Acrylic sheets are brittle and crack easily, but a hacksaw is a good way to cut it by hand. After cutting, [Marija] uses a small portable gas stove at its lowest setting to provide gentle heat until the acrylic becomes soft, then it can be formed into different shapes using common shop and household items. It’s a process that requires patience and practice, so she shares some useful tips:
Remove the protective film after cutting, but before heat forming. Otherwise the film will be much harder to remove.
Heating too aggressively will result in bubbles that ruin the acrylic.
Uneven heating will result in a bad bend, or “hot spots” which can result in bubbles as mentioned above.
This heating method naturally softens a wide area, but it’s still possible to get straight and flat bends by using wood forms and letting the acrylic cool before moving it.
[Marija] used this method of heating and bending acrylic to complete an earlier lamp project of hers that we featured in the past. Acrylic might laser-cut beautifully, and there may be inexpensive tools for heating and bending it, but it’s always nice to have some tried and true techniques that don’t require anything special.
There are a few common lessons that get repeated by anyone who takes on the task of assembling a few hundred PCBs, but there are also unique insights to be had. [DominoTree] shared his takeaways after making a couple hundred electronic badges for DEFCON 26 (that’s the one before the one that just wrapped up, if anyone’s keeping track.) [DominoTree] assembled over 200 Telephreak badges and by the end of it he had quite a list of improvements he wished he had made during the design phase.
Some tips are clearly sensible, such as adding proper debug and programming interfaces, or baking an efficient test cycle into the firmware. Others are not quite so obvious, for example “add a few holes to your board.” Holes can be useful in unexpected ways and cost essentially zero. Even if the board isn’t going to be mounted to anything, a few holes can provide a way to attach jigs or other hardware like test fixtures.
Other advice is more generic but no less important, as with “eliminate as many steps as possible.” Almost anything adds up to a significant chunk of time when repeated hundreds of times. To the basement hacker, something such as pre-cut and pre-tinned wires might seem like a shameful indulgence. But cutting, stripping, tinning, then hand-soldering a wire adds up to significant time and effort by iteration number four hundred (that’s two power wires per badge) even if one isn’t staring down a looming deadline.
There will always be those of us who yearn for an iron steed and the wind through your hair. (Or over your helmet, if you value the contents of your skull.) If having fun and turning heads is more important to you than speed or practicality, [Make it Extreme] has just the bike for you. Using mostly scrapyard parts, they built a monotrack motorcycle — no wheels, just a single rubber track.
[Make it Extreme] are definitely not newcomers to building crazy contraptions, and as usual the entire design and build is a series of ingenious hacks complimented by some impressive fabrication skills. The track is simply a car tyre with the sidewalls cut away. It fits over a steel frame that can be adjusted to tension the track over a drive wheel and a series of rollers which are all part of the suspension system.
Power is provided by a 2-stroke 100cc scooter engine, and transmitted to the track through a drive wheel made from an old scuba tank. What puts this build over the top is that all of this is neatly located inside the circumference of the track. Only the seat, handlebars and fuel tank are on the outside of the track. The foot pegs are as far forward as possible, which helps keep your center of gravity when stopping. It’s not nearly as bad as those self-balancing electric monocycles, but planning stops well in advance is advisable.
While it’s by no means the fastest bike out there it definitely looks like a ton of fun. Build plans are available to patrons of [Make it Extreme], but good luck licensing one as your daily driver. If that’s your goal, you might want to consider adding a cover over the track between the seat and handlebars to prevent your khakis from getting caught on your way to the cubicle farm.
Thingiverse user [The-Mechanic] shared a design for 3D printed enclosures that are made to house wire and cable junctions, which can then be rendered weatherproof by injecting them with a suitable caulking compound and allowing it to cure. It’s a cross between an enclosure and potted electronics. It’s also a one-way trip, because the result is sealed up like a pharaoh’s tomb. On the upside, it’s cheap, accessible, and easily customized.
The way it works is this: wires go through end caps which snap onto the main body, holding the junction inside. Sealant is then pumped in via the hole on the side, then the hole is plugged. Afterwards, all there is to do is wait until the sealant cures. [The-Mechanic] has a couple of companion designs, as well. For tubes of sealant that have threaded tops, one can more effectively save the contents of the tube for later with this design for screw-on caps. There are also 3D printed nozzles in a variety of designs.
One thing to keep in mind about silicone-based sealants is that thick gobs of it can take a really, really long time to cure fully. A thick gob of the stuff will tend to firm up on the outside but leave the inside gooey. If that will be a problem, maybe take a cue from Oogoo and mix in a bit of corn starch with the silicone sealant. The resulting mixture will be thicker, but it’ll cure throughout with no problems.
[Gzumwalt] did things a little differently with his Pink and Green Domino Machine II, a 3D printed device that drops dominoes in a neat row ready for toppling over. Unlike his earlier version, this one holds dominoes laying flat in a hopper that’s accessible from the top for easy loading. The previous unit had an elegance to it, but it was more limited with respect to how many dominoes it could hold at a time. This new version solves that problem while also showing off a slick mechanism that gracefully slides a domino from the bottom of the hopper, then gently positions it standing on end before opening a rear door to let it out as it moves to the next position. One of the interesting things [gzumwalt] discovered when designing this device was that there isn’t really a “standard” size of domino. That’s one of the reasons the demo uses 3D printed blocks.
Pulling this off with a single small DC motor is a remarkable achievement; the mechanism even stably ejects a positioned domino from the rear without halting its forward motion in the process. An animation of how the mechanism works is embedded below, be sure to check it out!
Anybody interested in building their own robot, sending spacecraft to the moon, or launching inter-continental ballistic missiles should have at least some basic filter options in their toolkit, otherwise the robot will likely wobble about erratically and the missile will miss it’s target.
What is a filter anyway? In practical terms, the filter should smooth out erratic sensor data with as little time lag, or ‘error lag’ as possible. In the case of the missile, it could travel nice and smoothly through the air, but miss it’s target because the positional data is getting processed ‘too late’. The simplest filter, that many of us will have already used, is to pause our code, take about 10 quick readings from our sensor and then calculate the mean by dividing by 10. Incredibly simple and effective as long as our machine or process is not time sensitive – perfect for a weather station temperature sensor, although wind direction is slightly more complicated. A wind vane is actually an example of a good sensor giving ‘noisy’ readings: not that the sensor itself is noisy, but that wind is inherently gusty and is constantly changing direction.
It’s a really good idea to try and model our data on some kind of computer running software that will print out graphs – I chose the Raspberry Pi and installed Jupyter Notebook running Python 3.
The photo on the left shows my test rig. There’s a PT100 probe with it’s MAX31865 break-out board, a Dallas DS18B20 and a DHT22. The shield on the Pi is a GPS shield which is currently not used. If you don’t want the hassle of setting up these probes there’s a Jupyter Notebook file that can also use the internal temp sensor in the Raspberry Pi. It’s incredibly quick and easy to get up and running.
It’s quite interesting to see the performance of the different sensors, but I quickly ended up completely mangling the data from the DS18B20 by artificially adding randomly generated noise and some very nasty data spikes to really punish the filters as much as possible. Getting the temperature data to change rapidly was effected by putting a small piece of frozen Bockwurst on top of the DS18B20 and then removing it again.
I’m often asked to design customer and employee tracking systems. There are quite a few ways to do it, and it’s an interesting intersection of engineering and ethics – what information is reasonable to collect in different contexts, anonymizing and securely storing it, and at a fundamental level whether the entire system should exist at all.
On one end of the spectrum, a system that simply counts the number of people that are in your restaurant at different times of day is pretty innocuous and allows you to offer better service. On the other end, when you don’t pay for a mobile app, generally that means your private data is the product being bought and sold. Personally, I find that the whole ‘move fast and break things’ attitude, along with a general disregard for the privacy of user data, has created a pretty toxic tech scene. So until a short while ago, I refused to build invasive tracking systems – then I got a request that I simply couldn’t put aside…