Build Your Own Digital Panel Meter

A popular purchase from the usual stockists of imported electronic modules is a digital panel meter. A very small amount of money secures a module with a seven-segment display that you can stick on the front of your power supply or project for an easy readout. Even before the advent of these ultra-cheap Chinese products there have been readily available digital meters, in a line stretching back to the 1970s with chips such as the Intersil 7106.

[Marcus Taciuc] is eschewing the off-the-shelf parts, and creating his own digital panel meter. He’s using an MSP430 microprocessor as the brain of his device, and a Hitachi HD44780 compatible LCD display at the front end. The appropriate combinations of resistors and op-amps feeding the MSP’s ADC inputs allow his meter to be used to measure up to 40 VDV, and up to 10A.

He’s put up a video which we’ve included below the break, showing the use to which this meter has been put: replacing the moving-coil meter in what looks like a classic piece of Heathkit equipment. A 3D printed bracket allows the new meter to fit the circular hole of the original meter, with the LCD on the front. You might still order a prefab meter module, but you can’t deny this looks good.

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Exploring The BBC Micro:Bit Software Stack

The BBC micro:bit has been with us for about eighteen months now, and while the little ARM-based board has made a name for itself in its intended market of education, we haven’t seen as much of it in our community as we might have expected.

If you or a youngster in your life have a micro:bit, you may have created code for it using one of the several web-based IDEs, a graphical programming system, TypeScript, or MicroPython. But these high level languages are only part of the board’s software stack, as [Matt Warren] shows us with his detailed examination of its various layers.

The top layer of the micro:bit sandwich is of course your code. This is turned into a hex file by the web-based IDE’s compiler, which you then place on your device. Interestingly only the Microsoft TypeScript IDE compiles the TypeScript into native code, while the others bundle your code up with an interpreter.

Below that is the micro:bit’s hardware abstraction layer, and below that in turn is ARM’s Mbed OS layer, because the micro:bit is at heart simply another Mbed board. [Matt] goes into some detail about how the device’s memory map accommodates all these components, something essential given that there is only a paltry 16 kB of RAM in hand.

You might wish to program a micro:bit somewhat closer to the metal with the Mbed toolchain, but even if that is the case it’s still of interest to read a dissection of its official stack. Meanwhile, have a look at our review of the board, from summer 2016.

We Need To Have A Chat About Something Important

Yes, I really did print this the day before the story broke.
Yes, I really did print this the day before the story broke.

With hindsight, I picked the wrong day to 3D print a Cap’n Crunch whistle downloaded from Thingiverse. I was covering the hackspace textile evening, so I set the Ultimaker going and headed off to spend my evening making a laptop pouch. My whistle, a reasonable reproduction of the famous cereal packet novelty whose 2600 Hz tone allowed special access to American telephone networks, was ready for me to take away as I headed home.

The next day, there it was. The legendary phreaker [John Draper], also known as [Captain Crunch] after his use of that free whistle, was exposed as having a history of inappropriate conduct towards teenage boys and young men who he encountered in his tours of the hacker community as a celebrity speaker.

My whistle will no longer go on a lanyard as a piece of cool ephemera, it’s sitting forlornly on my bench. The constant procession of harassment allegations that have been in the news of late have arrived at our doorstep. Continue reading “We Need To Have A Chat About Something Important”

Retrotechtacular: Circuit Boards The Tektronix Way

Printed circuit boards are a fundamental part of both of commercial electronic equipment and of the projects we feature here on Hackaday. Many of us have made our own, whether done so from first principles with a tank of etchant, or sent off as a set of Gerbers to a PCB fab house.

To say that the subject of today’s Retrotechtacular is the manufacture of printed circuit boards might seem odd, because there is nothing archaic about a PCB, they’re very much still with us. But the film below the break is a fascinating look at the process from two angles, both for what it tells us about how they are still manufactured, and how they were manufactured in 1969 when it was made.

Board artwork laid out at four-times actual size

Tektronix were as famous for the manufacturer of particularly high quality oscilloscopes back then as they are now. The Tektronix ‘scopes of the late 1960s featured several printed circuit boards carrying solid-state electronics, and were manufactured to an extremely high standard. The film follows the manufacturing process from initial PCB layout to assembled board, with plenty of detail of all production processes.

In 2017 you would start a PCB design in a CAD package, but in 1969 the was incredibly manual. Everything was transcribed by hand from a paper schematic to transparent film. Paper mock-ups of component footprints four times larger than actual size are placed on a grid, and conductors drawn in pencil on an overlaid piece of tracing paper. Then the pads and pattern of tracks are laid out using black transfers and tape on sheets of film over the tracing paper, one each for top and bottom of the board. A photographic process reduces them to production size onto film, from which they can be exposed and etched in the same way that you would in 2017.

Pantograph drilling machine uses a manually moved styuls on a template to drill six boards at once

Most of the physical process of creating a PCB has not changed significantly since 1969. We are shown the through-plating and gold plating processes in detail, then the etching and silkscreening processes, before seeing component installation and finally wave soldering.

What are anachronistic though are some of the machines, and the parts now robotised that were done in 1969 by hand. The PCB drilling is done by hand with a pantograph drill for small runs, but for large ones a fascinating numerically-controlled drilling rig is used, controlled by punched tape without a computer in sight. Component placement is all by hand, and the commentator remarks that it may one day be done by machine.

The film remains simultaneously an interesting look at PCB production and a fascinating snapshot of 1960s manufacturing. It’s probable that many of the Tek ‘scopes made on that line are still with us, they’re certainly familiar to look at from our experience at radio rallies.

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Ask Hackaday: How On Earth Can A 2004 MP3 Player Read An SDXC Card?

What were you doing in 2004? Can you even remember 2004? Maybe it’s like the old joke about the 1960s, if you can remember it, you weren’t really there, man. Cast your mind back, [Lance Armstrong] was winning the Tour de France, and SpaceShipOne made it into space.

[Gregg Eshelman], wrote to us to say that in 2004 he bought an MP3 player. Ask your parents about them, they were what hipsters used before they had cassette tapes: portable music players that everyone thought were really cool back then, onto which music didn’t come from the Internet but had to be manually loaded from a computer.

Jokes about slightly outdated consumer electronics aside, [Gregg]’s player, a GPX MW3836, turned out to be a really good buy. Not only does it still work, it packs an unexpected bonus, it reads 64Gb SD cards when they are formatted as FAT32. This might not seem like a big deal at a cursory glance, but it’s worth considering a little SD card history.

Back when the GPX was made, the maximum capacity of an SD card was 2Gb, a figure that must have seemed huge when the standard was created, but by the middle of the last decade was starting to look a little cramped. The GPX player is designed to only read these original 2Gb cards. In the years since then there have been a couple of revisions to the standard, SDHC, and SDXC, which have given us the huge cards we are used to today. Many other devices from the 2Gb SD era, made before SDHC and SDXC existed, cannot read the modern cards, yet [Gregg]’s GPX can.

Hackaday’s readership constantly amaze us with the sheer breadth of their knowledge and expertise, so we are sure that among you reading this piece will be experts on SD card standards who can shed some light on this mystery. Why can a player designed for the original SD card standard read the much newer cards when other contemporary ones can not? [Gregg] would love to know, and now our curiosity has been whetted, so would we.

If you think you’ve heard [Gregg]’s name before, it might be for his expertise in resin casting automotive parts.

SD card image: Andreas Frank (CC BY 2.5).

Erika Earl: Manufacturing Hacks

Many of us will have casually eyed up the idea of turning a project into a product. Perhaps we’ve considered making a kit from it, or even taking it further into manufacture. But building a single device on the bench is an extremely different matter from having a run of the same devices built by someone else, and in doing so there are a host of pitfalls waiting for the unwary.

[Erika Earl] is the Director of Hardware Engineering at Slate Digital, and has a lengthy background in the professional audio industry. Her job involves working with her team to bring high-quality electronic products to market that do not have the vast production runs of a major consumer electronic brand, so she has a lot of experience when it comes to turning a hacked-together prototype into a polished final device. Her talk at the 2017 Hackaday Superconference: Manufacturing Hacks: Mistakes Will Move You Forward examined what it takes to go through this process, and brought her special insights on the matter to a Hackaday audience.

She started her talk by looking at design for manufacture, how while coming up with prototypes is easy, the most successful products are those that have had the ability to manufacture as a consideration from the start of the design process. Starting with the selection of components, carrying through to the prototype stage, and through design reviews before manufacture, everything must be seen through the lens of anyone, anywhere, being able to build it.

At the selection of components for the Bill of Materials level, she made the point that high quality certified components can be the key to a product’s success or failure, contributing not only to reliability but also to it achieving certification. In her particular field, she often deals with components that can be close enough to the cutting edge to be prototypes in their own right. She mentioned the certification angle in particular in the context of exporting a product, as in that case there is often a need to be able to prove that all components used to meet a particular specification.

When it comes to the prototype stage, she made the point that documentation is the key. Coming back to the earlier sentence about anyone anywhere being able to build the product, that can only be achieved if all possible stages of manufacture are defined. She mentioned an example of a product in which the prototypes had had PCB fixing screws tightened by hand; when the factory started using electric screwdrivers the result was damaged PCBs and broken tracks.

The design review should look at everything learned through the prototype stage, and examine everything supplied to the manufacturer to allow them to complete their work. She describes finding support documentation containing a poorly hand-drawn schematic, and seeing an electronic assembly in which a piece of gum had been used to secure something. She also made the point that another function at this point is to ensure that the product is affordable to produce. If any parts or procedures are likely to cost too much, they should be re-examined.

After the talk itself as described above there is a Q&A session where she reveals how persistent and cheeky she sometimes has to be to secure sample parts as a small-scale manufacturer and delivers some insights into persuading a manufacturer to produce prototypes at a sensible price. And yes, like most people who have tried their hand at this, she’s had the nightmare of entire runs of prototype boards returned with a component fitted incorrectly.

The talk is embedded in its entirety below the break, and represents an extremely interesting watch for anyone starting on the road to manufacturing, particularly in the electronic world. If this describes you, take a look!

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The Worst Piece Of Test Equipment You’ve Got To Try Hacking

A brand new meter in its blister pack
A brand new meter in its blister pack

I have a fascination with the various online vendors of electronics and other manufactured goods from China. Here are listed the latest wonders from Shenzhen or wherever, which you can have for a surprisingly reasonable price, with the mild inconvenience of a three week wait for the postage.

A particular pastime of mine is to look for the bottom end of the market. Once I’ve picked up the items I came to order I’ll trawl around with the search with low price first and see what can be had for a few dollars. Yes, I take a delight in finding absolute trash, because just sometimes that way you can find a diamond in the rough.

So when I was shopping for a multimeter recently I took a quick look to see what the cheapest model from that particular supplier was. For somewhere around £2.50 or just over $3, I could have a little pocket analogue multimeter, the kind of “My first multimeter” that one might have found in the 1980s. They weren’t too bad, I thought, and ordered one for less than a pint of beer in a British pub.

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