Avoiding PCB Crosstalk

Now that it is relatively cheap and easy to create a PCB, it is a common occurrence for them to be used in projects. However, there are a lot of subtleties to creating high-performance boards that don’t show up so much on your 555 LED blinker. [Robert Feranec] is well-versed in board layout and he recently highlighted an animation on signal crosstalk with [Eric Bogatin] from Teledyne LeCroy. If you want a good understanding of crosstalk and how to combat it, you’ll want to see [Eric’s] presentation in the video below.

Simplifying matters, the heart of the problem lies in running traces close together so that the magnetic fields from one intersect the other. The math is hairy, but [Eric] talks about simple ways to model the system which may not be exact, but will be close enough for practical designs.

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Lenticular Lens Makes Things Invisible

Sure it is a cheap stage trick, but using a lenticular lens at the right angle and in front of the right background can render what’s behind it invisible. That’s not news, but [Ian] spent some time investigating how to make the best one he could. His instructions cover how to create your own with polycarbonate, the right lens, and some optically clear adhesive. You can see some details about the shield along with some demonstrations in the video below.

The first iteration of the design worked, but it had some distracting lines and curvatures. The second version uses a large sheet of polycarbonate and liquid adhesive to attach the lens. It looks much better.

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OpenSCAD Prints Woodworking Aid

Home-based 3D printing is getting pretty unremarkable. Sure, printers aren’t as ubiquitous as, say, PCs. But you wouldn’t be any more surprised if your neighbor had a 3D printer than if you found out they had a drill press. In fact, sometimes the real value of 3D printing something isn’t to make a working part, but to make up something that helps you create other things using methods other than printing. That’s exactly what [iqless] does when he uses his printer to make some jigs to help him easily build shelves. (Video, embedded below.)

The issue is making dowel joints for the shelve’s feet. Sure, you could just drill a piece of scrap wood as a template, but with a 3D printer you can do better. Using OpenSCAD, it is possible to create a parameterized jig that fits exactly the job at hand.

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Low Cost Metal 3D Printing By Electrochemistry

[Billy Wu] has been writing for a few years about electrochemical 3D printing systems that can handle metal. He’s recently produced a video that you can see below about the process. Usually, printing in metal means having a high-powered laser and great expense. [Wu’s] technique is an extension of electroplating.

Boiling down the gist of the process, the print head is a syringe full of electroplating solution. Instead of plating a large object, you essentially electroplate on tiny areas. The process is relatively slow and if you speed it up too much, the result will have undesirable properties. But there are some mind-bending options here. By using print heads with different electrolytes, you can print using different metals. For example, the video shows structures made of both copper and nickel. You can also reverse the current and remove metal instead of depositing it.

This looks like something you could pretty readily replicate in a garage. Electroplating is well-understood and the 3D motion parts could be a hacked 3D printer. Sure, the result is slow but, after all, slow is a relative term. You might not mind taking a few days to print a metal object compared to the cost and trouble of creating it in other ways. Of course, since this is copper, we also have visions of printing circuit board traces on a substrate. We imagine you’d have to coat the board with something to make it conductive and then remove that after all the copper was in place. When you build this, be sure to tell us about it.

We’ve seen electroplating pens before and that’s really similar to this idea. Of course, you can also make your 3D prints conductive and plate them which is probably faster but isn’t really fully metal.

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A Computer In Your Pocket, 1980s Style

These days, having a little computer in your pocket is par for the course. But forty years ago, this was a new and high tech idea. [The 8-Bit Guy] has a great video covering the state of the art in pocket computers and personal digital assistants from the 1980s and 1990s. You can see the video below.

There are a lot of familiar faces on the video including the Radio Shack pocket computers, Palm Pilots, and some more obscure machines of varying quality.

It might impress you to know that the Radio Shack TRS-80 PC-1 pocket computer actually had two CPUs. Of course, each CPU was a 4-bit processor running at 256 kHz, so maybe not as impressive as it sounds. Still, what a marvel in its day, programming BASIC on a 24-character LCD.

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Do Androids Search For Cosmic Rays?

We always like citizen science projects, so we were very interested in DECO, the Distributed Electronic Cosmic-ray Observatory. That sounds like a physical location, but it is actually a network of cell phones that can detect cosmic rays using an ordinary Android phone’s camera sensor.

There may be some privacy concerns as the phone camera will take a picture and upload it every so often, and it probably also taxes the battery a bit. However, if you really want to do citizen science, maybe dedicate an old phone, put electrical tape over the lens and keep it plugged in. In fact, they encourage you to cover the lens to reduce background light and keep the phone plugged in.

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