How much power can I take off the COM-port?

cmxflash · - Joined: 11 Dec 2004 Posts: 872

I've been playing around with PHP and my serial port recently, and I discovered that my computer will output 12V when the port is opened.

I'm not really sure how much power the serial port can supply. I was thinking of using a relay to power up other more power-consuming devices, still, I'm not sure if the serial port is strong enough to power the relay. Since I don't want to risk any of my computers motherboards, I need to be sure before trying anything.

And yes, I've seached on Google without any results.

Anonymoose · - Joined: 09 Sep 2003 Posts: 2192

Are you wanting to know in terms of amps or watts? As far as I remember from when I used to play with COM ports, it's in the region of about 5-10 mA / 100mW at best. There are plenty of circuit diagrams floating around on how to boost this with external devices though - I'll dig through my old bookmarks and see if I can dig something up.

Edit - from my bookmarks,

http://www.tkk.fi/Misc/Electronics/circuits/rspower.html
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