spirilis 1,265 Posted June 5, 2013 Share Posted June 5, 2013 Starting this thread to chronicle my experiences building a solder reflow rig! I've had http://forum.43oh.com/topic/3495-group-buy-13msp430-reflow-oven-controler/ wulfman/yyrkoon's reflow control board for a short while now and I'm just getting around to making use of it. My plan is to use an electric skillet similar to this Sparkfun article -- https://www.sparkfun.com/tutorials/59 I finally bought the skillet yesterday and tested the thermocouple wulfman supplied with my multimeter that happens to have a K-type thermocouple driver built in- Did a mock run with one of my F5172 launchpad boards where I controlled it manually, got it hot enough to melt the solder but I don't think I let it sit long enough... Took it off & suspended it in mid-air for 10 seconds, then my hand slipped and the board flipped onto the floor with SMD components flying all over the place :grin: Whoops. Recovered all the high-dollar SMD components though so I'm going to give it another try soon once I get the reflow control board all hooked up & programmed. FYI I'm using a lead-based solder paste and just applying it by hand with a small wooden matchstick (minus the striker part)- http://www.ebay.com/itm/Kester-EP256-Lead-Solder-Paste-63-37-Syringe-Disp-Pak-/230916973401?pt=LH_DefaultDomain_0&hash=item35c3b96359 Going to just try using the attached needle to meter it out next time. I don't have a stencil for this board nor any rig to properly secure it while I apply the paste so that's another project for a later day. Next step is buying a suitable AC jack from the local home improvement store so I can get the reflow board rig set up properly with the existing AC plug on the skillet. Plug & play and all that... yyrkoon, RobG and Fred 3 Quote Link to post Share on other sites
Fred 453 Posted June 5, 2013 Share Posted June 5, 2013 Recovered all the high-dollar SMD components though. I'm just imaging you weighing up whether to look for some 0402 resistors and capacitors on that patterned floor and then working out what values they are... Quote Link to post Share on other sites
bluehash 1,581 Posted June 5, 2013 Share Posted June 5, 2013 Subscribing... Quote Link to post Share on other sites
spirilis 1,265 Posted June 5, 2013 Author Share Posted June 5, 2013 I'm just imaging you weighing up whether to look for some 0402 resistors and capacitors on that patterned floor and then working out what values they are... Haha, I did find a 1210 22uF ceramic cap I must have dropped some 6 months ago in the process... Could tell what it was b/c there was a tiny touch of red paint on it, from a previous board where I played with Testor paint pens as a faux soldermask for my home-etched boards. Quote Link to post Share on other sites
yyrkoon 250 Posted June 5, 2013 Share Posted June 5, 2013 Feel free to PM me with any questions concerning the code, as I know profile3.h is a complete mess atm. but it works :/ Quote Link to post Share on other sites
spirilis 1,265 Posted June 6, 2013 Author Share Posted June 6, 2013 Ok, got some whips installed with a jack & plug from lowes and part of an old server power cord... Got my "hello world" out of the way; an Energia sketch turns P1.4 on for 3 seconds, off for 3 seconds, repeats. Was able to attach a lamp to it and watch the CFL bulb turn on & off. Had the LaunchPad powered by a USB charger, wasn't about to trust having my laptop hooked up to it ;-) Seemed OK though. One oddity I noticed is the voltage across the hot/neutral output sits around ~11-18VAC when it's in the "off" mode. 18VAC with nothing attached, 11VAC with my CFL drop lamp attached. Lamp didn't turn on and I don't have any incandescent bulbs handy to test to see if there is appreciable current coming out, but it just struck me by surprise. Is that normal for triacs? I doubt it'll cause any problem for what I'm using it for though. yyrkoon 1 Quote Link to post Share on other sites
yyrkoon 250 Posted June 6, 2013 Share Posted June 6, 2013 For what it is worth, I've accidentally programmed the LP while the controller was plugged in. Unless you hit the "go button" everything is turned off. I've coded a very simple button trap to lock code execution down, until the button is pressed. Also, at the end of the reflow cycle, I've coded the same trap. To keep the fan from turning off in our oven until the user presses the button. Everything else aside from the fan, and LCD should be off in this state. Typically though, you can.. - unplug from the wall - Plug in the laptop / Desktop - Program the controller - Disconnect from laptop / Desktop. - Plug back into the wall. Then let er rip. I usually leave the USB programming cable that came with the LP plugged into the LP. EDIT: Also I'd image a switchable power strip would come in handy here. One with a light indicator. Quote Link to post Share on other sites
spirilis 1,265 Posted June 6, 2013 Author Share Posted June 6, 2013 Yeah I mean realistically, as long as you don't have stray wires touching, with this design there's no risk to the PC or MSP430 from the AC mains voltage... and the board is large enough that you shouldn't run the risk of accidentally zapping things out of carelessness. I did add some strain relief ties for the AC cords, will probably drill out those holes a little wider so I can use my large zipties for a permanent solution. That's probably something I'd suggest for a next revision if you ever do one later on (some extra large holes for strain-relief zipties) Quote Link to post Share on other sites
yyrkoon 250 Posted June 6, 2013 Share Posted June 6, 2013 We may very well do that, someday. Too many other things going on atm though, and last night I have a good idea to achieve something that I had been thinking about for a long time too. So yeah yet another pet project I will possibly be fleshing out 100% by myself, though Wulf may get interested at some point. Quote Link to post Share on other sites
spirilis 1,265 Posted June 8, 2013 Author Share Posted June 8, 2013 Decided after examining @@yyrkoon 's reflow code a bit that I'd like a go at doing it myself from the ground up in C. Been writing some pretty neat code over the past day IMO although none of it is tested yet... lol (it all compiles cleanly with -Wall -Werror so far) Attached is my triac code, it's basically a Soft PWM system whose period and stepping is clamped to work within the boundaries of 60Hz AC although being that it has to rely on the VLOCLK, it might not be the most accurate but it shouldn't freak anything out. Will know once I actually give it a test though... It uses TA1 on the G2553 with CCR0 for the period (~2.1sec or about 127 AC waveforms) and CCR1 for the duty cycle. ISRs perform the actual port bit swapping with duty cycle 0 and 255 treated as special hard-off or hard-on conditions (similar to how arduino does analogWrite()) triac_ctrl.c triac_ctrl.h Quote Link to post Share on other sites
yyrkoon 250 Posted June 8, 2013 Share Posted June 8, 2013 Well hopefully all / most of the driver code is still useful to you. Hell the max31855 driver code is pretty much exactly the code you wrote and linked me to a few months ago. Just in C++ instead of C. Been wondering for a while now if a PID wouldnt be the best way to go with the profile code. but after reading different post several times, and examining a few libraries it just seems too much for such a simple thing. The profile code there is also psuedo PWM based off of WDT, but there is no frequency / period, only a period. It's something I've been toying with most recently. I do not recall what period steppign im using in the most recent code but at one point I was experimenting with 32 counts /second. Atleast the limited form of PWM I experimented with had little effect on the temps with our oven. Namely I think because of heat loss issues. @@spirilis I have not given your code a look yet, but will asap. Currently working on iSCSI /root, for the BBB. Getting close, but not quite there yet. Quote Link to post Share on other sites
spirilis 1,265 Posted June 8, 2013 Author Share Posted June 8, 2013 Yeah I suspect the value of PWM duty cycles will hinge in the tuning of the PID loop. I have the PID code written based on an article you sent me about the Arduino PID library but after doing a swag "run" in the bc calculator it became obvious that using 1.0 for all 3 coefficients won't make sense. Now that you mention it, about heat loss... I wonder if it'll be worth introducing some bias in the loop to favor leaving the heating element on even at low duty cycle instead of letting it turn off. Will experiment once I have time to finally put this code in action. Sent from my Galaxy Note II with Tapatalk Quote Link to post Share on other sites
yyrkoon 250 Posted June 8, 2013 Share Posted June 8, 2013 @@spirilis based on input from nate, it wont make one bit of a difference. I was dubious when he first told me, but now im seeing a pattern. That is, where PID's and PWM are concerned. Although, if one wanted to spend money on that gold foil insulation . . . I've seen some results on youtube that do seem to do very well ( but results can be tampered with ). I seriously think the IR oven he ( nate ) wound up with here recently( or something close to it ) is the best way to go. But since I am not buying the physical hardware here, I do not have much choice. Been prodding wulf get get an IR oven, but no luck yet. Quote Link to post Share on other sites
yyrkoon 250 Posted June 8, 2013 Share Posted June 8, 2013 Just off the top of my head thinking though, maybe a solid surface that conducts heat well would help stabilize temperature readings over time ? DOnt know just kind of thinking outloud here. Quote Link to post Share on other sites
spirilis 1,265 Posted June 8, 2013 Author Share Posted June 8, 2013 Well conduction is a pretty reliable way to transfer heat, the bottom of the skillet is aluminized to minimize IR heat loss from the bottom (though the bottom edges are black and you can tell, notably warm on your hand from inches away) and the skillet has a glass lid. I think it insulates well for the application although time will tell. Main disadvantage with the skillet is the surface isn't heated evenly, best to lay things out in a ring like a donut, and you can't really solder PTH parts this way at all. Sent from my Galaxy Note II with Tapatalk Quote Link to post Share on other sites
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