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Usb ON/OFF switch device? Answered

I wanted to have a large amount of green LEDs power on with my xbox 360 slim for ambient lighting and just to look cool, with 30+ LEDs I cant power them directly from the USB port so I was wondering if there was a way to have them still turn on by only pressing the power button on the system.


Small relay -- or better, solid state relay, which would draw less current -- triggered by the USB power-supply lines.

Ok so what kind do I get? I need the trigger to be 5v then the power for the leds is going to be a 9v power supply, how do I wire this thing also?

You've mostly answered your own question.

You want a relay (an electrically-controlled switch) that responds to a 5V signal (+/- 5%), that draws under 100 mA of current (which is what USB will provide) and that can switch enough current to supply your lights (which, since they're LEDs, is probably not much of a constraint).

For the lights to go on when the machine goes on, you want the relay's output switch to be either single-throw normally open, or double-throw and you'll use the normally open terminals.

Websearch for "5V relay" finds several immediately which meet these constraints.

To hook it up:

Connect the control inputs (the coil) between USB 5V and ground. If this is a traditional coil relay rather than an electronic relay, and it doesn't already have one (most don't) you should also bridge these terminals with a quenching diode (sometimes called a snubber diode or suppression diode or protection diode) to protect the electronics from the surge a coil produces as it is turned off. A good description can be found at http://www.bcae1.com/relays.htm

Connect the relay's output contacts into the lighting loop just as you would a switch. Which is exactly what it is.