Shop Exhaust Fan Salvaged From Broken Microwave

You don’t have to look hard to find a broken microwave. These ubiquitous kitchen appliances are so cheap that getting them repaired doesn’t make economical sense for most consumers, making them a common sight on trash day. But is it worth picking one of them up?

The [DuctTape Mechanic] certainly thinks so. In his latest video, he shows how the exhaust fan from a dead microwave can easily and cheaply be adapted to blow smoke and fumes out of your workshop. While it’s obviously not going to move as much air as some of the massive shop fans we’ve covered over the years, if you’re working in a small space like he is, it’s certainly enough to keep the nasty stuff moving in the right direction. Plus as an added bonus, it’s relatively quiet.

Now as you might expect the exact internal components of microwave ovens vary wildly, so there’s no guarantee your curbside score is going to have the same fan as this one. But the [DuctTape Mechanic] tries to give a relatively high-level overview of how to liberate the fan, interpret the circuit diagram on the label, and wire it up so you can plug it into the wall and control it with a simple switch. Similarly, how you actually mount the fan in your shop is probably going to be different, though we did particularly like how he attached his to the window using a pair of alligator clips cut from a frayed jumper cable.

Got a donor microwave but not in the market for a impromptu shop fan? No worries. We recently saw a dud microwave reborn as a professional looking UV curing chamber that would be the perfect partner for your resin 3D printer. Or perhaps you’d rather turn it into a desktop furnace capable of melting aluminum, copper, or bronze.

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Exhaust Fan-Equipped Reflow Oven Cools PCBs Quickly

With reflow soldering, sometimes close is good enough. At the end of the day, the home gamer really just needs a hot plate or an old toaster oven and a calibrated Mark I eyeball to get decent results. This exhaust fan-equipped reflow oven is an attempt to take control of what’s perhaps the more challenging part of the reflow thermal cycle — the cool down.

No fan of the seat-of-the-pants school of reflow soldering, [Nabil Tewolde] started with a cast-off toaster oven for what was hoped to be a more precise reflow oven. The requisite temperature sensors and solid-state relays were added, along with a Raspberry Pi Zero W and a small LCD display. Adding the cooling assist started by cutting a gaping hole cut in the rear wall of the oven, which was then filled with a short stretch of HVAC duct and a stepper-controlled damper. The far end of the duct was fitted with a PC cooling fan; while it seems sketchy to use a plastic fan to eject hot air from the oven, [Nabil] says the exhaust isn’t really that hot by the time it gets to the fan. At the end of the reflow phase of the thermal profile, the damper opens and the fan kicks on, rapidly cooling the oven’s interior.

Unfortunately, [Nabil] still needs to crack open the oven door to get decent airflow; seems like another damper to admit fresh air would help with that. That would complicate things a bit, but it still wouldn’t be as over-the-top as some reflow builds we’ve seen. Then again, that calibrated eyeball thing can work pretty well too, even without a toaster oven.

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Fridge Compressor Turned Into Capable Little Four-Stroke Engine

Never underestimate the power of a well-stocked junk bin. Along with a TIG welder and mechanical ingenuity bordering on genius-level, all of which come to bear on this fridge compressor to four-stroke engine build.

The video posted by [Let’s Learn Something] is long, but watching it at double speed doesn’t take away much from the enjoyment. By using a piston-type compressor, a lot of the precision machining is already taken care of here. Adding the intake and exhaust valves, camshaft, timing chain, carburetor, and ignition system are still pretty challenging tasks, though. We loved the home-made timing chain sprockets, made with nothing more than a drill and an angle grinder. In a truly inspired moment, flat-head screws are turned into valves, rocker arms are fabricated from bits of scrap, and a bolt becomes a camshaft with built-up TIG filler. Ignition and carburetion are cobbled together from more bits of scrap, resulting in an engine that fired up the first time — and promptly melted the epoxy holding the exhaust header to the cylinder head.

Now, compressor-to-engine conversions aren’t exactly new territory. We’ve seen both fridge compressors and automotive AC compressors turned into engines before. But most of what we’ve seen has been simple two-stroke engines. We’re really impressed with the skill needed to bring off a four-stroke engine like this, and we feel like we picked up quite a few junk-box tips from this one.

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Building A Scooter Exhaust From Scrap Metal

When a part on a vehicle fails, oftentimes the response is to fit a new one fresh out the box. However, sometimes, whether by necessity or simply for the love of it, it’s possible to handcraft a solution instead. [Samodel] does just that when whipping up a new exhaust for his scooter out of scrap metal.

It’s a great example of classic backyard metalworking techniques. The flange is recreated using a cardboard template rubbed on the exhaust port, with the residual oil leaving a clear impression. Hard work with a grinder and drill get things started, with an insane amount of filing to finish the piece off nicely. A properly tuned pipe is then sketched out on the computer, and a paper template created. These templates are cut out of an old fridge to create the main muffler section.

There’s plenty of other hacks, too – from quick and dirty pipe bends to handy sheet forming techniques. It’s not the first time we’ve seen great metalworking with scrap material, either. Video after the break.

[Thanks to BrendaEM for the tip]

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See-Through Catalytic Converter

There’s always something to be learned from taking things apart. Sometimes the parts can be used for other things, sometimes they can be repaired or improved upon, but sometimes it’s all in good fun. Especially in this case where extremely high temperatures and combustible gasses are involved. This is from the latest video from [Warped Perception] that lets us see inside of a catalytic converter as its operating.

Catalytic converters are installed on most vehicles (and other internal combustion engines) in order to process unburned hydrocarbons from exhaust gasses with a catalyst. These can get extremely hot, and this high temperature complicated the build somewhat. There were two prototypes constructed for this build and the first was a cross-section of a catalytic converter with a glass window sealed on in order to allow the viewing of the catalyst during the operation of a small engine. It was easy to see the dirty exhaust gasses entering and cleaner gasses leaving, but the window eventually blew off. The second was a complete glass tube which worked much better until the fitting on the back finally failed.

A catalytic converter isn’t something we’d normally get to see the inside of, and this video was worth watching just to see one in operation in real life. You could also learn a thing or two about high-temperature fittings as well if you’re so inclined. It might be a nice pairing with another build we’ve seen which gave us a window into a different type of combustion chamber than ones normally found on combustion engines.

Thanks to [Ryoku] for the tip!

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Put A Smoke Detector To Some Use

While we’re certainly not denying that smoke detectors are useful, there’s a certain kind of tragedy to the fact that most of them will never realize their true purpose of detecting smoke, and alerting us to a dangerous fire. On the other hand, [Ben] really unlocks the potential hidden deep in every smoke detector with his latest project which uses the smoke-detecting parts of a smoke detector to turn on the exhaust fan over his stove.

The project didn’t start with the noble aim of realizing the hidden and underutilized quiescent nature of a smoke alarm, though. He wanted his range exhaust fan to turn on automatically when it was needed during his (and his family’s) cooking activities. The particular range has four speeds so he wired up four relays to each of the switches in the range and programmed a Particle Photon to turn them on based on readings from an MQ-2 gas-detecting sensor.

The sensor didn’t work as well as he had hoped. It was overly sensitive to some gasses like LPG which would turn the range on full blast any time he used his cooking spray. Meanwhile, it would drift and not work properly during normal cooking. He tried disabling it and using only a temperature sensor, which didn’t work well either. Finally, he got the idea to tear apart a smoke detector and use its sensor’s analog output to inform the microcontroller of the current need for an exhaust fan. Now that that’s done, [Ben] might want to add some additional safety features to his stovetop too.

Temperature Controlled Fan Keeps Printer Cool

There are many annoying issues associated with desktop 3D printers, but perhaps none are trickier than keeping the machine at the proper temperature. Too cold, and printed parts can warp or fail to adhere to the bed. Too hot, and the filament can get soft and jam, or the motors will start clanking and missing steps. High-end industrial 3D printers have temperature-controlled enclosures for precisely this reason, but the best you can hope for with a printer that’s little more than some aluminum extrusion and an Arduino is a heated bed that helps but is no substitute for the real thing.

Like many 3D printer owners chasing perfect prints, [Stephen Thone] ended up putting his machine into a DIY enclosure to help keep it warm. Unfortunately, there gets to be a point when things get a little too hot inside the insulating cube. To address this issue, he put together a simple but very elegant temperature controlled fan to vent the enclosure when the internal conditions go above the optimal temperature.

[Stephen] picked up the digital temperature controller on Amazon for about $4 USD, and found a 60mm fan in the parts bin. He then came up with a clever two-part printed enclosure that slides together to make the fan and controller one unit which he can place in a hole he cut in the enclosure.

A lot of attention was paid to the front panel of the device, including mid-print filament swaps to create highlighted text and separate buttons printed in different colors. The end result is a very professional looking interface that involved relatively little manual labor; often a problem when trying to come up with nice looking panels.

Whether it’s to keep from breathing ABS fumes, or to quiet the thing down enough so you can get some sleep, it looks like an enclosure of some type is becoming the latest must-have 3D printer accessory.