Supercon SMD Challenge Gets 3D Printed Probes: Build Your Own

This year was the second SMD challenge at Supercon, so it stands to reason we probably learned a few things from last year. If you aren’t familiar with the challenge, you are served some pretty conventional tools and have to solder a board with LEDs getting progressively smaller until you get to 0201 components. Those are challenging even with proper tools, but a surprising number of people have managed to build them even using the clunky, large irons we provide.

During the first challenge, we did find one problem though. The LEDs are all marked for polarity. However, since we don’t provide super high power magnification, it was often difficult to determine the polarity, especially on the smaller parts. Last year, [xBeau] produced some quick LED testers to help overcome this problem. This year we refined them a bit.

As you can see, the 2018 model was a very clever use of what was on hand. A CR2032 holder powered the probes and the probes themselves were two resistors. If you can get the LED to light with the probes you know which lead is the anode and which is the cathode. A little red ink makes it even more obvious.

Mess with Success

One school of thought was that these probes worked well in 2018 so we could just build up some more for the 2019 challenge. However, while these worked well enough, they were not very handy to use. The little wires aren’t really springs, and they would fatigue after long use.

I wanted something that would hold up to abuse better and have a little bit better ergonomics. I thought about 3D printing something. As I always do before I try to design something, I did a quick search to see if there was anything similar out there.

Over on Thingiverse, [Tom20170] had just what I needed. It was a simple 3D print for an SMD test clamp. It had a springy little plastic coil, and a housing to hold breadboard cables to use as probes.


Printing was easy, but I didn’t want to have too many wires or connections, so I wound up making two very simple modifications.

Here’s my bill of materials:

  • Eagle Plastic Devices 12BH443B-GR – 4 AAA battery holder with 9 V snaps
  • Keystone 237-M – 9 V battery snap with 8″ leads
  • 100 Ω resistors from my junk box (see below)
  • Molex 02-06-2132 – Crimp pins (only needed for the second version)
  • Heat shrink tubing
  • Electrical tape

The 9 V snaps were ideal. I got the better kind that has a molded body instead of the cheap ones that tend to break after 9 or 10 snaps. They do cost a little more, but even if you are only buying one they are still under a dollar. Saving fifty cents and breaking the connector every few months is definitely false economy.

I made a few with the Molex pins and decided the resistor leads were probably just as good bare, so I didn’t use the rest of the pins. I used heat shrink on them when I did use them. You could probably also use the wires the Thingiverse design calls for, if you wanted.

The resistors are what I had on hand. They aren’t super critical and if I had to do it over again, they are one of a few things I’d change.


I printed a bunch of probe bodies using PLA at 0.3 mm layer height on an ANET A8. I used 20% infill, but that probably wasn’t very important. They don’t take long to print, so I fit as many as I could put on the bed at one time, and then did a few runs.

The resistors slot nicely into the cavity on either side and a little heatshrink hides the solder joints. Electrical tape or heatshrink ties the wires to the sides to strain relief everything. As before, a little red ink makes it easy to see which lead is positive.

If you look closely, you’ll see that a permanent marker isn’t the best way to mark PLA. It sort of soaks into places you didn’t mean for it to go. However, for a positive mark, that’s not very important. I wouldn’t use it to color a 3D print, though, if it mattered that the color region was crisp.

More Tweaks?

We couldn’t really tell if anyone preferred the tips versus the bare resistor leads. Having the batteries detachable definitely made it easier to transport the probes.

The resistors limit the current depending on the LED’s forward voltage. Typically, an LED will have somewhere between 1.8 V and 3.3 V drop. With a 100 Ω resistor, that works out to a range between 13.5 mA and 21 mA. That’s a little hot on the high end, and you could probably safely increase the resistor values. With two 470 Ω resistors, you’d have the current run between roughly 3 mA and 8 mA. 1 kΩ should also work, but might be a little dim.

Instead of using a higher resistance, I had toyed with the idea of putting a second LED in series so the tweezers could double as a continuity probe.  A 1.8 V red LED, for example, would see about 12 mA if you short the probe, but would still let most LEDs under test to get 5 or 6 mA with a 100 Ω resistor.

The Right Stuff

Of course, if your multimeter has a diode setting, that’s probably the right tool for the job. The positive probe will indicate the anode of the LED if the device lights. If it doesn’t light, switch the probes around.

If you look at the LED datasheet, you should find a way to identify the polarity optically. For example, some have a green stripe, a dot, or a notch. You can also intuit the polarity by noting the connections inside the LED if it has a clear lens. Sometimes the shape of the solder pad will tell you. If the components are on a reel, the reel usually has a way to tell, but that doesn’t help you if you just have a few loose parts.

Have a look at this LED datasheet from Vishay. You can see the terminals and pad look a little different. This one from Kingbright clearly shows a cut-off corner. You can see many examples in this Digikey TechForum post.

If you want to see more about the SMD challenge, check out [Dan Maloney’s] experience. Perhaps you prefer your tweezers a bit smarter. However, if you do make a pair of these, post them up and send us a link. Meanwhile, you can start practicing for next year’s competition. It is never too early.

Linux Fu: Debugging Bash Scripts

A recent post about debugging constructs surprised me. There were quite a few comments about how you didn’t need a debugger, as long as you had printf. For that matter, we’ve all debugged systems where you had nothing but an LED to flash or otherwise turn on to communicate with the user. However, it is hard to deny that a debugger can help with complex code.

To say you only need printf would be like saying you only need machine language. Technically accurate — you can do anything in machine language. But it sure makes things easier to have an assembler or some language to help you work out your problem. If you write a simple bash script, you can use the equivalent to printf — maybe that’s the echo command, although there is usually a printf command on a typical system, if you want to use it. However, there are other things you can do with bash including a pretty cool debugger if you know how to find it.

I assume you already know how to use echo and printf, but let’s dig into how to use trace execution line by line without the need for echo statements on every other line. Along the way, you’ll learn how to get started with the bash debugger.

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Weird Substances: Hagfish Slime

In the cold, dark recesses of ocean floors around the world, hagfish slither around like sea snakes, searching for food. When a hagfish finds a suitable carcass, it devours the dead fish in two different ways. As it burrows face-first through the tissue, eating with its jaw-less, tentacled mouth, the hagfish also absorbs nutrients through its skin.

Hagfish are not the unholy result of dumping toxic waste in the ocean. They’re one of the oldest creatures on Earth, having been around for more than 300 million years. How have they lasted this long?

A coiled hagfish reveals its slime ports. Image via Oregon Coast Aquarium

These ancient creatures have no eyes, no backbones, and no scales. They are often misidentified as eel, and often called ‘slime eels’, but they are definitely fish. They just don’t look like conventional fish. In fact, when conventional, gill-faced fish come after hagfish, those guys are in for a surprise, because hagfish have a disgusting but ingenious defense mechanism.

Whenever hagfish are attacked or even just stressed by nearby fish or curious grabby humans, they immediately emit amazing amounts of mucus at an alarming rate. At the same time, the hagfish shoots out silky strands of protein that hold the slime together in a cohesive blob. Any predator that tries to bite down on one of these velvety frankfurters of the deep sea will find its mouth and gills covered in a wad of suffocating slime.

How is it that hagfish haven’t slimed themselves out of existence? Whenever they get get a taste of their own medicine, these boneless noodles quickly twist themselves into a pretzel. In the same motion, they use their paddle-shaped tails to squeegee off the slime.

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Open-Source Satellite Propulsion Hack Chat

Join us on Wednesday, December 11 at noon Pacific for the Open-Source Satellite Propulsion Hack Chat with Michael Bretti!

When you look back on the development history of any technology, it’s clear that the successful products eventually reach an inflection point, the boundary between when it was a niche product and when it seems everyone has one. Take 3D-printers, for instance; for years you needed to build one if you wanted one, but now you can buy them in the grocery store.

It seems like we might be getting closer to the day when satellites reach a similar inflection point. What was once the province of nations with deep pockets and military muscles to flex has become far more approachable to those of more modest means. While launching satellites is still prohibitive and will probably remain so for years to come,  building them has come way, way down the curve lately, such that amateur radio operators have constellations of satellites at their disposal, small companies are looking seriously at what satellites can offer, and even STEM programs are starting to get students involved in satellite engineering.

Michael Bretti is on the leading edge of the trend toward making satellites more DIY friendly. He formed Applied Ion Systems to address one of the main problems nano-satellites face: propulsion. He is currently working on a range of open-source plasma thrusters for PocketQube satellites, a format that’s an eighth the size of the popular CubeSat format. His solid-fuel electric thrusters are intended to help these diminutive satellites keep station and stay in orbit longer than their propulsion-less cousins. And if all goes well, someday you’ll be able to buy them off-the-shelf.

Join us for the Hack Chat as Michael discusses the design of plasma thrusters, the details of his latest testing, and the challenges of creating something that needs to work in space.

join-hack-chatOur Hack Chats are live community events in the Hack Chat group messaging. This week we’ll be sitting down on Wednesday, December 11 at 12:00 PM Pacific time. If time zones have got you down, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.

Teardown: 168-in-1 Retro Handheld Game

The holidays are upon us, and that can mean many furrowed brows trying to figure out what token gift they can give out this year as stocking-stuffers. Something that’s a bit more interesting than a coupon book or a lotto scratcher, but also affordable enough that you can buy a few of them without having to take part in that other great holiday tradition: unnecessary credit debit.

Includes the NES classic Super Militarized Police Bros 3

Which is how I came to possess, at least temporarily, one of these cheap handheld multi-games that are all over Amazon and eBay. The one I ordered carries the brand name Weikin, but there are dozens of identical systems available, all being sold at around the same $20 USD price point. With the outward appearance of a squat Game Boy, these systems promise to provide precisely 168 games for your mobile enjoyment, and many even include a composite video out cable and external controller for the less ambulatory classic game aficionado.

At a glance, the average Hackaday reader will probably see right through this ploy. Invariably, these devices will be using some “NES on a Chip” solution to emulate a handful of legitimate classics mixed in with enough lazy ROM hacked versions of games you almost remember to hit that oddly specific number of 168 titles. It’s nearly a foregone conclusion that at the heart of this little bundle of faux-retro gaming lies a black epoxy blob, the bane of hardware tinkerers everywhere.

Of course, there’s only one way to find out. Let’s crack open one of these budget handhelds to see what cost reduction secrets are inside. Have the designers secured their place on the Nice List? Or have we been sold the proverbial lump of coal?

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Hackaday Links: December 8, 2019

Now that November of 2019 has passed, it’s a shame that some of the predictions made in Blade Runner for this future haven’t yet come true. Oh sure, 109 million people living in Los Angeles would be fun and all, but until we get our flying cars, we’ll just have to console ourselves with the ability to “Enhance!” photographs. While the new service, AI Image Enlarger, can’t tease out three-dimensional information, the app is intended to sharpen enlargements of low-resolution images, improving the focus and bringing up details in the darker parts of the image. The marketing material claims that the app uses machine learning, and is looking for volunteers to upload high-resolution images to improve its training set.

We’ve been on a bit of a nano-satellite bender around here lately, with last week’s Hack Chat discussing simulators for CubeSats, and next week’s focusing on open-source thrusters for PocketQube satellites. So we appreciated the timing of a video announcing the launch of the first public LoRa relay satellite. The PocketCube-format satellite, dubbed FossaSat-1, went for a ride to space along with six other small payloads on a Rocket Lab Electron rocket launched from New Zealand. Andreas Spiess has a short video preview of the FossaSat-1 mission, which was designed to test the capabilities of a space-based IoT link that almost anyone can access with cheap and readily available parts; a ground station should only cost a couple of bucks, but you will need an amateur radio license to uplink.

We know GitHub has become the de facto standard for source control and has morphed into a collaboration and project management platform used by everybody who’s anybody in the hacking community. But have you ever wished for a collaboration platform that was a little more in tune with the needs of hardware designers? Then InventHub might be of interest to you. Currently in a limited beta – we tried to sign up for the early access program but seem to have been put on a waiting list – it seems like this will be a platform that brings versioning directly to the ECAD package of your choice. Through plugins to KiCad, Eagle, and all the major ECAD players you’ll be able to collaborate with other designers and see their changes marked up on the schematic — sort of a visual diff. It seems interesting, and we’ll be keeping an eye on developments.

Amazon is now offering a stripped-down version of their Echo smart speaker called Input, which teams up with speakers that you already own to satisfy all your privacy invasion needs on the super cheap — only $10. At that price, it’s hard to resist buying one just to pop it open, which is what Brian Dorey did with his. The teardown is pretty standard, and the innards are pretty much what you’d expect from a modern piece of surveillance apparatus, but the neat trick here involved the flash memory chip on the main board. Brian accidentally overheated it while trying to free up the metal shield over it, and the BGA chip came loose. So naturally, he looked up the pinout and soldered it to a micro-SD card adapter with fine magnet wire. He was able to slip it into a USB SD card reader and see the whole file system for the Input. It was a nice hack, and a good teardown.

Hackaday Podcast 045: Raspberry Pi Bug, Rapidly Aging Vodka, Raining On The Cloud, And This Wasn’t A Supercon Episode

Hackaday editors Mike Szczys and Elliot Williams talk over the last three weeks full of hacks. Our first “back to normal” podcast after Supercon turns out to still have a lot of Supercon references in it. We discuss Raspberry Pi 4’s HDMI interfering with its WiFi, learn the differences between CoreXY/Delta/Cartesian printers, sip on Whiskey aged in an ultrasonic jewelry cleaner, and set up cloud printing that’s already scheduled for the chopping block. Along the way, you’ll hear hints of what happened at Supercon, from the definitive guide to designing LEDs for iron-clad performance to the projects people hauled along with them.

Take a look at the links below if you want to follow along, and as always tell us what you think about this episode in the comments!

Direct download (71 MB)

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