Axial Flux Motors For Electric Vehicles

October 10, 2021 by Al Williams 37 Comments

In the everything old is new again folder, [Lesics] has a good overview of axial flux motors. These are promising for electric vehicles, especially aircraft, since the motors should have high torque to weight ratio. The reason this is actually something old is that the early generators built by Faraday were actually of the axial flux type. Soon, though, radial flux generators and motors became the norm.

The simple explanation is that in a radial system, the magnetic flux lines are perpendicular to the axis of rotation. In the axial system, the flux lines are parallel to the axis of rotation. There’s more to it than just that of course, and the video below has nice animations showing how it all works.

While these are not very common, they do exist even today. The Lynch motor, for example, is a type of axial flux motor that dates back to 1979. Usually, the impetus for using an axial flux motor is the ease of construction, but with the right design, they can be quite efficient (up to 96% according to the video).

We’ve seen plenty of PCB motors and most of those are axial in design. Not all of them, though.

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Ultrasonic Sonar Detects Hidden Objects

April 2, 2021 by Bryan Cockfield 14 Comments

While early scientists and inventors famously underestimated the value of radar, through the lens of history we can see how useful it became. Even though radar uses electromagnetic waves to detect objects, the same principle has been used with other propagating waves, most often sound waves. While a well-known use of this is sonar, ultrasonic sensors can also be put to use to make a radar-like system.

This ultrasonic radar project is from [mircemk] who uses a small ultrasonic distance sensor attached to a rotating platform. A motor rotates it around a 180-degree field-of-view and an Arduino takes and records measurements during its trip. It interfaces with an application running on a computer which shows the data in real-time and maps out the location of all of the objects around the sensor. With some upgrades to the code, [mircemk] is also able to extrapolate objects hidden behind other objects as well.

While the ultrasonic sensor used in this project has a range of about a meter, there’s no reason that this principle couldn’t be used for other range-finding devices to extend its working distance. The project is similar to others we’ve seen occasionally before, but the upgrade to the software to allow it to “see” around solid objects is an equally solid upgrade.

Putting Your Time In

March 27, 2021 by Elliot Williams 28 Comments

I was absolutely struck by a hack this week — [Adam Bäckström]’s amazing robot arm built with modified hobby servos. Basically, he’s taken apart and re-built some affordable off-the-shelf servo motors, and like the 6-Million-Dollar Man, he’s rebuilt them better, stronger, faster. OK, and smoother. We have the technology.

The results are undeniably fantastic, and enable the experienced hacker to get champagne robot motion control on a grape-juice budget by employing some heavy control theory, and redundant sensors to overcome geartrain backlash, which is the devil of cheap servos. But this didn’t come out of nowhere. In his writeup, [Adam] starts off with “You could say this project started when I ordered six endless servos in middle school, more than 15 years ago.” And it shows.

Go check out this video of his first version of the modified servos, from a six-axis arm he built in 2009(!). He’s built in analog position sensors in the motors, which lets him control the speed and makes it work better than any other hobby servo arm you’ve ever seen, but there’s still visible backlash in the gears. A mere twelve years later, he’s got magnetic encoders on the output and a fast inner loop compensates for the backlash. The result is that the current arm moves faster and smoother, while retaining accuracy.

Twelve years. I assume that [Adam] has had some other projects on his plate as well, but that’s a long term project by any account. I’m stoked to see his work, not the least because it should help a lot of others who are ready to step up their desktop servo-arm projects. But the real take-home lesson here is that if you’ve got a tough problem that you’re hacking on, you don’t have to get it done this weekend. You don’t have to get it done next weekend either. Keep hammering on it as long as you need, but keep on hammering. When you get it done, the results will be all the better for the long, slow, brewing time. What’s the longest project that you’ve ever worked on?

Don’t Fret Over The Ukulele

March 27, 2021 by Bryan Cockfield 17 Comments

A ukulele is a great instrument to pick to learn to play music. It’s easy to hold, has a smaller number of strings than a guitar, is fretted unlike a violin, isn’t particularly expensive, and everything sounds happier when played on one. It’s not without its limited downsides, though. Like any stringed instrument some amount of muscle memory is needed to play it fluidly which can take time to develop, but for new musicians there’s a handy new 3D printed part that can make even this aspect of learning the ukulele easier too.

Called the Easy Fret, the tool clamps on to the neck of the ukulele and hosts a series of 3D printed “keys” that allow for complex chord shapes to be played with a single finger. In this configuration the chords C, F, G, and A minor can be played (although C probably shouldn’t be considered “complex” on a ukulele). It also makes extensive use of compliant mechanisms. For example, the beams that hit the chords use geometry to imitate a four-bar linkage. This improves the quality of the sound because the strings are pressed head-on rather than at an angle.

While this project is great for a beginner learning to play this instrument and figure out the theory behind it, its creator [Ryan Hammons] also hopes that it can be used by those with motor disabilities to be able to learn to play an instrument as well. And, if you have the 3D printer required to build this but don’t have an actual ukulele, with some strings and tuning pegs you can 3D print a working ukulele as well.

An Alternator Powered Electric Bicycle Gives Rotor Magnetic Field Insight

January 24, 2021 by Jenny List 63 Comments

For anyone involved in the construction of small electric vehicles it has become a matter of great interest that a cheap high-power electric motor can be made from a humble car alternator. It’s a conversion made possible by the advent of affordable three-phase motor controllers, and it’s well showcased by [austiwawa]’s electric bicycle build video (embedded below).

The bike itself is a straightforward conversion in which the motor powers the rear wheel via an extra sprocket. He tried a centrifugal clutch with limited success, but removed it for the final version. Where the interest lies in this build is in his examination of Hall effect sensor placement.

Most alternator conversions work without sensors, though for better control it’s worth adding these magnetic sensors to allow the controller to more directly sense the rotation. He initially placed them at the top of the stator coils and found them to be ineffectual, with the big discovery coming when he looked at the rotor. The electromagnet in the rotor on a car alternator has triangular poles with the field concentrated in the centre of the stator, thus a move of the sensors to half way down the stator solved the problem. Something to note, for anyone converting an alternator.

Should you wish to give it a try, a year ago we published a primer on turning car parts into motors.

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DIY Automated Roller Blinds

December 5, 2020 by Rich Hawkes 11 Comments

Controlling blinds using off the shelf solutions can be expensive – more so if you have multiple blinds you want to control. [HumanSkunk87] felt the cost was too high, so they designed a controller to automatically open and close the blinds.

The main part of this build is a motor and a ball chain gear – a wheel that captures the balls of a ball chain so that the chain can be pulled. The wheel was designed using Fusion3D and then printed out. The motor requires enough power to pull the chain — [HumanSkunk87] figures it needs to be able to pull about 2.5kg in order to raise the blind. After giving up on stepper motors, a DC motor with a worm gear was found to have enough torque to work. A WEMOS D1 Mini controls the motor controller that drives the ball chain wheel. Two micro switches tell the WEMOS when to stop at the bottom and top of the window.

The WEMOS is programmed using ESPHome and it connects to [HumanSkunk87]’s HomeAssistant to complete the automation. Check out the descriptions in the link for the parts and the code used to run everything. There are many other creative ways to open your blinds, It’s even possible to automate curtains instead of blinds.

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Beer Pong Difficulty Level: 10

November 21, 2020 by Bryan Cockfield 2 Comments

Beer pong is a fun enough game for those of a certain age, but one thing that it lacks is a way of cranking up the difficulty setting independent of the amount of beer one has consumed. At least, that was the idea [Ty] had when he came up with this automated beer pong table which allows the players to increase the challenge of this game by sliding the cups around the top of the table.

The build uses a belt-driven platform under a clear cover with a set of magnets attached. Each of the cups on the table has a corresponding magnet, which allows them to slide fairly easily back and forth on the table. The contraption is controlled by an Arudino Nano with a small screen and dial that allows the players to select a difficulty level from 1 to 10. The difficulty levels increase the speed that the cups oscillate on the table, which certainly adds another layer of complexity to this already challenging game.

While we hope to eventually see a beer pong table that can automatically arrange the cups as the game is played, we do appreciate the effort to make an already difficult game even more difficult. Of course, if you have problems with the difficulty level you might want to pick up a PongMate CyberCannon Mark III to help with those clutch beer pong shots.

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