7/30/2020, 7:11:12 PM
This is actually the project that spawned the idea for this blog. I wanted a way to document this reflow over conversion in a non-tweet way.
A couple months ago I bought a Controleo3 conversion kit from Whizoo to turn a consumer toaster oven into a reflow oven so I could solder PCBs with lots of small SMD parts on them.
The process is basically to take a toaster oven, gut it, insulate it, and rewire it to be controlled by a little computer to heat the interior in a very controlled way to reflow solder paste on PCBs.
Let’s see how this goes!
7/30/2020, 7:21:18 PM
First up is removing the case so I can get at the guts.
After removing the case it was time to familiarize myself with the innards.
Don’t need the controls anymore! Time to disconnect everything.
7/30/2020, 7:27:39 PM
Next up is insulating the oven with this truly nasty silicone glue.
It gets absolutely everywhere and smells awful. I wore gloves and went through about 12 paper towels trying to keep everything clean. Not many photos of the process, but the goal is just to seal every gap in the oven so all the heat will stay inside the chamber during reflow.
7/30/2020, 7:39:06 PM
Next up is creating the housing for the Solid State Relays which will control the heating elements.
I don’t have a countersink bit, so I just took a 1/4” bit to these 3/8” holes for a few seconds to achieve a very DIY countersink. They won’t be visible, but they deburr the holes which is good for the mounting hardware.
The relays are installed on the steel bracket and await installation into the end of the oven.
Next it is time to do a quick test of the Controleo3 board before everything gets wired up and mounted.
The 5V power supply is going to live inside the end of the oven, so it needs some prep before going inside.
I didn’t have a good heat source for the heatshrink handy, so a couple of matches did the trick.... never mind the soot 😬
7/30/2020, 7:46:04 PM
Finally today, I prepared the control board enclosure by drilling some holes in the bottom for routing wires and mounting some hardware which will ultimately affix the Controleo3 to the oven itself.
The Controleo3 uses a servo motor to open and close the oven door to regulate the temperature inside.
And now..... we wait. The horrible silicon glue takes a few days to cure completely, and the next steps involve stuffing a bunch of insulation inside the chamber.
That will be next!
8/2/2020, 5:18:32 PM
Aaaand we’re back. Next is a series of 10 holes to be drilled in the housing for the various wires (boost element, thermocouple, power supply, relay panel, ...)
8/2/2020, 6:18:24 PM
Reflect-A-Gold is a metallic tape that reflects heat back to its source, making it good as an insulator near the door of the oven.
The guide suggested I use a bungee cord to hold the door open during the tape application, but having none, I improvised.
8/3/2020, 9:57:48 PM
The boost element is installed at the front of the oven. It quickly heats the inside of the oven since the main heating elements are a bit slow to come up to temperature.
8/3/2020, 9:59:39 PM
The thermocouple is the last internal piece (I think). It will measure the internal temperature of the oven so the controller can regulate the heat profile of the solder.
8/3/2020, 10:19:25 PM
Three more globs of nasty silicone glue to seal the holes for the boost element and thermocouple.
8/4/2020, 12:16:50 AM
Now to wire up all the high-voltage AC components to the relays and the main power cable.
Here I label all the wires and situate them before crimping on connectors.
And after lots of crimping and screwing, the AC wires are all in place.
8/4/2020, 11:01:51 PM
Next task is to position and connect the low-voltage wires inside the oven housing.
Above you can see a 4 wire conduit and red braided sleeve which will carry the low-voltage signals for the relays to the controller. Also in the sleeve are the 5V power supply and thermocouple cables.
The enclosure is mounted to the oven housing and the wires are brought through the bottom.
Common positive is connected to the relays.
Last, the individual wires for controlling the relays are connected (yellow, black, blue wires). Then everything is neatly arranged to try to separate the high and low voltage wires as much as possible to limit noise in the lines.
8/5/2020, 2:04:04 AM
Time to test the Controleo3 board and the thermocouple readings.
We can see that the lab is a moderate 20°C and that by holding the thermocouple between my fingers the temperature reading goes up. Good sign!
Now to wire up the relay control wires.
Running through the test cycle, we can see that the relays turn on (red LED) and it gets quite warm inside very quickly!
What a relief, all the wiring works! Only a few more steps before we reach the finish line.
8/6/2020, 1:01:41 AM
It’s time to add the last internal piece: ceramic fiber insulation.
That’s the only photo from this step. Ceramic fiber insulation creates a lot of dust full of tiny and sharp fibers. I wore gloves, a respirator, and goggles for protection while I wrapped the outer housing and shoved extra pieces behind the relay mount. The dust got everywhere despite my slow movements and cautious manipulation. Be EXTREMELY CAREFUL with this stuff.
Next step is to put the cover of the oven back on and secure it in place. Looking almost finished!
8/6/2020, 1:48:16 AM
Next step is to attach the, uh, attachment to the servo motor to allow it to open the oven door automatically to regulate the temperature and cool down.
Adding a little aluminum handle to the, uh, handle so the servo attachment can move the door.
The door needs to be able to open 1 inch to provide sufficient cooling.
8/6/2020, 2:20:03 AM
The LAST step in the build process is to add some Nomex gasket around the door to help prevent heat loss.
And TADA!! The oven is physically complete!
Now I have to run some calibration and test cycles with the software. I’m hoping to try reflowing an actual board in the next day or so...