How to implement a standby safety controller?

[jit_singh_tara]

how to implement a standby controller ,i.e if 1 controller fails the other should start operating and display 1st controller failure....i dont want to use uart.

 

[FvM]

Re: safety controller ?

i dont want to use uart

You should begin telling about the kind of controller. which kind of failure you expect and how you think to detect a failure.
If any kind of safety regulations are involved, the solution may be prescribed already.

 

[rikie_rizza]

safety controller ?

The system is called a redundant system, one system is guarding the main system in case of failure.

From your super short description, this is the only info I can give to you...you don't need UART (just feel like saying it because I don't know what system are you talking about).

Try to be more systematic in asking questions.

 

[ckshivaram]

Re: safety controller ?

you need to identify potential failures. Say your thermocouple failed on the first controller - the microprocessor is still working and should be able to identify the failure and take the appropriate action. In the case where your microcontroller has failed for whatever reason, the 'watchdog' or charge pump controlling the changeover relay would stop being 'kicked' and therefore the relay would drop out. If the controller is working correctly, your controller would toggle a port pin to kick the watchdog/ charge pump.

Therefore your watchdog circuit would drop the relay out if:
1/the unit lost power
2/the microcontroller stopped executing
3/a failure was detected

In addition, I would have at least thermal fuse or bimetal thermal switch in line with the heater in case the heater was turned fully on and caused an overtemperature condition. Never trust a computer!


The design of critical systems is outlined in an European Union document EN6xxxx whose exact number escapes me at the moment regarding machine safety and safety systems. I'd suggest you do a Google for this.