ssorrell Posted October 25, 2012 Share Posted October 25, 2012 (edited) I'm attempting to use an amber beacon light in my show this year. Of course it's 12v and I have an AC to DC converter. A few questions if you can help me...just to make sure I don't burn any of my circuits up...1. If the beacon light is 12v, 11.7 amp, what amperage will it pull once converted to 110v? I would assume it would be less than 2 amps, but I'm no electrical engineer...2. The converters are rated in amps. Is that the INPUT of amps, or the output? For example, this beacon light is 12v, 11.7amp. Does that mean I need a converter that is rated for a max 12 amps, or a converter that is rated for 2 amps? Edited October 25, 2012 by ssorrell Link to comment Share on other sites More sharing options...
ssorrell Posted October 25, 2012 Author Share Posted October 25, 2012 Never mind. I got my answers from some smart dudes on Facebook. Link to comment Share on other sites More sharing options...
k6ccc Posted October 25, 2012 Share Posted October 25, 2012 Your guess of less than 2 amps of draw at 120V AC for your 12V DC power supply is fairly reasonable.For the math, 12V x 11.7A = 140.4 Watts. Divide that by 120V to get 1.17 Amps (KEEP READING!)Now that may be a fancy book figure, but there are several problems with it. First of all, 12V DC power systems do not normally operate at 12 volts. They are generally planned to emulate vehicle operation and when the engine is running in a vehicle, the voltage is more like 13.5 - 14.0 volts. Therefore, most 12V DC power supplies actually output somewhere between 13.6 and 13.8 volts. So if we split the difference and go with 13.7 volts, the equation becomes:13.7V x 11.7A = 160.29 W. Again, divide that by 120V to get 1.336 Amps (but wait, there is more - keep reading)Second issue is that your 120V AC power line likely is not really 120 volts. You have likely heard several numbers given from various sources for the voltage that comes out of the wall outlet. For example 110V 115V 117V 120V. The actual voltage will vary somewhat, but is generally in the 110 - 120 range. The lower the AC voltage, the more current required for a certain power. So using the worst case of 110 volts, the current goes up to 1.457 amps (but wait, there is still more - so keep reading)Any power conversion has some power loss in it. Depending on the design of the power supply will substantially effect how much loss. As a general rule of thumb, the more heat that it produces, the more loss. Without knowing anything about the power supply, I would guess that you would be safe in assuming that the AC draw is 150% of the calculated value which puts it at 2.186 amps. Link to comment Share on other sites More sharing options...
Max-Paul Posted October 26, 2012 Share Posted October 26, 2012 K6CCC did a fine job hitting all of the major points. Only thing I will add is this. There are two major types of converters. The analog supply and the switching supply. The major difference is that the switching supply is more efficient. And usually smaller for the same wattage or current available at a given voltage. Link to comment Share on other sites More sharing options...
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