subelman@ttidca.TTI.COM (Ed Subelman) (08/25/88)
I have an AT based system that should operate 24 hours a day, 7 days a week.
It sometimes crashes (because of heat, I suspect) and I am looking for some
hardware device that will automatically reboot the system if there is a crash.
My idea is to build a card that has a timer and can be accessed via an
I/O port by the software. If the port is not accessed in N seconds, it
reboots the machine by grounding the "power good" signal.
Does anyone know if a device of this type is available commercially?
Any reference would be appreciated.
--
Ed Subelman subelman@ttidca.TTI.COM
Citicorp(+)TTI {csun|philabs|psivax}!ttidca!subelman
3100 Ocean Park Blvd.
Santa Monica, CA 90405 (213) 452-9191, x2972rlb@xanth.cs.odu.edu (Robert Lee Bailey) (08/28/88)
In article <3090@ttidca.TTI.COM> subelman@ttidca.tti.com (Ed Subelman) writes: >I have an AT based system that should operate 24 hours a day, 7 days a week. >It sometimes crashes (because of heat, I suspect) and I am looking for some >hardware device that will automatically reboot the system if there is a crash. >My idea is to build a card that has a timer and can be accessed via an >I/O port by the software. If the port is not accessed in N seconds, it >reboots the machine by grounding the "power good" signal. >Does anyone know if a device of this type is available commercially? >Any reference would be appreciated. I recently saw an ad in the Sept. 1988 issue of Computer SHopper that described just such a device. (page 556) It is called a "CPU Activity Watchdog". Price: 129.95 The ad says that it works with any computer that has a remote reset switch and an RS-232 port. Apparently, their software periodically strobes the serial port to reset a hardware timer. If the watchdog timer expires, then it closes the reset switch to cause a reboot. It is available from: VSSI One Technology Center Mannford, OK 74044 (910) 865-1000 If you are a proficient hardware & software hacker, you might be able to build a similar device using a 555 timer. Radio Shack has a 555 timer project book that has a circuit in it which might be adapted for this purpose. (catalog # 276-5010 pg. 9) The circuit is basically a monostable circuit that can be adjusted for various time delay periods. In the diagram, if you replace switch S1 with a 12 volt relay, you could use the serial port to periodically toggle the DSR (or DTR) line to apply power to the relay, thereby, reseting the 555 timer. If the timer is not reset within the time period, then, the 555 would close another relay which is connected to your PC reset switch. This circuit would, of course, require a TSR program to drive the serial port. The cost to build this should be under $10 assuming that you have an extra serial port available. I realize this is a VERY rough description, but, I hope it is of some help to you. If you want, I may be able to give you some more specifics on the hardware, but, I can't guarantee that it will work without some tweaking and experimenting. Bob Bailey