Quick Question (USB, IR LEDs)

**Un_discovered** · 04-10-2007, 01:38 PM

A quick question for the electrical wizards out there;

I'm making a friend a neat little IR illuminator for their webcam, and I want to know, would I be able to pull enough power out of a USB port to power it?

It'll just be 15-20 IR LEDs powered off of a single USB port.
Doesn't have to be insanely bright, just needs to work.

Any issues in the design?

Thanks ahead.

**kamikaze2112** · 04-10-2007, 01:49 PM

you can get 500mA MAX out of a USB port @ 5 VDC. Depending on how much current your IR leds draw, you might be able to get some powered off the USB bus

**Un_discovered** · 04-10-2007, 01:53 PM

I've got no idea how much current they draw.

I have the following info (probably useless though);

- 5mm diameter
- Dark blue lens
- 940 nm Intensity
- 20 degrees (this is under a heading of the theta symbol, followed by "1/2")

That's all the info I can get.
They're from Dick Smith Electronics (one of Australia's "leading" electronic component suppliers)

**kevinlekiller** · 04-10-2007, 01:56 PM

A 3 or 5mm uv l.e.d. is 20ma forward current , so thats 400ma , then you need to remember the cam takes power. Maybe use a powered usb hub?

**kevinlekiller** · 04-10-2007, 02:01 PM

Oh wait you wrote IR , then its about 100ma each. wich is 2 amps for 20.

**Un_discovered** · 04-10-2007, 02:15 PM

So I could only power 5.
Damn, that's not overly useful then. Or is it?
A powerpack is something like a $20 addition.
Still cheaper than buying one, the only ones I can find on eBay are for surveillance (and would be too powerful thus flooding the webcam's image sensor with light).

Would anyone know of any suitable products?