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Hardware hacking how-tos

Cheap Strain Relief By Casting Hot Glue In A 3D Print

February 11, 2020 by 52 Comments

[Daniel Roibert] found a way to add cheap strain relief to JST-XH connectors, better known to hobby aircraft folks as the charging and balance connectors on lithium-polymer battery packs. His solution is to cast them in hot glue, with the help of 3D printed molds. His project provides molds fitted for connectors with anywhere from two to eight conductors, so just pick the appropriate one and get printing. [Daniel] says to print the mold pieces in PETG, so that they can hold up to the temperature of melted glue.

The 3D models aren’t particularly intuitive to look at, but an instructional video makes everything clear. First coat the inside surfaces of the mold with a release agent (something like silicone oil should do the trick) and then a small amount of hot glue goes in the bottom. Next the connector is laid down on top of the glue, more glue is applied, and the top of the mold is pressed in. The small hole in the top isn’t for filling with glue, it’s to let excess escape as the mold is closed. After things cool completely, just pop apart the mold (little cutouts for a screwdriver tip make this easy) and trim any excess. That’s all there is to it.

One last thing: among the downloads you may notice one additional model. That one is provided in split parts, so that one can make a mold of an arbitrary width just by stretching the middle parts as needed, then merging them together. After all, sometimes the STL file is just not quite right and if sharing CAD files is not an option for whatever reason, providing STLs that can be more easily tweaked is a welcome courtesy. You can watch a short video showing how the whole thing works, below.

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Converted Car Lets Toddlers Tool Around

February 10, 2020 by 9 Comments

A few years ago, a professor at the University of Delaware started a project called Go Baby Go. It’s designed to bring fun and affordable mobility to small children with disabilities. The idea is to modify Power Wheels cars to make them easier for disabled kids to operate, and to teach as many people as possible how to do it in the process. The [South Eugene Robotics Team] is taking this a step further by replacing the steering wheel with a joystick that controls two motors with an Arduino Nano.

In the first instance you replace the foot pedal with a push button. The plans also call for a PVC frame, a high-backed seat, and a seat belt to make it safer. The end result is a fun ride the kid can control themselves that functions a lot like a power wheelchair, but is much more affordable. It has the added bonus of being a fun conversation piece for the other kids instead of a weird scary thing.

They also replace the front wheels with 5″ casters, because being able to spin around in circles is awesome. Their project shows how to do the entire conversion in great detail, starting with a standard ride-on car that comes with some assembly required. Motor past the break to check out a short demo with an extremely happy child tooling around in a fire truck.

If these kids get too wild, they’re gonna need traction control for these things.

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How To Hack A Portable Bluetooth Speaker By Skipping The Bluetooth

February 4, 2020 by 54 Comments

Portable Bluetooth speakers have joined the club of ubiquitous personal electronics. What was once an expensive luxury is now widely accessible thanks to a prolific landscape of manufacturers mass producing speakers to fit every taste and budget. Some have even become branded promotional giveaway items. As a consequence, nowadays it’s not unusual to have a small collection of them, a fertile field for hacking.

But many surplus speakers are put on a shelf for “do something with it later” only to collect dust. Our main obstacle is a side effect of market diversity: with so many different speakers, a hack posted for one speaker wouldn’t apply to another. Some speakers are amenable to custom firmware, but only a small minority have attracted a software development community. It doesn’t help that most Bluetooth audio modules are opaque, their development toolchains difficult to obtain.

So what if we just take advantage of the best parts of these speakers: great audio fidelity, portability, and the polished look of a consumer good, to serves as the host for our own audio-based hacks. Let’s throw the Bluetooth overboard but embrace all those other things. Now hacking these boxes just requires a change of mindset and a little detective work. I’ll show you how to drop an Arduino into a cheap speaker as the blueprint for your own audio adventures.

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Little Hex Tricks Make Little Displays A Little Easier

January 24, 2020 by 16 Comments

Depending on the device in hand and one’s temperament, bringing up a new part can be a frolic through the verdant fields of discovery or an endless slog through the grey marshes of defeat. One of the reasons we find ourselves sticking with tried and true parts we know well is that interminable process of configuration. Once a new display controller is mostly working, writing convenience functions to make it easier to use can be very satisfying, but the very first thing is figuring out how to make it do anything at all. Friend of Hackaday [Dan Hienzsch] put together a post describing how to use a particular LED controller which serves as a nice walkthrough of figuring out the right bitmath to make things work, and includes a neat trick or two.

The bulk of the post is dedicated to describing the way [Dan] went about putting together his libraries for a 7-segment display demo board he makes. At its heart the board uses the IS31FL3728 matrix driver from ISSI. We love these ISSI LED controllers because they give you many channels of control for relatively low cost, but even with their relative simplicity you still need to do some bit twiddling to light the diodes you need. [Dan]’s post talks about some strategies for making this easier like preconfigured lookup tables with convenient offsets and masking bits to control RGB LEDs.

There’s one more trick which we think is the hidden star of the show; a spreadsheet which calculates register values based on “GUI” input! Computing the bit math required to control a display can be an exercise in frustration, especially if the logical display doesn’t fit conveniently in the physical register map of the controller. A spreadsheet like this may not be particularly sexy but it gets the job done; exactly the kind of hack we’re huge fans of here. We’ve mirrored the spreadsheet so you can peek at the formulas inside, and the original Excel document is available on his blog.

Car Alternators Make Great Electric Motors; Here’s How

January 16, 2020 by 197 Comments

The humble automotive alternator hides an interesting secret. Known as the part that converts power from internal combustion into the electricity needed to run everything else, they can also themselves be used as an electric motor.

The schematic of a simple automotive alternator, from US patent 3329841A filed in 1963 for Robert Bosch GmbH .
The schematic of a simple automotive alternator, from US patent 3329841A filed in 1963 for Robert Bosch GmbH.

These devices almost always take the form of a 3-phase alternator with the magnetic component supplied by an electromagnet on the rotor, and come with a rectifier and regulator pack to convert the higher AC voltage to 12V for the car electrical systems. Internally they have three connections to the stator coils which appear to be universally wired in a delta configuration, and a pair of connections to a set of brushes supplying the rotor coils through a set of slip rings. They have a surprisingly high capacity, and estimates put their capabilities as motors in the several horsepower. Best of all they are readily available second-hand and also surprisingly cheap, the Ford Focus unit shown here came from an eBay car breaker and cost only £15 (about $20).

We already hear you shouting “Why?!” at your magical internet device as you read this. Let’s jump into that.

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Automate Your Life With Node-RED (Plus A Dash Of MQTT)

January 15, 2020 by 54 Comments

For years we’ve seen a trickle of really interesting home automation projects that use the Node-RED package. Each time, the hackers behind these projects have raved about Node-RED and now I’ve joined those ranks as well.

This graphic-based coding platform lets you quickly put together useful operations and graphic user interfaces (GUIs), whether you’re the freshest greenhorn or a seasoned veteran. You can use it to switch your internet-connected lights on schedule, or at the touch of a button through a web-app available to any device on your home network. You can use it as an information dashboard for the weather forecast, latest Hackaday articles, bus schedules, or all of them at once. At a glance it abstracts away the complexity of writing Javascript, while also making it simple to dive under hood and use your 1337 haxor skills to add your own code.

You can get this up and running in less than an hour and I’m going to tackle that as well as examples for playing with MQTT, setting up a web GUI, and writing to log files. To make Node-RED persistent on your network you need a server, but it’s lean enough to run from a Raspberry Pi without issue, and it’s even installed by default in BeagleBone distributions. Code for all examples in this guide can be found in the tutorial repository. Let’s dive in!

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Building A Real Wooden Table Saw

January 11, 2020 by 43 Comments

A table saw is one of those tools that aren’t strictly necessary to have, but immensely helpful if you do happen to have one around. The folks at [I Build It] have made a three part series that features a homemade table saw build, so you can finally get around to adding one to your makerspace.

The build uses a real table saw arbor and is made from Baltic birch plywood and solid wood, with some plastic sheets for the trunnions and top. The blade is housed in a blade lift made out wooden panels with a pivot point and slot for the lift mechanism. Bearings allow the blade the freedom of movement, while a curved cutout allows it to stay flat against the wall of the slot while the blade lift mechanism moves.

Meanwhile a reused motor from a previous table saw is dusted, cleaned, and rewired to run in reverse. While most table saws only need two trunnions, a third is used for supporting the motor, since it has to move with the lift and tilt. Once the lift/tilt mechanism is complete, the frame for the table saw is more straightforward, with many steps involving clamping, measuring, cutting, fitting, and painting the assembly. For the final few steps, a switched is mounted outside the table saw in a small box that connected to the power supply and motor, as well as a shop vac for handling dust collection from the saw. While the enclosure isn’t a metal box, as long as the connections are secured properly the wires shouldn’t come loose.

If you want to see other examples of homemade table saws, check out this teeny tiny saw and this kid-friendly table saw build.

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