After decades of reflowing LEDs using a blow torch, I decided it is time to move into the present millennium. So I built my own genuine reflow oven. I started with a $40 Black and Decker convection toaster oven from Walmart (the second item I have ever purchased from them), added a dual solid state relay to control the heaters and fan, added a touch screen microcontroller (mega-donkey.com … n.b. I designed it also) and a type K thermocouple. Voila… reflow oven. Actually my friend Ron built one first. I took his code and polished it up and added the precision temperature control PID.
The microcontroller implements a rather nice PID temperature controller (originally written for controlling the temperature of a high-precision oscillator to a few parts per million). You can create temperature profiles and the PID controller will follow them to a decent accuracy. With the door on the oven closed, it cannot cool down all that fast (needs a much better fan), so the unit signals when to open the door after the temperature peak has been reached. From start to finish a typical reflow cycle takes around 8 minutes.
The original oven timer, thermostat, and heating element (top/bottom/both) selector switches are still used. The timer and thermostat act as safety backups.
First test was on some old CREE XLAMP-7090 LEDs. Worked very well.
Here you can see a typical reflow run. The heavy line is the actual temperature and the lighter line (usually covered by the heavy one) is the desired temperature profile:
I'm sure it can be, and a good profile controller with PID Heating control makes AWESOME tollhouse cookies every single time. Not that I've ever tried it in the thirteen zone reflow oven at work or anything <grin>
Nice piece of equipment! I wonder what my girlfriend will do if I put one of those next to the computer on top of the one square foot pile that my flashlight hobby occupies
An interesting finding… the oven is sold as a 1500 watt oven. But the heater elements are marked as 450 watts each… total 1800 watts. Need to drag out the Kill-A-Watt meter and see what it really is. I have not run it with both elements yet… don’t trust where its plugged in at the moment to supply that much juice.
I’m just tickled with the masks, they work like a charm and make it super simple to re-flow on our glass-top stove.
Guess you might as well make bacon with your little Nichia eggs in the morning! (I wonder what bacon, or tollhouse cookies for that matter, taste like with flux smoke mixed in?) Just make the coffee a little stronger, it’ll be all right!
Great stuff! Just curious about your comment regarding a better fan. Would I be right in thinking there is only one convection fan and no secondary exhaust fan which you could modify or upgrade to separately control the cooling process, rather than having to open the door? Or is the cooling not critical in the grand scheme of things?
You did state that the convection oven was $40…you did NOT state what the rest of it cost. Can you give us all an idea what total cost is on this project of yours? And if someone “contracted” you to build one?
Yes, there is only one fan. It is mounted on the center of the right side of the inner oven wall. I put the fan under CPU control, but that probably isn’t needed. I have not done much testing to see how useful the fan actually is. One could get rather fancy and put the door under some kind of automatic servo control.
The touchscreen LCD controller is a bit pricey (around $150) considering some of the things available on the market these days, but I’m rather familiar with it and its extensive software features. Other parts were around $30.
The fan has blades on each end of the shaft. One end circulates air in the oven, the other in the electrical box. You can see the solid state relays that were added to control the heaters and the fan on the bottom of the box.
At least you wont get in trouble like me now. There is a massive brown burn mark in the stove top enamel the shape of the aluminium plate I put over the stove element. I ran away and hid, she did find me and did hurt me.
How much for the oven and $150.00 for a controller?
(I wonder what bacon, or tollhouse cookies for that matter, taste like with flux smoke mixed in?) Just make the coffee a little stronger, it’ll be all right! 
