DIY Vacuum Table Enhances PCB Milling

CNC milling a copper-clad board is an effective way to create a PCB by cutting away copper to form traces instead of etching it away chemically, and [loska] has improved that process further with his DIY PCB vacuum table. The small unit will accommodate a 100 x 80 mm board size, which was not chosen by accident. That’s the maximum board size that the free version of Eagle CAD will process.

When it comes to milling PCBs, double-sided tape or toe clamps are easy solutions to holding down a board, but [loska]’s unit has purpose behind its added features. The rigid aluminum base and vacuum help ensure the board is pulled completely flat and held secure without any need for external fasteners or adhesives. It’s even liquid-proof, should cutting fluid be used during the process. Also, the four raised pegs provide a way to reliably make double-sided PCBs. By using a blank with holes to match the pegs, the board’s position can be precisely controlled, ensuring that the back side of the board is cut to match the front. Holes if required are drilled in a separate process by using a thin wasteboard.

Milling copper-clad boards is becoming more accessible every year; if you’re intrigued by the idea our own [Adil Malik] provided an excellent walkthrough of the workflow and requirements for milling instead of etching.

Video: Putting High Speed PCB Design to the Test

Designing circuit boards for high speed applications requires special considerations. This you already know, but what exactly do you need to do differently from common board layout? Building on where I left off discussing impedance in 2 layer Printed Circuit Board (PCB) designs, I wanted to start talking about high speed design techniques as they relate to PCBs.  This is the world of multi-layer PCBs and where the impedance of both the Power Delivery Network (PDN) and the integrity of the signals themselves (Signal Integrity or SI) become very important factors.

I put together a few board designs to test out different situations that affect high speed signals. You’ve likely heard of vias and traces laid out at right angles having an impact. But have you considered how the glass fabric weave in the board itself impacts a design? In this video I grabbed some of my fanciest test equipment and put these design assumptions to the test. Have a look and then join me after the break for more details on what went into this!

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A Drum Set In Your Pocket

Cargo pants can fit drumsticks in the pockets if you don’t mind them sticking out. They can also hold this drum set and still have enough room for a pair of headphones, some pens, and a small notebook. At least, guy’s cargo pants can fit all that. Now your pocket is decked out with enough music gear to compose and drum few drum loops and even scribble some notes. We can’t speak for [Tomash Ghz] carrying a notebook, but he wanted a drum set in his pocket badly enough to make a custom circuit board to bring to the 2017 Fasma Festival in Athens. He wrote code for a Teensy 3.2 which fits on the back of his PCB next to a 9V battery. Don’t be afraid, the smallest components are 0805 so even clumsy fingers will be able to build their own. The Gerber files and BOM are all available, so nothing is stopping you.

On the board, we find an array of op-amps to support headphone and line-level outputs, four big ole’ buttons to activate each type of drum: kick, tom, snare, and hat. Then we have four potentiometers to change the sound of each like pitch, decay/length, modulation, and distortion. Once the perfect pattern is recorded, it can be saved in non-volatile memory in case you run out of juice although it can run up to seven-and-a-half hours on one battery. If you find yourself invested in the hardware, there is also a video walk-through about using the drum machine so grab your notebook and beat it.

We have seen simpler drums in simpler chips, and even drums on an entirely different type of chip.

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The Embroidered Computer

By now we’ve all seen ways to manufacture your own PCBs. There are board shops who will do small orders for one-off projects, or you can try something like the toner transfer method if you want to get really adventurous. One thing we haven’t seen is a circuit board that’s stitched together, but that’s exactly what a group of people at a Vienna arts exhibition have done.

The circuit is stitched together on a sheet of fabric using traditional gold embroidery methods for the threads, which function as the circuit’s wires. The relays are made out of magnetic beads, and the entire circuit functions as a fully programmable, although relatively rudimentary, computer. Logic operations are possible, and a functional schematic of the circuit is also provided. Visitors to the expo can program the circuit and see it in operation in real-time.

While this circuit gives new meaning to the term “wearables”, it wasn’t intended to be worn although we can’t see why something like this couldn’t be made into a functional piece of clothing. The main goal was to explore some historic techniques of this type of embroidery, and explore the relationship we have with the technology that’s all around us. To that end, there have been plenty of other pieces of functional technology used as art recently as well, but of course this isn’t the first textile computing element to grace these pages.

Thanks to [Thinkerer] for the tip!

 

CNC Turns a Single PCB into Origami Hemisphere

Trying to make a hemispherical surface out of a PCB is no easy feat. Trying to do that and make the result a working circuit is even harder. Doing it with one solid piece of FR4 seems impossible, right?

Not so much. [brainsmoke] came up with a clever way to make foldable, working PCBs that can be formed into hemispheres. The inspiration for this came from a larger project that resulted in a 32-cm diameter LED-studded sphere, which a friend thought would make a swell necklace if it was scaled down. That larger sphere was made somewhat like a PCB soccer ball, with individual panels soldered together. [brainsmoke] didn’t relish juggling dozens of tiny PCBs to make a necklace-sized version, so the unfolded pattern for half a deltoidal hexecontahedron was laid out as one piece on single-sided FR4. The etched boards were then cut out on a CNC mill, with the joints between the panels cut as V-grooves from the rear of the board. By leaving just enough material to act as a live hinge, [brainsmoke] was able to fold the pattern up into a hemisphere while leaving the traces intact. The process was fussy and resulted in a lot of broken FR4 and traces, but with practice and the use of thicker board material and heavier copper, the hemisphere came together. The video below shows the final product

This objet d’art is [brainsmoke]’s entry in the Circuit Sculpture Contest, which is just wrapping up wrapped up last week. We can’t wait to share some of the cool things people came up with in this contest, which really seemed to get the creative juices flowing.

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Teardown Shows Why Innovative Designs Sometimes Fail

Some ideas are real head-scratchers from a design standpoint: Why in the world would you do it that way? For many of us, answering that question often requires a teardown, which is what [Ben Katz] did when this PCB motor-powered weed whacker came across his bench. The results are instructive on what it takes to succeed in the marketplace, or in this case, how to fail.

The unit in question comes from an outfit called CORE Outdoor Power. The line trimmer was powered by a big lithium-ion battery pack, but [Ben] concentrated on the unique motor for his teardown. After a problematic entry into the very sturdy case at the far end of the trimmer’s shaft, he found what looks like a souped-up version of [Carl Bugeja]’s PCB brushless motors. The rotors, each with eight large magnets embedded, are sandwiched on either side of a very thick four-layer PCB with intricately etched heavy copper traces. The PCB forms the stator, with four flat coils. The designer pulled a neat trick with the Hall-effect sensors needed for feedback; rather than go with surface-mount sensors, which would add to the thickness of the board, they used through-hole packages soldered to surface pads, with the body of the sensor nestled in a hole in the board. The whole design is very innovative, but sadly, [Ben]’s analysis shows that it has poor performance for its size and weight.

Google around a bit and you’ll see that CORE was purchased some years back by MTD, a big player in the internal combustion engine outdoor power market. They don’t appear to be a going concern anymore, and it looks as though [Ben] has discovered why.

[Jozef] tipped us off to this one. Thanks!

Crawling PCB ‘Bot Is Flexible Where It Counts

20 years ago, PCB production was expensive and required a multitude of phone calls and emails to a fab with significant minimum order restrictions. Now, it’s cheap and accessible online, which in addition to curtailing the home etching market has created significant new possibilities for home projects. Now that flexible PCBs are also readily available, it’s possible to experiment with some cool concepts – and that’s precisely what [Carl] has been doing.

The aim is to build a walking robot that uses actuators made from flexible PCBs. The flexible PCB is printed with a coil, capable of generating a small magnetic field. This then interacts with a strong permanent magnet, causing the flexible PCB to move when energised.

Initial attempts with four actuators mounted to a 3D printed frame were unsuccessful, but [Carl] has persevered. With a focus on weight saving, the MK II prototype has shown some promise, gently twitching its way across a desk in testing. Future steps will involve building an untethered version. This will replace the 3D printed chassis with a standard fibreglass PCB acting as both control board and the main chassis to minimise weight, similar to PCB quadcopter designs we’ve seen in the past.

We can’t wait to see the next revision, and if you’ve been working on your own walking robots, make sure you let us know.