How to use RS 232 to close a circuit?

[twotails81]

Picture this: I got a regular LED and I got my switch, when i flip the switch the LED comes on, and off if i flip it again, its just a regular circuit. Now how can i flip the switch using my computer? I can manipulate my RS232 port through programming. Right now i think i need like a TTL chip to do so, but anybody have a better simpler idea to do this?

Thanks

 

[3v0]

I posted this a short while ago in answer to a similar question.

How about this.

Use a RS232 flow control signal that you can toggle on the PC. Maybe RTS.

Use that signal to switch a transistor.

Have that transistor switch a relay.
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The following circuit is more complex but it shows what transistor and discretes are needed to drive a relay from RS232.
A Hardware watchdog and shutdown button

You can do the same thing with the RTS signal but since you are just driving an LED all you need is resistor of the right value to limit the current to the LED.