Trying to power a 12v motor with 12v laptop power supply.


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Old 11-14-08, 08:28 AM
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Question Trying to power a 12v motor with 12v laptop power supply.

Hi everyone,
I've been wrestling with trying to power a 12v 4amp fan for several days. I purchased a 12v camcorder power adaptor that I would like to use. (This adaptor plugs into the wall at 110V and comes out 12V.) The question I have is it possible to cut the plug off the tip and wire the fan directly to the wiring inside. I cut the tip off to find a white wire inside and raw exposed wire surrounding it. I'm assuming the white is the power and the raw wire the ground? Any information would be greatly appreciated! Thanks in advance guys!
 
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Old 11-14-08, 08:48 AM
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Don't think the adapter you have will put out enough juice if the fan requires 4A. What the heck kind of 12V fan requires 4A? Was it off a car? What are the specs written on the P/S?
 
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Old 11-14-08, 09:00 AM
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It's an exhaust fan off an inboard boat. I purchased a Battery Eliminator - AC Input, DC Output that powers it great. But it is way to bulky for my application. Don't have the specs with me at the moment. All I know for sure is it is 12V 4amp. I've got to figure out a way to wire it for direct power from an outlet. Whaen I wired it to the charger I spoke of in my first post it ran then stopped ran then stopped. So I think you are absolutely correct when it comes to the power being insufficient.
 
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Old 11-14-08, 09:09 AM
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Found some specs online

Voltage 12 V, Power consumption 3.5 Amp, capacity 6 cu.m/min.
Dimensions :
A : 148 mm / B : 99 mm / C : 123 mm / D : 98 mm
Attwood blower, provides ventilation for engine compartment, bilge and marine head closets. Features a 5 blade fan generating optimum exhaust capacity.
Tough filled polypropylene plastic housing dampens sound and vibration and is corrosion-proof.
Built-in mounting feet allow horizontal or vertical installation
 
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Old 11-14-08, 09:16 AM
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A P/C power supply might work, just looked at a cheap one on Tigerdirect. 24A on the 12VDC line. If that would fit your usage requirements. Could probably find a used one at a PC shop for much less.

Would need some sort of enclosure of course.

You might also look here..
http://www.powerstream.com/12-volt.htm

If this will be used in a Marine environment, it will need to be more rugged and protected from elements.
 
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Old 11-14-08, 09:19 AM
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Thanks for your help, greatly appreciate it!
 
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Old 11-14-08, 11:07 AM
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A modern PC power supply is ATX. It requires a mother board in place to work. (Or a load especially made to insert for testing.) An AT supply might work.

My suggestion would be a six amp 12 volt battery charger. Unfiltered DC might be a bit rough on the motor, really not sure. I might add a filter capacitor. Don't know how they will hold up under load for extended time but their reasonably cheap so it my be worth experimenting.
 
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Old 11-14-08, 11:07 PM
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Those marine blowers are simple DC fans inside a plastic cowl. Any 12 volt power supply capable of delivering 4 amps (4,000 milliamps) will work. No need for an expensive regulated computer-style supply.
 
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Old 11-15-08, 06:21 AM
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As to your wire, you don't refer to DC as "hot" and "ground". There is POSITIVE side and NEGATIVE side. If you connect them opposite of what is required, the fan will turn backwards. You would need just a simple voltmeter to determine the polarity of the wires on you power pack.
 
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Old 11-15-08, 10:08 AM
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Let me add one more thing where this power supply device will be used in ?

If in marine useage like tempory useage that fine but there is a fine line it will crossover due the safety in marine appaction and many marine devices have a addtional label on it like USGC label added along the normal UL or CEC or CE logo.

The reason why I mention that due if you have gasoline fumes on the bottom of bilge area and a spark from the non marine approved type blowermotor it can blow up due they dont have spark arrester in there { belive or not majorty of the blower don't have this on hand }

Merci,Marc
 
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Old 11-15-08, 04:06 PM
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Correct, Marc. The term to look for on marine electrical devices is "ignition protected". It has nothing to do with protecting the boat engine's ignition system. I means it won't produce a spark and ignite a fire.
 
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Old 11-15-08, 05:24 PM
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So to alter my suggestion just a bit is get a marine grade six amp battery charger that is ignition protected.
 
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Old 11-15-08, 07:27 PM
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Gary,
It might be simpler and cheaper to replace the blower with a 120V AC model...
Just an idea!
Andy
 
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Old 11-15-08, 07:33 PM
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Andrew.,

Becarefull with suggest if this is in the marine useage if you can find 120 volt verison again it have to be listed for marine useage and " ingtion protected "

I Don't know how common is the 120v blower is for marine useage but I know normally 120v marine blower is typically not ingtion protected due some of larger blower used in the Diesel powered vessels and Diesel powered vessels have slightly diffrent regulations to deal with it { they are not that strict as gasoline powered vessels }

Merci,Marc
 
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Old 11-16-08, 07:18 PM
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Hi Marc,
From his posts, I was under the impression that the blower was not actually being used on a boat. I just thought he had a 12V marine blower he was using for something else. I agree with you though that he should not use a 120V AC blower in a boat.
Thanks,
Andy
 
 

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