Temperature regulation

jcruz · Jan 28, 2011

Hi to all plc fans,

I've a job that involves to regulate a heating curve, basically what is intended is:

In touch screen the client writes the temperature setpoint and the time.The plc reads the temperature via analog input.

The plc must command an 4KW resistor to achieve the desired temperature at the end of the desired time.

boo: This for me is the big problem, i dont have ideias how i can make this, any help please ?)

Tom Jenkins · Jan 28, 2011

It depends on the degree of precision needed. You may be able to use logic that emulates a thermostat - temp below setpoint, heater on. Temp above setpoin plus a deadband, heater off.

For more precise control you may need a PID loop with time proportioning output - the bigger the error, the larger percentage of time the heater is on.

TConnolly · Jan 28, 2011

Search the forum for sliding mode controller.

Peter Nachtwey · Jan 28, 2011

Alaric said:
Search the forum for sliding mode controller.

It depends on the dead time of the system. I have found that SMCs work well only if the dead time is small. Otherwise a Smith Predictor is needed. I have a nice example all worked out.

However, none of the answers the real problem about following a heating curve. What heating curve? This sounds like a school project.

ydtech · Jan 28, 2011

Is it for a temperature ramp, with set-point increasing over time?

jcruz · Jan 29, 2011

dry fruits system

Its for a system to dry fruits, so my client needs to define 16 temperature setpoints and 16 times setpoints, the systems start to heating to to achieve the temperature setpoint 1 at the end of a time setpoint 1, after the same thing with the second and up to 16 setpoints.

jcruz · Jan 29, 2011

ydtech said:
Is it for a temperature ramp, with set-point increasing over time?

Its for a system to dry fruits, so my client needs to define 16 temperature setpoints and 16 times setpoints, the systems start to heating to to achieve the temperature setpoint 1 at the end of a time setpoint 1, after the same thing with the second and up to 16 setpoints.

jcruz · Jan 29, 2011

Dry fruits system

Its for a system to dry fruits, so my client needs to define 16 temperature setpoints and 16 times setpoints, the systems start to heating to to achieve the temperature setpoint 1 at the end of a time setpoint 1, after the same thing with the second and up to 16 setpoints.

John Gaunt · Jan 29, 2011

Just use a PID for temperature control and other logic to update the PID setpoint in small steps according to the time/temperature curve.

Temperature regulation

jcruz

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Tom Jenkins

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TConnolly

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ydtech

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jcruz

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John Gaunt

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