@WBM,

Did you have any luck with the variables I asked about? I’ve been playing around with the frontend some more and I’m getting pretty excited.

Thanks.

@WBM,

Did you have any luck with the variables I asked about? I’ve been playing around with the frontend some more and I’m getting pretty excited.

Thanks.

Thanks for the prompt! Had fallen off my radar.

That is looking pretty sweet - I look forward to hearing about how it goes.

The website I took the formula from is here http://www.vandelogt.nl/uk_regelen_pid.php#PID3

There is a guide as to how to tune the calculations - see paragraph 3.

It is pretty difficult to follow unfortunately and requires some maths. I used the spreadsheet attached to help - I believe I would have pasted in the log from smartthings.

Midway down the linked page is come code - in this it defines k0 and k1 as this:

Kc.Ts k0 = ----- (for I-term) Ti Td k1 = Kc . – (for D-term) Ts

This means you need to work out Kc, Ts, Ti and Td to know all three of k0, k1 and kc.

I am assuming that the “.” in the calculations was also a reference to multiplication.

As for what Kc, Ts, Ti and Td mean:

Kc: The controller gain Ti: Time-constant for the Integral Gain Td: Time-constant for the Derivative Gain Ts: The sample period [seconds]

I think that smartthings has a limit as to how often the temperature can be updated and checked so I imagine that I set Ts to match this period in seconds (e.g. 60 seconds).

**Dead-Time (TD)**: the dead-time of the system is the time delay between the initial response and a 10 % increase in the process variable (which is the HLT temperature in our case). Unity is given in seconds.

I then think that I plugged in the various numbers to work out an approximate gradient for the graph which then meant I could use that in para 3.3 to get the final numbers.

Sorry this is probably a lot of information to digest. If you can’t follow the link, let me know and I’ll try and decipher exactly what I did.

(Attachment temp pid tune.xlsx is missing)

Thank you! I’ll take a look at this and see if I have any questions. This should get me started for now as I tinker along with the process.

FYI…I just noticed that it says the attachment is missing. Can you try uploading again?