Finding Perfect Part Fits With The Goldilocks Approach (and OpenSCAD)

June 9, 2020 by Donald Papp 33 Comments

There is something to be said for brute force or trial-and-error approaches to problems, especially when finding a solution has an empirical element to it. [Tommy] perceived that to be the case when needing to design and 3D print servo horns that would fit factory servos as closely as possible, and used OpenSCAD to print a “Goldilocks array” from which it was possible to find a perfect match for his printer by making the trial and error process much more efficient. By printing one part, [Tommy] could test-fit dozens of options.

What made doing this necessary is the fact that every 3D printer has some variance in how accurately they will reproduce small features and dimensions. A 6.3 mm diameter hole in a CAD model, for example, will not come out as exactly 6.3 mm in a 3D-printed object. It will be off by some amount, but usually consistently so. Therefore, one way around this is to empirically determine which measurements result in a perfect fit, and use those for production on that specific 3D printer.

That’s exactly what [Tommy] did, using OpenSCAD to generate an array of slightly different sizes and shapes. The array gets printed out, servos are test-fitted to them, and whichever option fits best has its dimensions used for production. This concept can be implemented in any number of ways, and OpenSCAD makes a decent option due to its programmatic nature. Interested in OpenSCAD? It will run on nearly any hardware, and you can get up and running with the basics in probably less than ten minutes.

Rolling Your Own LED Matrix Driver, With Copper Foil Tape To The Rescue

May 30, 2020 by Donald Papp 1 Comment

It all started when [Damien Walsh] got his hands on some surplus LED boards. Each panel contained 100 mini-PCBs hosting a single bright LED that were meant to be to be snapped apart as needed. [Damien] had a much better idea: leave them in their 20×5 array and design a driver allowing each LED to be controlled over WiFi. He was successful (a brief demo video is embedded down below after the break) and had a few interesting tips to share about the process of making it from scratch.

The first hurdle he ran into was something most of us can relate to; it’s difficult to research something when one doesn’t know the correct terms. In [Damien]’s case, his searches led him to a cornucopia of LED drivers intended to be used for room lighting or backlights. These devices make a large array of smaller LEDs act like a single larger light source, but he wanted to be able to individually address each LED.

Eventually he came across the IS32FL3738 6×8 Dot Matrix LED Driver IC from ISSI which hit all the right bases. Three of these would be enough to control the 100-LED panel; it offered I2C control and even had the ability to synchronize the PWM of the LEDs across multiple chips, so there would be no mismatched flicker between LEDs on different drivers. As for micontroller and WiFi connectivity, we all have our favorites and [Damien] is a big fan of Espressif’s ESP32 series, and used the ESP32-WROOM to head it all up.

LED pads bridged to copper tape, with Kapton (polyimide) tape insulating any crossovers.

The other issue that needed attention was wiring. Each of the LEDs is on its own little PCB with handy exposed soldering pads, but soldering up 100 LEDs is the kind of job where a little planning goes a long way. [Damien] settled on a clever system of using strips of copper tape, insulated by Kapton (a super handy material with a sadly tragic history.) One tip [Damien] has for soldering to copper tape: make sure to have a fume extractor fan running because it’s a much smokier process than soldering to wires.

A 3D-printed baffle using tracing paper to diffuse the light rounds out the device, yielding a 20 x 5 matrix of individually-controlled rectangles that light up smoothly and evenly. The end result looks fantastic, and you can see it in action in the short video embedded below.

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Self-Shutting Face Mask Is Hacker’s Delight

May 19, 2020 by Moritz v. Sivers 28 Comments

Most of us currently have to deal with wearing face masks in our daily life. An experience that is not entirely pleasurable as it is more difficult to breathe under the mask and can become hot after a while. In addition, you have to take off the mask whenever you want to eat or drink. [DesignMaker] has attempted to solve these problems by creating a mask with an opening that shuts automatically when other people are nearby.

While homemade masks are usually made from fabric [DesignMaker]’s version is much more to a hacker’s taste and includes 3D-printed parts, an Arduino Nano, PIR sensors, an SG90 servo, and some Neopixels. [DesignMaker]’s background in industrial design certainly helped him when modeling the mask as it looks just plain awesome.

His goal was to use PIR sensors to detect when a person is moving nearby. The servo then shuts an opening located at the mouth part of the mask. However, he soon found out that the mask often shuts when nobody is around. The reason is that the sensor can be triggered by ambient IR radiation when it is moving by itself. In the end [DesignMaker] decided that having the mask shut when you are moving is not a bug, it’s a feature.

Of course, the mask is just a prop and should not be used as protective equipment. As shown in the video below, also the false triggering of the PIR sensors can be annoying at times. But [DesignMaker] is already thinking of improvements like having the mask properly sealed with fabric or replacing the PIR sensors by a camera with face detection.

If you want to learn how to sew a proper fabric face mask have a look here. It’s a lot less ridiculous, but a lot more effective. You can’t have everything.

Video after the break.

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Whiteboard Plotter Rocks Three Colors And An Eraser

May 18, 2020 by Donald Papp 11 Comments

AutoWhiteboardBot’s business end, with three markers.

[td0g]’s AutoWhiteboardBot is not just any 3D printed whiteboard plotter, because it also sports a triple-marker carrier and on-board eraser! The device itself hangs from stepper motors, which take care of moving the plotter across the whiteboard, and the trick to making the three colors work was to incorporate retractable dry-erase markers. A spherical Geneva drive-based assembly on the plotter rotates the pen cartridge, and a plunger activates the chosen color. Erasing, arguably the easiest thing to do on a whiteboard, is done by a piece of felt. 3D printed parts are on Thingiverse and [td0g] says software is coming soon. It’s a clever device, especially the method of accommodating multiple colors with retractable markers.

AutoWhiteboardBot hangs from motors which pull it around, but we’ve also seen a SCARA-type robot writing away on a whiteboard. Watch the video embedded below, which begins with sped-up footage of AutoWhiteboardBot drawing in different colors as it slides across the board surface.

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Aladdin Lamp Shoots Flames With A Snap Of Your Fingers

May 13, 2020 by Moritz v. Sivers 4 Comments

Despite their dangers, even Marie Kondo would not convince us to abandon flamethrower projects because they literally spark joy in us. To make this flame shooting Aladdin lamp [YeleLabs] just used a 3D printer and some basic electronics.

The lamp body consists of two 3D-printed halves held together by neodymium magnets. They house a 400 kV spark generator, a fuel pump plus tank, and a 18650 Li-ion battery. The fuel pump is actually a 3 V air pump but it can also pump liquids at low pressure. As fuel [YeleLabs] used rubbing alcohol that they mixed with boric acid to give the flame a greenish tint. The blue base at the bottom of the lamp houses the triggering mechanism which magically lights up the lamp when you snap your fingers. This is achieved by a KY-038 microphone module and KY-019 relay module connected to a Digispark ATTiny85 microcontroller. When the microphone signal is above a certain threshold the relay module will simultaneously switch on the spark generator and fuel pump for 150 ms.

Although they proclaim that the device is a hand sanitizer it is probably safer to stick to using soap. The project still goes on the list of cool flamethrower props right next to the flame shooting Jack-o-Lantern.

Video after the break.

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Combine Broken Drone Propellers For A Second Spin

May 6, 2020 by Danie Conradie 8 Comments

If you’ve ever flown or watched anyone fly a racing drone for any length of time, you know that crashes are just part of the game and propellers are consumables. [Adam] knows this all to well, decided to experiment with combining multiple broken propellers into one with a 3D printed hub.

A damaged propeller will often have one blade with no damage, still attached to the hub. [Adam] trimmed the damaged parts of a few broken props, and set about designing a 3D printed hub to attach the loose blades together. The hubs were designed let the individual blades to move, and folding out as the motors spin up, similar to the props on many photography drones.

Once [Adam] had the fit of the hubs dialed in, he mounted a motor on a piece of wood and put the reborn propellers through their paces. A few hubs failed in the process, which allowed [Adam] to identify weak points and optimise the design. This sort of rapid testing is what 3D printing truly excels at, allowing test multiple designs quickly instead of spending hours in CAD trying to foresee all the possible problems.

He then built a test drone from parts he had lying around and proceeded with careful flight testing. The hubs were thicker than standard propellers so it limited [Adams] motor choices to ones with longer shafts. Flight testing went surprisingly well, with a hub only failing after [Adam] changed the battery from a 3 cell to a 4 cell and started with some aerobatics. Although this shows that the new props are not suitable for the high forces from racing or aerobatics/freestyle flying, they could probably work quite well for smoother cruising flights. The hubs could also be improved by adding steel pins into the 3D printed shafts, and some carefully balancing the assembled props.

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Quarantine Clock Answers The Important Question

May 5, 2020 by Tom Nardi 20 Comments

For many people, these last few weeks have been quite an adjustment. When the normal routine of work or school is suddenly removed, it’s not unusual for your internal clock to get knocked out of alignment. It might have started with struggling to figure out if it was time for lunch or dinner, but now it’s gotten to the point that even the days are starting to blur together. If it takes more than a few seconds for you to remember whether or not it’s a weekday, [whosdadog] has come up with something that might help you get back on track.

Rather than showing the time of day, this 3D printed clock tells you where you are in the current week. Each day at midnight, the hand will advance to the center of the next day. If you wanted, a slight reworking of the gearing and servo arrangement on the rear of the device could allow it to sweep smoothly through each day. That would give you an idea of your progress through each 24 hour period, but then again, if you don’t even know if it’s morning or night you might be too far gone for this build anyway.

The clock’s servo is driven by a Wemos D1 Mini ESP8266 development board, which naturally means it has access to WiFi and can set itself to the current time (or at least, day) with NTP. All you’ve got to do is put your network information into the Sketch before flashing it to the ESP, and you’re good to go.

Naturally this project is a bit tongue-in-cheek, but we do think the design has practical applications. With a new face and some tweaked code, it could be an easy way to show all sorts of data that doesn’t require a high degree of granularity. Our very own [Elliot Williams] recently built a display to help his young son understand his new at-home schedule which operates on a similar principle.