5v output from computer

Hello,

I was attempting to get a 5V output from a computer and into a
transistor to trigger an external circuit. Presently I am attempting
to use the serial output but I just cant get it. Would really
appreciate any advice.

thanks

am

 

There is very little power available at the serial port, it was not
designed for powering anything.
PS/2 and USB ports do have +5V power available; do not load more than
300mA.
You do not need any power (of merit) to trigger an external circuit,
or to drive the base of a transistor; 10uA is more than enough for most
devices and some will draw only a few microamps at most.
You need to be mor eXplicit about what you are trying to do and how.
For example, do you want to use an RS-232 output to turn something on
and off?
A CMOS gate has zero loading and might be part of a solution.

 

If you're trying to control something, parallel ports are more
commonly used for this:

http://www.hut.fi/Misc/Electronics/circuits/parallel_output.html

 

David & Robert,

thank you for your reply.

The link actually answers most of my questions.

thank you

Amit