Hi all, I think the decision whether to use an Arduino or some off-the-shelf PID controllers will not influence the total implementation effort too much, since the main effort probably goes into following the temperature profile over time. Even with an off-the-shelf controller (thermostat?) you still need some piece of software to run the profile. I’m not so sure if PID is really applicable here. You’ll basically just switch the heating elements on or off, so it’s a binary control. Unless you need a very high accuracy, I’d assume that a simple threshold/hysteresis based scheme (as in a household oven) would do fine. I think even the smallest of Arduino boards is up to the task. I agree with Nathan thas some means for logging the temperature data (e.g. an SD card) makes sense. An RTC module may be nice to have, but is not so essential. Relative time measurements can be done with the internal timers of the microcontroller, you just won’t know the exact time of day, which does not really make much difference anyway. DS18B20 temperature sensors are a good choice as long as the temperature does not exceed 125 degrees C (257 degrees F ?). They can be bought already mounted inside a little stainless steel tube and with a cable attached for around one dollar a piece. For higher temperatures your best choice would probably be thermocouples, which require some extra amplifier circuitry (not very cheap) to get the temperature value. Regarding heaters and fans: Would it be worth considering the use of electric hair driers or hot air guns? That might save some work regarding proper (and safe!) mounting of the heating elements. Cost might also be lower than buying the components individually. Have a good day! Mattias From: sugarshot-bounce@xxxxxxxxxxxxx [mailto:sugarshot-bounce@xxxxxxxxxxxxx] On Behalf Of Nathan Asdourian Sent: Monday, June 30, 2014 8:41 AM To: sugarshot@xxxxxxxxxxxxx Subject: [SS2S-Main] Re: temperature controller with arduino I'm a bit on the fence with the whole thing. On one hand ive had a reasonably good time helping a guy in france develop and refine an arduino plugin module for the home automation program homeseer. When I stumbled upon his project, the core module was semi reliable but had connection issues, used up enough of the available ram that the ide wasnt too happy, and had horribly duplicated code eating up like 80% of the flash. I looked at his sketch and without even really understanding all of it, I managed to help him isolate the two pieces which function independantly so the compiler knew which set of code to leave out, as well as an exhaustive review of his almost sinful was of ram due to which datatypes he used and just storage in general. That said, it should be taken into consideration that you could get an actual pid controller for around the same price as an arduino uno r3. Granted that is direct from china or Taiwan, but really with the available budget I dont think being picky is a reasonable thing. About the only thing that could keep going with the arduino reasonable is if we(the people in this conversation) are willing and able to donate most of the necessary hardware. The way I see it, we would need an arduino board, uno being the lowest, mega offers significantly more memory. Or possibly the due which is much more powerful as it is 32bit. Also needed are compatible thermocouples, I did see someplace you can get stainless steel tubes that a ds18b20 slides right into, I just havent checked on operating temps vs the temps you will be at. I imagine a rtc module will be necessary otherwise you may as well base the time on when your mother uses the restroom. An sd card slot should be included to facilitate logging the various temps and burner status. This will provide proof of the parameters and eliminate the question of if a part was cooked right. As for what I am prepared to offer up, here goes... I saw there was already an offer from a someone to write the arduino code, I can offer code review and collaboration, assuming your willing to put the code up on githib so we can easily communicate back and forth on multiple subjects without losing track of things. Assuming that the ds18b20 is used, I can also relatively quickly set up a test setup to validate the code and attempt to pinpoint any issues, which I would do with my own hardware I already have or will purchase on my own so no shipping involved. Hardware wise I can offer up a combo micro sd and sd adapter board, which has a switch to select card type. I also have a spare rtc I can dig out. Ds18b20's can be aquired for free via maxims samples program, you can order up to 2 of each kind, and last time I did it, I think there were 5 different versions available, all mostly the same, a couple were surface mount which makes using it as a probe difficult. I can also offer up soldering if needed. I consider myself well above average with an iron, and the fact I have a hakko fx-951 certainly doesnt hurt any. I think that about wraps it up for me, back to lurking unless its decided to go the arduino route, in which case just let me know. On Jun 29, 2014 3:53 PM, "Peter Johansson" <rockets4kids@xxxxxxxxx<mailto:rockets4kids@xxxxxxxxx>> wrote: On Sun, Jun 29, 2014 at 6:36 PM, Vicente Alvero Zambrano <vicente_alvero_14@xxxxxxxxxxx<mailto:vicente_alvero_14@xxxxxxxxxxx>> wrote: > My idea is to use an old oven heater like the picture. > With respect to the PID controller, maybe it is cheaper to do it manually, > without writing code. One option to consider -- and an advantage to going with a homebrew solution -- is to simply read a configuration file containing the temperature profile and PID tunings over over the serial port. This way you get the maximal possible control with the minimal hardware cost and minimal software development time. -p.