The PID control loop runs a 1 Hz. It calculates how many milliseconds the heater needs to be switched on for each one second interval. Many AC solid state relays have a zero crossing detector and can only switch full or half cycles of the AC waveform. Not really is issue in this application…
Folks here always amaze me!! Danged good thinkin! 
Dan.
Toaster and skillet mods for reflowing aren’t new. They have been around for quite a while. At one time Sparkfun sold a board for doing it (but they didn’t supply the code… for liability reasons, I think). You could get the code from elsewhere. A little googling should come up with quite a few toaster mods…
I’ve looked into this some, and no you didn’t invent it exactly but yours is one of the nicer ones I have seen. And the design is all yours. Bravo!
I covet it.
Take it on the chin like a man Mr pyro. You did good. 
[quote=texaspyro]
Toaster and skillet mods for reflowing aren’t new. They have been around for quite a while. At one time Sparkfun sold a board for doing it (but they didn’t supply the code… for liability reasons, I think). You could get the code from elsewhere. A little googling should come up with quite a few toaster mods… https://www.sparkfun.com/products/retired/81
[/quote]
Thanks TP... I don't do a lot of the re-flow stuff... I use a torch and chunk of aluminum when I do.... but this is neat. I may have to build me one of these just for fun.
Thanks Again. Dan.
Indeed that is a mighty fine take on the toaster oven reflow concept!
I’ve thought about building one myself and then I realize I’m not doing enough volume to necessitate any more than just a hot air rework station.
Well done texaspyro, really like the idea of trying a PID controller and toaster oven someday. I was introduced to the concept of a bang-bang controller, and have some working code. It is really cool to see the concept of self correcting code, to provide a stable set point, in action.
I am curious to know if a double sided component/board can be done in just one go in this type of environment?
You probably could… particularly if you used an adhesive under the parts on the bottom.
I managed to reflow a chip scale package color sensor chip with the oven. Those critters are SMALL. Pads are less than .01” in diameter. The whole package is less than .1” on a side. We tried making a stencil for the package, but my friend’s laser was having problems cutting that size hole in Kapton. Wound up hand pasting the pads under a microscope using a sewing needle… sucks.
The chip does have (lead-free) solder balls on it. I might try reflowing one without any paste. Data sheet says I need 260C to do it… may have to turn on both heating elements…
For those that don’t know what .01’’ is .25mm in metric. That’s seriously tiny. Nice effort.
Eww. Some HIGH Lead Content alloy, most likely.. SUCKS to work with and reflows like crap. Lots of highly active flux, and.. maybe..
Nope, it’s a lead free part. I HATE lead free slobber…
Even more eww. HMP (High Melting Point) Lead Free Solder. Yep. That should be like play-dough even when liquidus... Fun Fun Fun.
Plus they say I need to get from 217C up to 260C and back down to 217 in under 60 seconds…
In a toaster oven? Good luck with that... That would be a stretch for even a big reflow oven with a chilled cooling section.
I think that I can get the heating part of the curve with both elements… It works out to 1C per second. Cooldown might be a bit of a problem… or not… T^4 power radiative cooling goes a long way. They say the parts can handle 3 reflow cycles. I’m only doing one (hopefully).
Or just use good ole PbSn paste…
Solenoid controlled valve hooked to liquid nitrogen for cool down :)
I’ve got a tank ’o propane… would that work? J) It gets cold when it squirts out…
Into an oven with hot 260C+ heating elements.. Sure :) Video, please :)