I am building a DSP driven motor controller and I am looking for a way to implement fail on functionality. Currently the DSP controls a triac that turns on and off when needed. Unfortunately, it is driven by the on board power supply and in the event of a controller or power supply failure I would like the unit to continue to provide power to the load. So far the only solution I can come up with still requires the on board power supply to drive the triac when it is supposed to be on. This works if the error is in the DSP chip, but on a power supply failure it still turns off the load. Any ideas would be greatly appreciated.
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- Thread starter RocSolid
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Unless I have misunderstood your post I would say this is not good system design or safe practice. I don't know if your motor is driving say, a large bit of machinery, but whilst it may be "fault tolerant" by your standards, surely it's not designed as "fail-safe" if the motor can keep running independently? (Fault tolerance engineering is a completely different art form!)
If you must do this then why not add an external triggering circuit for the triac which is powered from the a.c. supply for the motor? (This would be normally gated off when the controller is functioning normally.)
If you must do this then why not add an external triggering circuit for the triac which is powered from the a.c. supply for the motor? (This would be normally gated off when the controller is functioning normally.)
BigTom2005
Electrical
What kind of DSP processor are u using, ROC? Tigris? TMS?
Brian's comments are good--do you want the motor to run when there is a fault?
BigTom
Brian's comments are good--do you want the motor to run when there is a fault?
BigTom
- Thread starter
- #5
Thanks for the input guys. I think I may not have been clear in my initial desciption. The system is designed to control the motor to optimize power savings. What I am looking to do is provide a way that if a fault in our control circuitry exists, the load will still be powered, it will just no longer be controlled for optimization. I have tried an arrangement where the triac is gated from the AC supply, but then the driving current for the gate must come from the on board power supply. I am trying to find a way to allow the DSP signals to optimize the motor during normal operation, but if the entire control circuit fails, the triac will just remain on providing power to the load. Again, thanks for all your help.
cbarn24050
Industrial
Have you managed to get this to work yet? Using a triac usually means you can never get it to turn off.
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