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| What will furnace pid values actually look like? |
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| SeanB:
This just begs for an off the shelf fully digital PIC industrial controller, from Omron, Braintech or such, that literally is programmed by selecting the ranges, the inputs and desired mode, then selecting "Auto Tune" which then ramps up the power in a controlled manner and sets all those parameters just by rate of rise initially then predicting the setpoint and adjusting to reach it with minimal overshoot. Simple DIN size panel cutout and you probably want a version with analogue output rather than a SSR or relay output, so you can control your power input using a 0-5V/10V/4-20mA or so signal, and in general they all come with input sensor failure detection, and in many there are auxillary relay connections that can be used for alarm, ready, fast heat or whatever control function based on either temperature or time or fault. The DIN units are reasonably RF immune as well, and the power needs are well defined. |
| coppercone2:
I really wanna try to do this myself. Any idea what the PID terms would actually look like from something autotuned, realistically? I don't have a good process model, I have a feeling that process time based on the most basic equations is gonna be off significantly. But I am pretty sure I will be able to put values in a circuit that will have the right order of magnitude for tuning, which can then be zoomed in. I will just make a little more space, chassis height and larger pads for the integrator and differentiator op-amps in case I need to change capacitors etc. |
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