Strobe Light Failure Sensing

[WonderG]

I have some warning strobe light installed in a hazardous area and I need a way to sense if the light has failed and report it to the PLC. If the light has failed the equipment should not run. Any help would be greatly appreciated.

 

[pebe]

Use a light sensor circuit to give a pulse every time the strobe lights. Use that pulse to hold off triggering of a monostable (a pulse omission detector), or bias off an astable oscillator.

When the strobe fails, the monostable will fire or the oscillator will run.

 

[ve7brz]

Simple set use a resettable timer triggered by a photo-cell. The time delay is set longer than the interval between flashes. If the flash does not occur within the allowed time the timer times out, sending a signal to the PLC. Here's a site giving information on the use of this timer for this type of application:

http://www.williamson-labs.com/555-AN170.htm

 

[busbar]

One aside: If the application is something legally required like FAA tower lights, it is unlikely that a locally fabricated means would keep you out of trouble with respect to compliance.