Hackaday Prize Entry: Very, Very Powerful Servos

A few years ago, [patchartrand] decided to build a robot arm. The specs were simple: he needed a drive system that would be at least as strong as a human arm. After looking at motors, [patch] couldn’t find a solution for under $3,000. This led to the creation of the Ultra Servo, an embiggened version of the standard hobby servo that provides more than ten thousand oz-in of torque.

Your typical hobby servo has three main components. The electronics board reads some sort of signal to control a motor. This motor is strapped into a gear train of some sort, and a potentiometer reads the absolute position of a shaft. This is basically what the Ultra Servo is doing, although everything is much, much bigger.

The motor used in the Ultra Servo is a very large brushed DC motor. This is attached to a 160:1 planetary gearbox and the electronics are built around four reasonably large MOSFETs. The electronics are built around the ATmega168 microcontroller, and the specs for the completed servo include 12 V or 24 V operation, TTL, SPI, and standard RC communication, 60 RPM no load speed, and 60 ft-lbs of torque.

This is not your standard servo. This is a massive chunk of metal to move stuff. If you’ve ever wanted a remote-controlled Cessna, here you go. That said, servos of this size and power will always be pricey, and [patch] is looking at a cost of $750 per unit. Still, that’s much less than the thousands of a comparable unit, and a great entry to the Hackaday Prize.

Balancing Robot Needs Innovative Controller and Motor

A self-balancing robot is a great way to get introduced to control theory and robotics in general. The ability for a robot to sense its position and its current set of circumstances and then to make a proportional response to accomplish its goal is key to all robotics. While hobby robots might use cheap servos or brushed motors, for any more advanced balancing robot you might want to reach for a brushless DC motor and a new fully open-source controller.

The main problem with brushless DC motors is that they don’t perform very well at low velocities. To combat this downside, there are a large number of specialized controllers on the market that can help mitigate their behavior. Until now, all of these controllers have been locked down and proprietary. SmoothControl is looking to create a fully open source design for these motors, and they look like they have a pretty good start. The controller is designed to run on the ubiquitous ATmega32U4 with an open source 3-phase driver board. They are currently using these boards with two specific motors but plan to also support more motors as the project grows.

We’ve seen projects before that detail why brushless motors are difficult to deal with, so an open source driver for brushless DC motors that does the work for us seems appealing. There are lots of applications for brushless DC motors outside of robots where a controller like this could be useful as well, such as driving an airplane’s propeller.

Thermal Panorama One Pixel At A Time

Inspiration can strike from the strangest places. Unearthing a forgotten Melexis MLX90614 thermopile from his  ‘inbox,’ [Saulius Lukse] used it to build a panoramic thermal camera.

[Lukse] made use of an ATmega328 to control the thermal sensor, and used the project to test a pair of two rotary stage motors he designed for tilt and pan, with some slip rings to keep it in motion as it captures a scene. That said, taking a 720 x 360 panoramic image one pixel at a time takes over an hour, and compiling all that information into an intelligible picture is no small feat either. An occasional hiccup are dead pixels in the image, but those are quickly filled in by averaging the temperature of adjoining pixels.

The camera  rig works — and it does turn out a nice picture — but [Lukse]  says an upgraded infrared camera to captured larger images at a time and higher resolution would not be unwelcome.

 

Another clever use of a thermopile might take you the route of this thermal flashlight. if you don’t build your own thermal camera outright.

[Thanks for the tip, Imn!]

Have Chainsaw, Will Travel

What’s the worst thing that could happen if you strapped a chainsaw motor to a tricycle? Turns out the worst that happened to [ThisDustin] and his friends is that it turned out hilariously awesome.

This aptly-named ‘chainsawtrike’ isn’t much in the way of comfort, so a pair of foot pegs had to be welded onto the front forks, along with a mount for the chainsaw motor. The rear axle had to be replaced with 5/8″ keyed stock, trimmed to fit the trike wheel and secured with keyed hubs. [ThisDustin] and crew also needed an intermediate sprocket to act as a reduction gear.

After a test that saw the chain jump off the sprockets and working out a few kinks — like the ability to turn — the chainsawtrike  can haul around its rider at a pretty decent clip. Check out the video of it in action after the break.

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Cordless Water Pump!

A water pump is one of those items that are uncommonly used, but invaluable when needed. Rarer still are cordless versions that can be deployed at speed. Enter [DIY King 00], who has shared his build of a cordless water pump!

The pump uses an 18 volt brushed motor and is powered by an AEG 18V LiPo battery. That’s the same battery as the rest of [DIY King]’s power tools, making it convenient to use. UPVC pipe was used for the impeller — with a pipe end cap for a housing. A window of plexiglass to view the pump in motion adds a nice touch.

A bit of woodworking resulted in the mount for the pump and battery pack, while a notch on the underside allows the battery to lock into place. Some simple alligator clips on the battery contacts and the motor connected through a switch are all one needs to get this thing running.

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Tiny Electric Motor Runs on Power from an LED

If you were not aware, LEDs can also work in reverse: they deliver tiny amounts of current, in the microamp range, when illuminated. If you look on YouTube you can find several videos of solar panels built with arrays of LEDs, but powering an electric motor with a single 3 mm LED is something that we’ve never seen before. [Slider2732] built a small electric motor that happily runs from a green LED in sunlight.

The motor uses four coils of 1,000 ohms each. Using coils with many turns of very fine wire helps to draw less current while keeping an appropriate magnetic field for the motor to run. To keep friction at a minimum, the rotor uses a needle that hangs from a magnet. Four neodymium magnets around the rotor are periodically pushed by the coils, generating rotation. A simple two-transistor circuit takes care of the synchronization and yes, the motor does run on the four microamps provided by the LED, and runs pretty well.

Building motors is definitely an enjoyable activity, these small pulse motors can be built in just a couple of hours. You can use coils with just a few tens of turns which are much more easy to make but of course you will need something more than four microamps! The nice part of making an ultralow current motor like this is that it can run for a very long time on a tiny battery or even a capacitor, we invite you to try building one.

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Turn Your New Years Resolution Into a Belt Grinder

We’re just over a month into the new year, and some people’s resolve on those exercise plans are already dwindling. There’s some good news though. That treadmill can be hacked into a nice belt grinder for your shop.

[Bob]’s treadmill belt grinder is based on a 2.5 horsepower motor he salvaged from a broken, donated treadmill. This motor needs 130 VDC to run, which is a bit of a challenge to generate. Fortunately, lots of treadmills seem to use the same MC-60 motor controller, which is compatible with this motor. Due to the widespread use of this controller, they can be found on eBay for about $30.

With the motor spinning, [Bob] built up a frame for the grinder, added rollers to hold the belt, and a spring based belt tensioner. The motor’s speed set point is controlled by a potentiometer, and the controller varies the power to keep a constant speed. Since the motor is capable of some serious RPM, a tachometer was added for feedback to prevent high-speed belt shredding.

The final result is a very professional looking tool for under $200. What would a grinder like this be used for? Knives of course! 2″ belt grinders are perfect for shaping and grinding knives and swords. In fact, you can see one in use in this sword hack.

Check out a video of the build after the break.

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