Comments on: Extruder PID Temperature Controller

By: madscifi

madscifi — Wed, 07 Apr 2010 02:48:11 +0000

… and the answer turns out to be a bug in my understanding. If I had spent 30 seconds to work out the algebra, I would have known that the two different approaches actually calculate exactly the same thing.

I’m going to go hide under a rock now.

By: madscifi

madscifi — Tue, 06 Apr 2010 06:17:16 +0000

I’m not an expert on PID design, but it seems that the code is taking the derivative of the input (temperature) and not of the error. Is there a reason for this?

Fragment of code:

dTerm = temp_dGain * (current_temperature – temp_dState);
temp_dState = current_temperature;

I would expect the fragment to be:

dTerm = temp_dGain * (error – temp_dState);
temp_dState = error;

Bug in the code or a bug in my understanding of PID?

–Jim

By: Tim

Tim — Thu, 10 Dec 2009 21:34:49 +0000

I’m working on a two channel temperature controller board right now. I’ve got it assembled and working here on my desktop. More info soon…

By: Prober

Prober — Wed, 09 Dec 2009 16:32:58 +0000

You made my day! Great thinking. Just wondering could a second temp reading i.e. the temp of the air inside the cabinet be sent to the Arduino to control the temperature?

By: Matt

Matt — Tue, 13 Oct 2009 21:58:11 +0000

Looking good. Whenever you get a chance put up the video of it moving !

By: Geert Bosch

Geert Bosch — Mon, 05 Oct 2009 19:23:14 +0000

Hi Tim,

You beat me to the punch. I had cooked up my own PID code, but not yet published it, as I decided to first redo the temperature reading code to get high resolution readings. I’ll try merging that with your changes, so we’ll have better info for the D part of the signal.

-Geert

By: Open Source FTW - MakerBot Industries

Open Source FTW - MakerBot Industries — Thu, 01 Oct 2009 21:45:47 +0000

[...] Tim at BotHacker coded up a patch which implements PID on the heater. The result is much, much better temperature control, yielding a smoother extrusion and less [...]