How to determine if a PC is running

  • Thread starter Thread starter Sam Carleton
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Sam Carleton

There is a little PC embedded in an instrument. The instrument needs
to know if the PC is turned on/powered up so that when the power to the
instrument is turned off, it can handle the internal PC correctly.
Cracking the case on the PC is not an option. The PC has the following
interfaces to work with: USB, Firewire, a mice input, and a speaker
output.

It has been determined that checking voltage on the USB does not work
on this PC because the PC continues to power the USB port even if the
PC itself is turned off.

Sam
 
Bob said:
How about checking voltage on the mouse input (PS/2) ?
Click to expand...

The mouse port is exposed on the back of the PC which is exposed on the
back of the instrument, thus, not an option:( The Firewire, USB, mice
and speaker ports are all on the front of the PC which are inside and
controlled.

Sam
 
Squire said:
You should see a light on the front of the computer when it is on.
Click to expand...

Too true, too true. That is one of the fallback idea's but it just
does not seem to be that hot of an idea taping a whatjamcallit to the
LED on the front of the PC.

Sam
 
Ok, perhaps you need to back up to the beginning, and review what
"outputs" you do have available on the PC to "check" for "life" and what
"inputs" on the instrument you have available to "read" the PC with.
 
A good instrument man would connect a couple of wires to the 12 volt output
from the computer power supply, and mount a lamp on the front of the
instrument. This 12 volts could also be used as an analog input to another
device/controller/recorder that could be used to perform an action,
depending upon whether the 12 volts was present, or not.

--
Regards,

Richard Urban
Microsoft MVP Windows Shell/User
(For email, remove the obvious from my address)

Quote from George Ankner:
If you knew as much as you think you know,
You would realize that you don't know what you thought you knew!
 
There is a little PC embedded in an instrument. The instrument needs
to know if the PC is turned on/powered up so that when the power to the
instrument is turned off, it can handle the internal PC correctly.
Cracking the case on the PC is not an option. The PC has the following
interfaces to work with: USB, Firewire, a mice input, and a speaker
output.
Click to expand...

If this is the speaker that's connected to the motherboard, the
voltage on the speaker wire should be +5 volts.
 
Sam said:
There is a little PC embedded in an instrument. The instrument needs
to know if the PC is turned on/powered up so that when the power to the
instrument is turned off, it can handle the internal PC correctly.
Cracking the case on the PC is not an option. The PC has the following
interfaces to work with: USB, Firewire, a mice input, and a speaker
output.

It has been determined that checking voltage on the USB does not work
on this PC because the PC continues to power the USB port even if the
PC itself is turned off.

Sam
Click to expand...

Why con't you rig something directly to the AC input, maybe Amps
instead of Volts? Yes, there's a bit of juice flowing when the PC is
off, but here's a lot more when it's on.
 
That "light" is powered by 5 volts from the motherboard. Can't you get to
that?
Click to expand...

Having done projects like this before, that is the best way. It's a
low-impedance output, probably delivers 5V @ 50 mA or thereabouts, and has
an easy connector.

-John O
 
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