Help with Mypin TD4-SNR PID. Overshooting temp by large amount

I am in the middle of building a KAL clone style system and I used Mypin PID's. I can not get accurate temperature control. I have done my best to understand the horrible English in the manual, but that really doesn't help.

When I am mashing, my temps do not hold at all. I will set for say 140 and the range will be from 139 - 149. I do not know what is wrong and I am going crazy! The overshooting happens at any set temp, not just 140 btw. I have tried to do autotune a few times and that doesn't seem to help. I have noticed the PID is sending out flickering on and off heat signals even when the temp is a few degrees over my target.

What am I doing wrong!

Thanks for the ideas in advance.

 

Try to set an "i" parameter to 1 or so.

 

Where are you measuring your temperature at? What is your process for mashing? I think we need a little more before a possible solution can be found.

 

I have measured my temp with a termapen in various spots to confirm. My rtd goes through my sight glass about 1/3 of the way up in the water. My pot is a keggle.

As to my mash process, I brought my water to mash temps then mixed in the grains. I have tested this problem though since then with just water a few times with no better luck. I did tighten things up a little yesterday by turning the P value all the way down to .1. Now it will bounce from the target by only about 3 degrees on average. Always higher though never really below.

 

Are you circulating at all during your mash? If not, I'd attribute this issue with that alone. Temperatures can very vastly from one spot to the next, especially when there's a mash going on. I've used a thermometer in one spot of the mash and then moved it 1 inch to the next side and there a couple degree difference. If you want 100% constant throughout your whole mash, you'll need to do some sort of re-circulation or constant mixing.

 

I was stirring ever few minutes. Didn't really help. I think the issue is that the Pid is turning the heater on even when I am already way over the set temp by few degrees.

 

Ok. From your mash process, it sounds like your doing BIAB. Is that right? If so, then I'd still try to recirculate throughout the whole mash and see what that does. Or do a water test trying this to see if it helps steady out temps.

If not, it still sounds like stratification. Other than that, I'm out of the running for ideas. If you've run auto tune and that didn't help, then the next culprit is usually probe placement.

 

Oops wasn't clear, sorry. Yes I I am biab. I have another probe for when I switch to 3 vessel so I tried hanging it into the pot and trying it at various locations. That's didn't help, so it's not probe placement.

I really think it is pid settings. Why would it be firing heat if my target was 150 and the pid temp readout was showing me at 154? That has nothing to do with the probe or circulation. I regret not going with an auber pid.

 

Well there are for sure stories of the My Pin's doing weird things. I've got 2 of them and they work perfectly. Maintaining temps in a RIMS tube practically to the degree of the ST.

Others will hopefully chime in here to shed light on other possible causes. Good luck.

 

Here is an example. Whole my temp was dropping, it never made it below 1.5 degrees over my target temp and then shot back to 5 degrees over target right after I stopped recording yesterday.

[ame]http://youtu.be/JWShIoPUXow[/ame]

 

It looks like it's "trying" to maintain a temp just not the right one. Could be something with the settings, but I haven't delved to far into them because they're so hard to understand with that great manual.

 

From the OP it sounds like you haven't done a good auto tune. What issues were you running into with that? Sounds to me like it doesn't know how long it needs to fire to raise temps.

 

I have autotuned, a few times actually. They seemed to go fine, it just didn't make it good temp any better afterwards.

 

P value should be bigger. .The I value responsible for an overhot. Set I to minimum (but not for a 0).
Try to set P=5, D =3, I=1

 

It could be that your flame is too high. I had the same problem and found that I had to lower the flame to avoid going over the set temp on the PID. It doesn't take much to warm the mash tun 1°F. When you do your strike temp, set the PID temp 5°F below your target temp and let the flame rip (high flame). You will find that when the flame goes out, the temp will continue to rise about 5°F within a minute or so. Also, moving the temp range to +/- 1° will keep it within 1° to 2° if your flame is low enough.


Good luck,

 

Thanks but I'm all electric. No flame, I'm using a water heater element.

 

Then, is the voltage too high? Remember that energy is stored as heat in surrounding metal. Once you turn off the element, the wort draws back in the heat it stored increasing the heat even though it is turned off. Thinking out loud.


Cheers,

 

For starters, the cycle time should be less than the time constant of the system. Is it?

 

I'm not sure what you mean?

 

I found the Mypin controllers to have terrible auto-tuning.
What exactly are your P, I, and D values?

 

Working on one of these myself right now. "I" is 240 by default on this thing. Its storing too many data points from early on the heating curve and projecting that you mash is going to cool faster than it actually is. I just set mine to 1 as suggest above and we're now AOK.