Using proportional VALVE control to run a HEATER

The controller does not care whether you are adding heat electrically or by any other means. One contact opens when heat is needed, the other closes. Pick the one you need and connect it to the source of heat in any way convenient.

Walter.

If your heater element is controlled via a relay, then you can turn it on with the "open" signal. Depending on your relay and configuration you can either stop sending the "open" signal or send a "closed" signal to the relay to get it to turn the heater off.

You may find that you really don't need any more advanced control than this for most heating applications. A lot of heating controls are simply on-off.

Bill,

I think Walter is half right. The heat source does not matter to the controller. However, the control of that heat source matters very much to the controller. Your Omrom controller has three-state outputs, where none, either one, but not both of the outputs can be on. The primary tuning constants are deadband and hysterisis. Controlling an electric heater through a relay normally uses a signle output with the duty cycle calculated by the controller to maintain setpoint.

That said, I think your exisiting controller will work, but not as well as you might want it to. Your temperature will always be cycling, as the heater turns on at setpoint-deadband and turns off at setpoint- deadband+hysterisis. If hysterisis = 2 * deadband, the temperature will at least cycle about the setpoint.

Mike

Walter, Mike and Michael,

Thanks a million !! The info about deadband and hysteresis are invaluable.

As this thing is intended to control a brick-insulated kiln, and that

As an aside, does anybody know of a website, or book, that explains controls like these in more detail ?? Not looking for a "dissertation" on controls, just a good book that covers the general aspects of the different kinds of controls.

Bill

It's a broad subject and there is much published material covering many aspects. Have a look at my site at

Walter.

Walter,

Nice site !! I will check ot out from work, where I have a high speed connection.

But, the Omron control continues to fight with me. It has a potentiometer input to get feedback about the position of the valve. Of course, a kiln doesn't have a "position indicator". I'm about ready to trash this one, and try something else.

Anybody got a cheap ramp/soak control suitable for heating ??

Bill

"Walter Driedger" wrote in message news: aspects. Have a look at my site at

Chromolux has a decent unit which would do what you need. Basically and sldc (single loop digital controller) will do.

You could just hook the potentiometer up to the same signal used to turn the heater on. That would amuse the dickens out of the unit, but it would serve the purpose. You might need a little signal conditioning for that.

I've used Watlow F4 programmer/controllers with good success on industrial dryers. A lot of features for the money. I've aslo built dozens of kiln control systems, but they were not cheap.

Good Luck