Need PID oven controller - Page 1
Forum section: electronics / projects

author: Rachie5272
author_rank: Regular Contributor
timestamp: August 07, 2016, 06:07:54 pm
content: I'm building an oven for curing composite materials, and need a PID temperature controller and timer. There are a plethora of PID controllers all over ebay, but they all seem to be clones of clones, and none of them have timers. Even an Omega controller I had laying around didn't have this function, and had an atrocious user interface as well.Can anyone suggest what to get? I only need a fairly simple profile: ramp up to a specified temperature, hold for a few hours, ramp down to ambient temperature, and off.

author: SeanB
author_rank: Super Contributor
timestamp: August 07, 2016, 06:16:44 pm
content: With most controllers you can set a rate of rise in the settings, so you can have a controlled rise to temperature over a period of time. Then use the alarm output, which is also programmable on them, to start the separate timer. At the end the timer simply turns off the temperature controller, allowing the cooling to ambient to occur.Available on BTC and Omron PID controllers, and you just have to get the version with alarm output to use it, or open the controller on those with that as option and add the small 24VDC low current relay on the board.For sanity sake I would also recommend getting a datalogger and using it to measure the profile for every run, so that you will pick up almost immediately if there is a cycle where you did not reach setpoint, or held it for too short a time. As I assume you will be doing this cure overnight there otherwise would be no indication that there was a fault otherwise. 2 channel logger to measure both temperature and the power to the heaters, so you can see duty cycle on them, and this will tell you if one fails from the increased duty cycle with otherwise no other indication.As to the programming interface, what else do you expect with only 3 keys to set everything, simply make a copy of the manual and stuff it in the control box, so that it is easy to refer to it when needed. There are controllers that you can program over RS 445, but that leads to another entire level of suckiness on the horrid clunky controller programming, which often required WinXP ( at a defined service pack level as well, nothing newer than SP1 in some cases) and a special version of IE with customised ActiveX controls for it, and a real serial ( no FTDI or Prolific, has to be genuine 16550 UART register set on the south bridge) port to actually work.

author: ConKbot
author_rank: Super Contributor
timestamp: August 07, 2016, 06:54:30 pm
content: Id suggest a seperate timer. We have an oven at work with a very nice controller, and only one person can make the timer function work. Even with then manual in hand I can never seem to make it work. The 3 button/4 character interface on a controller with ramping, stages, timing etc is pure garbage to use for every day adjustment, more suited to program once and leave it.One of the buttons on it is slowly failing, and it will be replaced with a pid temp controller and timer when I can find time.

author: uncle_bob
author_rank: Unknown
timestamp: August 07, 2016, 11:29:31 pm
content: HiThe gotcha is that as soon as you go from eBay to the "real world" the prices jump. What sort of budget do you have? Is $50 to much? Is $1,000 OK?Bob

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: August 07, 2016, 11:58:28 pm
content: I haven't used the ramp/soak function, but I know they exist on the Delta DTB series.http://www.delta-americas.com/Products/CategoryListT1.aspx?CID=060405&PID=1509&hl=en-US&Name=DTB%20Serieshttp://www.deltaww.com/filecenter/Products/download/06/060405/Catalogue/DELTA_IA-SS_DT_C_EN_20160204.pdfThese have an RS485 (modbus) interface, which you can use to program them if you'd rather not navigate the terrible UI on the front panel. This also helps to log the process temperature without needing a separate data logger. The DTCOM windows software helps set it up as well.

author: Seekonk
author_rank: Super Contributor
timestamp: August 08, 2016, 01:22:30 am
content: Those $15 ebay PID controllers are sufficient for most applications. Industry only used P for a long time. Don't be lulled into thinking autotune actually works well. No one takes it seriously. Some sort of charting is a must if you want fine tuning of the system. It doesn't have to be expensive. Even a cheap $65 Hantek USB digital scope has 83 minutes per division.

author: whalphen
author_rank: Regular Contributor
timestamp: August 08, 2016, 02:03:39 am
content: Auber Instruments sells some reasonably priced PID controllers. I've used one of these for my homebrew reflow oven for a few years and never have had a problem with it. Check the manuals to make sure you get one that's programmable. Many of the cheap controllers require manually changing the setpoint.http://www.auberins.com/index.php?main_page=index&cPath=1&sort=20a&page=1

author: ja421
author_rank: Contributor
timestamp: August 08, 2016, 02:33:26 am
content: I have used OSPID (available at rocketscream.com) and rocketscreams own reflow shield.OSPID is a little more work, but gives you tons of information and a pc-based graph showing it's progress.The reflow shield is a lot easier to use, but harder if you want to remap the curve.The cheap ebay ones work, but don't offer a true curve (at least the one I bought) -- I use the cheap ebay one to control a hot plate for pre-soldering/warming pcb's.There's a couple of reflow controllers on tindie; but if I were to recommend one or the other, I'd say RocketScream's Shield is worth it.

author: Rachie5272
author_rank: Regular Contributor
timestamp: August 08, 2016, 04:58:03 pm
content: I don't understand the three button limit. Why does everyone copy the worst feature of otherwise decent controllers? Even with the manual, programming barely makes sense. I tried one controller which claimed to have RS-232, but I couldn't get it to work at all.OSPID looks neat, but they're out of stock.Pico Reflowlooks neat too, but it's entirely DIY.Data logging would be great as well. As would ethernet/wifi. I doubt I can get these on a $200 budget though, unless I build it myself.

author: SeanB
author_rank: Super Contributor
timestamp: August 08, 2016, 06:48:02 pm
content: 99.9% of these controllers are used in an industrial use, where you only set it up once, then it will only need the occasional setpoint adjustment. You are limited as well by the need to fit the industry standard cutout ( choose any one that has the word DIN in it for size) plus have a bright easy to read display that works in both direct sunlight and in a dark recess of a cabinet. Thus you get a 7 segment display or two, and there is only room for 3 or 4 buttons after that.Be glad you have not met those with only a single button, where the duration of press determines if it is an increment, digit select or enter programming mode.