DVD Optics Power This Scanning Laser Microscope

February 2, 2021 by 35 Comments

We’ve all likely seen the amazing images possible with a scanning electron microscope. An SEM can yield remarkably detailed 3D images of the tiniest structures, and they can be invaluable tools for research. But blasting high-energy cathode rays onto metal-coated samples in the vacuum chamber of a bulky and expensive instrument isn’t the only way to make useful images, as this home-brew laser scanning microscope demonstrates.

This one comes to us by way of [GaudiLabs], a Swiss outfit devoted to open-source lab equipment that enables citizen science; we saw their pocket-sized thermal cycler for PCR a while back. The basic scheme here is known as confocal laser scanning fluorescence microscopy, where a laser at one wavelength excites fluorescent tags bound to structures in a sample. Light emitted by the tags is collected, and a 3D image is built up from multiple scans of the sample at different focal planes.

Like many DIY projects, this microscope is built from old DVD parts, specifically the pickup heads. The precision optics in these commonly available assemblies, which are good enough to read pits as small as 150 nm on a Blu-Ray DVD, are well-suited for resolving similarly sized microstructures. One DVD pickup is used to scan the laser in the X-axis, while the other head is modified to carry the sample and move it in the Y-axis. The pickup head coils and laser are driven by an Arduino carried on a custom PCB along with the DVD heads. Complete build files are posted on GitHub for anyone interested in recreating this work.

We love tips like this that dig back a bit and find things we missed the first go-around. And the equipment [GaudiLabs] lists really has potential for the budding biohacker, which we also like.

Thanks for the tip on this one, [Bill].

Upgrading The Batteries In A BMW I3

February 1, 2021 by 42 Comments

The BMW i3 debuted on the market in late 2013, one of the brand’s first electric cars. Also available with an optional range-extending engine, early models featured a 60 Ah battery providing up to 130km range on a full charge. However, times have changed, and over the years, BMW have updated the model with larger capacity batteries over the years. So what does it take to retrofit an older model with the newer, fatter, juicer 120 Ah pack?

It’s all helpfully laid out in a video by [Daniel], who notes that it’s not a job for the faint of heart or poorly equipped. The good news is that, mechanically, the newer batteries have the same external dimensions as the older packs, meaning they can be bolted in without requiring any cutting, welding or, adapters. But that’s about it for the good news. The batteries are cooled by the air conditioning system, meaning that removal and replacement means draining the system of refrigerant using highly expensive specialised hardware. Additionally, many batteries in crashed cars are disabled when the airbags are triggered for safety reasons, requiring unlocking through BMW’s proprietary software or replacement of the internal battery controller. Then there’s the usual laundry list of gradual changes that happen across any automotive line, meaning that certain model years and trim packages can have incompatible plugs and connectors or other features.

Overall, it can be quite a bit of work to do, and with the tools required, something that needs the services of a dedicated mechanic’s workshop. However, find an experienced shop that regularly works with EVs, and you might find they can facilitate the upgrade for you without too much fuss. We’ve seen [Daniel] tackle upgrades before, such as a much easier swap on the Nissan Leaf. Video after the break.

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This Isn’t Your Father’s Yellow Card

February 1, 2021 by 59 Comments

As the global vaccination effort rolls out in many countries, people will increasingly be required to provide evidence for various reasons, especially travelers. Earlier this month a coalition which includes Microsoft, the Mayo Clinic, Oracle, MITRE, and others announced an effort to establish digital vaccination records called the Vaccination Credential Initiative (VCI). This isn’t going to be a brand new thing, but rather an initiative to provide digital proof-of-vaccination to people who want it, using existing open standards:

  • Verifiable Credentials, per World Wide Web Consortium Recommendation (VC Data Model 1.0)
  • Industry standard format and security, per the Health Level Seven International (HL7) FHIR standard

In addition, the World Health Organization formed the Smart Vaccination Certificate Working Group in December. Various other countries and organizations also have technical solutions in the works or already deployed. If a consensus doesn’t form soon, we can see this quickly becoming a can of worms. Imagine having to obtain multiple certifications of your vaccination because of non-uniform requirements between countries, organizations, and/or purposes.

Older readers and international travelers may be wondering, “don’t we already have a vaccination card system?” Indeed we do: the Carte Jaune or Yellow Card. The concept of a “vaccination passport” was conceived and agreed upon at the International Sanitary Convention for Aerial Navigation in 1933. Over the years the names and diseases of interest have changed, but since 2007 it has been formally called the International Certificate of Vaccination or Prophylaxis (ICVP). In recent times, yellow fever was the only vaccination of interest to travelers, but other vaccinations or booster shots can be recorded as well. One problem with the paper Yellow Card is that it is ridiculously easy to forge. Nefarious or lazy travelers could download it from the WHO site, print it on appropriate yellow card stock, and forge a doctor’s signature. The push for a more secure ICVP is not completely unreasonable.

Reading the instructions on the Yellow Card brings up a couple of interesting points:

  • This certificate is valid only if the vaccine or prophylaxis used has been approved by the World Health Organization — Currently the Pfizer vaccine is the only one to be approved by WHO, and even that is only an emergency approval. If you receive a non-Pfizer vaccination, what then?
  • The only disease specifically designated in the International Health Regulations (2005) for which proof of vaccination or prophylaxis may be required as a condition of entry to a State Party, is yellow fever — This one is interesting, and suggests that member states cannot require proof of Covid19 vaccination as an entry requirement, a situation that will no doubt be quickly revised or ignored.

Note: This writeup is about vaccinations, not about immunity. While immunity certificates have been used from time to time throughout modern history, the concept of an international immunity passport is not well established like the ICVP.

Upgrading An Old MIG Welder Wire Feeder With Arduino

February 1, 2021 by 6 Comments

Older industrial equipment is often a great option if you’re on a budget, and you might even be able to add some premium features yourself. [Brett] from [Theoretically Practical] has done with his old MIG welder, adding premium control features with the help of an Arduino.

The main features [Brett] were after is pre-flow, post-flow, and a spot welding timer. Pre-flow starts the flow of shielding gas a moment before energizing the filler wire, while post-flow keeps the gas going after the weld is complete. This reduces the chances of oxygen contaminating the welds. A spot welding timer automatically limits welding time, enabling consistent and repeatable spot welds.

The Miller S-22A wire feeder can have these features, but it requires an expensive and difficult to find control unit. All it does is time the activation of the relays that control the gas flow, power, and wire feeder, so [Brett] decided to use an Arduino instead. The welders control circuit runs at 24V, so an optoisolator receives the trigger signal, and relays are used for outputs. Potentiometers were added to the original control panel, and all the wiring was neatly fitted behind it. The upgrade worked perfectly and allowed [Brett] to increase the quality of his welds. See the video after the break for the full details.

Inverter welders can be picked up for ridiculously cheap prices, if you’re willing to live with the trade-offs. We’ve also seen some other DIY welder upgrades, on small and large machines.

Handy Tool Drains 18650 Cells So You Don’t Have To

February 1, 2021 by 29 Comments

Draining a battery is easy. Just put a load across the terminals, maybe an incandescent bulb or a beefy power resistor, and wait. What’s quite a bit trickier is doing so safely. Put too large a load on, or leave it connected for longer than necessary, and you can end up doing damage to the cell. Not convinced he’d always remember to pull the battery out of his jury-rigged discharger at the opportune moment, [Jasper Sikken] decided to come up with a simple tool that could automatically handle the process with the cold and calculating precision of silicon.

V4 used the protection module from a pouch battery.

At a glance we can see the major components you’d expect in a discharger: a fairly simple PCB, four ceramic power resistors, a holder for a single 18650 cell, and a rocker switch to connect it all together. But wait, what’s that a TP4056 charging module doing in there?

While its presence technically makes this device a battery charger, [Jasper] is actually using it for the onboard protection IC. With the charging module between the cell and the power resistors, it will cut the connection when the voltage drops to 2.4 V. Oh yeah, and it can charge the battery back up if you connect up a USB cable.

[Jasper] says his little tool works great, with the resistor array putting just enough load on the battery to pull it down quickly without getting so hot that they’re dangerous to have exposed. He estimates the BOM for this gadget runs around $2 USD, and is considering offering it as a kit on Tindie in the near future.

If you’re looking for something a bit more advanced, [Jasper] built a programmable load a few years back that can discharge batteries and test power supplies all while logging the data to your computer for later analysis.

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All The Best Computers From Cambridge Boot To Basic

February 1, 2021 by 77 Comments

The Raspberry Pi is a fine machine that appears in many a retrocomputing project, but its custom Linux distribution lacks one thing. It boots into a GNU/Linux shell or a fully-featured desktop GUI rather than as proper computers should, to a BASIC interpreter. This vexed [Alan Pope], who yearned for his early days of ROM BASIC, so he set out to create a Raspberry Pi 400 that delivers the user straight to BASIC. What follows goes well beyond the Pi, as he takes something of a “State of the BASIC” look at the various available interpreters for the simple-to-code language. Almost every major flavour you could imagine has an interpreter, but as is a appropriate for a computer from Cambridge running an ARM processor, he opts for one that delivers BBC BASIC.

It would certainly be possible to write a bare-metal image that took the user straight to a native ARM BASIC interpreter, but instead he opts for the safer route of running the interpreter on top of a minimalist Linux image. Here he takes the unexpected step of using an Ubuntu distribution rather than Raspberry Pi OS, this is done through familiarity with its quirks. Eventually he settled upon a BBC BASIC interpreter that allowed him to do all the graphical tricks via the SDL library without a hint of X or a compositor, meaning that at last he had a Pi that boots to BASIC. Assuming that it’s an interpreter rather than an emulator it should be significantly faster than the original, but he doesn’t share that information with us.

This isn’t the first boot-to-BASIC machine we’ve shown you.

Header image:  A real BBC Micro BASIC prompt. Thanks [Claire Osborne] for the picture.

It Costs WHAT?! A Sounding Into Hearing Aids

February 1, 2021 by 153 Comments

We are accustomed to medical devices being expensive, but sometimes the costs seem to far exceed reasonable expectations. At its most simplistic, a hearing aid should just be a battery, microphone, amplifier, and speaker, all wrapped in an enclosure, right? These kinds of parts can be had for a few dimes, so why do modern hearing aids cost thousands of dollars, and why can’t they seem to go down in price?

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