dgfoster
Diamond
- Joined
- Jun 14, 2008
- Location
- Bellingham, WA
I have finished designing and building a small heat-treat oven 5 feet long, 16 inches wide and 12 inches high for stress relieving cast iron castings I make. It uses an excellent Bartlett kiln control board that switches a 4000W to a16ga Kanthal A heating element. I am using an electromechanical relay to control heating driven by the board. It works fine. But, as an added safety feature I would like to add a switch triggered by a 12V signal from the board that occurs should an over-temperature condition occur.
The board procvides a pin which will output 12VAC (easily converted to DC with a bridge rectifier if needed) in the event of an over-temperature condition. I am thinking an electromechanical circuit breaker-like switch would be ideal. So that when the 12V signal occurs the switch opens and has to be reset mechanically for current to once again flow through the heating element. I imagine such a switch exists. But, not knowing a proper name for such makes finding it difficult. I suppose once someone tells me the proper name I will feel like a dunce (I actually already feel that way for being clueless), but I can live with that.
The reason for the added switch is to take care of the situation where the primary relay fails closed and power is delivered uniterupted to the heating coils leading to meltdown or fire. Yes, I know the EM relays usually fail open. But....
Denis
The board procvides a pin which will output 12VAC (easily converted to DC with a bridge rectifier if needed) in the event of an over-temperature condition. I am thinking an electromechanical circuit breaker-like switch would be ideal. So that when the 12V signal occurs the switch opens and has to be reset mechanically for current to once again flow through the heating element. I imagine such a switch exists. But, not knowing a proper name for such makes finding it difficult. I suppose once someone tells me the proper name I will feel like a dunce (I actually already feel that way for being clueless), but I can live with that.
The reason for the added switch is to take care of the situation where the primary relay fails closed and power is delivered uniterupted to the heating coils leading to meltdown or fire. Yes, I know the EM relays usually fail open. But....
Denis