Michael O'Donnell writes of using X10 as a means to reboot a
wedged computer without having to take a walk down to the lab. He
mentions using the relay modules to emmulate the reset switch, rather
than the "no technical talent required" approach of powering the boxes
through an X10 module so that it can be reset by being turned off and
on, the original IBM PC way (no reset button, remember?). He asks for
wild speculation as to alternate approaches.
By relay modules, I presume that you mean the so called
appliance modules. They go "click" when you turn them on or off
because they use a relay to control the load, which allows larger
loads, inductive loads (like the motors in many "appliances") at the
cost of not being able to "dim" the appliance. (The lamp modules use
a triac which allows dimming by controlling conduction (phase) angle.)
Actually, these are the kind of module you should use for doing the
power cycle trick, because you wouldn't want to accidently "dim" your
computer, and the triac's can't quite reach 100% conduction angle,
which may or may not bother the switching power supply in the
computer.
If that's not what you mean by "relay module", then ignore the
following, because I'm not on the same page. But if so, be aware they
you're going to have to modify the modules to drive the reset switch
directly. As wired, the relay connects things to the module input,
which must be connected to the AC line for the X10 signals to get
through, and to provide the expected operating conditions for the X10
chip. But to drive the reset circuit, you have to be referenced to
computer signal ground, not the AC line, so you need completely
floating contacts from the X10 device. Also, on my appliance modules,
they are never completely "off" because they supply a sensing current,
so that you can get your appliance to turn on without having to find
an X10 control box: you switch the appliance off and on, the modules
sees the interruption in continuity, and turns on.
The bottom line is that you'ld have to modify the module to
get a floating contact. That's probably not hard, but it is at least
some screwdriver and soldering iron work per module. And if you
wanted a UL approved solution, you're out of luck...
Perhaps simpler to produce while still using X10 would be to
plug a wall wart ("AC adaptor") into the X10 module, and connect that
to the coil of a low voltage relay or opto-isolator (the reset line
can probably be driven by an open collector output pulling it to
computer signal ground). The relay or opto-isolator could be loacted
inside the computer cabinet, meaning that you wouldn't have to expose
mother board signals to the threat of getting shorted to a nasty
voltage outside the cabinet. Parts easily available even from Radio
Shack, or All Electronics, MPJA, Jameco, DigiKey, etc.
There are any number of commercial controller boards that let
you send commands over, say, a serial line to switch digital outputs
on and off, some of which will have relays on board. I don't seem to
have the right catalogs/magazines here today (DigiKey, Circuit
Cellar). The one reference I can find is to the Weeder Technologies
(www.weedtech.com) "RS-232 Stackable" modules, which includes on with
14 digital I/O pins, which each could probably drive a relay or
opto-isolator ($49). ("Stackable" means that it has two RS-232 (sic)
9 pin connectors, one of each gender, and you can plug up to 32 of
them together in a chain to control from one RS232 port.)
The circuits (like the Weeder) that don't include relays or
opto-isolators of their own require you to supply your own, but I kind
of like the idea of not having the computer's reset signal run outside
the box. That way if someone puts his chair leg on top of where the
control cable and a power cable are crossing, you just fry the $49
Weeder board and maybe the relay or opto-isolator, not the computer.
Finally, a PIC based project to control both the reset signal
and a power control relay could speak whatever protocol you wanted:
RS-232, CAN, I2C, etc., even an X10 derived varient that would never
be triggered by your neighbor's new X10 lights control installation.
But it would be a project. (Do you think there's a worthwhile market
for such things?)
Bill
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