PID controller woes

I’ve been having trouble with my composites oven. I think it lies in two areas:

  1. it’s a little leaky – can be fixed with a bit of expanding foam and a more careful cut of the kingspan i’ve used to make it. I could build a wooden frame for it as well, but that seems a lot of faff
  2. The sestos PID controller I have is a bit hard to use – it’s well understood the chinglish instructions are abominable.

So, how to fettle this myself?

I’ve found this great page at which gives a great description of what the variables mean and how to set up a PID. Now at least I am armed with the info I need to fix this.

I’m actually thinking of making my own and the plan is:

  • keep the triad switch for the oven, fan, etc.
  • write a C++ application to do the PID control from a PC
  • configure multiple ramping profiles that are saved and can be selected at will
  • the application can have multiple learning points, so the PID can be most efficient at each ramping step
  • use a pair of xbees to provide wireless sensing and control of the oven
  • have 3 temperature sensors – two in the oven and one for ambient temperature
  • have a set of fans in the oven as well as the initial fan so that hot-spots can be eliminated
  • logging so you can see what the temp was doing

Saying that, there’s also this quite sophisticated controller which does most of the above and has a serial interface and instructions in English. So, I could write the application to control the PID and just use it for logging – but I wouldn’t get the wireless control of the oven (mine is in the shed).

Your thoughts?

Choices, choices.

2 thoughts on “PID controller woes

    • Well, if I’m going microcontroller, I’d go Arduino. However I am happy to go on and do it using xbees (they have three analogue IO and 3 digital IO which are network addressable) – then it’s just knock up a simple C++ app in Embarcadero. However, the second controller I linked to has a cousin that sells for £75 which is serial addressable and also has an application for configuration and logging – this will save me a shed load of time. If I still want it to be wireless, I can just put a pair of xbees in there – they make wireless serial be transparent – it just appears as either /dev/tty/ or COM depending on unix or windows.

Feed the attention-whore