldn't try one for your lighthouse beacon.

Here is a link that might be useful: Surplus AC gear motors

    Bookmark   March 20, 2011 at 8:08PM
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Did someone mention surplus motors?


    Bookmark   March 21, 2011 at 12:43AM
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