RIP John Birkett, Parts Vendor Extraordinaire

May 20, 2022 by Jenny List 50 Comments

It is with sadness that we note the passing of John Birkett, proprietor of the legendary eponymous surplus radio and electronics store on an unassuming street in the British city of Lincoln, at the age of 93. He has been a fantastic source of esoteric parts and electronic assemblies for many decades, and though many of you from beyond where this is being written may never have heard of him the chances are that if you follow electronics enthusiasts from the UK you will have unwittingly seen parts which passed through his hands.

A typical Birkett advert from 1986 — Gateway to a world of wonders: a typical Birkett advert from 1986.

There was a time when surplus stores were a relatively common sight, given their window of opportunity by the huge quantity of post-war and Cold War military gear at knock-down prices. My town had one when I was a kid, but though it sold its share of electronic goodies it was more of a place for sturdy olive green outdoor wear or all the 1930s British military uniform items you might ever need. J. Birkett was different, as a purely electronics store the shop rapidly became the go-to place for both the most necessary and the most unexpected of parts.

His motto was “Not a piece of junk in sight”, and though as with much surplus equipment there is plenty of junk to be found it was his eye in managing to stock the junk which was most interesting and useful that made his selection special. Such was its reach that most of his customers including me never made it to Lincoln and the store itself, instead we came to him through his mail-order business and attendance at radio rallies. I fondly remember the anticipation of receiving a Birkett parcel, and I still have plenty of parts that came from him. An FM tuner converted for use as a 2 meter receiver is still in a box somewhere, and I’m pretty certain my storage unit still holds a pair of Pye Cambridge VHF transceivers he supplied.

According to Google the shop remains open, and we hope that state of affairs will continue. Surplus may not be what it once was, but we thank John Birkett for what he gave to generations of British hardware hackers. May he rest in peace.

Header image: Oliver Mills, (CC BY-SA 2.0).

Finding The Right Hack Is Half The Battle

September 18, 2021 by Elliot Williams 25 Comments

Sometimes you just get lucky. I had a project on my list for a long time, and it was one that I had been putting off for a few months now because I loathed one part of what it entailed — sensitive, high-accuracy analog measurement. And then, out of the blue I stumbled on exactly the right trick, and my problems vanished in thin air. Thanks, Internet of Hackers!

The project in question is a low-vacuum regulator for “bagging” fiberglass layups. What I needed was some way to read a pressure sensor and turn on and off a vacuum pump accordingly. The industry-standard vacuum gauges are neat devices, essentially a tiny little strain gauge on a membrane between the vacuum side and the atmosphere side, in a package the size of a dime. (That it’s a strain gauge is foreshadowing, but I didn’t know that at the time.) I bought one for $15 ages ago, and it sat on my desk, awaiting its analog circuitry.

See, the MPX2100 runs on 12 V and puts out a signal around 40 mV on top of a 6 V offset. That voltage level is inconvenient for modern 3.3 V microcontroller ADCs, and the resolution would get clobbered by the 6 V signal if I just put a voltage divider on it. This meant whipping together some kind of instrument amplifier circuit to null out the 6 V and amplify the 40 mV for the ADC. The circuits I found online all called for 1% resistors in values I didn’t have, and mildly special op-amps. No fun, for me at least. So there it sat.

Picture of sketchy-looking vacuum apparatus. — Cut the blue wire or the red wire? HX711 module and pressure sensor on the left.

Until I ran into this project that machetes through the analog jungle with one part, and it happened to be one I had on hand. A vacuum pressure sensor is a strain gauge, set up like a Wheatstone bridge, just like you would use for weighing something with a load cell. The solution? A load-cell ADC chip, the HX711, found in every cheap scale or online for under a buck. The only other trick was finding a low-voltage pressure sensor to work with it, but that turns out to be easy as well, and I had one delivered in two days.

In all, this project took months of foot-dragging, but only a few clicks and five minutes of soldering once I got the right idea. The industrial applications and manufacturers’ app notes all make sense if you are making hundreds or millions of these devices, where the one-time cost of prototyping up the hard bits gets amortized, but the hacker solution of using a weight-scale chip was just the ticket for a one-off. That just goes to show how useful sharing our tips and tricks can be — you won’t get this from the industry. So send us your success stories, and your useful failures too, and Read More Hackaday!

Should You Be Able To Repair It? We Think So.

August 11, 2021 by Jenny List 179 Comments

You own it, you should be able to fix it. So much equipment on sale today has either been designed to be impossible to maintain, unnecessarily too complex to maintain, maintainable only with specialist tooling only available to authorised service agents, or with no repair parts availability. It’s a hot-button issue in an age when sustainability is a global concern, so legislators and regulators worldwide now finally have it in their sights after years of inaction and it’s become a buzzword. But what exactly is the right to repair, and what do we want it to be?

Is It Designed For Repair?

A Nestle Dolce Gusto machine — For some reason, pod coffee makers are especially resistant to repair. Andy1982, CC BY 3.0

The first question to consider is this: does it matter whether or not you have the right to repair something, if it’s designed specifically with lack of repairability in mind? Consider a typical domestic pod coffeemaker such as a Tassimo or similar: despite being physically quite a simple device, it is designed to be especially complex to dismantle and reassemble. You just can’t get into it when something goes wrong.

Should it be the preserve of regulators to require design for easy repair? We think so. There are other forces working on the designers of home appliances; design-for-manufacture considerations and exterior appearance concerns directly affect the firm’s bottom line, while the end users’ repair experience is often at the bottom of the list, even though the benefit at a national level is obvious. That’s what laws are for.
Continue reading “Should You Be Able To Repair It? We Think So.” →

Build A Barebones 68000

July 30, 2021 by Bryan Cockfield 31 Comments

The 68000 chip was ubiquitous in the computing world well past its heyday in the 1980s. It was used as the basis for many PCs and video game consoles, and even in embedded microcontrollers. Now, one of its niche applications is learning about the internal functions of computers. 68000 builds are fairly common when building homebrew computers from scratch, but projects like these can be complicated and quickly get out of hand. This 68000 project, on the other hand, gets the job done with the absolute minimum of parts and really dives into the assembly language programming on these chips. (Google Translate from Spanish)

[osbox68] built this computer by first simulating its operation. Once he was satisfied with that, the next step was to actually build the device. Along with the MC68008 it only uses two other TTL chips, a respectable 32 kilobytes of ram, and additionally supports a serial port and an expansion bus. A few 74-series chips round out the build including a 74HC574 used for debugging support. With a custom PCB to tie everything together, it’s one of the most minimal 68000 builds we’ve seen that still includes everything needed to be completely functional.

After all, including the TTL and 74XX chips the entire circuit board only uses 10 integrated circuits and a few other passive elements for a completely functional retro computer. [osbox68] also includes complete schematics for building a PCB based on these chips to make construction that much easier. Of course, emulating an old microcontroller instead of using TTL components can save a lot of real estate on a PCB especially if you’re using something like an FPGA.

Ask Hackaday: How Is The Chip Shortage Affecting You?

May 24, 2021 by Jenny List 133 Comments

Some friends of mine are designing a new board around the STM32F103 microcontroller, the commodity ARM chip that you’ll find in numerous projects and on plenty of development boards. When the time came to order the parts for the prototype, they were surprised to find that the usual stockholders don’t have any of these chips in stock, and more surprisingly, even the Chinese pin-compatible clones couldn’t be found. The astute among you may by now have guessed that the culprit behind such a commodity part’s curious lack of availability lies in the global semiconductor shortage.

A perfect storm of political unintended consequences, climate-related crises throttling Taiwanese chip foundries and shutting down those in the USA, and faulty pandemic recovery planning, has left the chipmakers unable to keep up with the demand from industries on the rebound from their COVID-induced slump. Particularly mentioned in this context is the automotive industry, which has seen plants closing for lack of chips and even models ditching digital dashboards for their analogue predecessors.

Chips on order everywhere on the Mouser website.

The fall-out from all this drama in the world’s car factories has filtered down through all levels that depend upon semiconductors; as the carmakers bag every scrap of chip fab capacity that they can, so in turn have other chip customers scrambled to keep their own supply lines in place. A quick scan for microcontrollers through distributors like Mouser or Digi-Key finds pages and pages of lines on back-order or out of stock, with those lines still available being largely either for niche applications, unusual package options, or from extremely outdated product lines. The chances of scoring your chosen chip seem remote and most designers would probably baulk at trying to redesign around an ancient 8-bit part from the 1990s, so what’s to be done?

Such things typically involve commercially sensitive information so we understand not all readers will be able to respond, but we’d like to ask the question: how has the semiconductor shortage affected you? We’ve heard tales of unusual choices being made to ship a product with any microcontroller that works, of hugely overpowered chips replacing commodity devices, and even of specialist systems-on-chip being drafted in to fill the gap. In a few years maybe we’ll feature a teardown whose author wonders why a Bluetooth SoC is present without using the radio functions and with a 50R resistor replacing the antenna, and we’ll recognise it as a desperate measure from an engineer caught up in 2021’s chip shortage.

So tell us your tales from the coalface in the comments below. Are you that desperate engineer scouring the distributors’ stock lists for any microcontroller you can find, or has your chosen device remained in production? Whatever your experience we’d like to know what the real state of the semiconductor market is, so over to you!

Tape Cutter Makes Short Work Of Through-Hole Resistor Reels

May 16, 2021 by Jenny List 9 Comments

As the world of electronics makes its inexorable movement from through-hole parts to surface-mount, it’s easy to forget about the humble wire-ended resistor. But a stack of them is still a very useful resource for any experimenter, and most of us probably have a bunch of them with their accompanying twin strips of tape. We’re entranced by [Sandeep]’s automated resistor tape cutting machine, which uses a fearsome looking pair of motorized knives to slice the tape into predetermined lengths.

At its heart is an Arduino and a set of stepper drivers, and it uses a PCB that he’s designed as a multipurpose board for motor-based projects. One motor advances the reel of resistors, while the other two operate those knives that simultaneously slice the two tapes. The whole is held in a wooden frame with 3D-printed parts, and control is through a touch screen. This feels more like an industrial machine than a maker project, and as can be seen in the video below, it makes short work of those tapes. Full details can be found on his website, including code.

We’ve not had so many through hole tape cutters, but we’ve seen at least one SMD cutter.

Continue reading “Tape Cutter Makes Short Work Of Through-Hole Resistor Reels” →

Spare Parts Express

October 17, 2020 by Elliot Williams 33 Comments

I’ve got spare parts, and I cannot lie.

This week I’m sending out two care packages to friends and coworkers because I’ve got too many hackables on hand, and not enough time to hack them all. One is a funky keyboard, and the other is an FPGA dev board, but that’s not the point. The point is that the world is too interesting, and many of us have more projects piled up in the to-do box, with associated gear, than we’ll ever have time to complete.

Back in the before-times, we would meet up, talk about our ongoing hacks, and invariably someone would say “oh you need an X, I’ve got half a box of them” and send you one. Or maybe you’d be the one with the extra widgets on hand. I know I’ve happily been in both positions.

Either way, it’s a win for the giver, who gets to take a widget off the widget pile, for the receiver, who doesn’t have to go to the widget store, and for the environment, which has to produce fewer widgets. (My apologies to the widget manufacturers and middlemen.)

This reminded me of Lenore Edman and Windell Oskay’s Great Internet Migratory Box Of Electronics Junk back in the late aughts. Trolling through the wiki was like a trip down memory lane. This box visited my old hackerspace, and then ended up with Bunnie Huang. Good times, good people, good hacker junk! And then there’s our own Brian Benchoff’s Travelling Hacker Box and spinoffs.

These are great and fun projects, but they all end up foundering in one respect: to make sense, the value of goods taken and received has to exceed the cost of the postage, and if you’re only interested in a few things in any given box, that’s a lot of dead weight adding to the shipping cost.

So I was trying to brainstorm a better solution. Some kind of centralized pinboard, where the “have too many h-bridge drivers” folks can hook up with the “need an h-bridge” people? Or is this ad-hoc social network that we already have working out well enough?

What do you think? How can we get the goods to those who want to work on them?