# Adding up wall warts



## Aquayne (Sep 1, 2008)

I have a motor that needs 12v 6amp
Can I use two 12v 3amp wall warts to power it?


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## pshort (May 6, 2008)

Not safely, as there is nothing to equalize the current from the two sources. Since the output voltages (and output resistances) are unequal, one of the supplies will try to source more than the other, meaning more than 3A.


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## Aquayne (Sep 1, 2008)

Thanks, It's not worth burning down the house.


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## stagehand1975 (Feb 22, 2010)

Know anyone with a junk computer, salvage the powersupply. They are easy to hack and newer ones put out enough to do more than the one motor.


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## HomeyDaClown (Oct 3, 2009)

Aquayne said:


> I have a motor that needs 12v 6amp
> Can I use two 12v 3amp wall warts to power it?


"_Coitainly_!"

It's no different than the wiring for solar panels to charge batteries. The diodes (use a minimum of 4 amp diodes for this) keep current flowing the right direction and will prevent one power supply from feeding back into the second.

You can get a pack of these at Radio Shack for under $3: http://www.radioshack.com/product/index.jsp?productId=2062591


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## Aquayne (Sep 1, 2008)

Homey,
To wire two together do I put a diod on + and - ? I am simply ignorant. How do I know the direction of the diode. Are they labeled in some way?


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## Otaku (Dec 3, 2004)

Looking at the drawing, I'd say that the diodes are on the V+ terminals. The diodes will have a ring printed on one end, you can't miss them. Make sure that the rings on the diode packages are facing the correct way, per Homey's drawing.

pshort makes a good point. If the warts were the same make, model, and specs would it be more likely to work correctly? I understand that spec's are more of a range than a point, but at least the warts would be in the same ballpark.


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## Aquayne (Sep 1, 2008)

Thanks for the drawing. My computer did not download it the first time I read your post. Thanks Otaku for adding to the response. I have read your posts for years and admired your technical skill. Thank you both so much.
Aquayne
Wayne


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## pshort (May 6, 2008)

It shouldn't matter much, but two-diode approach lowers the voltage by about 0.7V (down to 11.3V), and doesn't guarantee that the current is equally divided between the two wall-warts. But it should be close enough on both accounts to not cause problems.


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## HomeyDaClown (Oct 3, 2009)

Yeah, what they said....

Most wall warts will supply the rated voltage at a specific load (what they were designed to operate). Otherwise the voltage is higher or lower depending on the actual load (what you decide to use them with) unless they are of the regulated variety. Either way, if they are rated at 12v 3a each, you should be close enough when pulling 6 amps. Sounds like a hefty motor, a wiper motor by chance? Wiper motors are really forgiving in theri demands for voltage and current (close enough is good enough). I've run them for hours on end on 5 volt 1 amp wall warts at reduced speed and torque.

In the diagram the arrows point to the bar (bar on the diode itself) as Otaku said.


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## Aquayne (Sep 1, 2008)

The power is for a demand pump. It is to pressurise the water system to 70psi. The water if for mist emmiters that will simulate cannon fire. I also have to power a brass electric water valve that needs 4 amps to open.


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