[HH] cheapest/simplest way to control a relay from a PC

[David Kramer]

On 11/08/2012 02:18 PM, Tom Metro wrote:
...

> wired to the parallel port (the server has one, and it is unused), and
> controlled with some software, like parashell:
> http://sourceforge.net/projects/parashell/
> 
> (More info on parallel port control here:
> http://www.epanorama.net/circuits/parallel_output.html )
> 
> You can't get much simpler than a relay, DB25 connector, a 3.5mm jack
> and plug, and some wire. The relays above even have an internal diode.
> 
> (The other obvious choice is an optocoupler, but for the duty cycle this
> will undergo I'm not that concerned, and the mechanical relay provides
> the simplest interface to the emitter, where polarity, high-side vs.
> low-side, and voltages are irrelevant, and thus more apt to work the
> first try.)
> 
> Anything simpler? Any skepticism for running the relay directly from the
> port without a buffer? Any recommendations to use a serial port control
> line instead?


If you go this route, I own the book Parallel Port Complete, and you can
borrow it (http://www.lvr.com/parprtib.htm).  It might be of some help.

Personally I would use X10 for super simple and complete isolation from
the computer, but I know there are a lot of folks here that don't trust
X10.   I still use it every day with much success.