Building One Test Fixture To Rule Them All

Test and programming fixtures are great time-savers for anyone who needs to deal with more than a handful of PCBs. Instead of plugging in connectors (or awkwardly holding probe tips or wires) to program some firmware or run tests, one simply pops a PCB into a custom fixture with one hand, and sips a margarita with the other while a program decides whether everything is as it should be. Test fixtures tend to be custom-made for specific board layouts, meaning one tester is needed per board or device type, but this work is easily justified by the huge time savings they offer.

An inserted PCB sits atop the thick acrylic piece, with pogo pins making contact from below. Generous space on the left and right make sure there is clearance for any mounted components. Visible near the bottom of the green board are output LEDs, and two touch-sensitive pads.

But the fine folks at Sparkfun’s quality control department figured they could save even more time by exploiting common design features across different boards, and shared details about designing a single test fixture flexible enough to handle multiple board types and designs.

The test unit looks like pretty familiar stuff at first glance: some hardware responsible for running the test program, laser-cut acrylic jig to hold a test PCB in a consistent position, spring-loaded pogo pins to make temporary electrical connections, and LEDs to clearly indicate PASS and FAIL states. The clever part is the way the fixture is designed to accommodate multiple board designs, and how it uses several 74LVC4066 quad bilateral switch ICs to take care of switching which pogo pins are connected and to where.

As mentioned, to be compatible with multiple boards there must be common design elements to exploit. In Sparkfun’s case, the through-hole connections on their breakout boards are all in a row with standard 0.1″ spacing. By using the aforementioned pogo pins and 4066 ICs, different pinouts can be accommodated and multiple board types can be used without any need to swap to different test hardware.

Test and programming fixtures, being one-offs, tend to have a lot of space for creativity and often show clever design or re-purposing of parts. Our own [Bob Baddeley] explains all about them here.

Modular Keyboards For CAD, Gaming, And Video Editing

Of all the input devices, the keyboard is the greatest. This comes at a cost, though: there were times back in the Before Days, when video and music editing applications came with custom keyboards. There were Pro Tools keyboards, Final Cut keyboards, and innumerable Adobe keyboards. What’s the solution to this problem? More keyboards, obviously, and this time we’ll make them modular.

For his Hackaday Prize entry, [Cole B] is building modular, programmable USB keyboards. It’s got everything: a standard 3×3 keypad, a keyboard that’s just four potentiometers, a keyboard that’s a rotary encoder, and a keyboard that’s a set of faders.

The design of these keyboards is inherently modular, and that means there needs to be a way to connect all these modules together, preferably without a bunch of USB cables strewn about. Right now, the best idea [Cole] is working with is pogo pins and magnets. It’s a great idea although Apple Thinks Differently™ and probably wouldn’t be too keen on seeing the whole ‘magnets and pins’ idea stolen out from under them.

Nevertheless, it’s an excellent project that shows how far you can go with manufacturing on a limited budget. These are fantastic keyboard modules already, and the connector scheme already pushes this project into the upper echelon of keyboard hacks.

A Peek Into A Weed-Eating Robot’s Test Fixtures

When it comes to production, fast is good! But right the first time is better. Anything that helps prevent rework down the line is worth investing in. Some of the best tools to catch problems are good test fixtures. The folks at Tertill (a solar-powered robot for killing weeds that kickstarted last year) took the time to share two brief videos of DIY test fixtures they use to test components before assembly.

The videos are short, but they demonstrate all the things that make a good test: on the motor tester there are no connectors or wires to fiddle with, the test starts automatically, and there is clear feedback via prominent LEDs. The UI board tester also starts automatically and has unambiguous LED feedback, and sports a custom board holder with a recess just the right shape for the PCB. Once the board is in, the sled is pushed like a drawer to make contact with the test hardware and begin the test. The perfectly formed recesses in both units serve another function as well; they act as a go/no-go test for the physical shape of the components and contacts being tested.

Both videos are embedded below; and while there isn’t much detail on the actual test hardware, we do spy a Raspberry Pi and at least two Adafruit logos among other hacker-familiar elements like laser-cut acrylic, 3D printed plastic, pogo pins, and a PVC junction box.

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3D Printed ESP8266 Programming Jig

The various development boards such as the NodeMCU or Wemos D1 make working with the ESP8266 an absolute breeze. If they have a downside, it is that they are larger than the bare ESP2866, and of course cost a bit more. Just as with the Arduino, once you have the wiring sorted out and the code more or less finalized, your best bet is to ditch the unnecessary support hardware and use the bare module to save space and money in your final design.

The design took a few revisions to get right

Unfortunately, the ESP8266 form factor isn’t terribly forgiving when it comes time for hooking up a programmer. Rather than having to solder a serial adapter to the chip to flash it, [Ryan] came up with a slick 3D printed programming jig that uses pogo pins. If you have to program these boards in bulk, a jig like this can save a massive amount of time and aggravation.

Beyond the 3D printed holder for the pogo pins, this programmer uses a FTDI USB-to-serial adapter, a couple passive components to smooth out the power going into the chip, and a couple buttons.

In the video after the break, [Ryan] walks through the many iterations it took to get the 3D printed aspect of the jig worked out. The design went through a few rather large revisions, including one that fundamentally changed the whole form factor. Even with the jig now working, he mentions that he might circle back around and try it from a different angle.

Programming jigs are a staple of electronics manufacturing, and we’ve covered quite a few that have helped transformed a proof of concept into a small scale production runs.

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Hackaday Links: December 3, 2017

Remember the Psion? Back when PDAs were a thing, the Psion was the best you could get. It was, effectively, a palm-top computer with a real qwerty keyboard. It didn’t have Bluetooth, it couldn’t browse the web, and it didn’t have WiFi, but this was an AA-powered productivity machine that could fit in your pocket. Now there’s a new palmtop from Psion engineers. The Gemini PDA is basically a smartphone with a real keyboard that runs Ubuntu. It’s also has a smaller battery than other devices with this form factor, meaning the TSA thinks it’s a smartphone. This thing is going to be cool.

TechShop, Inc. has reached an agreement to sell the company to TechShop 2.0, LLC. New ownership seeks to re-open, continue running makerspaces. Details coming soon.

Arcade monitors are cool, and vector monitors are even cooler. [Arcade Jason] created a gigantic 36″ vector monitor. It’s thirty-six inches of Gravitar, in all its vector glory.

A few links posts ago, I pointed out someone was selling really awesome, really cheap LED panels on eBay. I got my ten panels, and [Ian Hanschen] bought sixty or some other absurd amount. Now, these panels are going for $300 for a 10-pack instead of $50. Sorry about that. Nevertheless, the reverse engineering adventure is still ongoing, and eventually, someone is going to play Mario on these things.

The ESP32 is finding its way into all sorts of consumer electronics. Check this thing out. It’s an ESP32, four buttons, and a circular display. If you want to make your own Nest thermostat, or anything else that needs an awesome circular display, there you go.

Speaking of circular displays, are there any non-CRT displays that come with a polar coordinate system? Every circular LCD or OLED I’ve ever seen uses a Cartesian system, which doesn’t really make sense when you can’t see 30% of the pixels.

Hold the phone, this is far too clever. [Eduardo] needed to flash an ESP-12 module before soldering it onto a PCB. The usual way of doing this is with an absurd pogo pin jig. You know what’s cheaper than pogo pins? Safety pins. Clever overwhelming.

Pogo Pin Serial Adapter Thing

A few weeks ago, I was working on a small project of mine, and I faced a rather large problem. I had to program nearly five hundred badges in a week. I needed a small programming adapter that would allow me to stab a few pads on a badge with six pogo pins, press a button, and move onto the next badge.

While not true for all things in life, sometimes you need to trade quality for expediency. This is how I built a terrible but completely functional USB to serial adapter to program hundreds of badges in just a few hours.

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Jump Into Pogo

A lot of modern PCBs have small pads with no components attached. They are often used as test points, JTAG ports, or programmer connections. There’s no connector on the board, just pads. To use those, test equipment and programmers utilize pogo pins. These are small pins with a spring inside, reminiscent of a tiny pogo stick.

To use pogo pins effectively, you need a way to hold them in the right position and something to put pressure on them while they are in use. [Joshua Brooks] used a strip board to hold them in place and clothes pin to keep the pressure on them.

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