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Old 05-13-2012, 01:25 AM   #1
SimBrew
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Default PID settings on arduino based hlt

I got a arduino controlled hlt with 1500w element heating like 5 gal.

I overshoot my setpoint by about 10 F.

The integral is too slow to shut the element off once it get to the setpoint

My process class are far away and I don't have a lot of time with the kid to test differents settings.

What are your PID settings on setup like mine ?

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Old 05-13-2012, 07:21 PM   #2
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I haven't gotten to the HLT part yet, but I've got an Arduino controlled crockpot going here. I used this library to determine the correct p, i, & d.

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Old 05-14-2012, 01:38 AM   #3
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I will try for sure.
Would you happen to have your autotune code ?

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Old 05-14-2012, 11:13 AM   #4
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Quote:
Originally Posted by SimBrew
I will try for sure.
Would you happen to have your autotune code ?
I'm pretty sure I do. It's the same as what's right there on the site, though, with two minor exceptions.

- I added what I needed to get a Fahrenheit setpoint and readout in the serial monitor from a DS18B20

- I did a cut & paste swap of the part from the 'to control a relay' example, also located on that site.

I have *not* been successful getting the front end up in Processing, though. I just opened up a serial monitor in the Arduino IDE.
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Old 05-15-2012, 01:49 AM   #5
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I just got the autotune up and running on my arduino HERMS. How long did it take for the Auto tune to run?

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Old 05-15-2012, 04:08 AM   #6
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FOREVER! Or so it seems. Maybe 6 heat/cool cycles? In my crockpot, that must have been a couple of hours or so.

I watched Hudson Hawk while it ran.

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Old 05-15-2012, 04:13 AM   #7
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Oh... if this is obvious, forgive me for bringing it up.

Watch that last line just before void setup(), it will run a simulation until you change that value to false.

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Old 05-15-2012, 11:12 AM   #8
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Quote:
Originally Posted by chuckjaxfl View Post
FOREVER! Or so it seems. Maybe 6 heat/cool cycles? In my crockpot, that must have been a couple of hours or so.

I watched Hudson Hawk while it ran.
Thanks. I tried running it last night on my brewery and it about 2 hours for it to get to the setpoint once. My setpoint is at 154. The output would only go to 50. I will look at my code and try running it again tonight.

When I first ran i had it in simulation mode as you said and took me a couple of minutes to find the line to change it to tuning mode.
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Old 05-16-2012, 01:16 AM   #9
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Quote:
Originally Posted by SimBrew View Post
The integral is too slow to shut the element off once it get to the setpoint
This is a slow, integrating temperature loop. You don't want a lot of integral gain in this type of loop, because it will cause unnecessary controller windup.
Integral is not going to do anything at setpoint. More derivative can help to decrease overshoot. In fact, more proportional will help get your output high enough when you are far from setpoint but bring it down as you approach setpoint.

All of these suggestion are assuming your heating element is appropriately sized.
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Old 05-16-2012, 01:54 AM   #10
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TO chuckjaxfl:

Do you mind sharing your code. I cant get the auto tune portion to work. I don't have a problem reading temperatures and even have the arduino send outputs to processing but cant seem to get the auto tune to work correctly.

Thanks in Advance.

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