A bit OT..control logic

I am trying to get my head around this but it is escaping me..

Omron temp controller (ON-OFF type) E5CSV with one output relay and one alarm relay.

Set point is 500 deg C and i want hysterisis of 50 deg C on either side which means heater shoud be ON to enable temp between 450 deg to 550 deg C.

How would the control logic would be using the available output relay (NO contact) and one alarm contact (NO contact)on the controller.

Any ideas appreciated..

cheers.

As always it depends on your appication. Most people use the alarm output to look for a runaway condition. That is if the temperature gets too high or the thermocouple or temp sensor malfunctions. The other contact might be used for detecting an operating temperature. Useful for knowing when the machine is ready to run or if you are heating something that draws the temperature down, when it has recovered.

One thing I would add that if the setpoint is 500 and the hysteresis is 50, the heating element will turn off once the temperature reaches 500. The temperature may continue to climb and then it will eventually decrease. The heating element will not turn on again until the temperature reaches 450.

That is what i want to achieve but it does not happen.as there is no hysterisis in ON-OFF type controller,.as soon as the temperature comes down to 495 deg C the heater starts again and cuts OFF at 500 deg C which is putting stress on the contactors heaters etc. I want to use the alarm contact to disable the output contact between 450 deg c and 550 deg C and above 550 deg C.

This alarm contact is programmable to 50 deg C above and below setpoint to HI condition (relay activated).

But to get to these contacts to activate the heater in the band of 450 deg c to 500 deg C is what is tricky...( to me atleast..)

cheers..

I recently purchased and installed two SOLO temperature controllers from Automationdirect.com for $100 each. They can be configured for ON/OFF heating control with hysteresis. In my application the setpoint is 400 and the hysteresis is set at 10. Everything works great. Mine also controls a contactor and I had similar concerns about overworking the contactor.

I have not dealt with the Omron temp controller, so i cannot be more specific with my advice.

Looks like you are pretty limited with that unit. Here is the tech sheet if you don't have it.

http://www.ia.omron.com/data_pdf/data_sheet/e5csv_ds_csm212.pdf

Might want to try selecting a higher scale, the hysteresis would be wider.