154Views7Replies

Author Options:

What is the maximum number of LEDs I can fit on USB ? Answered

As Far as I know USB is 5V and wikipedia told me it supports 900mA Current Output.
What is the maximum number of LEDs I can hook upto to a USB port SAFELY ?
I have 3V LEDs (20mA I GUESS)and they come very cheap here around Rs.2 for 1 LED (25 for $1)
And how do I do that? Parallel would be the best I guess...,,I really don't know what current my PC can give safely...!
Thank You

Discussions

0
None
mayur.phadte

8 years ago

I am pretty sure my ipod takes something more than 100mA !

0
None
lemonie

8 years ago


USB is only good for some things, don't use it as a power-supply. You've probably got a spare MOLEX inside the case. (unless it's a laptop)

L

0
None
Re-design

8 years ago

I don't think you can get more out of a usb than 100ma unless you have a circuit to tell the port to send more. In other words yoy must communicate to the port.

0
None
frollardRe-design

Answer 8 years ago

I thought they generally by spec put out 500mA but got really mad at you if you exceeded it, and shut it down out of spite. I know older 1.1 ports had the 100mA limit unless you communicated with the host.

0
None
Re-designfrollard

Answer 8 years ago

You may be right, I'm going by memory and didn't check my facts before posting. SO, that means that it is just a fact to check up on before anyone constructs a circuit running off usb port.

0
None
steveastroukRe-design

Answer 8 years ago

You're right. ANY fully compliant port is supposed to allocate 100mA, until negotiation.