When your publication is about to hold a major event on your side of the world, and there will be a bring-a-hack, you abruptly realise that you have to do just that. Bring a hack. With the Hackaday London Unconference in the works this was the problem I faced, and I’d run out of time to put together an amazing PCB with beautiful artwork and software-driven functionality to amuse and delight other attendees. It was time to come up with something that would gain me a few Brownie points while remaining within the time I had at my disposal alongside my Hackaday work.
Since I am a radio enthusiast at heart, I came up with the idea of a badge that the curious would identify as an FM transmitter before tuning a portable radio to the frequency on its display and listening to what it was sending. The joke would be of course that they would end up listening to a chiptune version of [Rick Astley]’s “Never gonna give you up”, so yes, it was going to be a radio Rickroll.
I evaluated a few options, and ended up with a Raspberry Pi Zero as an MP3 player through its PWM lines, feeding through a simple RC low-pass filter into a commercial super-low-power FM transmitter module of the type you can legally use with an iPod or similar to listen on a car radio. To give it a little bit of individuality I gave the module an antenna, a fractal design made from a quarter wavelength of galvanised fence wire with a cut-off pin from a broken British mains plug as a terminal. The whole I enclosed in a surplus 8mm video cassette case with holes Dremmeled for cables, with the FM module using its own little cell and the Pi powered from a mobile phone booster battery clipped to its back. This probably gave me a transmitted field strength above what it should have been, but the power of those modules is so low that I am guessing the sin against the radio spectrum must have been minor.
At the event, a lot of people were intrigued by the badge, and a few of them were even Rickrolled by it. But for me the most interesting aspect lay not in the badge itself but in its components. First I looked at making a PCB with MP3 and radio chips, but decided against it when the budget edged towards £20 ($27). Then I looked at a Raspberry Pi running PiFM as an all-in-one solution with a little display HAT, but yet again ran out of budget. An MP3 module, Arduino clone, and display similarly became too expensive. Displays, surprisingly, are dear. So my cheapest option became a consumer FM module at £2.50 ($3.37) which already had an LCD display, and a little £5 ($6.74) computer running Linux that was far more powerful than the job in hand demanded. These economics would have been markedly different had I been manufacturing a million badges, but made a mockery of the notion that the simplest MCU and MP3 module would also be the cheapest.
The proliferation of breakout boards that the DIY electronics movement has allowed has been staggering. Buy a few different boards, wire them together to a microcontroller or credit-card computer (both on their own breakout board) and write a bit of code, and you can create some really interesting things. Take Reddit user [Lord_of_Bone]’s Nerf Gun ammo counter and range finder, for example, a great example of having a great idea and looking around for the ways to implement it.
For the range finder, [Lord_of_Bone] looked to an ultrasonic rangefinder. For the ammo counter, [Lord_of_Bone] chose a proximity sensor. To run everything, the Raspberry Pi Zero was used and the visuals were supplied by a Rainbow Hat. The range finder is self-explanatory. The proximity sensor is located at the end of the gun’s muzzle and when it detects a Nerf dart passing by it reduces the ammo count by one. Blu-tack is used to hold everything in place, but [Lord_of_Bone] plans to use Sugru when he’s past the prototype stage.
The one problem [Lord_of_Bone] has with the build is that there’s no way to tell how many Nerf bullets are in the magazine. Currently the wielder must push a button when reloading to reset the count to a preset amount. We’re sure that [Lord_of_Bone] would appreciate any suggestions the Hack-A-Day crowd could offer.
One of the biggest lessons learned by first time 3D printer users is that not everything can be replicated and a printer is a machine and not a miracle worker. It has limitations in terms of what it can print as well as the quality of the output. For teeny tiny objects, the 0.8 mm nozzle will just not do and with resin printers on the rise, the question is, ‘are extruder printers obsolete?’
[Dorison Hugo] has made a mini version of the PS One using a Raspberry Pi which you can play games one. The kicker is that in his video, he does a comparison of an SLA printer and a cheaper extruder one for his enclosure. He goes through a laundry-list of steps to print, file, fill, repair, sand paint, sand, paint etc to try to get a good model replica of the original PS One. He then proceeds to print one with an SLA printer and finishes it to compare with the first model. The decals are printed on an inkjet for those who are wondering, and there is a custom cut heatsink in there as well that was salvaged from an old PC.
Spoiler alert! The SLA wins but in our view, just slightly. The idea is that with enough elbow grease and patience, you can get pretty close to making mini models with a cheaper machine. The SLA print needs work too but it is relatively less and for detailed models, it is a much better choice. We really enjoyed watching the process from start to finish including the Dremel work, since it is something that is forgotten when we see a 3D print. Creating something of beauty takes time and effort which stems from a passion to make.
FabDoc is an interesting concept that attempts to tackle a problem many of us didn’t realize we had. There are plenty of version control systems for software, but many projects also have a hardware element or assembly process. Those physical elements need to be documented, but that process does not easily fit the tools that make software development and collaboration easier. [Kevin Cheng] sums FabDoc up as “a system to capture time-lapse pictures as pre-commits.”
With FabDoc a camera automatically records the physical development process, allowing the developer to focus on work and review later. The images from the camera are treated as pre-commits. Upon review, the developer selects relevant key images (ignoring dead ends or false starts) and commits them. It’s a version control and commit system for the physical part of the development process. The goal is to remove the burden of stopping the work process in order to take pictures, automatically record the development process and attach it to a specific project, and allow easy management of which images to commit.
The current system uses a Raspberry Pi Zero with a camera mounted on safety glasses, and some support software. Some thought has certainly gone into making the system as easy to use and manage as possible; after setting up a repository, scanning a QR code takes care of telling the system what to do and where to put it. The goal is to make FabDoc fast and easy to use so that it can simply work unattended.
We saw a visual twist on version control some time ago with a visual diff for PCBs, which was a great idea to represent changes between PCB designs visually, diff-style. It’s always exciting to see someone take a shot at improving processes that are easy to take for granted.
The Raspberry Pi Zero is a beautiful piece of hardware, fitting an entire Linux computer into a package the size of a pack of gum (don’t chew it, though). However, this size comes with limited IO options, which can be a complication for some projects. In this case, [Hugatry] wanted extra storage, and devised a smart method to add a second SD card to the Pi Zero.
The problem with the Pi Zero is that with only a single USB port, it’s difficult to add any other storage to the device without making things bulkier with hubs or other work arounds. Additionally, the main SD card can’t be removed while the Pi is running, so it makes sense to add an easy-to-use removable storage option to the Pi Zero.
It’s quite a simple hack – all that’s required to pull it off is a few resistors, an SD card connector, and some jumper wires. With everything hooked up, a small configuration change enables the operating system to recognise the new card.
[James West] has a young Doctor Who fan in the house and wanted to build something that could be played with without worrying about it being bumped and scratched. So, instead of creating a replica, [James] built a simple remote controlled K9 toy for his young fan.
K9 was a companion of the fourth Doctor (played by Tom Baker) in the classic Doctor Who series. He also appeared in several spin-offs. A robotic dog with the infinite knowledge of the TARDIS at hand, as well as a laser, K9 became a favorite among Who fans, especially younger children. [James] wanted his version of K9 to be able to be controlled by a remote control and be able to play sounds from the TV show.
Using some hand-cut acrylic, [James] built K9’s body, then started on plans for the motion control and brains. [James] selected the Raspberry Pi Zero for the controller board, a Speaker pHat for the audio, a couple of motors to move K9 around, and a motor controller. K9 is controlled by a WiiMote and has a button on his back to start pairing with the WiiMote (K9 answers with “Affirmative” when the pairing is successful.) When it came to the head, [James] was a little overwhelmed by trying to make the head in acrylic, so he got some foam board and used that instead. A red LED in the head lights up through translucent red acrylic.
It’s a great little project and [James] has put the Python code up on Github for anyone interested. We’ve had a couple of robot dog projects on the site over the years, like this one and this one.
All the trap mechanisms are based on a 555 monostable solenoid triggering circuit that ensures that a pulse of sufficient duration is sent to the solenoid to trigger the trap correctly. This way even intermittent contacts will trigger the trap rather than just causing the solenoid to twitch without fully actuating. This is the same technique used to debounce a switch using a 555 timer.
A Raspberry Pi Zero detects motion using an IR camera to film the interesting parts. This is also a good indicator for when you’ve trapped your quarry – if you’re trying be humane then leaving it in a trap for days is counterproductive.