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On-off swict for LEDs? Answered


I'm going to install an LED bank into a stereo cabinet. Powered by a standard 120VAC power supply, I want to put in a simply on/off swicth. I can solder but know little about electronics. Can I use a simple toggle? The PS output is 12 V (I assume DC).

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jeff-o (author)2010-09-11

Yup, a toggle switch is enough, but make sure you put a resistor in there too (the value will depend on how many resistors you're using). If you have a multimeter, make sure you check for shorts before powering it up.

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dsdurkes (author)jeff-o2010-09-12

So I would put a resistor between the switch and power suppy (12 VDC side) or between the lights and switch? Why would I need a resistor? See the pic I posted in response to yokozuna's reply.

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jeff-o (author)dsdurkes2010-09-12

Oh! OK, no need for a resistor then. But, you should put the switch on the 120V side, because it will save a lot of power. When it's turned off, it won't draw any power. If you put the switch on the 12V side, the power supply will always draw a bit of power.

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dsdurkes (author)jeff-o2010-09-12

Ah. Good point. Thank you. I wanted to stay away from the 120 side, to tell the truth. I looked at some 120 V toggles and they all have three leads. I know power and ground but how would I wire neutral?

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orksecurity (author)dsdurkes2010-09-13

In 120V wiring, current flows between power and _neutral_. Ground is "safety ground" and should never connect to either of those under normal circumstances.

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rickharris (author)2010-09-12

LED calculator
 
Will help you sort out the resistor value needed - i would pick off the 12 volt PS NOT the 120 volt side.

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dsdurkes (author)rickharris2010-09-12

Couldn't agree more. That much I do know - picking off the 12 VDC side! Thanks much but as you can see, the assembly I have is already constructed (see my pic in reply to yokozuna) and I just want to toggle them on/off.

Thanks!

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yokozuna (author)2010-09-11

You really shouldn't be messing around with 120 until you understand it a little better. Plus, not sure how big your cabinet is, but I'm guessing you don't need nearly that much juice for LEDs.

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dsdurkes (author)yokozuna2010-09-12

The LED assembly I have has a basic AC-DC transformer to drive the LEDS from household current. I figure the switch should NOT be on the 120 side, to be sure as Rick pointed out.

as the pic shows, the output to the light banks is 12V 4170 mA. I would love to drive these via a battery pack but want to keep this simple. The LEDs are preferred due to their low temp.

Thanks!

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