The Diaphragm is the Coil in These Flexible PCB Speakers

Speakers used to be largish electromechanical affairs, with magnets, moving coils, and paper cones all working together to move air around in a pleasing way. They’ve gotten much smaller, of course, small enough to screw directly into your ears or live inside the slimmest of smartphones and still delivery reasonable sound quality. The basic mechanism hasn’t changed much, but that doesn’t mean there aren’t other ways to make transduce electrical signals into acoustic waves.

Take these speakers made from flexible printed circuit boards, for instance. While working on his flexible PCB soft actuators, [Carl Bugeja] noticed that the PWM signals coursing through the coils on the thin PCB material while they were positioned over a magnet made an audible beeping. He decided to capitalize on that and try to make a decent speaker from the PCBs. An early prototype hooked to a simple amplifier showed promise, so he 3D-printed a ring to support the PCB like a diaphragm over a small neodymium magnet. The sound quality was decent, but the volume was low, so [Carl] experimented with a paper cone attached to the PCB to crank it up a bit. That didn’t help much, but common objects acting as resonators seemed to work fairly well. Check out the results in the video below.

This is very much a work in progress, but given [Carl]’s record with PCB creations from robotic fish to stepper motors built right into the PCB, we’d say he’ll make substantial improvements. Follow his and others’ progress in the Musical Instruments Challenge part of the 2018 Hackaday Prize.

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Modular Keyboards For CAD, Gaming, And Video Editing

Of all the input devices, the keyboard is the greatest. This comes at a cost, though: there were times back in the Before Days, when video and music editing applications came with custom keyboards. There were Pro Tools keyboards, Final Cut keyboards, and innumerable Adobe keyboards. What’s the solution to this problem? More keyboards, obviously, and this time we’ll make them modular.

For his Hackaday Prize entry, [Cole B] is building modular, programmable USB keyboards. It’s got everything: a standard 3×3 keypad, a keyboard that’s just four potentiometers, a keyboard that’s a rotary encoder, and a keyboard that’s a set of faders.

The design of these keyboards is inherently modular, and that means there needs to be a way to connect all these modules together, preferably without a bunch of USB cables strewn about. Right now, the best idea [Cole] is working with is pogo pins and magnets. It’s a great idea although Apple Thinks Differently™ and probably wouldn’t be too keen on seeing the whole ‘magnets and pins’ idea stolen out from under them.

Nevertheless, it’s an excellent project that shows how far you can go with manufacturing on a limited budget. These are fantastic keyboard modules already, and the connector scheme already pushes this project into the upper echelon of keyboard hacks.

OpenSCAD handles the Math in 3D Printed Holder for Magnetic Spheres

3D printed holder mounted to bike wheel, fitting precisely 38 magnetic spheres around its perimeter. Tedious math? Not if you make OpenSCAD do it.

Off-the-shelf components are great; the world and our work simply wouldn’t be the same without. But one of the constraints is that one has to design around them, and that’s what led [Antonio Ospite] to create a parametric design in OpenSCAD for a 3D printed holder which snugly fits a number of magnetic spheres around its diameter.

If that sounds a bit esoteric, it will become much clearer in the context of [Antonio]’s earlier work in making a DIY rotary encoder out of a ring of magnetic spheres. He found that such a ring in front of two Hall effect sensors was low in cost, high in precision, and thanks to 3D printing it also had a lot of potential for customizing. But hampering easy design changes was the need for the spheres to fit snugly around whatever shape was chosen for the hardware, which meant constraints on the encoder diameter.

In this case, [Antonio] wished to create an encoder that could be attached to a bicycle wheel but needed to know what outer diameter would best fit a ring of magnetic balls perfectly, given that the balls were each 5 mm. OpenSCAD did the trick, yielding a design that fit the bike wheel and spokes while perfectly nestling 38 magnetic balls around the outside edge with a minimum of wasted space.

OpenSCAD is a CAD program that’s really more like a programming language than anything else. For those who are not familiar with it, [Brian Benchoff] walked through how to make a simple object in OpenSCAD, and [Elliot] has sung the praises of a few advanced functions. Now that this project makes DIY encoders easier, perhaps they could be used to add intuitive new controls to OpenSCAD itself.

Flexible PCB Becomes The Actuator

An electromagnetic coil gun takes a line of electromagnets working together to form a moving electromagnetic field. These fields accelerate a project and boom, you have electricity moving matter, often at an impressive rate of speed.

[Carl Bugeja] has taken the idea and in a sense turned it upon its head with his flexible PCB actuator. Now the line of electromagnets are the moving part and the magnetic object the stationary one. There is still a line of flat PCB inductors in the classic coil gun configuration, but as the title suggests on a flexible substrate.

The result is a curiously organic motion reminiscent of some lizards, caterpillars, or snakes. It can move over the magnet in a loop, or flex in the air above it. It’s a novel moving part, and he’s treated us to a video which we’ve placed below the break.

He has plans to put it to use in some form of robot, though while it certainly has promise we’d be interested to know both what force it can produce and whether flexible PCB is robust enough for repeated operation. We salute him for taking a simple idea and so effectively proving the concept.

We’ve brought you [Carl]’s work before, most notably with his PCB motor.

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An Integrated Electromagnetic Lifting Module for Robots

The usual way a robot moves an object is by grabbing it with a gripper or using suction, but [Mile] believes that electromagnets offer a lot of advantages that are worth exploring, and has designed the ELM (Electromagnetic Lifting Module) in order to make experimenting with electromagnetic effectors more accessible. The ELM is much more than just a breakout board for an electromagnet; [Mile] has put a lot of work into making a module that is easy to interface with and use. ELM integrates a proximity sensor, power management, and LED lighting as well as 3D models for vertical or horizontal mounting. Early tests show that 220 mW are required to lift a 1 kg load, but it may be possible to manage power more efficiently by dynamically adjusting drive voltage depending on the actual load.

[Mile]’s focus on creating an easy to use, integrated solution that can be implemented easily by others is wonderful to see, and makes the ELM a great entry for The Hackaday Prize.

The Magic that Goes into Magnets

Every person who reads these pages is likely to have encountered a neodymium magnet. Most of us interact with them on a daily basis, so it is easy to assume that the process for their manufacture must be simple since they are everywhere. That is not the case, and there is value in knowing how the magnets are manufactured so that the next time you pick one up or put a reminder on the fridge you can appreciate the labor that goes into one.

[Michael Brand] writes the Super Magnet Man blog and he walks us through the high-level steps of neodymium magnet production. It would be a flat-out lie to say it was easy, but you’ll learn what goes into them and why you don’t want to lick a broken hard-drive magnet and why it will turn to powder in your mouth. Neodymium magnets are probably unlikely to be produced at this level in a garage lab, but we would love to be proved wrong.

We see these magnets everywhere, from homemade encoder disks, cartesian coordinate tables, to a super low-power motor.

Dollar Store PCB Holder System

As you get into electronic fabrication and repair, one of the first things you realize is how hard it can be to hold a PCB still while you work on it. Securing them is difficult due to their very nature: they’re often weird shapes, quite fragile, and of course need to be electrically isolated. If you don’t mind spending the money, and have the time to wait on it getting delivered, you can order some nice purpose-built systems for holding PCBs online. But what if you need something fast and cheap?

[Paul Bryson] might have the solution for you. On his blog he’s documented how a trip to the dollar store and some parts from the junk bin allowed him to create a practical system for holding multiple PCBs of various shapes and sizes. The most exotic element of the build here are the hexagonal standoffs; and if you haven’t already salvaged a bunch of those from a curbside computer, he even gives the Mouser link where you can buy them new for a few cents each.

Each individual stanchion of the system is made up of a 3/4″ round magnet with a hex standoff glued to the top. Over the standoff, [Paul] slipped a rubber grommet which gives a nice non-conductive slot to put the edge of the PCB in. Otherwise, a second hex standoff screwed into the first can be used to clamp down on the board. Adjusting the height is as simple as adding a couple more magnets to the stack.

Of course, magnets need something metal to stick on. For that, [Paul] purchased some steel pie pans and matching rack from the dollar store. The round pans are easy to handle and give him plenty of surface area, and the rack makes for an exceptionally convenient storage unit for all the components. The conductivity of the pans might be a concern, but nothing the application of a rubberized spray coating couldn’t fix.

We’ve covered similar systems before, but this one certainly looks to take the top spot in terms of economics. The only thing that would be cheaper would be a few feet of PLA filament and a rubber band.