+ PID Temperature Controller Teardown
Last weekend, I went to the Guangzhou markets with my buddy Matt. There was lots of good stuff there, but one of the things that caught my eye were these PID temperature controller modules. Its the sort of industrial process control gear that is normally inaccessible to mortals. Fortunately for me, this was China, so I plunked down 80yuan and took one home with me.
The unit is an elongated cube with interface on one side and terminals on the other. Its got a schematic silkscreened on one side to make hooking it up possible without a reference manual. Pretty snazzy.
Getting inside was pretty easy. The thing has tabs that you press and all the guts slide right out.
The first thing I noticed was that the interior is pretty much all PCB. There are 3 PCBs + the terminal block that are all soldered together for electrical and mechanical strength.
Elsewhere there 2 PCBs connecting. They designed pads onto each PCB where they needed to connect. Then someone simply bridged the pads with solder. Very clever. Not the strongest connection in the world, but it is certainly cheap and effective.
The interface board is interesting. Nothing too fancy here. A couple buttons, some LEDs, and some 7-segment displays. Nice and simple.
The board appears to be controlled by an Atmega and they kindly left the ICSP header exposed and labeled. Probably for their manufacturing process, but if I wanted to hack this device I could load my own firmware too.
+ Wiring it up
The controller is powered with AC wall current (110-230v) so I hacked up a power cable to control it. I took a thermocouple and a heater cartridge and taped them together with Kapton. I wired up my desktop bench supply to provide current to the heater.
Unfortunately my PID settings were way off and this thing has too many options that I didn’t want to mess with. After a couple minutes though it settled in an the appropriate temperature.
Nice teardown! It seems the form factor is pretty similar to the open source osPID controller http://www.ospid.com/blog/
Saw this on reddit. Was hoping to see the controller portion if you get a chance.
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Yeah, I scored one of these for $20 on FleaBay, of course free postage and no tax. ‘Even came with a free thermocouple and complete documentation. i.e. Input can be TC, platinum (or copper or iron) resistance sensors too! I plan to use it for a large “oven” which creates a stable environment for my high precision temperature calibration equipment. Of course, protective over temp thermostats are already built into the old electric blanket which will be my 200 watt heater.
Nice teardown! But fwiw re: “… normally inaccessible to mortals,” um… ask eBay about “PID temperature” and you’ll find many options from ~$20 on up, often with thermocouples. These things are amazing– a lot in a little box for cheap– and happily accessible to anyone 🙂
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