Drive Big Servos With Ease

CNC machines of all types are a staple here at Hackaday, in that we have featured many CNC builds over the years. But the vast majority of those that we see are of relatively modest size and assembled in a home workshop, using small and readily available components such as small stepper motors. These drives are a world away from those used in industrial CNC machines, where you will find high-voltage servos packing a much greater punch. With good reason: driving a small low-voltage motor is easy while doing the same with a high-voltage servo requires electronics that have hitherto been expensive.

STMBL (for STM32 microprocessor and BrushLess motor) is a servo driver for STM32F4 microcontrollers that is specifically designed to use in retrofit projects to industrial CNC machines that have those high-voltage servos. When assembled, it takes the form of two PCBs arranged in a T configuration over a heatsink, with high-power connectors for the motor terminals, and RJ45s for feedback and serial control. In fact each of the boards has its own STM32, one on the high voltage side and the other on the low voltage, to enable only the simplest of isolated serial connections between them.  A significant variety of combinations of motor and feedback system is supported, making it as versatile as possible a module for those whose CNC needs have escaped their home bench setup. We’re sure we’ll see this module pop up in quite a few builds we show you over the coming years.

Thanks [Andy Pugh] for the tip.

Bandpass Filters from the CNC Mill

A bandpass allows a certain electrical signal to pass while filtering out undesirable frequencies. In a speaker bandpass, the mid-range speaker doesn’t receive tones meant for the tweeter or woofer. Most of the time, this filtering is done with capacitors to remove low frequencies and inductors to remove high frequencies. In radio, the same concept applies except the frequencies are usually much higher. [The Thought Emporium] is concerned with signals above 300MHz and in this range, a unique type of filter becomes an option. The microstrip filter ignores the typical installation of passive components and uses the copper planes of an unetched circuit board as the elements.

A nice analogy is drawn in the video, which can also be seen after the break, where the copper shapes are compared to the music tuning forks they resemble. The elegance of these filters is their simplicity, repeatability, and reproducability. In the video, they are formed on a CNC mill but any reliable PCB manufacturing process should yield beautiful results. At the size these are made, it would be possible to fit these filters on a business card or a conference badge.

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Replace your Calipers with a Microscope and Image Analysis

Getting a good measurement is a matter of using the right tool for the job. A tape measure and a caliper are both useful tools, but they’re hardly interchangeable for every task. Some jobs call for a hands-off, indirect way to measure small distances, which is where this image analysis measuring technique can come in handy.

Although it appears [Saulius Lukse] purpose-built this rig, which consists of a microscopic lens on a digital camera mounted to the Z-axis of a small CNC machine, we suspect that anything capable of accurately and smoothly transitioning a camera vertically could be used. The idea is simple: the height of the camera over the object to be measured is increased in fine increments, with an image acquired in OpenCV at each stop. A Laplace transformation is performed to assess the sharpness of each image, which when plotted against the frame number shows peaks where the image is most in focus. If you know the distance the lens traveled between peaks, you can estimate the height of the object. [Salius] measured a coin using this technique and it was spot on compared to a caliper. We could see this method being useful for getting an accurate vertical profile of a more complex object.

From home-brew lidar to detecting lightning in video, [Saulius] has an interesting skill set at the intersection of optics and electronics. We’re looking forward to what he comes up with next.

Putting More Tech Into More Hands: The Robin Hoods of Hackaday Prize

Many different projects started with the same thought: “That’s really expensive… I wonder if I could build my own for less.” Success is rewarded with satisfaction on top of the money saved, but true hacker heroes share their work so that others can build their own as well. We are happy to recognize such generosity with the Hackaday Prize [Robinhood] achievement.

Achievements are a new addition to our Hackaday Prize, running in parallel with our existing judging and rewards process. Achievements are a way for us to shower recognition and fame upon creators who demonstrate what we appreciate from our community.

Fortunately there is no requirement to steal from the rich to unlock our [Robinhood] achievement, it’s enough to give away fruits of price-reduction labor. And unlocking an achievement does not affect a project’s standings in the challenges, so some of these creators will still collect coveted awards. The list of projects that have unlocked the [Robinhood] achievement will continue to grow as the Hackaday Prize progresses, check back regularly to see the latest additions!

In the meantime, let’s look at a few notable examples that have already made the list:

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A Pick-And-Place That Is A Work Of Art

It’s a Holy Grail among hackerspaces, the possession of a pick-and-place machine. These robotic helpers for placing surface-mount components on PCBs are something of a gateway to electronic production, but they can carry a fearsome cost. Happily for the cash-strapped would-be electronic manufacturer, it is possible to build a pick-and-place for yourself. [Mcuoneclipse] has demonstrated this with a rather impressive build that works with the freely available OpenPnP software.

Superficially it shares much with what you might expect from a small CNC mill, in that it has a frame made from extruded aluminium that carries rails that trace an X and a Y axis supporting a tool head. But instead of a blade it has a box made from laser-cut ply that contains a camera and a vacuum pick-up tool that can collect a component from the tapes and deposit it in the correct point on the board. At the machine’s heart is a Smoothieboard, and the work is done by an assortment of solenoid valves and actuators. A huge amount of attention to detail has been paid to this build, with a holder for all the interchangeable nozzles for different component sizes, laser-cut mountings for all the motorised components, and automatic feeders for the SMD tapes all being carefully designed and built. Several iterations of the design are presented, in particular around the head itself which has passed through more than one form to remove as much vibration as possible. But don’t take it from us, have a look at the video we’ve pasted in below the break.

This isn’t the first pick-and-place machine we’ve brought you here at Hackaday. If you already have a 3D printer, would you consider this upgrade?

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Building A Mini Electric Bike In Between Projects

What do you do when you suddenly find you have some free time because you’re waiting on parts or have run up against other delays for your current project? If you’re [James Bruton], you design and build a mini electric bike.

Being a prolific builder, [James] already had the parts he needed. Some of them were left over from previous projects: a small motor, a 24 volt LiPo battery, an SK8 electronic speed controller, and a twist grip for the handlebars. He cut a wooden frame using his CNC machine and 3D printed various other components. Normally he uses ABS for motor mounts but this time he went with PLA and sure enough, the motor heated up and the mounting screws got hot enough to melt the plastic. But other than that, the bike worked great and looks like a polished, manufactured product. How many of us can say the same for our own unplanned projects using only parts from around the workshop? Check out his build and watch him whizzing around on it in the video below.

As for the former projects from which he had leftover parts, he says that some came from skateboard projects such as his pimped out electric LEGO longboard.

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Makerbot Printer Reborn As PCB Engraver

Makerbot 3D printers were among the first to hit the market, so it makes sense that old and broken ones now litter the shelves of hackerspaces and home workshops alike. Rather than throw his one out, [Foaly] saw an opportunity to convert it to some sort of CNC machine. Given its lack of inherent rigidity and relatively weak motors, he opted to make a low-impact circuit board engraver which he appropriately calls the MakerbotCNC. We like the thought he put into this project, and it was clearly backed by plenty of experience.

Circuit board etched using MakerbotCNC

Fortunately, his Makerbot Replicator 2 stemmed from a time when MakerBot was more open, meaning he could control the machine using a simple, open library. A little more open software handled his conversion of Gerber files to G-code. First tests drawing with a pen were successful, so he moved on to the carving head. He opted for an inrunner brushless motor to minimize dust getting into the motor but since these motors have a tendency to heat up he had to add fans to cool it. That still didn’t stop the heat from melting and bending his attempt at a 3D printed PLA carriage, so he switched it to a laser-cut MDF board to fix it. Finding the right collet proved tricky but eventually, he found the perfect fit was a collet clutch normally used to couple flex shafts to RC boat motors.

The result, as you can see was worth it. Using shallow passes, he can even cut carbon fiber parts.

While [Foaly] didn’t opt to replace more parts and go for a more powerful CNC, check out this 3D printer to CNC conversion which can cut wood, acrylic, and even aluminum.