Scratch Built Tricycle Maximizes Fuel Efficiency

May 16, 2021 by Bryan Cockfield 27 Comments

While the bicycling community is welcoming an influx of electric bikes, there’s a group of tuners on the fringes that are still intent on strapping gas motors of all sizes to bicycles and buzzing down the roads in a loud and raucous fashion. Kits are readily available and are much cheaper than comparable e-bike kits, and with a little bit of work it’s possible to squeeze a lot of excitement from these small motors. With a lot of work, though, you might end up with something like this incredibly fuel efficient and fully customized reverse trike from [Paul Elkins].

The entire goal with this build was fuel efficiency, so the plan is to eventually enclose the vehicle in aerodynamic fairings, most likely using his favorite material, Coroplast. The frame itself is completely hand-made from square tube and welded by [Paul] himself to his own custom specifications. He bolts on a suspension and custom steering rack with levers to control the two front wheels, and the small engine and gas tank are attached to the back above the single drive wheel. The engine hadn’t been started in ten years, but once he got it all put together, it started right up and he was able to take his latest prototype out on the road for a test drive.

While the build isn’t completely finished, the video below (eleventh so far in the build log) is far enough along to show the fruits of years of [Paul]’s labor. It’s taken a while to get a design that worked like he wanted, but with this iteration, he finally has what he was looking for.

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3D Printed Tank Takes On The Elements

May 16, 2021 by Lewin Day 4 Comments

Commercially available radio control tanks are fun and all, but sometimes you’ve just got to build your own. [Let’s Print] did just that, whipping up a tank on his 3D printer before taking it out in the snow.

The tank is a fairly straightforward build, relying on a pair of brushed motors for propulsion, controlled by twin speed controllers hooked up to standard radio control hardware. Everything else is bespoke, however, from the 3D printed gearboxes, to the chassis and the rather aggressive-looking tracks. The pointed teeth of the latter leave deep indentations when the tank cruises around on mud, though weren’t quite enough to stop the little tank from getting high-centered in deep snow.

The build isn’t for the impatient, however. [Let’s Print] notes that the tracks alone took over 80 hours to run off in PETG, let alone the rest of the frame and gearboxes. However, we’re sure it was a great learning experience, and great fun to drive outside. Now the next step is surely to go bigger. Video after the break.

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Tape Cutter Makes Short Work Of Through-Hole Resistor Reels

May 16, 2021 by Jenny List 9 Comments

As the world of electronics makes its inexorable movement from through-hole parts to surface-mount, it’s easy to forget about the humble wire-ended resistor. But a stack of them is still a very useful resource for any experimenter, and most of us probably have a bunch of them with their accompanying twin strips of tape. We’re entranced by [Sandeep]’s automated resistor tape cutting machine, which uses a fearsome looking pair of motorized knives to slice the tape into predetermined lengths.

At its heart is an Arduino and a set of stepper drivers, and it uses a PCB that he’s designed as a multipurpose board for motor-based projects. One motor advances the reel of resistors, while the other two operate those knives that simultaneously slice the two tapes. The whole is held in a wooden frame with 3D-printed parts, and control is through a touch screen. This feels more like an industrial machine than a maker project, and as can be seen in the video below, it makes short work of those tapes. Full details can be found on his website, including code.

We’ve not had so many through hole tape cutters, but we’ve seen at least one SMD cutter.

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Vintage HP-25 Calculator Gets Wireless Charging

May 15, 2021 by Chris Lott 9 Comments

[Jan Rychter] really likes his multiple HP-25C calculators, but the original battery pack design is crude and outdated. No problem — he whips up a replacement using Fusion 360 to design an enclosure, prints a few on his SLS 3D printer, and packs them with LiPo batteries and Qi/WPC wireless charging circuits.

In his blog post, he explains the goals and various design decisions and compromises that he made along the way. We like [Jan]’s frank honesty as he remarks on something we have all been guilty of at one time or another:

In the end, I went with design decisions which might not be optimal, but in this case (with low power requirements) provide acceptable performance. In other words, I winged it.

One problem which proved difficult to solve was how to provide a low battery indicator. Since low voltage on a LiPo is different from the original HP-25’s NiCad cells, it wasn’t straightforward, especially since [Jan] challenged himself to build this without using a microcontroller. He discovered that the HP-25’s internal low battery circuit was triggered by a voltage of 2.1 volts or lower.

In a really clever hack, [Jan] came up with the idea of using an MCU reset supervisor chip with a low voltage threshold of 3.0 volts, which corresponds with the low voltage threshold of the LiPo battery he is using. The reset signal from the supervisor chip then drives one of the pins of the TPS62740 programmable buck converter, changing its output from 2.5 volts to 2.1 volts.

This project is interesting on several levels — extending the life of a useful but end-of-life calculator, improving the original battery design and introducing new charging techniques not available in the early 1970s, and it is something that a hobbyist can afford to do in a home electronics lab. We do wonder, could such a modification could turn an HP-25 into an HP-25C?

We’ve written about battery pack replacement project before, including one for the Sony Discman and another for an electric drill. Let us know if you have any battery pack replacement success (or failure) stories in the comments below.

Robotic Bartender Built With Industrial-Grade Hardware

May 15, 2021 by Lewin Day 12 Comments

Robotic bartenders are a popular project around these parts. If there’s one thing hackers love, after all, it’s automating tasks – as much for the challenge as for the actual time saved. This build from a group of [Teknic Servo] engineers is an impressive example of what can be done with some industrial-grade hardware.

The bartender is built as a demo project for the ClearCore controller, [Teknic’s] industrial-grade device capable of interfacing with a whole bunch of servomotors and sensors to get the job done. The controller is hooked up to a bunch of ClearPath servomotors that handle spinning the bottle carousel, muddling or stirring the beverage, or transporting the drinking glass through the machine. There’s also several interlocks to avoid the patron coming into contact with the bartender’s moving parts while it’s working, and a standard bar-style mixer dispenser actuated with solenoids to keep things simple. Drink selection and control is via a touch screen, with sliders for selecting preferences such as alcohol content and sweetness.

The bartender is certainly capable of producing a neat drink (pun intended), and serves as a great example of how easily a project can be put together with industrial-grade hardware. If you’ve got the budget, you might find using an industrial plug-and-play components quicker than assembling development boards, motor controller shields and other accessories on breakout boards. There’s always more than one way to get the job done, after all.

We’ve seen some great barbots over the years, from builds relying on robotic arms to those focused on ultimate speed. Video after the break.

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A Phased-Array Ultrasonic 3D Scanner From Scratch

May 15, 2021 by Jenny List 6 Comments

Who wouldn’t want an autonomous drone to deliver cans of fizzy drink fresh from the fridge? [Alex Toussaint] did, and in thinking how such a machine might work he embarked on a path that eventually led him to create a fully functional ultrasonic 3D scanner. In writing it up he’s produced a straightforward description of how the system works, which should also be of interest to anyone curious about phased array radar. He starts with an easy-to-understand explanation of the principle behind phased array beam forming, and there follows his journey into electronics as he uses this ambitious project to learn the art from scratch. That he succeeded is testament to his ability as well as his sheer tenacity.

He finally arrived at a grid of 100 ultrasonic emitters controlled from an Arduino through a series of shift register boards. Using this he can steer his ultrasonic beam horizontally as well as vertically, and receive echoes from objects in three-dimensional space. The ornamental bird example he uses for his scanning tests doesn’t quite emerge in startling clarity, but it is still clear that an object of its size and rough shape is visible enough for the drone in his original idea to detect it. If you would like to experiment with the same techniques and array then all the resources can be found in a GitHub repository, meanwhile we’re still impressed with the progress from relative electronics novice to this. We hope the ideas within it will be developed further.

We’ve seen ultrasonic arrays before, but mainly used in levitation experiments.

3D Printing Espresso Parts

May 15, 2021 by Bryan Cockfield 28 Comments

Virtually any hobby has an endless series of rabbit holes to fall into, with new details to learn around every corner. This is true for beekeeping, microcontrollers, bicycles, and gardening (just to name a few), but those involved in the intricate world of coffee roasting and brewing turn this detail dial up to the max. There are countless methods of making coffee, all with devout followers and detractors alike, and each with its unique set of equipment. To explore one of those methods and brew a perfect espresso, [Eric] turned to his trusted 3D printer and some compressed gas cylinders.

An espresso machine uses high pressure to force hot water through finely ground coffee. This pressure is often developed with an electric pump, but there are manual espresso machines as well. These require expensive parts which can withstand high forces, so rather than build a heavy-duty machine with levers, [Eric] turned to compressed CO2 to deliver the high pressure needed.

To build the pressure/brew chamber, he 3D printed most of the parts with the exception of the metal basked which holds the coffee. The 3D printed cap needs to withstand around nine atmospheres of pressure so it’s reasonably thick, held down with four large bolts, and holds a small CO2 canister, relief valve, and pressure gauge.

To [Eric]’s fine tastes, the contraption makes an excellent cup of coffee at minimal cost compared to a traditional espresso machine. The expendable CO2 cartridges only add $0.15 to the total cost of the cup and for it’s simplicity and small size this is an excellent trade-off. He plans to improve on the design over time, and we can’t wait to see what he discovers. In the meantime, we’ll focus on making sure that our beans are of the highest quality so they’re ready for that next espresso.

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