TechyMagThings

[Brian] had an absolute monster of a PCB with thousands of nets to be routed, the kind of design that stopped traditional routers in their tracks. It would take months to route by hand, likely trying the patience of a saint in the process. To solve this specific problem he created OrthoRoute, a GPU-accelerated autorouter that he cautions is no more trustworthy than any other autorouter, but at least it’s fast!

A KiCad plugin, OrthoRoute is so named because traces are laid down in a Manhattan lattice, a grid of orthogonal segments. All components (surface-mount only, no through-hole stuff) go on the top layer of the PCB, and all lower levels contain a grid of traces, connected as needed with blind and buried vias to route everything. OrthoRoute takes a structured and iterative approach, eventually converging on a satisfactory layout.

How does OrthoRouter actually decide how to connect things? [Brian] adapted PathFinder, an algorithm designed for routing FPGAs. Laying out a grid of orthogonal traces and punching down through them with vias to make connections has a lot in common, conceptually, with routing FPGAs. GPU acceleration makes the whole thing far more efficient than pipelining the calculations through a CPU.

OrthoRoute was built to solve a very specific problem, but in the process showed that GPU-accelerated routing is definitely feasible. Check it out in the videos, embedded below the page break.

[Brian] cautions that as-is, OrthoRoute is useful to maybe a handful of people at best, but as a KiCad plugin it’s highly modular and the hard parts are all done. If you want a closer look, or have some ideas about how to repurpose or extend it, check out the GitHub repository.

We’ve seen some nifty KiCad plugins for all kinds of purposes, from breadboarding to giving PCB traces an old-timey look, and even one specifically for designing custom keyboards. It’s not every day we see a plugin aimed at handling high-density boards with thousands of nets, though.

The first known use of humans using wind to perform mechanical work with machines dates back to ninth-century Persian windmills. But if we count sailing vessels among those machines, the history goes back to sometime just before the invention of written language. Since then, humans have been sailing everything from the tiniest of Sunfish to the largest of shipping vessels, and even sailing boats like canoes that aren’t typically designed for efficient sailing. For those who already own a canoe, the conversions can be straightforward but often involve drilling into the hull. This homemade conversion kit, on the other hand, requires no drilling at all.

The first, and most obvious, part of the conversion is to add a mast and sail. [Tea]’s primary setup does involve drilling a mast thwart into the gunwales of the canoe, but he also built an alternative setup which clamps to the gunwales and the bow deck instead. The standing lug sail is then hoisted on an unstayed wooden mast. The next major component of the build are a pair of leeboards which also clamp to the gunwales and function like a centerboard, and can be adjusted for one’s preferred amount of weather helm. Rounding out the stern of the boat is a custom-built rudder with a pair of lines in lieu of a tiller which can be positioned anywhere along the length of the boat.

All of the wooden parts of this build were custom-built from common lumber with finishing touches from a router to soften all of the hard edges. Canoe sailing is fairly popular, although without the leeboards these common sailing kits are often meant for downwind sailing only. A complete setup like this turns it into a much more capable craft. Without a canoe as a base vessel to start with, though, a complete sailing vessel can be built from common lumber as well.

We’re all used to satellite navigation systems such as GPS or GLONASS, sheer magic in which the combination of a set of reference transmitters and super-accurate timing information can be used to calculate a position to an astounding precision. They had land based predecessors such as LORAN and Decca Navigator which worked in a similar fashion but with fixed land-based reference transmitters. Terra is an attempt to do the same thing without a network of dedicated transmitters, instead using FM broadcast transmitters as its fixed points.

This might seem like an impossible task without access to the transmitters, but they have a workaround using the Internet as a backhaul. Instead of transmitting their timing information like the systems mentioned above, they rely on a set of reference receivers sharing it online to the client’s receiver software. So far they have a demo running in Denver.

The interesting thing about this system is that it’s open-source, and requires only a relatively inexpensive software defined radio receiver and a computer to operate. Now anyone with a group of internet-connected friends to set up reference receivers can have their own positioning system, it’s no longer the exclusive preserve of governments. We like this idea, and we look forward to seeing it being tested more widely.

If you’d like to know where we’ve come from, we’ve taken a look at LORAN before.

This week Jonathan chats with Andy Gryc and Aaron Basset about QNX, and the interesting Open Source history and future of that embedded OS. Why does QNX Everywhere feel more open, and why do you need to register an account to download images? All that and more — Watch to find out!

• Open-source Dashboard: https://oss.qnx.com/
• GitHub Repository: https://github.com/qnx-ports
• QNX Everywhere webpage: https://qnx.software/en/developers/get-started/qnx-everywhere

Did you know you can watch the live recording of the show right on our YouTube Channel? Have someone you’d like us to interview? Let us know, or have the guest contact us! Take a look at the schedule here.

Direct Download in DRM-free MP3.

If you’d rather read along, here’s the transcript for this week’s episode.

Theme music: “Newer Wave” Kevin MacLeod (incompetech.com)

Licensed under Creative Commons: By Attribution 4.0 License

We all love a good bit of bounce now and then, with everything from trampolines to bouncy castles and bouncy balls forming the staple of a wholesome childhood for many. That said, most of our bouncy experiences in day to day life concern bouncy objects that meet immovable or rigid objects, including said child having a blast in a bouncy castle. Where the physics get arguably more interesting and less intuitive is when you combine two objects that are both bouncy, with [Steve Mould] recently taking a look at the tuning of said bounciness to even kill the bounce completely.

Understanding how to achieve this tuning means understanding how the kinetic energy is stored in each flexible material, and how to dissipate it in a way that doesn’t result in the aforementioned bounciness. In the simple physical demonstration setup the addition or removal of weights to the lower sprung platform tunes the response to the bouncy ball that is dropped on top of it.

After going through the science behind bounciness and springiness using the practical application of this science in the context of golf balls and clubs, [Steve] introduces the simulation tool that he created. This allows you to tweak the parameters of such a double spring system, which may bring back some high school physics lessons for some.

In a system like that of a golf club and the ball, having undesirable oscillations (bouncing) reduces the final kinetic energy transferred to the ball. Although ‘bouncy’ is perhaps not the first thought that comes to mind when handling a golf ball or a club, ultimately they are just as bouncy as a bouncy ball or an electric switch, just on their own scales, with their own opportunities for optimization and analysis.

Laser diodes are convenient light sources, but for precise optical work their often-elliptical beam profile leaves something to be desired. One way to get around this is to couple the beam into a single-mode optical fiber, which then emits a circular Gaussian beam from the other end. For more advanced experiments, therefore, [Diffraction Limited] built this fiber-coupled laser source.

The simplest approach is to place the fiber directly against a light source, but this results in most of the light missing the three-micron fiber core. Optical fibers have an acceptance cone, and only light approaching from within this cone is coupled into the fiber. The design therefore uses an aspheric lens to focus light from the laser diode down to a tiny point matching the diameter of the fiber core, creating a cone of incoming light narrower than the acceptance cone.

The body of the laser source was CNC machined out of brass, with the laser-diode press-fit in one end. The lens stands in front of the diode, and was glued in place so that its focal point was just above the end of a mounting pin for the glass fiber. Positioning and fixing the fiber in place was the biggest challenge; [Diffraction Limited] could use the micro-manipulator from a previous video to position the fiber, but the UV-set glue used to fix it in place shrinks during curing, pulling it out of position. To deal with this, two set screws under the mounting pin allowed its position to be adjusted slightly after gluing. As expected, adhesive shrinkage meant that the completed source initially produced no light, but after the set screws were adjusted, the beam appeared.

For more on fiber-coupled lasers, check out [Les Wright]’s work. If you don’t have access to an aspheric lens, an anti-bumping bead could be a reasonable alternative.

The phenomenon of cable-shaped indents in the plastic cases of retro systems is one that’s probably painfully familiar to many a collector of such systems. Although in these situations neither side got hot enough to cause any melting – especially while disconnected in storage – it still has that same melted appearance. The real cause here is not heat, but plasticizer migration, as detailed in a recent video by [Run Stop Restored] over on YouTube.

Plasticizers are an additive to many plastics that aim to make it more flexible (‘plastic’), as well as improve other characteristics of the base material, with PVC in particular relying on plasticizers to give it its desired properties for applications where PVC has to be flexible. Here the flexible cable insulation of these devices generally uses PVC, which over time can migrate to other polymers when brought into close contact for extended periods of time.

The – usually ABS – enclosures of e.g. Commodore tape drives as in this video demonstration thus get correspondingly inundated with the same type of plasticizers that ABS is also highly susceptible to. Since in storage the cables tend to be wrapped – tightly – around the device they’re attached to, this results in a solid contact which thus enables this gradual process to work its magic, whether it’s a Commodore datasette or a power supply brick.

Correspondingly the PVC insulation becomes brittle as it loses its plasticizer, with the process sped up by higher environmental temperatures. To prevent this, never wrap a PVC cable around a device, and keep it physically separated from susceptible plastics like ABS as much as reasonably possible. Along with a cool environment this should prevent plasticizer migration from ruining what used to be a pristine case.

This problem is particularly significant for retro gear from the 1980s and thereabouts, before phthalate-free plasticizer alternatives were developed, along with other changes such as more stable formulations that prevent this migration process. Adding a coating can also help, especially for protecting older gear, but flexible PVC in particular should be viewed with suspicion and treated carefully.