PID-filter routine (2nd try).

[andywpg]

Hi,

One thing you might consider is to run the heater/fan/furnace whatever "open loop" until the temperature starts to approach the setpoint and only then switch on the PID. A more elegant but also a bit more complicated way is to create a ramping action in a way that the setpoint, instead of being bumped from ambient to "working temp" is ramped up at a rate that the "plant" can actually follow.

I had actually planned to run the fan in manual mode until I am near the setpoint, then allow the PID loop to take over in auto mode.

The other question I had is on the reset. In the example, it is set to .5. What causes the integral ramp to get steeper? Would that be an increase in the number? What kind of range of numbers are you expecting on the reset .1 to 1 or even higher than that?

BTW, while running it in simulation last night, I discovered that a derivative of 0 causes unpredictable results - to remove the derivative, you have to set it to 1.

In my reading and conversations with people who deal with PID (one of which was an instructor at a local community college) I am told that temperature control only requires process and integral, not derivative.

Thanks again,

Andy