In order to reset the PC when it locks up you must have a reset header on your PC motherboard.
These are typically two pin headers or 2 pins on a multi-pin front panel header.
You remove the reset cable (from front panel reset button) from the header and install it onto
a header on one of our boards. We provide a cable that goes from another header on our board back to the
motherboard reset header. All of our boards use a reed relay which performs the same action as pushing
the reset switch to re-boot the PC.
If you have not purchased a PC for your application yet, you might want to consider buying a "white box"
type PC or building your own. Building your own is extremely simple nowdays with parts sourced from
on-line vendors like Newegg.
That way you are sure to get a reset header on the motherboard. Some rack mount style computers also
have a reset headers.
Major vendors of PCs like HP, IBM, Dell etc have decided to remove reset switches and the headers on
their motherboards. In a lot of cases these PCs may be using the industry standard ATX power supply
connector that has a signal in the cable that will reset the PC. Check our
ATX Reset Adapter page
to see if your PC has the standard pin out ATX power connector on the motherboard.
Most newer PCs are using the 24 Pin type ATX power connectors.
- HP's COMPAQ computers are not recommended.
If you have not purchased your system yet, then do not consider them. They do not have a reset header
and they do not use a standard ATX style power connector. The only option we have for Compaq is to
use our External Serial PC Watchdog and an AC power module to cycle the AC power.
- Some Dell computers also use a non-industry standard power connector on some of their PCs.
We think they do this to make sure you can only buy replacement parts from them - rather than cheaper outlets
like Newegg? Check with them first to see if the computer they are going to ship you has an Industry
Standard ATX power supply. We do have a Reset Adapter for newer Dell PCs that use a
mini-ATX 24 pin connector: ATX Reset Adapter page
"Tickling" the PC Watchdog
Here are some ways that a computer/PC can fail and be restarted by the watchdog board:
- The hardware freezes or locks up typically as a result of a power glitch.
- The operating system (OS) freezes and kills all applications running on the PC.
Also commonly called "Blue Screen Of Death" (BSOD) on Windows OS.
- Your application progam dies or is terminated by the OS.
In all these cases, if your application was doing the “tickling” of the watchdog,
the tickles would stop and the watchdog would countdown to zero and reboot the PC.
This is by far the best option.
It is possible to have a separate program tickle the watchdog and that solution would cover the
first two scenarios.
But it would not cover the last one where the OS terminates your application program, since
the separate ap would continue to run and keep tickling the watchdog. We do supply programs to
"tickle" the Watchdog but by far the best solution is to make a minor change to your application program
to do the "tickling".