Power Stacker, A Modular Battery Bank

Many of us will own a lithium-ion power pack or two, usually a brick containing a few 18650 cylindrical cells and a 5 V converter for USB charging a cellphone. They’re an extremely useful item to have in your carry-around, for a bit of extra battery life when your day’s Hackaday reading has provided a worthy use for most of your charge. These pack are though by their very nature inflexible, no matter how many cells you own, the pack will only ever contain the number with which it was shipped. Worse, when those cells are discharged or even  reach the end of their lives, they can’t be swapped for fresh ones. [Isaacporras] has a solution for these problems which he calls the Power Stacker, a modular battery pack system.

At its heart is the Maxim MAX8903 lithium-ion charge controller chip, of which one is provided for each cell. A single cell and MAX8903 with a DC to DC converter for 5 V output makes for the simplest configuration, and he has a backplane allowing multiple boards to be connected and sharing the same charge and output buses.

An infinitely configurable battery bank sounds great. It’s looking for crowdfunding backing, and for that it has an explanatory video which you can see below. Meanwhile if you’d  like to try for yourself you can find the necessary files on the hackaday.io page linked above.

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RIP Rex Garrod, Creator Extraordinaire

Earlier this month, the youth motocross champion, special effects creator, inventor, TV presenter, and Robot Wars competitor, [Rex Garrod] died at the age of 75 after a long battle with dementia. We do not often carry obituaries here at Hackaday, and it’s possible that if you are not a Brit you may not have heard of [Rex], but his work in the time before YouTube would have made him an international must-watch star had he been operating in the age of on-demand Internet video.

I first became aware of Rex when he appeared as assistant to [Tim Hunkin] on his Secret Life of Machines TV series in the late 1980s. He was the man whose job we all wanted, making the most incredible machines and operating them for our entertainment. Our Hardware heroes tribute to [Tim] has a picture of him operating the needle on a giant mock-up of a sewing machine, but he appeared in many more episodes. Of the many tributes to [Rex] that have appeared over the last few days it is [Tim]’s one that probably says the most about his appeal to our community. His propensity for picking up interesting parts from junkyards strikes a chord, and the tale of hugely overpowering car wiper motors by allowing them to be submerged in water is pure genius.

To a slightly younger generation he is best known for his appearances in the British Robot Wars series‘ with his Cassius series of fighting robots. He created one of the first really potent flipper robots in UK robotic combat, and incidentally the first effective self-righting mechanism. As one of the many members of the SMIDSY team that didn’t appear on the recorded TV series’ I encountered him only peripherally, but I remember his work being a major influence on SMIDSY’s run-any-way-up design. Meanwhile for a younger generation still he created the models for the popular children’s TV character Brum, an anthropomorphised scale-model Austin 7 car.

We’ll leave you with a couple of videos featuring [Rex]. The first is from The Secret Life of Machines, in which along with [Tim] he helps explain electronics from first principles, while the second is a fan-created medley of his Robot Wars appearances. Rest in peace [Rex], and thank you.

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Characterising A Potentiometer With A Stepper Motor

Potentiometers, or variable resistors, are a standard component that we take for granted. If it says “10k log” on a volume pot, than we fit and forget. But if like [Ben Holmes] you are modelling electronic music circuitry, some greater knowledge is required. To that end he’s created a rig for characterising a potentiometer to produce a look-up table of its values.

It’s a simple enough set-up in which a voltage controlled current source feeds the pot while an Arduino with a motor controller turns it through a stepper motor, and takes a voltage reading from its wiper via an analogue pin. Probably most readers could assemble it in a fairly short time. Where it becomes interesting though is in what it reveals about potentiometer construction.

Audio potentiometers are usually logarithmic. Which is to say that the rate of change of resistance is logarithmic over the length of the track, in an effort to mimic the logarithmic volume response of the human ear in for example a volume control. If you are taught about logarithmic pots the chances are you’re shown a nice smooth logarithmic curve, but as he finds out in the video below that isn’t the case. Instead they appear as a set of linear sections that approximate to a logarithmic curve, something that is probably easier to manufacture. It’s certainly useful to know that for [Ben]’s simulation work, but for the rest of us it’s a fascinating insight into potentiometer manufacture, and shows that we should never quite take everything for granted.

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Dollar Store Garden Lights As ATtiny Power Supplies

Solar garden lights are just another part of the great trash pile of our age, electronics so cheap as to be disposable. Most of you probably have a set lurking somewhere at home, their batteries maybe exhausted. Internally though they are surprisingly interesting devices. A solar cell, a little boost converter chip, and a little NiCd battery alongside the LED. These are components with potential, as [Randy Elwin] noted with a mind to his ATtiny85 projects.

The YX805A chip he references in his write-up is one of several similar chips that function in effect as joule thieves, extending the available charge in the battery to keep the LED active as long as possible when their solar panel is generating nothing, and turning it off in daylight when the panel can charge. Their problem is that they are designed as joule thieves rather than regulators, so using them as a microcontroller PSU without modification can result in overvoltage.

His solution is to use the device’s solar panel input as a feedback pin from his ATtiny, allowing the microcontroller to keep an eye on its supply voltage and enable or disable the converter as necessary while it keeps running from the reservoir capacitor. Meanwhile the solar panel now charges the NiCd cell through a single diode. It’s not perfect and maybe needs a clamp or something, he notes that there is a condition in which the supply can peak at 8 volts, a level which would kill an ATtiny. But still, we like simple hacks on dollar store parts, so it’s definitely worth further investigation.

This isn’t the first garden light hack we’ve shown you, there was this flashlight, and some LED hacks.

Solar light picture: Leon Brooks [Public domain].

This Old Korg Can’t Have Too Many Samples

The Korg DW-6000 is an entry-level synthesiser from the mid 1980s that has the classic sounds, but not enough of them. At least that was [Mateusz Kolanski]’s  view, as he hacked his model with a 16-fold increase in its wavetable memory.

At the heart of the DW-6000 is NEC’s UPD7810 16-bit microcontroller, a device stuffed with ports aplenty. The Korg doesn’t use all of those ports, so he was curious as to whether its relatively small 256 kbit ROMs could be upgraded to something much bigger with the use of four unused lines to drive their addresses. This proved to be no easy task, not least because the UPD7810 is hardly a chip with a lot of published work to learn from. A manual for it came from an unexpected source: an obscure game console used it so there is support within MAME.

A significant quantity of hardware reverse engineering and software experimenting later, and he had a ROM piggyback board to plug into his lightly-modified DW-6000. The initial model used stripboard, but naturally a decent PCB was created. That might be everything, but of course some means of working with those samples was required. Enter a Windows wavetable editor and organiser to create new ROM images, for the complete DW-6000 upgrade kit.

This project took several years, proving that persistence can pay off. If you’re not used to the way microcontrollers did their interfacing back in the 1980s then it’s definitely worth a read even if old synths aren’t your thing.

This isn’t the first bit of Korg reverse engineering we’ve brought you, either.


A USB -C Soldering Iron For Weller Tips

There was a time when a decent temperature controlled soldering iron took the form of the iron itself and a box of electronics, but now it’s just as likely to be a miniaturised affair with the temperature controller built into a slim and lightweight handle. Irons such as the Miniware TS series have become firm favourites, displacing a traditional soldering station for many.

[Thomas.lepi] has combined the best of both worlds, with a TS-style microprocessor-driven handle driving the familiar Weller RT elements. Its interface is very simple, but through its USB power socket a serial port provides opportunities for adjustment. Providing control is an STM32F042G6U6 ARM Cortex M0 microcontroller, with USB power control coming from an STUSB4500QTR .

If you are used to irons such as the Miniware TS100 then this one with its smartly 3D-printed case will be very straightforward to use. Whether or not the ready availability of the TS100 or its USB-C sibling would remove the need to build this iron is up to you, but then again that’s hardly the point. The Weller tips are some of the better ones of their type, so perhaps that might make this project worth a second look.

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Retrotechtacular: Transputer

Back in 2016, Hackaday published a review of The National Museum of Computing, at Bletchley Park. It mentions among the fascinating array of computer artifacts on display a single box that could be found in the corner of a room alongside their Cray-1 supercomputer. This was a Transputer development system, and though its architecture is almost forgotten today there was a time when this British-developed microprocessor family had a real prospect of representing the future of computing. So what on earth was the Transputer, why was it special, and why don’t we have one on every desk in 2019?

An Inmos RAMDAC (the 28-pin DIP) on the motherboard of a 1989 IBM PS/55. Darklanlan [CC BY 4.0]
An Inmos RAMDAC (the 28-pin DIP) on the motherboard of a 1989 IBM PS/55. Darklanlan [CC BY 4.0]
Inmos, based in Bristol, were a — no, make that the — British semiconductor company, in the days when governments saw such things as a home-grown semiconductor manufacturing capability to be of strategic importance. They made microcomputer peripheral chips, RAM chips, and video chips (the workaday silicon of 1980s computing) but their exciting project was the Transputer.

This microprocessor family addressed the speed bottlenecks inherent to conventional processors of the day by being built from the ground up to be massively multiprocessor.  A network of Transputer processors would share a web of serial interconnects arranged in a crosspoint formation, allowing multiple of them to connect with each other independently and without collisions. It was the first to feature such an architecture, and at the time was seen as the Next Big Thing. All computers were going to use Transputers by the end of the 1990s, so electronic engineering students were taught all about them and encountered them in their group projects. I remember my year of third-year EE class would split into groups, each of tasked with a part of a greater project that would communicate through the crosspoint switch at the heart of one of the Transputer systems, though my recollection is that none of the groups went so far as to get anything to work. Still how this machine was designed is fun to look back on in modern times. Let’s dig in!

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