turn any toaster oven into a reflow oven!

It's time to tackle reflow.

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[mitchellhw]

Hawes - Consider using a GFI outlet at your power strip just in case. Most mishaps in life make you stronger....except for electricity. It just kills you.

[cnc-maker]

You have essentially created a very expensive light dimmer, which is why it buzzes, as you have learned. The triac is burning itself out because you are turning it on in the middle of the cycle, thus it needs to dissipate the switching current at that point and generates a huge amount of harmonics in doing so.

Your second idea is on point, and you can use a slightly larger triac (80% over rated) with a heat sink. You can still PWM, but you need to think about doing it over something like N cycles. If N = 100, and you want a 50% duty cycle, on for 50 half cycles and off for the next 50 cycles. The temp won’t vary that fast, so even using 256 over 2 seconds is perfectly fine. It will dissipate much less heat as well.

[mikeselectricstuff]

Note that chopping the input may mess up ovens that have timer electronics.
Fan ovens probably have better uniformity, but also may be unhappy with chopped mains

[BinaryCounter]

Bold choice to leave your board with an untested mains circuit plugged into the USB of your laptop haha. Great project, really interested in the result.
I feel like since heat is such a slow moving thing, you don't really need that fast of a PWM signal. You could probably get away with switching 2-4 times a second and still get super precise control. Most older microwaves literally have a 5 second duty cycle.

[UnexpectedMaker]

That is is a wicked project Stephen! An "all in one box" to plug a toaster into was something I was looking at for a long time, but as you now see, the SSR is mandatory, and you'll likely find an SSR mounted to the main PCB still an issue (I did, I couldn't find anything that didn't still require active cooling on the PCB) which is why I landed on an external SSR requirement. They still get quite hot, and I always recommend folks don't even mount them inside their toaster without some thermal shielding as mounting a device that gets hot to a unit that is designed to generate a lot of heat.. um, danger danger Will Robinson! hahaha.

I look forward to seeing your next steps on this, and thanks for the nice shoutout at the start and the RMP link in the description!

[tincoandringa]

When i was in college I liked to work on Hi-Fi gear. One day I was working on the power supply for an amp, and I had it all bare on my bench, plugged into mains running a test. I thought I was being safe, but while I was testing i was on my other bench using the computer. My buddy walks into the room, and as i turn to him he says "oh that's a beefy looking transformer" and he picks it up! I almost had a heart attack as i yelled at him to drop it.

It's cool that you built a box so you don't have to handle the mains side of the board, but it's not just you that you have to worry about. My buddy was fine, he managed to out it down without touching copper, but that was a lesson i wouldn't forget.

[ketv]

Yeah, you need a zero-crossing SSR. There are a ton of open-source reflow oven controller projects to adapt. The AQ-A series of SSR's from Panasonic seem to be popular. a 15 amp, 75-250VAC model is about 20 bucks for onesies, 15 bucks in quantity. The heat sink can sometimes be more expensive than the part, they need beefy ones.

[chopperlw]

Im sure it's been said before in the comments, but I'm too lazy to scan. The hysteresis of a heating element (not to mention the oven as a whole) is _Long_, so PID controlling at mains frequency might be overkill and harder than using bang-bang controller with an allowable temperature range. Just imagine trying to control your home HVAC with both methods and my comment will make make more sense.

[PCBWay]

Well done, Stephen! Really enjoyed watching this video where you shared your passion and knowledge with us.❤️

[mukha]

Hey :)
There are optocouplers with diodes both ways on the inputs so you can detect zero-corssing without external diode bridge (4 diodes). Like LTV-814.
And yeah, it is better to regulate heaters by switching on / skipping a whole wave halves instead of chopping the wave (you can count the waves by an MCU).
That sound you heard (like a PWM sound as you called it) was the heater hit by a sharp front of the wave. The closer to the wave peak you chop it, the louder the sound.
I am driving a 400-Watt heater plate by BT138 (TO-220 package) without any heatsinks and it is not even warm...

[thomasvilhar]

A tip is to connect a light bulb in series when you test electronics with 230 or 120 volts for the first time. If there is a shortcut the light bulb will light up and no danger.

[VolvoJesse]

First reflow oven was a Hamilton Beach I picked up on the side of the road on trash day - full blast with multimeter TC to run up to 247-250 w/ GC10 paste made a lot of boards, just had to watch it close to turn off and open the door (wish I had one of the diy kits with the door opener puller to reduce chance of burning boards). Last year I went with a T-937M reflow oven in their 120v variant. The 220v variant has its issues but may have worked. Either case, running high current 120 or 220 isnt great for most users :/ so this project is definitely going to help the community! Best feature on the 937M for me is the exhaust and intake fan for unattended cooldown for sure. Duct for the exhaust is great to get fumes out, and the intake fan also runs for temp regulation and circulation fan. Oven in the unconditioned garage so 3000W heating keeps up in the winter time :)

[funkimunky]

I rebuilt a controller board for my kitchen oven. I went through exactly the same process with zero crossing detector and triac, finding out i needed a ton of cooling and had loads of noise then ending up with SCR.
It turns out that you don't need so much fine control over the on / off period. Seconds of time are good enough and the tuning can be done with PID.
Reducing the amount of switching also lengthens the life span of the SCR.

[Spirit]

SSRs are also just this triac circuit with a zero crossing controller chip(something like the MOC3041M), potted and on a heatsink.
There's nothing magical about them. But yes, I'd recommend that you buy a pre-made unit if you want to avoid the hassle of bringing mains onto your PCBs, which can complicate certification.

[oswynfaux]

Nice. be careful around those exposed mains pads. Hope that quartz heater will hold up to rapid pulsed current.

[tad]

I built my reflow oven some years ago using the Whizoo Controleo3 full kit. It was a bit expensive, but I liked their due to coming with everything but the oven for a full overkill build, separate control for each heating element, and auto door opening for cool down.

The benefit of doing the overkill build with full insulation and heat reflection is the oven being able to easily follow profiles. One of my projects had some components with some pretty strict reflow curves, and the oven was able to do it on the first try.

You absolutely want an oven with top and bottom quartz heating elements. The oven I went with was the BLACK+DECKER TO1313SBD for a whole $30 shipped.

I wouldn't reinvent the SCR.... Properly rated, commercial available SCRs are pretty cheap from Digikey or Mouser.

[Zanthum]

In general switching elements (and the things they power) also don't like to switch in and out in the middle of the sine wave. A better approach might be to apply power for a percentage of counts instead of a percentage of every count. Very easy change since you already have a microcontroller.

These were literally the next words you spoke after I wrote my comment lol.

[KeithOlson]

Honestly, the best 'don't touch anything inside' might just be to pop the temperature control knob off and mount a servo with double-sided tape. You won't have to touch mains OR the oven itself, and switching ovens would be a matter of five minutes for moving the hardware over followed by recalibrating everything. (That being said, a simple relay to turn the oven on and off would also be handy.)

[epremeaux]

12:38 and here is where you probably should have covered the top side of the board around the AC section, because all that exposed area is ripe for finger touching while its live.

[Patrik]

hum...a few thought about the slow reaction curve
i assuming the heating elements are some kind of threded/induction elements
...when on a magnetic flow builds up (magnetic flux)
..when thay are rapidly turned off...the element(inductor) will react by reversing the flow of electrons.. aka puch back effect, and since thay cant flow back trough the turned off triac ther will be residual energy left when the next switch on comes...
solution:
...u add an inverter to the triac gate signal, connected to a shunt triac and a diode connected to a large capacitor with a discharge resistor to slowly drain it safely (no short)
...this should increase the responsivness of the owan itself...

...to test, u should check with a lage capacitor and no way of discharge it how what voltage u get after some time so u know of much excess puchback u need to dispose...
..u can checkup puchback or flyback effect to understand this better...