Annoy Your Neighbors with MIDI Musical Siren

[Yannick], aka [Gigawipf] brings us this (mostly) musical delicacy: a 3D-printed siren that’s driven by a brushless quadcopter motor, and capable of playing (mostly) any music that you’ve got the MIDI score for. This is a fantastic quickie project for any of you out there with a busted quad, or even some spare parts, and a 3D printer. Despite the apparent level of difficulty, this would actually be a great quickie weekend build.

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3D Printing Makes Electronics A Snap

For just about as long as there have been electronics, there’s been a search for a way to let students and hobbyists build projects without a lot of effort. A board with Fahnestock clips was probably the first attempt. Today, it is more often the ubiquitous solderless breadboard. In between, we’ve seen copper pipe pieces and rubber bands, components mounted on magnets that hold them and make connections, and other even less probable schemes. A few years back, a new method appeared: Snap Circuits. The name almost says it all. A baseboard has mounting holes for different components. All the components make their electrical connections and mechanical connections through a common snap like you might find on clothing. Even the wires are little segments with snaps at both ends.

One problem with any system like this is how to integrate custom components. Of course, with the snaps, that’s not very hard, but [Chuck Hellebuyck] got creative with TinkerCad and worked out how to 3D print custom modules for the system. You can see his video, below.

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Electronic Prototyping with a 3D Printer

It would be nice if your 3D printer could spit out PC boards. There’s been lots of work done to make that happen, mostly centered on depositing conductive material, although we’ve been surprised no one has worked out how to just 3D print a plastic resist mask.

We recently found a GitHub group for [PCBPrints] which has small modules that would be useful in prototyping and breadboarding. They are really just carriers that create plug in modules for switches, LEDs, and the like. It looks like this is a aggregated list of other GitHub projects that realize these designs. The group is in Spanish, but Google Translate is your friend, as usual. You can see a video of one of the button modules in action, below.

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Multiextrusion 3D Printing and OpenSCAD

In a recent posting called Liar’s 3D Printing, I showed you how you can print with multiple filament colors even if your printer only has one extruder and hot end. It isn’t easy, though, and a lot of models you’ll find on sites like Thingiverse are way too complicated to give good results. An object with 800 layers, each with two colors is going to take a lot of filament changes and only the most patient among us will tolerate that.

What that means is you are likely to want to make your own models. The question is, how? The answer is, of course, lots of different ways. I’m going to cover how I did the two models I showed last time using OpenSCAD (seen below). The software is actually really well suited for this hack, making it easy for me to create a framework of several models to represent the different colors.

About OpenSCAD

I’m not going to say much about OpenSCAD. It is less a CAD package and more a programming language that lets you create shapes. We’ve covered it before although it changes from time to time so you might be better off reading the official manual.

The general idea, though, is you use modules to create primitives. You can rotate them and translate them (that is, move them). You can also join them (union) and take the difference of them (difference). That last is especially important. For example, look at the callsign plate above. Forget the text for now. See the two holes? Here’s the OpenSCAD that creates that shape:

 difference() {
 cube([basew,basel,basez]);
 // cut holes
 translate([4,basel/2,0]) cylinder(r=2,h=basez+2);
 translate([basew-4,basel/2,0]) cylinder(r=2,h= basez+2);
 }

The cube “call” creates the base. The cylinders are the holes and the difference “call” is what makes them holes instead of solid cylinders (the first thing is the solid and everything after is taken away). One key point: instead of numbers, the whole thing uses (mostly) variables. That means if you change the size of something, everything will adjust accordingly if you wrote the script well. Let’s look at applying these techniques for multiple colors.

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Print Flexible PCBs with a 3D Printer

Let’s get it out of the way right up front: you still need to etch the boards. However, [Mikey77] found that flexible plastic (Ninjaflex) will adhere to a bare copper board if the initial layer height is set just right. By printing on a thin piece of copper or conductive fabric, a resist layer forms. After that, it is just simple etching to create a PCB. [Mikey77] used ferric chloride, but other etchants ought to work, as well.

Sound simple, but as usual, the devil is in the details. [Mikey77] found that for some reason white Ninjaflex stuck best. The PCB has to be stuck totally flat to the bed, and he uses spray adhesive to do that. Just printing with flexible filament can be a challenge. You need a totally constrained filament path, for one thing.

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This Tampon Gun Won’t Cramp Your Style

Finally, there’s a way to get rid of those applicator-less tampons that literally no one uses while also destroying a bunch of Axe body spray. Just use the Axe as the propellant in a 3D-printed, gas-powered tampon gun.

As you’ll see in the assembly and demonstration video after the break, most of the parts in [HarambesLabs]’ modular gun design are 3D-printed. Aside from those, you just need to add a PVC tube for a barrel, a bottle that fits the threading on the body, and a pair of o-rings to make a nice, tight seal. Snap in the piezo mechanism from a lighter, fill the bottle with an Axe cloud, and screw it on to the body. If the gas/air mixture is close enough, the compacted cotton bullet should fly. The gun is single-shot, but [HarambesLabs] is working on a mod to make it fully automatic.

We love a good gun build around here, be it mostly benign or downright terrifying. This build isn’t necessarily tampon-dependent but the size, weight, and plastic covering (reducing friction) make it ideal for this particular design. Nerf darts may be another option if you can find the correct fit for the barrel.

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Where There’s Smoke, There’s a Knockoff 3D Printer

These days, it’s possible to buy clones of popular 3D printers from China for satisfyingly low prices. As always, you get what you pay for, and while usable, often they require some modification to reach their full potential. [g3ggo] recently laid down €270 for a clone of the Prusa i3 by Geeetech, knowing it would require some modifications for safety and performance.

First on the bill was a wobbly Z-axis, which was dealt with by printing some new parts designed to fix this issue which have already been developed by the community. Forums are your friend here – often an enterprising user will have already developed fixes for the most common issues, and if they haven’t, you can always step up to be the hero yourself. There was a darker problem lurking inside, though.

[g3ggo] began to wonder why the MOSFETs for the hot end were running so hot. It turned out to be an issue of gate drive – the FETs were only being driven with 5V, which for the given part, wasn’t enough to reach its lowest R_DS(on) and thus was causing the overheating issue. It gets worse, though – the heatsinks on the MOSFETs were bolted on directly without insulation, and sitting fractions of a millimeter above traces on the PCB. Unfortunately, with a small scratch to the soldermask, this caused a short circuit, destroying the hot end and MOSFETs and narrowly avoiding a fire. This is why you never leave 3D printers unattended.

The fix? Replacing the MOSFETs with a part that could deal with a 5V gate drive was the first step, followed by using insulating pads & glue to stop the heatsinks contacting the PCB. Now with the cooler running MOSFETs, there’s less chance of fire, and the mainboard’s cooling fan isn’t even required anymore. Overall, for a small investment in time and parts, [g3ggo] now has a useful 3D printer and learned something along the way. Solid effort!