Putting LEDs In Motorcyle Tail Light Shows How Trivial Becomes Tough

May 25, 2021 by Donald Papp 57 Comments

[Maarten Tromp]’s replacement of his motorcycle’s tail light with LED equivalents is a great example of something that every hacker learns sooner or later: interfacing to and working around existing parts can turn a trivial-seeming task into a much bigger job than expected. The more one has to work within the constraints of an existing system, the more opportunities there are for roadblocks and surprise issues to stall progress, and this project is a great example of that.

[Maarten]’s 1999 Honda ST1100 Pan European motorcycle had no aftermarket options for an LED rear light assembly, and he wasn’t too keen on just installing a generic module to replace the original. Instead, he resolved to purchase and disassemble a used factory assembly, and replace the incandescent lamps with some equivalent LEDs. Replacing bulbs with LEDs sounds easy, but doing the job right took [Maarten] almost two weeks in the end.

Problems started early with simple things like how to open up the light assembly itself. The unit isn’t user-serviceable and isn’t intended to be opened, and the parts are sealed shut with a waxy substance. Fortunately, heat does the trick. Another early hitch was the curved base of the light assembly, which made mounting flat perfboard or veroboard a challenge. In the end, [Maarten] settled on a triangular grid of high-brightness LEDs, driven with LM317 regulators configured as constant-current supplies, mounted on some protoboard cut to fit the unique curve of the assembly. The result accepts the wide voltage range of the motorcycle’s battery (from 10.5 V to 14.5 V) and can still function even if some individual LEDs stop working.

The project has one more example of how working around existing hardware can be a pain. [Maarten] had originally intended to swap out the turn signal lamps for LEDs as well, but there is a glitch. The motorcycle’s turn signal relay will do a fast blink pattern if burnt-out turn signal lamps are detected. Since LEDs consume considerably less current than the original bulbs, the relay will remain stuck in the fault condition. There are a few different ways around this, but it’s a problem for another day. For now, the tail light LED replacement is a success.

Working around existing hardware frequently brings unexpected challenges, but when safety systems (such as lights on a vehicle) are involved, it’s extra-important to make sure things are done right.

Simple MicroPython Game Is A 30 Minute Game Dev Course

May 25, 2021 by Donald Papp 7 Comments

Sometimes, it’s really useful to watch a project’s parts come together one piece at a time in order to get a complete understanding and mental picture of the whole, and we found that to be the case with this simple, retro-inspired sample game from [ezContents]. (Video, embedded below.) The code is on GitHub but if you’re at all interested in what goes on behind the scenes in a game like that, don’t miss the video.

In the video, each game element and function is illustrated, showing exactly what gets done and why. This part is collision detection (click to enlarge.)

These sprite-based games are mostly about moving a small graphical object (a sprite) around a screen in response to user input, and managing what happens when collisions are detected between the player’s sprite and other sprites like enemies, projectiles, and so forth. The development process is wonderfully documented and demonstrated in a video, as each separate part of functionality gets built and explained one piece at a time.

The simple game is made using ArduPy (which is MicroPython combined with Arduino APIs) using Seeed Studios’ Wio Terminal, a small microcontroller development board with integrated screen, sensors, and button inputs including a little directional clicker that [ezContents] uses as a joystick.

The video of the whole process is embedded below; give it a watch and you’ll maybe come away with inspiration, but you’ll definitely have a much better understanding of how these types of games are developed, even if you’re not using the same hardware or development environment.

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Iridescent Rainbow Chocolate, Just Add Diffraction Grating!

May 23, 2021 by Donald Papp 15 Comments

Chocolate plus diffraction grating equals rainbow chocolate

Here’s a great picture from [Jelly & Marshmallows] that shows off the wild effects of melted chocolate poured onto a diffraction grating. A diffraction grating is a kind of optical component whose micro-features act to disperse and scatter light. Diffraction gratings are available as thin plastic film with one side that is chock full of microscopic ridges, and the way light interacts with these ridges results in an iridescent, rainbow effect not unlike that seen on a CD or laserdisc.

It turns out that these micro-ridges can act as a mold, and pouring chocolate over a diffraction grating yields holo-chocolate. These photos from [Jelly & Marshmallows] show this effect off very nicely, but as cool as it is, we do notice that some of the letters seem a wee bit hit-or-miss in how well they picked up the diffraction grating pattern.

Fortunately, we know just what to suggest to take things to the next level. If you want to know more about how exactly this effect can be reliably accomplished, you’ll want to check out our earlier coverage of such delicious optics, which goes into all the nitty-gritty detail one could ever want about getting the best results with either melted sugar, or dark chocolate.

Omnibot From The 80s Gets LED Matrix Eyes, Camera

May 18, 2021 by Donald Papp 8 Comments

[Ramin assadollahi] has been busy rebuilding and improving an Omnibot 5402, and the last piece of hardware he wanted to upgrade was some LED matrix eyes and a high quality Raspberry Pi camera for computer vision. An Omnibot was something most technical-minded youngsters remember drooling over in the 80s, and when [ramin] bought a couple of used units online, he went straight to the workbench to give the vintage machines some upgrades. After all, the Omnibot 5402 was pretty remarkable for its time, but is capable of much more with some modern hardware. One area that needed improvement was the eyes.

The eyes on the original Omnibot could light up, but that’s about all they were capable of. The first upgrade was installing two 8×8 LED matrix displays to form what [ramin] calls Minimal Expressive Eyes (MEE), powered by a Raspberry Pi. With the help of a 3D-printed adapter and some clever layout, the LED matrix displays fit behind the eye plate, maintaining the original look while opening loads of new output possibilities.

Adding a high quality Raspberry Pi camera with wide-angle lens was a bit more challenging and required and extra long camera ribbon connector, but with the lens nestled just below the eyes, the camera has a good view and isn’t particularly noticeable when the eyes are lit up. Having already upgraded the rest of the hardware, all that remains now is software work and we can’t wait to see the results.

Two short videos of the hardware are embedded below, be sure to give them a peek. And when you’re ready for more 80s-robot-upgrading-action, check out the Hero Jr.

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Retro ISA Card Means Old, Slow Computers No Longer Need Old, Heavy Monitors

May 18, 2021 by Donald Papp 66 Comments

One thing about vintage computers is that they depend greatly on whether or not one can plug a compatible monitor into them. That’s what’s behind [Tube Time]’s Graphics Gremlin, a modern-design retro ISA video card that uses an FPGA to act just like a vintage MDA or CGA video card on the input end, but provides a VGA port for more modern display output options. (Actually, there is also an RGBI connector and a composite video out, but the VGA is probably the most broadly useful.)

Handy silkscreen labels make everything crystal clear. Click to enlarge.

Why bother making a new device to emulate an old ISA video card when actual vintage video cards are still plentiful? Because availability of the old cards isn’t the bottleneck. The trouble is that MDA or CGA monitors just aren’t as easy to come across as they once were, and irreplaceable vintage monitors that do still exist risk getting smashed during shipping. Luckily, VGA monitors (or at least converters that accept VGA input) are far more plentiful.

The board’s design files and assembly notes are all on the project’s GitHub repository along with plenty of thoughtful detail about both assembly and troubleshooting, and the Verilog code has its own document. The Graphics Gremlin is still under development, but you can also watch for the latest on [Tube Time]’s Twitter feed.

Thanks to [NoxiousPluK] for the tip!

Soil Moisture Sensors, How Do They Work?

May 17, 2021 by Donald Papp 19 Comments

In a way, the magic of a soil moisture sensor’s functionality boils down to a simple RC circuit. But of course, in practice there is a bit more to it than that. [rbaron] explains exactly how capacitive soil moisture sensors work simply, clearly, and concisely. He also shows, with a short video, exactly how their output changes in response to their environment, and explains how it informed his own sensor design.

At its heart, a moisture sensor measures how quickly (or slowly) a capacitor charges through a resistor, but in these sensors the capacitor is not a literal component, but is formed by two PCB traces that are near one another. Their capacitance — and therefore their charging rate — changes in response to how much water is around them. By measuring this effect on a probe sunk into dirt, the sensor can therefore indirectly measure the amount of water in the soil.

This ties into his own work on b-parasite: an open-source, all-in-one wireless soil moisture sensor (which was also a runner-up in our Earth Day contest) that broadcasts over BLE and even includes temperature readings. One thing to be mindful of if you are making your own PCBs or ordering them from a fab house is that passing current through metal in a moist environment is a recipe for oxidation, so it’s important not to expose bare traces to wet soil. A good coated PCB should avoid this problem, but one alternative we have seen proposed is to use graphite rods in place of metal.

3D-Printed Desiccant Container Exploits Infill

May 11, 2021 by Donald Papp 15 Comments

Desiccant is common in 3D printing because the drier plastic filament is, the better it prints. Beads of silica gel are great for controlling humidity, but finding a porous container for them that is a convenient size is a little harder. 3D printing is a generally useful solution for custom containers, but suffers from a slight drawback in this case: printing dense grills or hole patterns is not very efficient for filament-based printers. Dense hole patterns means lots of stopping and starting for the extruder, which means a lot of filament retractions and longer print times in general.

The green model is used as a modifier to the orange container (of which only the corners are left visible here)

[The_Redcoat]’s solution to this is to avoid hole patterns or grills altogether, and instead print large wall sections of the container as infill-only, with no perimeter layers at all. The exposed infill pattern is dense enough to prevent small beads of desiccant from falling through, while allowing ample airflow at the same time. The big advantage here is that infill patterns are also quite efficient for the printer to lay down. Instead of the loads of stops and starts and retractions needed to print a network of holes, infill patterns are mostly extruded in layers of unbroken lines. This translates to faster print speeds and an overall more reliable outcome, even on printers that might not be as well tuned or calibrated as they could be.

To get this result, [The_Redcoat] modeled a normal, flat-walled container then used OpenSCAD to create a stack of segments to use as a modifier in PrusaSlicer. The container is printed as normal, except where it intersects with the modifier, in which case those areas get printed with infill only and no walls. The result is what you see here: enough airflow for the desiccant to do its job, while not allowing any of the beads to escape. It’s a clever use of both a high infill as well as the ability to use a 3D model as a slicing modifier.

There’s also another approach to avoiding having to print a dense pattern of holes, though it is for light-duty applications only: embedding a material like tulle into a 3D print, for example, can make a pretty great fan filter.