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Old 09-05-2012, 08:53 PM   #1
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Default Has anyone had a Sestos PID controller working ?

I recently bought a Sestos D1S PID temperature controller, but I am finding it very difficult to get it to work as expected. I have poured over the manual, and even read the Auber manual to no avail.

I think my main problem is that the Control period seems to be much longer than I expect. These are the settings I have programmed into it:

  • dF 0.3 (Hysteresis)
  • Ctrl 3 (PID mode)
  • M50 0 (Integral)
  • P 1000 (Proportional?)
  • t 0 (Derivative?)
  • Ctl 1 (Control Period: 1 second)
  • oP1 0 (Output method: Time Duty)
  • oPL 0 (Output minimum: 0%)
  • oPH 50 (Output maximum: 50%)
  • run 1 (Automatic)

If you press the SET button, yo can switch the display between showing the SV (set value) and the output level. It's currently showing 'A 50', which means 50% output duty. With a control period of 1, I would expect the output to be on for 0.5s, then off for 0.5s. However, what I'm seeing is the output is on for 35s, then off for 35s!

Is this what I should expect? Can someone verify this behaviour on their device?

Many thanks in advance.

Hugo
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Old 09-05-2012, 09:14 PM   #2
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After a bit more experimentation, I am pretty sure there is a bug in the Sestos for low control periods. I tried several Ctl values, and recorded the following periods:

Ctl Period
40 = 40s
20 = 20s
10 = 10s
8 = 8s
6 = 6s
4 = 4s
3 = 3s
2 = 2s
1 = 1s
0 = 0s

Has anyone else had any success with short control periods?

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Old 09-05-2012, 11:38 PM   #3
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oops, there was a typo in the previous post. Those numbers should have been

Ctl Period
40 = 40s
20 = 20s
10 = 10s
8 = 8s
6 = 8s
4 = 8s
3 = 8s
2 = 70s
1 = 70s
0 = 70s

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Old 09-05-2012, 11:54 PM   #4
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Ive had a few, so take this advice with a grain of salt.

In auto mode you the controller should be handling its on off cycles internally.

In manual mode you simply dial in a percentage, say 50%, and during your control cycle, the element will be on 50% of the time. If that cycle was 10s, then it would be on 5s, off 5s.

You shouldnt be using the manual mode when holding a very specific temperture is important.

You will find that in auto mode as you begin to hit your temp, the PID will cycle the element off and on periodically in order to not overshoot.

Hope this helps. If I misunderstood your question I apologize

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Old 09-06-2012, 11:42 AM   #5
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Hi aquenne,

Thanks for the reply. I'm familiar with PID controllers (I'm a robotic engineer and have created many PID controllers myself). I know what the Sestos is supposed to do. My problem is that it doesn't seem to be doing what I expect, and the terrible manual doesn't help.

Have you managed to get one working?

Did you manage to get it to auto tune properly? When mine auto tunes, it comes up with stupid settings, which simply boil the water rather than holding the 50ºC temperature I ask for.

Have you tried setting a control period less than 8? Does it have the effect you expect, or does it produce control periods of 70s?

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Old 09-06-2012, 12:28 PM   #6
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Hey,

Yes I have had a Sesto's working for around 8 months now. It worked right from the get go, I followed the Auber manual, a few of the settings are named slightly different but they are in the same order as the Auber as you cycle thru them.

Yes I have run the auto tune a few times. The process I went thru when auto tunning was take the temp to within about 20 degrees of your typical set point (for my setup the PID controls the HLT element (HERMS setup)).. so I normally want that around 155-160 for mashing. So I take it to 140. Turn off the PID, then restart and place it in the auto tune mode with a 155 setpoint. It will overshoot a few times and dial in the P, I and D gains.

In terms of control period, I have mine set for 10s, which I find is absolutely fine for the process I run. I am only using the manual mode for boiling, nothing temperature critical.

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Old 09-06-2012, 12:31 PM   #7
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Was the red output light on the PID lit after the actual temperature passed 50deg?

If it wasnt, I would check your SSR to see if it is operating normally. I actually went thru a couple SSR's (cheap china ebay specials), until i got one that works fine. I was having the same problem as what you desrcibed.

If the red output light remained lit after it passed the checkpoint, and you verified that there is voltage present at the SSR terminals of the PID i would say you may have a defective PID.

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Old 09-06-2012, 04:30 PM   #8
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Yes, the red 'Out' light on the front of the Sestos came on and stayed on for quite a few seconds while the temperature soared about 30ºC above the setpoint. This was way longer than the control period. When I checked the PID settings, I had been auto tuned to 9999! This is clearly a nonsense value, and could have been responsible for the bad behaviour. This has happened twice.

The SSR is operating correctly. The red 'Out' light, the SSR light, and the Kettle light all go on and off at the same time.

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Old 09-06-2012, 04:31 PM   #9
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If you have time, would you be able to check if your Sestos is able to do a control period less than 8? (Especially less than 3).

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Old 09-06-2012, 05:58 PM   #10
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Unfortunately, im in the midst of an major brewery upgrade which most likely wont be completed until my return from Oktoberfest (yes.. Germany ..)

Sorry, if you still need the assistance when I have things setup, I would be more than happy make that change.

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