Displays are crucial to modern life; they are literally everywhere. But modern flat-panel LCDs and cheap 7-segment LED displays are, well, a bit boring. When we hackers want to display the progress of time, we want something more interesting, hence the plethora of projects using Nixie tubes and various incantations of edge-lit segmented units. Here is [upir] with their take on the simple edge-lit acrylic 7-segment design, with a great video explanation of all the steps involved.

The idea behind this concept is not new. Older displays of this type used tiny tungsten filament bulbs and complex light paths to direct light to the front of the display. The modern version, however, uses edge-lit panels with a grid of small LEDs beneath each segment, which are concealed within a casing. This design relies on the principle of total internal reflection, created by the contrast in refractive indices of acrylic and air. Light entering the panel from below at an angle greater than 42 degrees from normal is entirely reflected inside the panel. Fortunately, tiny LEDs have a wide dispersion angle, so if they are positioned close enough to the edge, they can guide sufficient light into the panel. Once this setup is in place, the surface can be etched or engraved using a CNC machine or a laser cutter. A rough surface texture is vital for this process, as it disrupts some of the light paths, scattering and directing some of it sideways to the viewer. Finally, to create your display, design enough parallel-stacked sheets for each segment of the display—seven in this case, but you could add more, such as an eighth for a decimal point.

How you arrange your lighting is up to you, but [upir] uses an off-the-shelf ESP32-S3 addressable LED array. This design has a few shortcomings, but it is a great start—if a little overkill for a single digit! Using some straightforward Arduino code, one display row is set to white to guide light into a single-segment sheet. To form a complete digital, you illuminate the appropriate combination of sheets. To engrave the sheets, [upir] wanted to use a laser cutter but was put off by the cost. A CNC 3018 was considered, but the choice was bewildering, so they just went with a hand-engraving pick, using a couple of 3D printed stencils as a guide. A sheet holder and light masking arrangement were created in Fusion 360, which was extended into a box to enclose the LED array, which could then be 3D printed.

If you fancy an edge-lit clock (you know you do) check out this one. If wearables are more your thing, there’s also this one. Finally, etched acrylic isn’t anywhere near as good as glass, so if you’ve got a vinyl cutter to hand, this simple method is an option.

Have you ever tired of playing with your latest robot invention and wished you could just eat it? Well, that’s exactly what a team of researchers is investigating. There is a fully funded research initiative (not an April Fools’ joke, as far as we know) delving into the possibilities of edible electronics and mechanical systems used in robotics. The team, led by EPFL in Switzerland, combines food process engineering, printed and molecular electronics, and soft robotics to create fully functional and practical robots that can be consumed at the end of their lifespan. While the concept of food-based robots may seem unusual, the potential applications in medicine and reducing waste during food delivery are significant driving factors behind this idea.

The Robofood project (some articles are paywalled!) has clearly made some inroads into the many components needed. Take, for example, batteries. Normally, ingesting a battery would result in a trip to the emergency room, but an edible battery can be made from an anode of riboflavin (found in almonds and egg whites) and a cathode of quercetin, as we covered a while ago. The team proposed another battery using activated charcoal (AC) electrodes on a gelatin substrate. Water is split into its constituent oxygen and hydrogen by applying a voltage to the structure. These gasses adsorb into the AC surface and later recombine back into the water, providing a usable one-volt output for ten minutes with a similar charge time. This simple structure is reusable and, once expired, dissolves harmlessly in (simulated) gastric fluid in twenty minutes. Such a device could potentially power a GI-tract exploratory robot or other sensor devices.

But what use is power without control? (as some car tyre advert once said) Microfluidic control circuits can be created using a stack of edible materials, primarily oleogels, like ethyl cellulose, mixed with an organic oil such as olive oil. A microfluidic NOT gate combines a pressure-controlled switch with a fluid resistor as the ‘pull-up’. The switch has a horizontal flow channel with a blockage that is cleared when a control pressure is applied. As every electronic engineer knows, once you have a controlled switch and a resistor, you can build NOT gates and all the other logic functions, flip-flops, and memories. Although they are very slow, the control components are importantly edible.

Edible electronics don’t feature here often, but we did dig up this simple edible chocolate bunny that screams when you bite it. Who wouldn’t want one of those?

Tiny Tapout is an interesting project, leveraging the power of cloud computing and collaborative purchasing to make the mysterious art of IC design more accessible for hardware hackers. [Yeo Kheng Meng] is one such hacker, and they have produced their very first custom IC for use with their retrocomputing efforts. As they lament, they left it a little late for the shuttle run submission deadline, so they came up with a very simple project with the equivalent behaviour of the Covox Speech Thing, which is just a basic R-2R ladder DAC hanging from a PC parallel port.

The plan was to capture an 8-bit input bus and compare it against a free-running counter. If the input value is larger than the counter, the output goes high; otherwise, it goes low. This produces a PWM waveform representing the input value. Following the digital output with an RC low-pass filter will generate an analogue representation. It’s all very simple stuff. A few details to contend with are specific to Tiny Tapout, such as taking note of the enable and global resets. These are passed down from the chip-level wrapper to indicate when your design has control of the physical IOs and is selected for operation. [Yeo] noticed that the GitHub post-synthesis simulation failed due to not taking note of the reset condition and initialising those pesky flip-flops.

After throwing the design down onto a Mimas A7 Artix 7 FPGA board for a quick test, data sent from a parallel port-connected PC popped out as a PWM waveform as expected, and some test audio could be played. Whilst it may be true that you don’t have to prototype on an FPGA, and some would argue that it’s a lot of extra effort for many cases, without a good quality graphical simulation and robust testbench, you’re practically working blind. And that’s not how working chips get made.

If you want to read into Tiny Tapeout some more, then we’ve a quick guide for that. Or, perhaps hear it direct from the team instead?

Something that’s a bit of fun at hacker camps such as the recent EMF Camp is to bring along a wired phone and hook it up to the on-camp copper network. It’s a number on the camp network, but pleasingly retro. How about doing the same thing at home? Easy enough if you still have a wired landline, but those are now fast becoming a rarity. Help is at hand though courtesy of [Remy], who’s written about his experiences using a 1960s Dutch phone as a SIP device.

The T65 was the standard Dutch home phone of the 1960s and 1970s, and its curvy grey plastic shape is still not difficult to find in that country.  The guide covers using various different VoIP boxes between such an old machine and the Internet, but there’s more of interest to be found in it. In particular the use of an inline pulse-to-tone converter, either the wonderfully-named DialGizmo, or perhaps closer to our world, a PIC-based kit.

So if you can lay your hands on a VoIP box it’s completely possible to use an aged phone here in 2024. Remember though, a SIP account isn’t the only way to do it.

J. de Kat Angelino, CC BY 3.0.

We would not be surprised if DSI screens made up the majority of screens on our planet at this moment in time. If you own a smartphone, there’s a 99.9% chance its screen is DSI. Tablets are likely to use DSI too, unless it’s eDP instead, and a smartwatch of yours definitely will. In a way, DSI displays are inescapable.

This is for a good reason. The DSI interface is a mainstay in SoCs and mobile CPUs worth their salt, it allows for higher speeds and thus higher resolutions than SPI ever could achieve, comparably few pins, an ability to send commands to the display’s controller unlike LVDS or eDP, and staying low power while doing all of it.

There’s money and power in hacking on DSI – an ability to equip your devices with screens that can’t be reused otherwise, building cooler and cooler stuff, tapping into sources of cheap phone displays. What’s more, it’s a comparably underexplored field, too. Let’s waste no time, then!

Decently Similar Internals

DSI is an interface defined by the MIPI Alliance, a group whose standards are not entirely open. Still, nothing is truly new under the sun, and DSI shares a lot of concepts with interfaces we’re used to. For a start, if you remember DisplayPort internals, there are similarities. When it comes to data lanes, DSI can have one, two or four lanes of a high-speed data stream; smaller displays can subsist with a single-lane, while very high resolution displays will want all four. This is where the similarities end. There’s no AUX to talk to the display controller, though – instead, the data lanes switch between two modes.

The first mode is low-speed, used for sending commands to the display, like initialization sequences, tweaking the controller parameters, or entering sleep mode. You can capture this with a logic analyzer. If you’ve ever sniffed communications of an SPI display, you will find that there are many similarities with how DSI commands are sent – in fact, many SPI displays use a command set defined by the MIPI Alliance that DSI displays also use. (If your Sigrok install lists a DSI decoder, don’t celebrate too soon – it’s an entirely different kind of DSI.)

The second mode is high-speed, and it’s the one typically used for pixel transfer. A logic analyzer won’t do here, at least not unless it’s seriously powerful when it comes to capture rate. You will want to use a decent scope for working with high-speed DSI signals, know your way around triggers, and perhaps make a custom PCB tap with a buffer for the the DSI signal so that your probe doesn’t become a giant stub, and figure out a way to work with the impedance discontinuities. Still, it is very much possible to tap into high-speed DSI, like [Wenting Zhang] has recently demonstrated, sometimes an approximation of the high-speed signal is more than enough for reverse-engineering.

Got a datasheet for your panel? Be careful – the initialization sequence in it might be wrong; if your bringup is not successful or your resulting image is weird, this just might be the culprit, so even if you have procured the correct PDF, you might still end up having to capture the init sequence with a logic analyzer. Whether your display’s initialization are well-known, or you end up capturing them from a known-working device, you will need something to drive your display with – a typical Arduino board will no longer do; though, who knows, an RP2040 just might, having seen what you all are capable of.

Ideally, you will want a microcontroller or a CPU that has a DSI peripheral, with decent documentation and/or examples on how to use it – that part is important. Linux-capable Raspberry Pi boards can help you here a surprising amount – you may remember the Raspberry Pi DSI header as being proprietary, but that was only true initially. With developments like the official Raspberry Pi screen and open-source graphics drivers aided by that $10k driver bounty they put out, it became viable to connect custom screens. WaveShare DSI screens are a known alternative if you want to get a DSI display for your Pi. On the regular Pi, you only get two lanes of DSI, but that is good enough for many a display. Funnily enough, you can get a third-party display for your Pi that uses the same panel, with two extra chips that seem to run the display without a driver like the official Pi display (this thread on these displays is fascinating!); the display is still limited to the same resolution, the only advantage is a slightly lower price, and the ability to overload your 3.3V rail is a questionable benefit. It’s not quite clear why this display exists, but you might want to resist the temptation.

If you’re using a Pi Compute Module, you get entire two DSI peripherals to play with, one four-lane and one two-lane, and it doesn’t take long to find a good few examples of Raspberry Pi Compute Module boards with DSI screens. If you have a Compute Module and its devboard somewhere on a shelf, you can do four-lane DSI, with a Linux-exposed interface that works in the same way alternative OSes do on your phone. Given that CMs are typically used for custom stuff and a hacker using one is more likely to have patience for figuring out DSI panel parameters, a Compute Module baseboard is a pretty popular option to hack on that one cheap DSI display from a tablet that caught your eye! Don’t have a baseboard? You can even etch one, here’s a single-layer breakout with a DSI socket. Not that you don’t need a Compute Module if you’re doing two-lane DSI: a regular Pi will do.

So, get out there and hack – there is a ton of unexplored potential in the never-ending supply of aftermarket screens for older iPhone and Samsung models!  Speaking of phones, they are the forefront of DSI hacking, as you might suspect, thanks to all the alternative OS projects and Linux kernel mainlining efforts. You can enjoy fruits of their labour fairly easily, sparing you a logic analyzer foray – reusing a seriously nice DSI display might be as easy as loading a kernel module.

Want A Panel? Linux Is Here To Help

There’s a fun hacker tactic – if you’re looking for an I2C GPIO expander chip, you can scroll through the Linux kernel config file that lists supported GPIO expanders, and find a good few ICs you’ve never known about! What’s great is, you know you’re getting a driver, too.

The same goes for DSI screens, except the payoff is way higher. If you’re on the market for a DSI screen, you can open the list of Linux kernel drivers for various DSI panels. Chances are, all you need is just the physical wireup part, maybe some backlight driving, and a Device Tree snippet.

Want a $20 1920 x 1200 IPS display for your Compute Module? Who doesn’t! Well, wouldn’t you know, the Google Nexus 7 tablet uses one, and the driver for it is in mainline Linux! Just solder together a small FPC-to-bespoke-connector adapter board (or order PCBA), add a Device Tree snippet into your configuration, and off you go; there are even custom boards for using this display with a CM4, it’s that nice.

New displays get added into the kernel all the time; all it takes is someone willing to poke at the original firmware, perhaps load a proprietary kernel module into Ghidra and pull out the initialization sequence, or simply enable the right kind of debug logging in the stock firmware. All of this is thanks to tireless efforts of people trying to make their phones work beyond the bloatware-ridden shackles of the stock Android OS; sometimes, it’s some company doing the right thing and upstreaming a driver for a panel used by hundreds of thousands of devices in the wild.

There are some fun nuances in the display scene, as much as of a “scene” it is – people are just trying to make their devices work for them, then share that work with other people in the same situation, figuring out a display is part of the process. It’s not uncommon that a smartphone will use slightly different screens in the same batch – it’s an uncommon but real issue with alternative OSes like LineageOS, where, say, 10% of your firmware’s users might have their panel malfunction because, despite the phone listing the same model on the lid, their specific phones use a display with a different controller, that only the manufacturer’s firmware properly accounts for.

Our DSI Role Models

These are the basics of what you need to reuse DSI displays as if effortlessly. Now, I’d like to highlight a good few examples of people hacking on DSI, from our coverage and otherwise.

Without a doubt, the first one that springs to mind is [Mike Harrison] aka [mikeselectricstuff], from way back in 2013. I’ve spent a lot of time with the exact iPod Nano being reverse-engineered, and [Mike]’s videos gave me insight into a piece of tech I relied on for a fair bit. For instance, in this video, [Mike] masterfully builds a scoping jig, solders microscoping wires to the tiny PCB, walks us through the entire reverse-engineering process, and successfully reuses the LCD for a project.

Following in [Mike]’s footsteps, we’ve even seen this display reused in an ESP32 project, thanks to a parallel RGB to DSI converter chip!

[Wenting Zhang] reverse-engineering a Macbook Touchbar display is definitely on my favourites list. In this short video, he teaches us DSI fundamentals, and manages to show the entire reverse-engineering process from start to end., no detail spared. Having just checked the video description, the code is open-source, and it’s indeed a RP2040 project – just like I forecasted a good few paragraphs above.

Are mysterious ASICs your vibe, and would you like to poke at some firmware? You should see this HDMI-to-DSI adapter project, then. The creator even turns it into a powerbank with a built-in screen as a demo – that’s a hacker accessory if I’ve ever seen one. More of a gateware fan? Here’s an FPGA board doing the same, and another one, that you can see here driving a Galaxy S4 screen effortlessly. Oh, and if you are friends with a Xilinx+Vivado combination, there are DSI IP cores for you to use with barely any restrictions.

The Year Of DSI Hacking

DSI is an interface that is becoming increasingly hacker-friendly – the economies of scale are simply forcing our hand, and even the microcontroller makers are following suit. The official devboard for Espressif’s ESP32-P4, a pretty beefy RISC-V chip, sports a DPI interface alongside the now-usual CSI for cameras. We will see DSI more and more, and I raise a glass of water for numerous hackers soon to reap the fields of DSI. May your harvest be plentiful.

I thank [timonsku] for help with this article!

With companies desperate to keep adding more and more seemingly random features to their products, Oral-B made the logical decision to add Alexa integration to its Oral-B Guide electric toothbrush. Taking it one step beyond just Bluetooth in the toothbrush part, the Guide’s charging base also acted as an Alexa-enabled smart speaker, finally adding the bathroom to the modern, all-connected smart home. Naturally Oral-B killed off the required Oral-B Connect smartphone app earlier this year, leaving Guide owners stranded in the wilderness without any directions. Some of the basics of this shutdown are covered in a recent Ars Technica article.

Amidst the outrage, it’s perhaps good to take a bit more of a nuanced view, as despite various claims, Oral-B did not brick the toothbrush. What owners of this originally USD$230 device are losing is the ability to set up the charging base as an Alexa smart speaker, while the toothbrush is effectively just an Oral-B Genius-series toothbrush with Bluetooth and associated Oral-B app. If you still want to have a waterproof smart speaker listening in while in the bathroom, you’ll have to look elsewhere, it seems. Meanwhile existing customers can contact Oral-B support for assistance, while the lucky few who still have the Connect app installed better hope it doesn’t disconnect, as reconnecting it to the smart speaker seems to be impossible, likely due to services shut down by Oral-B together with the old “oralbconnect.com” domain name.

We recently looked at a WiFi-enabled toothbrush as well, which just shows how far manufacturers of these devices are prepared to go, whether they intend to support it in any meaningful fashion or not.

Over the last several years, DIY projects utilizing e-paper displays have become more common. While saying the technology is now cheap might be overstating the situation a bit, the prices on at least small e-paper panels have certainly become far more reasonable for the hobbyist. Pair one of them with a modern microcontroller such as the RP2040 or ESP32, sprinkle in a few open source libraries, and you’re well on the way to creating an energy-efficient smart display for your home or office.

But therein lies the problem. There’s still a decent amount of leg work involved in getting the hardware wired up and talking to each other. Putting the e-paper display and MCU together is often only half the battle — depending on your plans, you’ll probably want to add a few sensors to the mix, or perhaps some RGB status LEDs. An onboard battery charger and real-time clock would be nice as well. Pretty soon, your homebrew e-paper gadget is starting to look remarkably like the bottom of your junk bin.

For those after a more integrated solution, the folks at Soldered Electronics have offered up a line of premium open source hardware development boards that combine various styles of e-paper panels (touch, color, lighted, etc) with a microcontroller, an array of sensors, and pretty much every other feature they could think of. To top it off, they put in the effort to produce fantastic documentation, easy to use libraries, and free support software such as an online GUI builder and image converter.

We’ve reviewed a number of previous Inkplate boards, and always came away very impressed by the attention to detail from Soldered Electronics. When they asked if we’d be interested in taking a look at a prototype for their new MOTION 6 board, we were eager to see what this new variant brings to the table. Since both the software and hardware are still pre-production, we won’t call this a review, but it should give you a good idea of what to expect when the final units start shipping out in October.

Faster and Stronger

As mentioned previously, the Inkplate boards have generally been differentiated by the type of e-paper display they’ve featured. In the case of the new MOTION, the theme this time around is speed — Soldered says this new display is capable of showing 11 frames per second, no small feat for a technology that’s notoriously slow to refresh. You still won’t be watching movies at 11 FPS of course, but it’s more than enough to display animations and dynamic information thanks to its partial refresh capability that only updates the areas of the display where the image has actually changed.

But it’s not just the e-paper display that’s been swapped out for a faster model. For the MOTION 6, Soldered traded in the ESP32 used on all previous Inkplates for the STM32H743, an ARM Cortex-M7 chip capable of running at 480 MHz. Well, at least partially. You’ll still find an ESP32 hanging out on the back of the MOTION 6, but it’s there as a co-processor to handle WiFi and Bluetooth communications. The STM32 chip features 1 MB of internal SRAM and has been outfitted with a whopping 32 MB of external DRAM, which should come in handy when you’re throwing 4-bit grayscale images at the 1024 x 758 display.

The Inkplate MOTION 6 also features an impressive suite of sensors, including a front-mounted APDS-9960 which can detect motion, proximity, and color. On the backside you’ll find the SHTC3 for detecting temperature and humidity, as well as a LSM6DSO32 accelerometer and gyroscope. One of the most impressive demos included in the MOTION 6’s Arduino library pulls data from the gyro and uses it to rotate a wireframe 3D cube as you move the device around. Should you wish to connect other sensors or devices to the board, you’ve got breakouts for the standard expansion options such as I²C and SPI, as well as Ethernet, USB OTG, I²S, SDMMC, and UART.

Although no battery is included with the MOTION 6, there’s a connector for one on the back of the board, and the device includes a MCP73831 charge controller and the appropriate status LEDs. Primary power is supplied through the board’s USB-C connector, and there’s also a set of beefy solder pads along the bottom edge where you could wire up an external power source.

For user input you have three physical buttons along the side, and a rather ingenious rotary encoder — but to explain how that works we need to switch gears and look at the 3D printed enclosure Soldered has created for the Inkplate MOTION 6.

Wrapped Up Tight

Under normal circumstances I wouldn’t go into so much detail about a 3D printed case, but I’ve got to give Soldered credit for the little touches they put into this design. Living hinges are used for both the power button and the three user buttons on the side, there’s a holder built into the back for a pouch battery, and there’s even a little purple “programming tool” that tucks into a dedicated pocket — you’ll use that to poke the programming button when the Inkplate is inside the enclosure.

But the real star is the transparent wheel on the right hand side. The embedded magnet in the center lines up perfectly with a AS5600 magnetic angle encoder on the Inkplate, with an RGB LED just off to the side. Reading the value from the AS5600 as the wheel rotates gives you a value between 0 and 4048, and the library offers macros to convert that to radians and degrees. Combined with the RGB LED, this arrangement provides an input device with visual feedback at very little cost.

It’s an awesome idea, and now I’m looking for an excuse to include it in my own hardware designs.

The 3D printed case is being offered as an add-on for the Inkplate MOTION 6 at purchase time, but both the STLs and  Fusion 360 files for it will be made available with the rest of the hardware design files for those that would rather print it themselves.

An Exciting Start

As I said in the beginning of this article, the unit I have here is the prototype — while the hardware seems pretty close to final, the software side of things is obviously still in the early stages. Some of the libraries simply weren’t ready in time, so I wasn’t able to test things like WiFi or Bluetooth. Similarly, I wasn’t able to try out the MicroPython build for the MOTION 6. That said, I have absolutely no doubt that the team at Soldered Electronics will have everything where it needs to be by the time customers get their hands on the final product.

There’s no denying that the $169 USD price tag of the Inkplate MOTION 6 will give some users pause. If you’re looking for a budget option, this absolutely isn’t it. But what you get for the price is considerable. You’re not just paying for the hardware, you’re also getting the software, documentation, schematics, and PCB design files. If those things are important to you, I’d say it’s more than worth the premium price.

So far, it looks like plenty of people feel the same way. As of this writing, the Inkplate MOTION 6 is about to hit 250% of its funding goal on Crowd Supply, with more than 30 days left in the campaign.

[befi] brings us a project as impressive as it is reminiscent of older times, a Blu-Ray mini disk player. Easily fitting inside a pocket like a 8 cm CD player would, this is a labour of love and, thanks to [befi]’s skills both in electronics and in using a dremel tool.

A BluRay drive was taken apart, for a start, and a lot of case parts were cut off; somehow, [befi] made it fit within an exceptionally tiny footprint, getting new structural parts printed instead, to a new size. The space savings let him put a fully custom F1C100S-powered board with a number of unique features, from a USB-SATA chip to talk to the BluRay drive, to USB pathway control for making sure the player can do USB gadget mode when desired.

There’s an OLED screen on the side, buttons for controlling the playback, power and battery management – this player is built to a high standard, ready for day-to-day use as your companion, in the world where leaving your smartphone as uninvolved in your life as possible is a surprisingly wise decision. As a fun aside, did you know that while 8 cm CDs and DVDs existed, 8 cm BluRay drives never made it to market? If you’re wondering how is it that [befi] has disks to play in this device, yes, he’s used a dremel here too.

Everything is open-sourced – 3D print files, the F1C100S board, and the Buildroot distribution complete with all the custom software used. If you want to build such a player, and we wouldn’t be surprised if you were, there’s more than enough resources for you to go off. And, if you’re thinking of building something else in a similar way, the Buildroot image will be hugely helpful.

Want some entertainment instead? Watch the video embedded below, the build journey is full of things you never knew you wanted to learn. This player is definitely a shining star on the dark path that is Blu-Ray, given that our most popular articles on Blu-Ray are about its problems.

The Rewind Pendant is an upcoming wearable device that gives you a personalized AI assistant that can understand everything you say and hear. It automatically transcribes, encrypts, and stores conversations and ambient sounds locally on your phone. Key features include automatic to-do list generation from verbal commitments, capturing ideas or memories throughout your day, insights […]

Source

As the debate rages on about the value of AI-generated art, [Chris Borge] printed his own version of another technology that’s been the subject of debate about what constitutes real art. Meet the camera lucida.

Developed in the early part of the nineteenth century by [William Hyde Wollaston], the camera lucida is a seemingly simple device. Using a prism or a mirror and piece of glass, it allows a person to see the world overlaid onto their drawing surface. This moves details like proportions and shading directly to the paper instead of requiring an intermediary step in the artist’s memory. Of course, nothing is a substitute for practice and skill. [Professor Pablo Garcia] relates a story in the video about how [Henry Fox Talbot] was unsatisfied with his drawings made using the device, and how this experience was instrumental in his later photographic experiments.

[Borge]’s own contribution to the camera lucida is a portable version that you can print yourself and assemble for about $20. Featuring a snazzy case that holds all the components nice and snug on laser cut felt, he wanted a version that could go in the field and not require a table. The case also acts as a stand for the camera to sit at an appropriate height so he can sketch landscapes in his lap while out and about.

Interested in more drawing-related hacks? How about this sand drawing bot or some Truly Terrible Dimensioned Drawings?

[Jens] wanted a subscriber counter for his YouTube channel. He could have gone with a simple OLED, LCD, or LED display, but he wanted something more tactile and interesting. So he built a mechanical 7-segment display instead!

Currently, [Jens]’s channel is in the four-digit subscriber range, so he planned to build a four-digit display. He started by searching for existing projects in this space, and came across the designs of [shiura] on Thingiverse. [shiura] had a 3D printed cam-driven 7-segment digit that runs on a single servo motor. Once armed with four of the digits, he hooked them up to a Pi Pico W to drive them all with four servo outputs. The Pico W is responsible for querying the channel subscriber count online, and updating the display in turn.

It’s a neat build, and [Jens] learned some things along the way—like how Super Lube seemed to ruin filament for him. Ultimately, the build came good, and it looks great. We’ve seen some other mechanical 7-segment builds before, too!

Most of the Hackaday community would never wire a power supply to a circuit without knowing the expected voltage and the required current. But our mechanical design is often more bodged. We meet folks who carefully budget power to their microcontroller, sensors, and so on, but never measure the forces involved in their mechanical designs. Then they’re surprised when the motor they chose isn’t big enough for the weight of their robot.

An obstacle to being more numbers oriented is lack of basic data about the system. So, here are some simple tools for measuring dynamic properties of small mechanisms; distances, forces, velocities, accelerations, torques, and other things you haven’t thought about since college physics. If you don’t have these in your toolkit, how do you measure?

Distance

For longer distances the usual homeowner’s tools work fine. The mechatronics tinkerer benefits from two tools on the small end. A dial or electronic caliper for measuring small things, and a thickness gauge (or leaf gauge) for measuring small slots.

A thickness gauge is just metal leaves in different thicknesses, bolted together at one end. Find a combination of leaves that just fits in the space.

Force

Here’s four force measuring tools we use to cover different magnitudes of force: a postage scale, a push stick, a spring scale, and a letter scale. The postage scale is best purchased. For big things, the bathroom scale works.

A push stick is a force measurement device that you can make yourself. We first saw one of these used to tune slot cars, but they’re universally useful. It’s a simple pen shaped device made with a barrel from any small transparent parts tube, a spring, and a plunger with a protruding pin. Grasp the barrel and push the gizmo with the pin, and you can read the force off the tube.

If you need it to be calibrated, remember that you just bought a postage scale. Push it into the scale and mark off reasonable increments. Make several, in different sizes. A Z or L shaped plunger is useful for hard to reach places.

The conventional spring tension scale is useful, but most commercial ones are terribly made and inaccurate. You can make yourself a better one. They are useful for measuring the spring constant of springs, for learning the tractive effort needed to move a robot, finding the center of gravity of a robot arm, and a hundred other ‘how much oomph’ things. Again, it’s just a matter of connecting a hook to a spring, and measuring its deflection.

For yet lighter weights, you could buy a letter scale, at least in the old days. Today you might have to make your own.  It can be as simple as a piece of spring steel fixed to a sheet of calibrated cardboard.

Torque

Torque measurements are good not only for sizing actuators, but for measuring efficiency.

How you do torque measurements depend on the speed you want to make them at. For static loads, just put a lever of known length on the shaft and measure the force. Torque = distance * force. For fast rotating systems, you can run the system at a known speed and measure the electrical energy used.

If you just want to apply a varying known torque to measure efficiency, your life is much easier. Mount a broad wheel of some sort on the shaft — RC airplane tires work well. Drape a piece of ribbon over the tire. Anchor it at the “out” end and hang a small weight at the “in” end. This is a Prony Brake, and it’s a useful device to know about. The force on the outside of the wheel is just enough to lift the weight – after that the ribbon slips. The measured torque is then the weight times the wheel radius.

You may also want to measure speeds and accelerations. Here, the ubiquity of cell phone cameras is your friend. Suppose you’re animating a crane on your model railroad. Record yourself on video moving the crane with your hands against a protractor to get a feel for speed and acceleration. In video editing software check the positions for various frames, and you now have position changes. The number of frames and distance can help you calculate the speed, and the change in speed vs time is acceleration.

If your mechanism is moving too fast for video, use a fast phototransistor or hall effect device and an oscilloscope, or gear down by holding a toy wheel against the shaft and measure the more slowly rotating wheel.

In the crane example, the torque you need to supply is the frictional torque plus the acceleration torque, and to calculate the acceleration torque you need the moment of inertia. For refresher: angular acceleration = torque / moment of inertia (ω = τ / I) and moment of inertia = mass * radius² (I = m * r² ) for point mass.

You can drive the crane with a repeatable torque, say using a pulley and weight or a motor, and get the acceleration ω₁ from the still frames on your video. If you repeat this with a known mass m a known distance r from the shaft axis, like a lump of putty on the end of the crane arm, you can get a second value: ω_2. 

Write the ω = τ / I equations, ω₁ = τ / I_crane and ω₂ = τ / (I_crane + r ² * m). Combining and isolating I_crane and holding our tongues just right, I_crane = r² * m / (ω₁ / ω₂ – 1).

Be careful to subtract the moment of inertia of your measuring apparatus, and add in the moment of inertia of the final drive if needed. Now you can size your servo with some confidence. Believe me, once you’ve done this a couple times, you’ll never go back to winging it.

Power

The easiest way to get a ballpark feel for power is to simply measure the system’s consumed power by measuring the electrical power at the motor, but this ignores losses in the drive train. And losses are one of the really interesting things to measure. Bad performance is usually friction, and efficiency is a goal for other reasons than just motor sizing or battery life. It’s a measure of how janky your setup is.

Does your model train or robot run poorly? Set it to climb a steep grade on a test track. Calculate the work it does: mass * height change. Measure the input electrical power and the time, Energy = V*I*T. You now have an idea of how much the actual power consumption differs from the maximally efficient system. Any power that went in but didn’t appear as potential energy in the choo-choo’s new position is frictional loss. Now you can experiment with loosening and tightening screws, changing gear mesh, and such, and have some idea if you’re making things better or worse.

Conclusion

None of the above was rocket science, and you don’t need to do some complex FEM analysis to make the average hacker project. But a bit of real engineering can go a long way towards more reliable mechanisms, and that starts with knowing the numbers you’re dealing with. Taking the required measurements can be simple if you know how to build the tools you need,  and your life will be easier with some numbers to guide you.

iSCSI is a widely used protocol for exposing SCSI devices over a network connection, and some scanners have in the past been equipped with SCSI ports. So, could you have an iSCSI network scanner? [xssfox] details her journey making a Canoscan FS4000US film scanner work over iSCSI, sparked by someone’s overly-confident StackOverflow comment that it couldn’t be done. Nothing in the spec said it couldn’t actually work, however, and after figuring out a tentative architecture, a hardware setup was put together.

No flatbed scanners with SCSI ports could be found on the cheap, so a film scanner had to be procured. After figuring out a few hitches with the loading mechanism and getting a test image locally, it was time to try and build up the software setup, tearing through SCSI compatibility and cabling, driver and PCI pass-through woes, bluescreens, and intermediate software having dropped some of the necessary features by now. Still, [xssfox] eventually exported the scanner as an iSCSI target – and, on the other end of the network, successfully connected to it and completed a scan. The StackOverflow answer was wrong, after all.

It’s fun to see how far old technology can go, and get answers to questions you never knew you had. Whether you’re reminiscing about SCSI days or wondering what the technology about, we’ve talked about it aplenty, from a retrospective to modern-day experiments, repurposing old SCSI hardware for modern SATA ports, a Raspberry Pi implementation, an emulator, and a fair bit more.

We thank [Valentijn Sessink] and [adistuder] for sharing this with us!