Author: Jenny List

3489 Articles

Converting Your Bike To Electric: Why You Should, And When You Shouldn’t

March 29, 2022 by 96 Comments

A decade ago I was lucky enough to work for an employer that offered a bicycle loan scheme to its employees, and I took the opportunity to spend on a Brompton folding bike. This London-made machine is probably one of the more efficiently folding cycles on the market, and has the useful feature of being practical for longer journeys rather than just a quick run from the train. A 3-speed hub gearbox is fine for unhurried touring, but sadly my little folder has always been a bit of a pain on the hills. Thus around the start of the pandemic I splashed out again and bought a Swytch electric upgrade kit for it, and after a few logistical and life upheavals I’ve finally fitted it to the bike. I’ve ridden a few electric bikes but never had my own, so it’s time to sit down and analyse the experience. Is an electric bike something you should have, or not?

A Box Of Bits Becomes An Electric Bike

All the parts of a Swytch kit
All the parts of a Swytch kit. From the Swytch assembly manual.

Swytch sell their kits via crowdfunding rounds, so I’d been on a waiting list for a while and got an early-bird price on my kit. It took quite a while to arrive, much longer than the expected time in mid-2020 because of the pandemic, finally being delivered some time in February last year. It came in a modestly-sized cardboard carton which would be an easy carry on the Brompton’s luggage rack, containing neatly packed a new front wheel with motor, as well as the battery and all sundry parts.

Fitting the kit shouldn’t stretch the capabilities of a Hackaday reader, with probably the trickiest part being the positioning of a Hall-effect sensor near the crank. The kit works by providing a motor assist when you pedal, so part of it is a set of magnets on a plastic disk with various attachments for different cranks and pedal sets. The Brompton front wheel is removed and its tyre and tube transferred to the Swytch one, which is then put on the bike. Once the magnet disk and Hall sensor are attached, the cables follow the existing ones and emerge at the handlebars where a sturdy bracket for the battery box is fitted. Continue reading “Converting Your Bike To Electric: Why You Should, And When You Shouldn’t” →

Hacker Camps Are Back. To Get You In The Mood, Here’s A Story From 1997

March 26, 2022 by 6 Comments

The past couple of years of the COVID pandemic have been rough in some unexpected ways, and it’s clear that our world will never be quite the same as it was beforehand. In our community, the hackerspaces are open again, and while the pandemic hasn’t gone away this year shows the promise of hosting the first major hacker camps to be held since 2019. We’re sure a number of you will be making your way to them. To give a taste of what is to come we’ve got a rare glimpse into hacker camps past.

The Netherlands events are held every four years outside pandemic disruptions, and we’re going back as far as 1997 for HIP, or Hacking In Progress, where [Christine Karman] kept a daily diary of the event. 25 years later it’s both a familiar account of a hacker camp and an interesting glimpse into a time when for much of the wider population an Internet connection was still a novelty. Continue reading “Hacker Camps Are Back. To Get You In The Mood, Here’s A Story From 1997” →

Reverse Engineering Your Own Bluetooth Audio Module

March 26, 2022 by 32 Comments

There was a time when we would start our electronic projects with integrated circuits and other components, mounted on stripboard, or maybe on a custom PCB. This is still the case for many devices, but it has become increasingly common for an inexpensive ready-built module to be treated as a component where once it would have been a project in its own right. We’re pleased then to see the work of [ElectroBoy], who has combined something of both approaches by reverse engineering the pinout of a Chinese Bluetooth audio chip with minimal datasheet, and making his own take on an off-the-shelf Bluetooth audio module.

The JL_AC6939B comes in an SOIC16 package and requires a minimum number of components. The PCB is therefore a relatively simple proposition and indeed he’s fitted all parts and traces on one side with the other being a copper ground plane. It’s dangerous to assume that’s all there is to a board like this one though, because many an engineer has come unstuck trying to design a PCB antenna. We’d hazard a guess that the antenna here is simply a wavy PCB line rather than an antenna with a known impedance and bandwidth, at the very least it looks to have much thicker traces than the one it’s copying.

It’s possible that it’s not really worth the effort of making a module that can be bought for relative pennies ready-made, but to dismiss it is to miss the point. We make things because we can, and not merely because we should.

A Robot Game To Open Your Hackerspace

March 25, 2022 by 1 Comment

It’s always good to welcome a new hackerspace to the fold, and thus we’re pleased to hear about the upcoming opening of Hackerspace Drenthe, on the north-eastern edge of the Netherlands. Starting a new space during a global pandemic is something of a feat. As part of their opening something is required to demonstrate a robot for the curious public, and what could be more accessible than a robot arm playing tic-tac-toe!

It would be correct to say that a robot moving blocks with precision is not necessarily a ground-breaking achievement, but in its purpose of providing eye-candy for a hackerspace opening while also serving as an experiment for some of the students from the school adjacent to the space it is a success. The interface is a pleasingly retro War Games style terminal, and the software is written in Python. For the curious all can be found on a GitHub repository, and should you be in that region of Europe you can find Hackerspace Drenthe in the Netherlands border town of Coevorden and attend their opening on the 2nd of April.

Continue reading “A Robot Game To Open Your Hackerspace” →

Label Your SMD Tapes With An Inkjet Printer

March 25, 2022 by 15 Comments

If you’ve ever had to use SMD components on tape outside the realm of the automated assembly machines for which they were designed, you’ll know that one tape looks very like another and it can be very annoying to keep track of which is which. We can’t help admiring [Yvo de Haas’] inkjet printer for SMD tapes then, which efficiently prints whatever identifying marks you need on the back of your tapes.

The printer uses the venerable HP45 inkjet cartridge, and teams it with a 3D printed mechanism and [Yvo]’s self-designed driver board. A worm gear motor and a sprocket take care of advancing the tape through the mechanism past the printhead, and there is a well-assembled piece of software to drive it all. With extremely comprehensive build instructions it should be within the reach of anyone who handles component tape, and from our experience of hand-labeling tape for kits we can see that it could be a Godsend. Take a look at it in action in the video below.

So far the tape-handling machinery we’ve seen has mostly been for cutting sections rather than labeling. We can see that this printer paired with a tape cutter should be essential equipment for anyone starting a kit business.

Continue reading “Label Your SMD Tapes With An Inkjet Printer” →

A MiniDisc Optical Head Has A Few Surprises Up Its Sleeve

March 24, 2022 by 46 Comments

There was an odd era at the start of the 1990s when CDs had taken the lead from vinyl in pre-recorded music, but for consumer recordable formats the analogue cassette was still king. A variety of digital formats came to market to address this, of which Sony’s MiniDisc was the only one to gain significant traction outside the studio. These floppy-disk-like cartridges held a magneto-optical medium , and were the last word in cool until being swept away around the end of the decade by MP3 players. Hackaday alum [Nava Whitford] has disassembled a MiniDisc optical head to document how the physical part of the system worked.

The first surprise is that the MiniDisc was in fact a two-in-one system. The recordable discs were magneto-optical and wrote data by heating the disc with a laser under a magnetic field, while the pre-recorded discs used etched pits and lands in a similar way to the CD. Remembering the technical buzz around the system back in the day, either we audio enthusiasts glossed over this detail, or more likely, Sony’s PR did so to emphasize the all-new aspect of the system.

The teardown goes in depth into how while like a CD player there is a photodiode array involved, the extra components are a diffraction grating and a Wollaston prism, an optical component which splits polarized light into two beams. The photodiode array is more complex than that of a CD player, it’s speculated that this is to detect the different polarized beams as well as for the task of maintaining alignment with the track.

All in all this is a rare chance to look at something we know, but which few of us will probably have dismantled due to its relative scarcity compared to CD mechanisms. Definitely worth a look. Meanwhile if this era is of interest, take a look at a Hack Chat we did a while back looking at the MiniDisc’s would-be competitor.

Satellite Snoopers Pick Up Surprising TV Broadcast

March 22, 2022 by 25 Comments

While Internet based streaming services appear to be the future of television, there are still plenty of places where it comes into the home via a cable, satellite, or antenna connection. For most satellite transmissions this now means a digital multiplex carrying a host of channels from a geostationary satellite, for which a set-top box or other decoder is required. Imagine the surprise of satellite-watchers than when the Russian polar communications satellite Meridian 9 which has a highly elliptical orbit was seen transmitting old-style terrestrial analogue TV (ThreadReader Link). What on earth was happening?

How a Russian polar comms satellite picked up a TV station.
How a Russian polar comms satellite picked up a TV station.

The TV signal in question comes from Turkmenistan, so were some homesick Turkmenistanis in an Antarctic base being treated to a taste of their country? The truth is far more interesting than that, because the signal in question comes from a terrestrial transmitter serving domestic TV viewers in Turkmenistan.

We’ve all heard of the idea that somehow every TV show ever transmitted is somewhere out there still traveling as radio waves across space, and while perhaps we can’t fly far enough out to check for 1960s Doctor Who episodes it’s true that the horizontal transmissions from a TV tower pass out into space as the earth curves away from them.

Thus Meridian 9 passed through the beam from the Turkmenistan transmitter which happened to be on a UHF frequency that matched one of its transponders, and the result was an unexpected bit of satellite TV. We’re indebted to the work of [@dereksgc] and [Scott Tilley] for bringing us this fascinating observation. We’ve featured [Scott]’s work before, most notably when he relocated a lost NASA craft.