Production PCB And Pogo Pins Produce A Clever Test Jig

January 7, 2022 by Dave Rowntree 13 Comments

[Hans Summers] runs a site qrp-labs.com, selling self-assembly kits mostly for radio gear and GPS applications, and had some production problems with his QCX-mini QRP transceiver kit. They were using an assembly house that had some problems with a sub-contractor going under during the pandemic, and the replacement service was somewhat below the expected level of quality, resulting in a significant number of SMT populated boards coming out non-functional. Obviously, not wanting to pass these on to customers as a debug problem, they set to work on an in-house QA test jig, to give them the confidence to ship kits again. The resulting functional test jig, (video, embedded below) takes a fairly interesting approach. Skip the video to 9:00 for the description of the test jig and detailed test descriptions.

By taking an existing known-good PCB, stripping off all the SMT parts, and moving the through hole components to the rear PCB side, pogo pins could be soldered to strategic locations. Building the assembly into a rudimentary enclosure made from sawn-up raw copper clad board, with the pogos facing upwards, and a simple clamp on top, allowed the PCB-under-test (let’s call it the UUT from hereon) to be located and clamped in place. This compressed the pogos in order to make a firm electrical contact. A piece of MDF that had been attacked with a dremel did duty as a pressure plate, with cutouts around the SMT component areas to achieve the required uniform board pressure and keeping the force away from the delicate soldered parts. All this means that with an UUT connected via pogo pins to a through-hole only test PCB, the full circuit would be completed, if and only if the UUT was completely functional, and that means defect-free soldering and defect-free components.

Next the firmware was rewritten to do duty as the test controller, which when powered up would step through a sequence of test scenarios and measurements, logging the results to an OLED display and a serial interface. This rig survived 1,000 SMT tests without failing, giving [Hans] the confidence to ship out new kits and providing a database of datalog results as a backup should a customer have an issue during final assembly. All-in-all a smart idea to solve a difficult problem, with nary a custom test jig PCB in sight!

These pages have been graced with many a pogo-based test rig over the years. Here’s one to start, and if you’ve got a handy laser cutter and some scrap wood, making an accurate test rig is no bother either.

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PsyLink An Open Source Neural Interface For Non-Invasive EMG

January 7, 2022 by Dave Rowntree 30 Comments

We don’t see many EMG (electromyography) projects, despite how cool the applications can be. This may be because of technical difficulties with seeing the tiny muscular electrical signals amongst the noise, it could be the difficulty of interpreting any signal you do find. Regardless, [hut] has been striving forwards with a stream of prototypes, culminating in the aptly named ‘Prototype 8’

The current prototype uses a main power board hosting an Arduino Nano 33 BLE Sense, as well as a boost converter to pump up the AAA battery to provide 5 volts for the Arduino and a selection of connected EMG amplifier units. The EMG sensor is based around the INA128 instrumentation amplifier, in a pretty straightforward configuration. The EMG samples along with data from the IMU on the Nano 33 BLE Sense, are passed along to a connected PC via Bluetooth, running the PsyLink software stack. This is based on Python, using the BLE-GATT library for BT comms, PynPut handing the PC input devices (to emit keyboard and mouse events) and tensorflow for the machine learning side of things. The idea is to use machine learning from the EMG data to associate with a specific user interface event (such as a keypress) and with a little training, be able to play games on the PC with just hand/arm gestures. IMU data are used to augment this, but in this demo, that’s not totally clear.

All hardware and software can be found on the project codeberg page, which did make us double-take as to why GnuRadio was being used, but thinking about it, it’s really good for signal processing and visualization. What a good idea!

Obviously there are many other use cases for such a EMG controlled input device, but who doesn’t want to play Mario Kart, you know, for science?

Checkout the demo video (embedded below) and you can see for yourself, just be aware that this is streaming from peertube, so the video might be a little choppy depending on your local peers. Finally, if Mastodon is your cup of tea, here’s the link for that. Earlier projects have attempted to dip into EMG before, like this Bioamp board from Upside Down Labs. Also we dug out an earlier tutorial on the subject by our own [Bil Herd.]

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New Part Day: The RISC-V Lichee-RV Module And Dock

January 6, 2022 by Dave Rowntree 47 Comments

Sipeed have been busy leveraging developments in the RISC-V arena, with an interesting, low-cost module they call the Lichee RV. It is based around the Aliwinner D1 SoC (which contains a Pingtou Xuantie C906 for those following Chinese RISC-V processor development) with support for an optional NAND filesystem. This little board uses a pair of edge connectors, similar to the Raspberry Pi CM3 form factor, except it’s based around a pair M.2 connectors instead. The module has USB-C, an SPI LCD interface, as well as a TF card socket on-board, with the remaining interfaces provided on the big edge connector.

The minimalist Allwinner D1-based Lichee RV

So that brings us onto the next Sipeed board, the Lichee RV Dock which is a tiny development board for the module. This breaks out the HDMI, adds USB, a WiFi/Bluetooth module, audio driver, microphone array interface and even a 40-way GPIO connector. Everything you need to build your own embedded cloud-connected device.

Early adopters beware, though, Linux support is still in the early stages of development, apparently with Debian currently the most usable. We’ve not tested one ourselves yet, but it does look like quite useful for those projects with a small budget and not requiring the power-hungry multi-core performance of a Raspberry Pi or equivalents.

We’ve seen the Sipeed MAix M1 AI Module hosted on a Pi Hat a couple of years ago, as well as a NES emulator running on the Sipeed K210. The future for RISC-V is looking pretty good if you ask us!

Thanks [Maarten] for the tip!

A Simple Touch Probe Made With Basic Tools

January 5, 2022 by Dave Rowntree 14 Comments

Six points of contact detect any displacement.

LinuxCNC contributor and machining enthusiast [Andy Pugh] is certainly not afraid to try making specialised tools to see how well they work out, and this time he’s been busy making a touch probe (video, embedded below) for checking the accuracy of machining operations and general measuring applications.

These things are not cheap, since they are essentially ‘just’ a switch with a long probe, But, as with anything specialised and machined with tight tolerances, you can understand why they cost what they do.

After inspecting and spending some time reverse-engineering such a unit, [Andy] then proceeded to grab some PEEK bar he had lying around and chuck it into the lathe (get it?). He notes Delrin would be more cost effective for those wishing to reproduce this, but as long as you have the ability to machine it and it’s non-conductive, there are many other options you could try.

Using no special tools other than a collet block (like this one) all the angled holes and slots were made with ease, with the help of a specially 3D-printed mount for the vise. A nice, simple approach, we think!

[Andy] tested the repeatability of the probe, mounted over his CNC-converted Holbrook lathe, reporting a value of 1 um, which seems rather good. Centering of the probe tip within the probe body was off a bit, as you’d expect for something made practically by hand, but that is less of a problem as it would seem, as it results in a fixed offset that can be compensated for in software. Perhaps the next version will have some adjustability to dial that out manually?

The whole assembly is formed from two plastic parts, a handful of ground-finished hardened steel pins, and a big spring. The only part remotely special is an off-the-shelf probe tip. During the electrical hookup, you may notice the use of a self-fluxing verowire pen, which was something this scribe didn’t know existed and has already placed an order for!

The reference 3D model for the design is shared from [Andy]’s Autodesk Drive for your viewing pleasure.

Of course, this isn’t the first DIY touch probe we’ve seen, here’s one for example, and over on Hackaday.IO, here’s an attempt to make one using a piezoelectric transducer.

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Improved Thermochromic Clock Uses PCB Heaters For Better Contrast

January 4, 2022 by Dave Rowntree 11 Comments

We love timepiece projects round these parts, so here we are with another unusual 7-segment clock design. Hackaday’s own [Moritz Sivers] wasn’t completely satisfied with his last thermochromic clock, so has gone away and built another one, solved a few of the issues, and this time designed it to be wall mounted. The original design had a single heater PCB using discrete resistors as heating elements. This meant that the heat from active elements spread out to adjacent areas, reducing the contrast and little making it a bit hard to read, but it did look really cool nonetheless.

This new version dispenses with the resistors, using individual segment-shaped PCBs with heater traces, which gives the segment a more even heat and limited bleeding of heat into neighbouring inactive air-gapped segments. Control is via the same Wemos D1 Mini ESP8266 module, driving a chain of 74HC595 shift registers and a pile of dual NMOS transistors. A DS18B20 thermometer allows the firmware to adjust for ambient temperature, giving more consistency to the colour change effect. All this is wrapped up in an aluminium frame, and the results look pretty nice if you ask us.

Both PCB designs and the Arduino firmware can be found on the project GitHub, so reproducing this should be straightforward enough for those so inclined, just make sure your power supply can handle at least 3 amps, as these heaters sure are power hungry!

Got a perfectly good clock, but desperately need a thermochromic temperature/humidity display? [Moritz] has you covered. And if this digital clock is just too simple, how about a mad 1024-element analog thermochromic clock instead?

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Angel Investor Gives Open Source PnP A Massive Boost

January 4, 2022 by Dave Rowntree 18 Comments

We love it when an Open Source hardware project grows up and turns into a sustainable business, bootstrapped with nothing but hard work and great ideas, but it’s a really tough prospect to do it using your own money, ploughing the profits from any sales back into development and not taking a dime in wages whilst you do so. People obviously need an income to live off, and that time spent working on a startup is time you can’t spend earning your keep. So it’s with great pleasure that we can bring you the latest news from [Stephen Hawes] and his pick-and-place machine plans. In the year since we last checked in with the project, development has continued at a steady pace, with the guys quickly outgrowing the garage workspace, whilst they prepare PnP machine kits ready for sale.

The big news is that [Joel Spolsky], co-founder of Stack Exchange, creator of Kanban management tool, Trello, and angel investor, has made a sizable ($100K USD) investment in the company which has allowed them to take on a 3,000+ sq. ft office space, and given them the funds for stock and all that boring business overhead stuff. [Stephen] takes time to explain that [Joel] will not have any control of the company, and all hardware and software will remain fully Open Source. For those interested [Joel] implemented his investment as a SAFE note (Simple Agreement for Future Equity) and as such, [Joel] will only make a return in the form of a small share allocation, if they hit the big-time in the future. Can’t really say fairer than that!

[Stephen] did recently receive a ‘cease and desist’ notice regarding his use of the ‘Index’ name for the project, since that is already a trademarked term, defended by somebody else, the project will need change name very soon. A minor setback, but it is a bit annoying that a chunk of that investment now has to go to a lawyer to make sure that the name they do eventually choose isn’t already taken and is safe to use.

In terms of the machine itself, it is now is fully operating, with multiple automatic tape feeders, featuring up and down-facing machine vision, and all that OpenPnP goodness. It has even been demonstrated placing parts for its own custom motherboard PCB, reprap style. Nice!

We wish [Stephen] and partner [Lucian] all the success they deserve, and hope they get those kits out there, because there are people around these parts that need an affordable, hackable, desktop PnP machine ASAP, this scribe included!

Here’s the earlier story covering the machine, but it’s not the only Open Source PnP machine we’ve seen – here’s another one from a few years ago.

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Metal mechanoid security patrol ride-on made from scrap

Homemade Scrapyard Security Mech Gives Uncle Super Powers

January 3, 2022 by Dave Rowntree 26 Comments

[Handy Geng] is back again with another bonkers build, that we just can’t not cover. His Uncle came to visit the workshop one day and said he’d love to go there every day, and could even watch over it when [Handy Geng] was away. But being an older chap and needing a stick to get around, he would not be much use if ‘bad guys’ decided to pay a visit. The obvious solution was to build a ride-on security mech which Uncle could ride on, (video, embedded below) and use to defend the shop from bandits.

The build starts with him unloading a large pair of tracked wheel units from his truck, which caused a chuckle around these parts when we tried to imagine the scrap yard he’d just visited! The build video is more of a spot-weld-come-assembly log, with the less interesting sub assembly construction omitted. If he’d included all the details, this video would have been hours long. Though, we’d probably watch that anyway.

Features of the final construction include, but not limited to, dual motors for on-the-spot turns, night-time patrol lights, dual pneumatic fists for attack mode, dual water cannons for a more gentle approach and rear facing speakers blasting out Chinese opera for the ultimate deterrent. Practical touches include an integrated glasses case for the ready-readers, and a walking cane holder, so the mech was Uncle-ready. He seemed impressed from the grin on his face!

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