Reflow Rig Makes SMD Soldering a Wok in The Park

For a DIY reflow setup, most people seem to rely on the trusty thrift store toaster oven as a platform to hack. But there’s something to be said for heating the PCB directly rather than heating the surrounding air, and for that one can cruise the yard sales looking for a hot plate to convert. But an electric wok as a reflow hotplate? Sure, why not?

At the end of the day [ThomasVDD]’s reflow wok is the same as any other reflow build. It has a heat source that can be controlled easily, temperature sensors, and a microcontroller that can run the proportional-integral-derivative (PID) control algorithm needed for precise temperature control. That the heating element he used came from an electric wok was just a happy accident. A laser-cut MDF case complete with kerf-bent joints holds the heating element, the solid-state relay, and the Arduino Nano that runs the show. A MAX6675 thermocouple amp senses the temperature and allows the Nano to cycle the temperature through different profiles for different solders. It’s compact, simple, and [ThomasVDD] now has a spare wok to use on the stove top. What’s not to like?

Reflow doesn’t just mean oven or hotplate, of course. Why not give reflow headlights, a reflow blowtorch, or even a reflow work light a try?

PID Control with Arduino

Experience — or at least education — often makes a big difference to having a successful project. For example, if you didn’t think about it much, you might think it is simple to control the temperature of something that is heating. Just turn on the heater if it is cold and turn it off when you hit the right temperature, right? That is one approach — sometimes known as bang-bang — but you’ll find there a lot of issues with that approach. Best practice is to use a PID or Proportional/Integral/Derivative control. [Electronoob] has a good tutorial about how to pull this off with an Arduino. You can also see a video, below.

The demo uses a 3D printer hot end, a thermocouple, a MAX6675 that reads the thermocouple, and an Arduino. There’s also an LCD display and a FET to control the heater.

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Digital Kiln

A kiln or foundry is too often seen as a piece of equipment which is only available if a hackspace is lucky enough to have one or individuals are dedicated enough to drop the cash for one of their own. [The Thought Emporium] thought that way until he sourced materials to make his own kiln which can also be seen after the break. It costs half the price of a commercial model not including a failed—and exploded—paint can version.

As described in the video, these furnaces are tools capable of more than just pottery and soft metal baubles. Sure, a clay chess set would be cool but what about carbon fiber, graphene, aerogel, and glass? Some pretty hot science happens at high temperatures.

We get a nice walk-through of each part of the furnace starting with the container, an eleven-gallon metal tub which should set the bar for the level of kiln being built. Some of the hardware arrangements could be tweaked for safety and we insist that any current-carrying screw is safely mounted inside an enclosure which can’t be opened without tools. There’s good advice about grounding the container if metal is used. The explanation of PID loops can be ignored.

What else can you do with a kiln? How about jewelry, heat treating metal, or recycle your beer cans into an engine.

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The Chemistry and Engineering of DIY Photochromic Glass

[Ben Krasnow] is no stranger to exploring the more arcane corners of hackerdom, and the latest video on his “Applied Science” channel goes into a field few DIYers have touched: homemade glass, including the photochromic variety.

That DIY glassmaking remains a largely untapped vein is not surprising given what [Ben] learned over the last months of experimenting. With searing temperatures bordering on the unobtainable, volatile ingredients that evaporate before they can be incorporated, and a final product so reactive that a platinum crucible is the best vessel for the job, glassmaking is not easy, to say the least. Glassmaking doesn’t scale down from an industrial process very well, it seems. Nonetheless, [Ben] came up with a process that could be replicated using common enough ingredients and a simple electric kiln modded with a PID controller for pinpoint temperature setting. And while Luxottica has nothing to worry about yet, he did manage to get some clearly if subtly photochromic samples, despite the challenges.

Without a doubt, [Ben] crossed over into “mad scientist” territory a while back, and we think it’s great. What other way is there to describe a guy who has an electron microscope, a high-power ruby laser, a CT scanner, and a cookie making robot in his basement? Whatever you call it, we like the results.

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Hackaday Prize Entry: Reflowduino, the Open Source Reflow Oven Controller

Face it — you want a reflow oven. Even the steadiest hands and best eyes only yield “meh” results with a manual iron on SMD boards, and forget about being able to scale up to production. But what controller should you use when you build your oven, and what features should it support? Don’t worry — you can have all the features with this open source reflow oven controller.

Dubbed the Reflowduino for obvious reasons, [Timothy Woo]’s Hackaday Prize entry has everything you need in a reflow oven controller, and a few things you never knew you needed. Based on an ATMega32, the Reflowduino takes care of the usual tasks of a reflow controller, namely running the PID loop needed to accurately control the oven’s temperature and control the heating profile. We thought the inclusion of a Bluetooth module was a bit strange at first, but [Timothy] explains that it’s a whole lot easier to implement the controller’s UI in software than in hardware, and it saves a bunch of IO on the microcontroller. The support for a LiPo battery is somewhat baffling, as the cases where this would be useful seem limited since the toaster oven or hot plate would still need a mains supply. But the sounder that plays Star Wars tunes when a cycle is over? That’s just for fun.

Hats off to [Timothy] for a first-rate build and excellent documentation, which delves into PID theory as well as giving detailed instructions for every step of the build. Want to try lower-end reflow? Pull out a halogen work light, or perhaps fire up that propane torch.

Control System Fundamentals by Video

If you’ve had the classic engineering education, you probably have a hazy recollection of someone talking about control theory. If you haven’t, you’ve probably at least heard of PID controllers and open loop vs closed loop control. If you don’t know about control theory or even if you just want a refresher, [Brian Douglas] has an excellent set of nearly 50 video lectures that will give you a great introduction to the topic. You can watch the first lecture, below.

You might think that control systems are only useful in electronics when you are trying to control a process like a chemical plant or a temperature. However, control theory shows up in a surprising number of places from filters to oscillators, to the automatic gain control in a receiver. You’ll find the background behind many familiar results inside control theory. Sort of like when you take calculus and you discover how they came up with all the formulas you memorized in geometry.

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PID Controlled Charcoal BBQ – Put an Arduino on it!

At Maker Faire Milwaukee this past weekend, [basement tech]  was showing off his latest build, a PID controlled charcoal grill. While it hasn’t QUITE been tested yet with real food, it does work in theory.

PID (a feedback loop with some fancy math used to adjust the input to get a consistent output) controlled cooking is commonly used for sous vide, where one heats up a water bath to a controlled temperature to cook food in plastic bags. Maintaining water temperature is fairly easy. Controlling a charcoal barbecue is much more difficult. [basement tech] accomplishes this with controlled venting and fans. With the charcoal hot and the lid on, there are two ways to control temperature; venting to let hot air out, and blowing air on the coals to make them hotter. A thermocouple sensor stuck through the grill gives the reading of the air inside, and an Arduino nearby reads that and adjusts the vents and fans accordingly.

The video goes into extensive detail on the project, and describes some of the challenges he had along the way, such as preventing the electronics and servos from melting.

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