to ignite a led with usb port

[jhonilson]

  Hi, I want to make a lamp similar to some webcam, is to say, i want to ignite some led with the usb port, but i think that it will need some resistors. I think that if i connect a resistor (330 ohm for example) with a led (ultra brilliant) perhaps the usb port died because is too corrent for it.
  Anybody can help me about that?? I visited usb.org but in the datasheet not speak about the current only voltages.
Thanks

[ed1380]

usb ports handle 500ma. do you want the led to turn on always or be program activated?

heres a site to help you calculate the resistor needed http://led.linear1.org/1led.wiz

[jhonilson]

  Thank you so much for you answer. 500 mA is fine for me. The leds use 25 to 30 mA aproximately. Yes i would want to control when turn on the leds. i am thinking to make a software with visual basic, but may be any software.
 Gracias

[ed1380]

with USB you'll need a translator. too complicated for me to help you with.

but there is this http://www.codeproject.com/KB/cs/csppleds.aspx

[airman00]

with USB you'll need a translator. too complicated for me to help you with.

but there is this http://www.codeproject.com/KB/cs/csppleds.aspx

get a USB to serial converter

[jhonilson]

  Thank Ed1380 i saw the same webpage yesterday and other nice website but i not found many details about how controlling the usb port really.
 Airman00  i think that the port converter i will help too much because i will need to control the usb port anyway i think and that is the real problem.

  Thank you so much

[ed1380]

you could try this and modify the code to do a constant on or off to power the leds intead of the pwm for the servo's
http://www.societyofrobots.com/member_tutorials/node/25