Reliability and Safety


Safety and Thermal Runaway


Every product will eventually fail but in most cases the failure does not cause other damage. One exception is when the failure leads to thermal runaway and overheating to the point of creating a fire. The last line of defense against this serious problem is to cut off power which when done in time removes the source of energy that causes the overheating. Thermal fuses act in this manner but cannot be reset and need to be replaced. In spite of this disadvantage the added safety is often worth the added maintenance. See TF-152C link below for details.

  • ThermalFuse: Cuts power to a system when the temperature exceeds a limit.

Watchdog Power Supply


Any system which includes a computer is subject to "crashing" or "hanging" which means the program fails to operate properly. Such failures or often due to software bugs but are also caused by external events such as static discharge. In these cases the only way to clear the fault is a cold reboot or power cycle. This can be done using a "remote power switch" accessible via the Internet and a web page. The other option, perhaps more reliable, is a watchdog timer (WDT). A WDT works without a computer interface or internal CPU but from digital circuitry which causes a cold restart if the WD pulse is missing for a certain period of time. It is also automatic so no user interaction is needed. The WDPS-5V (see link below) provides this functional as well as an external line which can be used to restart other devices.

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