# Converting 110v AC to 12v DC

1. ### rolinger

11
Hello all. First thing I have to say is I don't understand much about power and electricity conversion rates. But I do have a need to have two different motors, each requiring a different power load, to run off of a single source AC 110 house outlet.

First device: Volts: 12, Amps: 3.3, uses a 12V car cigarette lighter (I assume this is DC power)

Second device is a 2 speed motor: Watts: 37/27, Amps: 0.57/0.39 and runs off of standard 110v AC plug

I am looking for a cheap solution that will allow me to power both devices off of household 110v AC power but really have no idea on to go about doing this since this is my first project I have ever done that requires me to toy with power/electrical sources.

3. ### rolinger

11
So is watts DC math any different from watts AC ?

Watts DC = Volts x amps (12 Volts x 3.3 amps = 39.6 watts)​

Would the second device simply be:

Watts AC = Volts x Amps (120 volts x 0.57 amps = 68.4 watts)​

The second device "advertises" 37 watts with a pull of 0.57 amps off of a standard 110AC outlet. But the math shows different with 120v AC x 0.57 amps = 68.4 watts. Something isn't adding up right.

Thanks.

Last edited: Feb 17, 2008

### Staff: Mentor

Perhaps there is an inefficiency such as power factor in the AC device.

Anyway, I'm not sure what you are really trying to do here. 110V Ac is wall power and 12V is a pretty standard power supply. If you the motor and a 12V power supply into a power strip, then you have it all connected together. I'm not really sure what you could do that would be more complex (or useful) than that.

5. ### HuskerEE

9
When you buy a 120VAC to 12VDC converter make sure the current rating is atleast 3.3A. That's a decent size wall wart. Using a wall wart with that rating is probably one of the safer options you have, especially if you don't feel comfortable with 120VAC circuits.

6. ### Danger

9,878
Any time that I've run into a similar situation (quite a few times), I just run a dual outlet extension cord into the device housing and plug the adapter into one of the receptacles. Then a regular cord can be plugged into the other to run the AC stuff. For additional safety, if you're not sure of the power draws involved, use a power bar with an internal breaker.

7. ### Bits

2
I would like to know if there is an inverter to go from my household current to power my 12 v winch. I have a 4x4 super winch LP 8500 12 v DC 4.5 hp 3.3 kw motor.

8. ### Bob S

AC Motors, with few exceptions, look inductive from the ac power lines. The 120v ac x 0.57 amps is 68.4 volt-amps or VA (reactive load).
Bob S

Last edited: Oct 23, 2009