[rustyclockwork]

I would like to add a blue led or two under my Kesington turbo mouse pro trackball...

would the voltage taken from the USB power bother anything?

I don't even know what voltage USB uses, nor do I know what voltage the LED's will take, I know they are diodes, so I'm assuming the color of an led depends on the voltage? am I wrong here?

does anyone think this would screw with the voltage needed to run the trackball?

Jason

[Carl Norum]

Originally posted by rustyclockwork:
I would like to add a blue led or two under my Kesington turbo mouse pro trackball...

would the voltage taken from the USB power bother anything?

I don't think the amount of power two LEDs would draw would cause any problems. You can always put a 1K resistor in series with them if you are worried about power consumption. USB can't provide a WHOLE lot of power, but it should be OK for you.

I don't even know what voltage USB uses, nor do I know what voltage the LED's will take, I know they are diodes, so I'm assuming the color of an led depends on the voltage? am I wrong here?

The red wire in the USB cable is +5 V and the black wire is ground. The other two are the data connections. Any LED you get should be able to handle 5 V.

LED colour depends solely upon the material from which they are manufactured - not to do with the voltage at all. Brightness will be affected by voltage and duty cycle. If you are just dropping these across the USB power lines, they will have 100% duty cycle.

Good luck with your mod!

[rustyclockwork]

thanks!

[Tom N]

You can't just put your LED across the power lines without the potential of blowing out the LED. LEDs have very limited current handling capabilties. A USB port is suppose to be able to source 500 MA of current. Many LEDs can only handle 10 to 20 MA of current. You may need to add a resitor between the LED and the power feed. Try a resistor between 270 and 470 ohm rating, the resistors wattage isn't to important here, just about any one will do.

Set it up like this:

Power +5v ---------Resistor-----LED-----Ground

You resistor will also control the brightness of the LED, a higher resistance will produce less light output, and a lower resistance will increase light output, going to low will increase the light output unitl your LED becomes a DED (Dark Emittting Diode. AKA Dead).

Tom N.

[Secret Vampire]

Originally posted by Tom N:
You can't just put your LED across the power lines without the potential of blowing out the LED. LEDs have very limited current handling capabilties. A USB port is suppose to be able to source 500 MA of current. Many LEDs can only handle 10 to 20 MA of current. You may need to add a resitor between the LED and the power feed. Try a resistor between 270 and 470 ohm rating, the resistors wattage isn't to important here, just about any one will do.

Set it up like this:

Power +5v ---------Resistor-----LED-----Ground

You resistor will also control the brightness of the LED, a higher resistance will produce less light output, and a lower resistance will increase light output, going to low will increase the light output unitl your LED becomes a DED (Dark Emittting Diode. AKA Dead).

Tom N.

For regular LEDs this holds, but a lot of the Blue ones I've seen are rated at 5v, and should operate fine off the USB bus, but they'll be very bright, almost white, so it might be worthwile fitting a resistor anyway