Here is the reconfigured oven. I reckon I could easily cook two humans in there without too much legwork.
So, I and many others it seems, have been struggling to set up their Sestos D1S controller. It was a great buy, about £35 from ebay with a solid state relay and thermocouple. I can’t complain about that. It was also relatively easy to wire into the oven I’d made. I put this together with a load of kingspan and the internals of a domestic fan oven I’d wombed up (again from ebay) for £10. Add a project case and some other bits and wire and we’re off. It went together and in theory powered up properly. The light on the front came on, the relay activated and the element came on. From that though, it never really settled on to a value; it would just overshoot in an unnerving way. What you’re meant to do is let it auto-tune itself (which can take a few hours) and then it should be super-lovely. What actually happens is:
- you read the manufactures instructions and realise that the single sheet of A4 isn’t going to help. You scratch your head, you have a go at fiddling with it, and it makes no sense. So you stop.
- Then what happens is you go googling and find a whole bunch of people who’d had issues with this (weirdly brewers and gourmets from America) and I found this far more excellent page from a chap I think is called Claes Junk. It gives great instructions about how to set up the controller, but doesn’t help with the auto tune I’m struggling with.
- You throw your hands in the air and buy a PID from a different spot – I ebay’d PID controllers, and went looking for distance nearest first from my house. I found Simon at Harrogate Automation Controls who has a massive amount of PIDs and other magnificent bits of gear. He knows his stuff and had things like cabinets and contractors to PIDs and compressors. We spent a happy hour chatting and I came away with a new controller for an outstanding price
- Feeling like your oven is getting a new start, you ring Warren and tell him what you’ve done, and he also reminds you that he has the same PID and his works. So, I got Warren to give me his config and I fed it in
- Now it kind of works, but it overshoots by 10 degrees. It doesn’t overshoot and then nicely hold the new temperature, but wavers around +- 10 degrees.
- Yo go back to Claes’ instructions and rerun the autoconfig.
- forget you’d left it on and leave it running overnight
- Bugger me – it works. rather than finding fire, I found a nicely working oven which was holding the temperature within 0.2 degrees.
So, for those of you wanting to configure your Sestos, do what I did and lift my config values (below) and then run the auto-config. The ones that matter are:
|CTRL||Control output (3 = PID)||3|
Thus endeth the lesson
I’ve been having trouble with my composites oven. I think it lies in two areas:
- 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
- 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’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).
So, every good shed needs an oven. Oh, and a work-bench. Bearing this in mind, it make sense to combine the two, and put it on castors so I can move it about.
I have made the bench deep and that’s for two reasons. Firstly, one needs a lot of room to lay up parts. Secondly that was the quickest way to make it using roofing boards and pressed boards. They’re already pre-cut to a certain size so there was less jig-saw action.
Here it is laid out and on castors. What I didn’t realise is that the roofing boards aren’t remotely stiff on their own so there’s some reinforcing under the floor to hold it all together. Once the sizes are on and the top is on, it will get more rigid.
Sides are on. Top is on. It’s now stiffer, but not fully priapic.
Here’s a perspective of the bench – big innit?
In the true spirit of being an oven, I dismantled an oven I got from ebay for £10. All the wiring and controls get gutted, and it’s a simple wiring job after that. Fans and lights are always on (rather than under control of the controls) and the element itself is under control of the PID controller.
Here is the PID arrangement. Again, £30 from ebay gets you a PID and a very heavy duty solid state relay. The case and assorted bits and pieces came from maplin. You can see two bolts on the front there, where the solid state relay is bolted to the case to act as a bit of a heat-sink if needed. The 3-pin plug on the front is the output power supply for the heating element. I deliberately did it this way in case I then wanted to power something like a convection-air heater or summit else. Up the back of it is a kettle-lead which powers the PID. The kettle-lead is hard-wired into the main power of the oven. If the oven is plugged in, the fans are always on and the PID is powered. You can’t have heat without fans.
The oven now needs king-span to insulate it (sat in the garage gathering dust) and a thorough soak-testing with a fire-extinguisher near by to be sure it works. I don’t think I’ll be leaving it unattended but at least it’s in a shed if there is a fire.