Brushed DC Servo Drive

Brushless DC motors, and their associated drive electronics, tend to be expensive and complicated. [Ottoragam] was looking for a cheaper alternative and built this Brushed DC motor servo controller and the results look pretty promising. Check out the video after the break.

He needed a low cost, closed loop drive for his home-brew CNC. The servo drive is able to supply a brushed DC motor with up to 7 A continuous current at up to 36 V which works out to about 250 W or 1/3 HP. It does closed loop control with feedback from a quadrature encoder. The drive accepts simple STEP and DIRECTION signals making it easy to interface with micro controllers and use it as a replacement for stepper motors in positioning applications. All of the control is handled by an ATmega328P. It takes the input signals and encoder data, does PID control, and drives the motor via the DRV8701 full bridge MOSFET driver. There’s also some error detection for motor over-current and driver under-voltage. Four IRFH7545 MOSFETs in H-bridge configuration form the output power stage.

This is still work in progress, and [Ottoragam] has a few features pending in his wish list. The important ones include adding a serial interface to make it easy to adjust the PID parameters and creating a GUI to make the adjustment easier. The project is Open Source and all source files available at his Github repository. The board is mostly surface mount, but the passives are all 0805, so it ought to be easy to assemble. The QFN footprint for the micro controller could be the only tricky one. [Ottoragam] would love to have some beta testers for his boards, and maybe some helpful comments to improve his design.

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Adding Position Control To An Open Source Brushless Motor Driver

Brushless motors are everywhere now. From RC planes to CNC machines, if you need a lot of power to spin something really fast, you’re probably going to use a brushless motor. A brushless motor requires a motor controller, and for most of us, this means cheap Electronic Speed Controllers (ESC) from a warehouse in China. [Ben] had a better idea: build his own ESC. He’s been working on this project for a while, and he’s polishing the design to implement a very cool feature – position control.

We’ve seen [Ben]’s work on his custom, homebrew ESC before. It is, by any measure, a work of art. It’s capable of driving brushless and brushed motors with a powerful STM32F4 microcontroller running ChibiOS that’s able to communicate with other microcontrollers through I2C, UART, and CAN bus. If you want to build anything with a motor – from a CNC machine to an RC helicopter to an electric long board – this is the motor controller for you.

[Ben]’s latest update considers position encoders. Knowing how fast a motor is turning is very important to knowing how fast a wheel is turning, how much torque the motor is generating, and an awesome step in building the finest motor controller ever made.

Like the last update, [Ben] demonstrates the great control program written for this ESC. This GUI programs the microcontroller on the controller, with protection from high and low voltages and currents, high RPMs, duty cycle changes, and support for regenerative braking.

Thanks [Dudelbert] for sending this one in.

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There Is No Spoon; Automatic Self Stirring Mug

Sometimes it’s helpful to realize the truth that there is no spoon. At least, not with [Ronaldo]’s automatic self-stirring mug. At first it was just a small propeller in the bottom of the mug that turned on by pushing a button in the handle, but this wasn’t as feature-rich as [Ronaldo] hoped it could be, so he decided to see just how deep the automatic beverage-mixing rabbit hole goes.

The first thing to do was to get a microcontroller installed to handle the operation of the motor. The ATtiny13a was perfect for the job since it’s only using one output pin to control the motor, and can be configured to only draw 0.5 microamps in power-saving mode. This ensures a long life for the two AAA batteries that power the microcontroller and the motor.

As far as operation goes, the motor operates in different modes depending on how many times the button in the handle is pushed. It can be on continuously or it can operate at pre-determined intervals for a certain amount of time, making sure to keep the beverage thoroughly mixed for as long as the power lasts. Be sure to check out the video below for a detailed explanation of all of the operating modes. We could certainly see some other possible uses for more interesting beverages as well.

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“Who is John Galt?” Finally Answered

For those who haven’t read [Ayn Rand’s] philosophical tome Atlas Shrugged, there’s a pretty cool piece of engineering stuffed in between the 100-page-long monologues. Although fictional, a character manages to harness atmospheric static electricity and convert it into kinetic energy and (spoilers!) revolutionize the world. Harnessing atmospheric static electricity isn’t just something for fanciful works of fiction, though. It’s a real-world phenomenon and it’s actually possible to build this motor.

who-is-john-galt-thumbAs [Richard Feynman] showed, there is an exploitable electrical potential gradient in the atmosphere. By suspending a tall wire in the air, it is possible to obtain voltages in the tens of thousands of volts. In this particular demonstration, a hexacopter is used to suspend a wire with a set of needles on the end. The needles help facilitate the flow of electrons into the atmosphere, driving a current that spins the corona motor at the bottom of the wire.

There’s not much torque or power generated, but the proof of concept is very interesting to see. Of course, the higher you can go the more voltage is available to you, so maybe future devices such as this could exploit atmospheric electricity to go beyond a demonstration and do useful work. We’ve actually featured the motor that was used in this demonstration before, though, so if you’re curious as to how a corona motor works you should head over there.

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Open Source ESC Developed for Longboard Commute

For electric and remote control vehicles – from quadcopters to electric longboards – the brains of the outfit is the Electronic Speed Controller (ESC). The ESC is just a device that drives a brushless motor in response to a servo signal, but in that simplicity is a lot of technology. For the last few months, [Ben] has been working on a completely open source ESC, and now he’s riding around on an electric longboard that’s powered by drivers created with his own hands.

esc-for-longboardThe ESC [Ben] made is built around the STM32F4, a powerful ARM microcontroller that’s able to do a lot of computation in a small package. The firmware is based on ChibiOS, and there’s a USB port for connection to a sensible desktop-bound UI for adjusting parameters.

While most hobby ESCs are essentially black boxes shipped from China, there is a significant number of high performance RC pilots that modify the firmware on these devices. While these new firmwares do increase the performance and response of off-the-shelf ESCs, building a new ESC from scratch opens up a lot of doors. [Ben]’s ESC can be controlled through I2C, a UART, or even a CAN bus, greatly opening up the potential for interesting electronic flying machines. Even for ground-based vehicles, this ESC supports regenerative braking, sensor-driven operation, and on-board odometry.

While this isn’t an ESC for tiny racing quadcopters (it’s complete overkill for that task) this is a very nice ESC for bigger ground-based electric vehicles and larger aerial camera platforms. It’s something that could even be used to drive a small CNC mill, and certainly one of the most interesting pieces of open source hardware we’ve seen in a long time.

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CD Execution Chamber Sends old Discs off with a Bang

Welded steel safety cage? Check! Polycarbonate blast shield? Check! Vacuum cleaner motor wired to an inviting red button? Double check! Stack of CDs to dispose of as destructively as possible? [Firas Sirriyeh] has got you covered with his CD Terminator 1.0.

While [Firas’s] build log is a little short on descriptive text, there’s really no need for it. His pictures tell the tale. The combination media shredder and interactive performance art piece is a stoutly constructed affair, which you’d want anything capable of flinging razor-sharp plastic and Mylar shrapnel to be. [Firas] has displayed his CD execution chamber at the Jerusalem Mini Maker Fair 2015 (in Hebrew; English link) and the Musara Mix Festival where the must-see video after the break was shot (mildly NSFW language). Some CDs give up the ghost very quickly, but one held out for a remarkable long time before finally exploding; you can see it flexing and warping in a way that almost appears to be slow-motion.

For those who’d rather not fuss with all that bothersome safety, there’s always this automatic CD launcher to play with.

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Fully-Automatic CD Launcher Looks Dangerously Fun

When [JZSlenker] was challenged to find a creative way to destroy a bunch of compact discs that were burned incorrectly, he did not disappoint. He came up with a rather simple but fun contraption that launches the CD’s at high speeds and with a fast rate of fire. He doesn’t share many details about how this machine was built, but the 18 second video makes it pretty obvious how it works.

The CD gun is built mainly from a piece of plywood. This provides a flat base with which to mount the other components. A stack of compact discs is held in place by what appears to be a metal cage that was welded together. An inexpensive angle grinder is used as the propulsion mechanism. The grinding wheel is mounted just in front of the stack of CD’s in a vertical orientation. The wheel must be placed just high enough above the plywood base for a CD to fit in between the wheel and the base. This design is remarkably similar to the Sticker Gun which our own [Brian Benchoff] is building.

Some type of linear actuator is used as the firing mechanism. The actuator is hooked up to a thin piece of metal, cut into an L shape. It almost looks like a reaper tool. When a button is pressed, the actuator fires instantly. This pushes the metal hammer into the CD on the bottom of the stack. The CD is pressed forward into the grinder wheel which then shoots the CD into the air. Based on the below video, it looks like [JZSlenker] is able to fire at a rate of about three CD’s per second with this rig.

This has got to be a super-villain weapon for an upcoming movie, right? Maybe AOL-man?

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