motor

199 Articles

Mobile Coffee Table Uses Legs To Get Around

September 10, 2024 by 22 Comments

For getting around on most surfaces, it’s hard to beat the utility of the wheel. Versatile, inexpensive, and able to be made from a wide array of materials has led to this being a cornerstone technology for the past ten thousand years or so. But with that much history it can seem a little bit played out. To change up the locomotion game, you might want to consider using robotic legs instead. That’s what [Giliam] designed into this mobile coffee table which uses custom linkages to move its legs and get itself from place to place around the living room.

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An Open Source 6kW GaN Motor Controller

August 19, 2024 by 30 Comments

We don’t know how you feel when designing hardware, but we get uncomfortable at the extremes. High voltage or current, low noise figures, or extreme frequencies make us nervous.  [Orion Serup] from CrabLabs has been turning up a few of those variables and has created a fairly beefy 3-phase motor driver using GaN technology that can operate up to 80V at 70A. GaN semiconductors are a newer technology that enables greater power handling in smaller packages than seems possible, thanks to high electron mobility and thermal conductivity in the material compared to silicon.

The KiCAD schematic shows a typical high-power driver configuration, broken down into a gate pre-driver, the driver itself, and the following current and voltage sense sub-circuits. As is typical with high-power drivers, these operate in a half-bridge configuration with identical N-channel GaN transistors (specifically part EPC2361) driven by dedicated gate drivers (that’s the pre-driver bit) to feed enough current into the device to enable it to switch quickly and reliably.

The design uses the LM1025 low-side driver chip for this task, as you’d be hard-pushed to drive a GaN transistor with discrete components! You may be surprised that the half-bridge driver uses a pair of N-channel devices, not a symmetric P and N arrangement, as you might use to drive a low-power DC motor. This is simply because, at these power levels, P-channel devices are a rarity.

Why are P-channel devices rare? N-channel devices utilise electrons as the majority charge carrier, but P-channel devices utilise holes, and the mobility of holes in GaN is very low compared to that of electrons, resulting in much worse ON-resistance in a P-channel and, as a consequence, limited performance. That’s why you rarely see P-channel devices in a circuit like this.

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You Can Build A Little Car That Goes Farther Than You Push It

July 11, 2024 by 25 Comments

Can you build a car that travels farther than you push it? [Tom Stanton] shows us that you can, using a capacitor and some nifty design tricks.

[Tom]’s video shows us the construction of a small 3D printed trike with a curious drivetrain. There’s a simple generator on board, which charges a capacitor when the trike is pushed along the ground. When the trike is let go, however, this generator instead acts as a motor, using energy stored in the capacitor to drive the trike further.

When put to the test by [Tom], both a freewheeling car and the capacitor car are pushed up to a set speed. But the capacitor car goes farther. The trick is simple – the capacitor car can go further because it has more energy. But how?

It’s all because more work is being done to push the capacitor car up to speed. It stores energy in the capacitor while it’s being accelerated by the human pushing it. In contrast, after being pushed, the freewheeling car merely coasts to a stop as it loses kinetic energy. However, the capacitor car has similar kinetic energy plus the energy stored in its capacitor, which it can use to run its motor.

It’s a neat exploration of some basic physics, and useful learning if you’ve ever wondered about the prospects of perpetual motion machines.

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A Drone Motor Does E-Bikes

April 5, 2024 by 37 Comments

On paper, the motors from both an electric bicycle and a drone can both take about 500 watts or so of power. Of course, their different applications make them anything but equivalent, as the bike motor is designed for high torque at low speed while the drone motor has very little torque but plenty of speed. Can the drone motor do the bike motor’s job? [Pro Know] makes it happen, with a set of speed reducing and torque increasing belts.

The build takes a pretty ordinary bicycle, and replaces the rear brake disk with a large pulley for a toothed belt, which drives a smaller pulley, and through a shaft another set of pulleys to the drone motor. The bracket to hold all this and the very large pulley on the wheel are all 3D printed in PLA-carbon fiber mix.

When it’s assembled, it runs the bike from a small lithium ion pack. That’s not unexpected, but if we’re honest we’d have our doubts as to whether this would survive the open road. It’s evidently a novelty for a YouTube video, and we’d be interested to see how hot the little motor became. However what’s perhaps more interesting is the choice of filament.

Could carbon fibre PLA be strong enough to print a toothed belt pulley? We’d be interested to know more. We saw the same filament combo being tested recently, after all.

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How Much Thrust Is Your Prop Really Making?

April 4, 2024 by 12 Comments

The problem of components not conforming to their claimed specification is one that must challenge engineers in all fields, including it seems, that of multi-rotors and remote controlled aircraft. A motor can boast an impressive spec on the website which sells it, but overheat or just not deliver when it’s on your bench. Thus [Valkyrie Workshop] has come up with a simple but ingenious rig to evaluate a motor and propeller combo without breaking the bank.

It tales the form of a L-shaped wooden bracket clamped to a pivot point at its corner with one arm pointing upwards, with motor and propeller in a 3D printed holder on the upwards arm. The other arm extends horizontally and lies on a digital kitchen scale the same distance from the pivot as the motor. The same force as is exerted by the motor is transmitted via the bracket to the kitchen scale, allowing a direct readout of the thrust in grams or kilograms. This is a first version of the rig, further work will move to a load cell and Arduino for more flexibility in measurement.

We’ve featured similar devices here in the past, including one version which can be mounted to an automobile so it can be tested at speed.

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Washing Machine Motors Unlocked

February 29, 2024 by 19 Comments

There’s great potential in salvaging a motor from a broken appliance, but so often the part in question is very specific to its application, presenting a puzzle of wires to the experimenter. This was very much the case with older washing machines and other white goods, and while their modern equivalents may have switched to more understandable motors, there are still plenty of the older ones to be had. [Matthias random stuff] sheds a bit of light on how these motors worked, by means of a 1980s Maytag washing machine motor.

Many of us will be used to old-style induction motors, in which two windings were fed out of phase via a large capacitor. This one doesn’t have a capacitor, instead it has a primary winding and a secondary one with a higher resistance. We’re not quite sure the explanation of the resistance contributing to a phase shift holds water, however this winding is connected in for a short time at start-up by a centrifugal switch. Even better, reversing its polarity reverses the direction of the motor.

The result is a mess of wires demystified, and a mains powered motor with a bit of strength for your projects. We’ve let a few of these motors slip through our fingers in the past, perhaps we shouldn’t have been so hasty.

This is a subject that we’ve looked at in the past.

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Double Fed Induction Motors: Clever Motor Control Through Frequency

February 18, 2024 by 27 Comments

Somewhere in most engineering educations, there’s a class on induction motors. Students learn about shaded-pole motors, two-phase and three-phase motors, squirrel cage motors, and DC-excited motors. It’s a pre-requisite for then learning about motor controllers and so-called brushless DC motors. [Jim Pytel] takes this a step further in a series of videos, in which he introduces the doubly fed induction motor. If a conventional three-phase motor can have its coils in either rotor or stator, here’s a motor with both. The special tricks with this motor come in feeding both rotor and stator with separate frequencies, at which point their interactions have useful effects on the motor speed.

There are two videos, both of which we’ve put below the break. Understanding the complex interaction of the two sets of magnetic fields is enough to make anyone’s brain hurt, but the interesting part for us is that the motor can run faster than either of the two drive frequencies.

Sadly we’re not aware of any easily available motors using this configuration, so we don’t think it will be possible to easily experiment. But if you want to amaze your friends with an in-depth knowledge of motors, take a look at the videos below.

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