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

[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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Hackaday Links: December 15, 2019

When you’re right, you’re right. Back in January, we predicted that exoskeletons were about to break out as a mainstream product, and gave several examples of prototypes poised to become products. So it was with interest that we read about Sarcos Robotics and their new Guardian XO, a cyber suit aimed at those doing heavy lifting tasks. The wearable, full-body exoskeleton is supposed to amplify the wearer’s effort 20-fold, making a 200-pound load feel like lifting 10 pounds. It runs untethered for two hours on hot-swappable battery packs, and will be offered for lease to civilian heavy industries and the military for $100,000 a year. Honestly, it seems like you could hire a fair number of meat-robots for that sum, but still, it’s an interesting technology and a promising development.

Aficionados of 3D printing know all too well the limitations of the technology. While we’ve come a long way with things like a print in place, multiple materials, embedded electronics, and even direct 3D printing of complex mechanisms like electric motors, there’s been a long-standing obstacle to turning the 3D printer into the replicators of the Star Trek universe: batteries. But even that barrier is falling, and a new paper shows just how far we’ve come to printing batteries right into our designs. Using an off-the-shelf Prusa Mk 3 and specially formulated lithium iron phosphate/PLA and silicon dioxide/PLA filaments, the group was able to print working batteries in one shot. It’s exciting news because previous 3D-printed batteries required special printers or laborious post-processing steps. We’ll be watching for developments here.

Speaking of laboratory work, anyone who has been around labs is probably familiar with LabVIEW, the de facto standard for programming data capture and automation applications in the laboratory setting. The graphical programming language makes it easy to throw together a quick interface, and many lab-rats regret not having the expensive, proprietary environment available for their after-hours hacking. That might no longer be true, though, with special LabVIEW licensing for non-commercial users. It looks like there are two levels: LabVIEW Home Edition and a Community Edition of LabVIEW, which is currently in Beta. Either way, it’s good news for LabVIEW fans.

Friend of Hackaday Eric Strebel released a video the other day that we just had to comment on. It has nothing to do with electronics – unless you’re into circuit sculpture, that is. In the first of a two-part series, Eric covers the basics of modeling with brass and copper, using both wire and tubing. He has some great tips, like work-hardening and straightening copper wire by stretching it, and the miniature roll bender seen at 7:40 looks like something that could easily be 3D-printed. We recently did a Hack Chat on circuit sculpture with Mohit Bhoite, and saw his Supercon talk on the subject, so this video really got the creative juices flowing.

If you’re local to the Elkhorn, Wisconsin area, consider stopping by the Elkhorn Mini Maker Faire on February 15 and 16. Elkhorn looks like it has a nice central location between Milwaukee and Madison, and doesn’t appear too far from Chicago either, which is probably why they drew 1,200 people to the inaugural Faire last year. They’re looking to get that up to 2,000 people this year and over 150 booths, so if you’ve got something hackish to show off, check it out. The organizers have even set up a Hackaday.io event page to coordinate with the Hackaday community, so drop them a line and see what you can do to pitch in.

And finally, this one has us scratching our head. Activist group Extinction Rebellion (XR) has claimed they’ve “decommissioned” thousands of electric scooters in French cities. Why they’ve done this is the puzzler; they claim that the scooters-for-hire are an “ecological disaster” due to the resources needed to produce them compared to their short lifespan. We haven’t done the math. What is interesting, though, is the mode of decommissioning: XR operatives simply defaced the QR code on the scooters, rendering them un-rentable with the vendor’s smartphone app. Scooter companies might want to look into alternative rental methods if this keeps up.

Protect Your Batteries Before You Wreck Your Batteries

[Jan] is solving a problem many of us have had, deeply discharging our project’s batteries and potentially damaging the cells.

His board can handle batteries from 6 to 34 volts and supports both LiPo or Lion batteries. The board can be flexible about its cut-off voltage. It also has a feature we really like; the user can set a delay before it shuts off the battery: useful in cases where a heavy peak current draw causes the battery to operate at a lower-than-threshold voltage for a few seconds. Once the board is shut down it takes a manual reset to allow power to be drawn again.

His latest iteration of the board is an impressive 1 sq. inch in size! This can fit in just about any project and it’s even flexible in the choice of battery connector. Next time we have a high current draw project with expensive batteries or maybe a monitoring device that’s expected to run a long time we may throw one of these boards in there just to be safe.

Gutted Hoverboard Becomes Formidable Track-Drive Robot

When “hoverboards” first came out, you may have been as disappointed as we were that they did not even remotely fulfill the promises of Back to the Future II. Nothing more than a fancified skateboard, hoverboards are not exactly groundbreaking technology. That doesn’t mean they’re not useful platforms for hacking, though, as this hoverboard to track-propelled robot tank conversion¬†proves.

Most of the BOM for this build came from the junk bin – aluminum extrusions, brackets, and even parts cannibalized from a 3D-printer. But as [pasoftdev] points out, the new-in-box hoverboard was the real treasure trove of components. The motors, the control and driver electronics, and the big, beefy battery were all harvested and mounted to the frame. To turn the wheels into tracks, [pasoftdev] printed some sprockets to fit around the original tires. The tracks were printed in sections and screwed to the wheels. Idlers were printed in sections too, using central hubs and a clever method for connecting everything together into a sturdy wheel. Printed tank tread links finished the rolling gear eventually; each of the 34 pieces took almost five hours to print. The dedication paid off, though, as the 15-kg tank is pretty powerful; the brief video below shows it towing an office chair around without any problems.

We noticed that [pasoftdev] found the assembly of the tread links a bit problematic. These 3D-printed links that are joined by Airsoft BBs might make things a little easier next time.

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Better Battery Management Through Chemistry

The lead-acid rechargeable battery is a not-quite-modern marvel. Super reliable and easy to use, charging it is just a matter of applying a fixed voltage to it and waiting a while; eventually the battery is charged and stays topped off, and that’s it. Their ease is countered by their size, weight, energy density, and toxic materials.

The lithium battery is the new hotness, but their high energy density means a pretty small package that can get very angry and dangerous when mishandled. Academics have been searching for safer batteries, better charge management systems, and longer lasting battery formulations that can be recharged thousands of times, and a recent publication is generating a lot of excitement about it.

Consider the requirements for a battery cell in an electric car:

  • High energy density (Lots of power stored in a small size)
  • Quick charge ability
  • High discharge ability
  • MANY recharge cycles
  • Low self-discharge
  • Safe

Lithium ion batteries are the best option we have right now, but there are a variety of Li-ion chemistries, and depending on the expected use and balancing and charging, different chemistries can be optimized for different performance characteristics. There’s no perfect battery yet, and conflicting requirements mean that the battery market will likely always have some options.

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Replacement Batteries For The Sony Discman

Some of the first Sony Discmans included rechargeable batteries. These batteries were nickel metal hydride batteries (because of the technology of the time) and are now well past their service life. The new hotness in battery technology is lithium — it offers greater power density, lighter weight, and a multitude of ready-to-go, off the shelf cells. What if someone were to create a new battery pack for an old Sony Discman using lithium cells? That’s exactly what [sjm4306] did for their entry into this year’s Hackaday Prize.

The Discman [sjm] is working with uses a custom, Sony-branded battery based on NiMH technology with a capacity of around 500 mAH. After carefully measuring the dimensions of this battery, it was replicated in plastic with a 3D printer. This enclosure was then stuffed with a small lithium cell scavenged from a USB power bank.

The only tripping points for this build were the battery contacts. The originally battery had two contacts on the end that fit the Discman exactly; these were replicated with a small PCB wired up to the guts of the USB powerbank. The end result is a direct, drop-in replacement for the original Discman battery with a higher capacity, that’s also rechargeable via USB. It’s a fantastic project, with the entire build video available below.

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Charge All Your Batteries With USB PD

USB-C has been around for a while, and now that it can charge phones and Macbooks and Thinkpads, the hackers are starting to take note of power adapters that can supply lots of current. [Alex] was turned on to USB-C after he charged a laptop, Nintendo Switch, and phone with one power adapter. This led him to create a USB-C battery charger for all your LiPos.

The high-level design of this project is simply a board with a USB C port on one end, an XT60 plug on the other, and some support for balance leads. Plug this board into a USB C adapter, plug a battery in, and the battery will charge automagically. The only UI is an RGB LED. It’s difficult to imagine a battery charger that’s easier to use.

For the electronics, [Alex] is using an STM32G0 for the smarts of the device, which includes handling the USB PD spec. This gives the charger 20 Volts to play with, and this is then regulated and sent into the battery. Right now, this board will charge 2-4c batteries. That’s a good enough proof of concept to charge some quadcopter batteries, or just as a really simple way to charge some LiPo cells.