Avoiding PCB Crosstalk

January 25, 2021 by Al Williams 13 Comments

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.

Continue reading “Avoiding PCB Crosstalk” →

Buzzer Does Input And Output

January 25, 2021 by Al Williams 2 Comments

Piezo elements have the useful property of being bidirectional; that is they can move when you apply electricity to them, but they can also generate electricity when you move them. [Carl] takes advantage of this fact to make buttons that can provide haptic feedback. You can see a video of his efforts below the break.

He made two versions of the buttons. One uses a 3D printed housing and the other used a 3D printed spacer in a sandwich configuration. It took a few tries to get it right, as you’ll see. The elements take and produce relatively high voltages, so the bulk of the work was adapting the voltages back and forth. In fact, he even managed to fry his CPU chip with some of the higher voltages involved.

We’d probably look for an easier way to sense the button push, since it seems like a good bit of circuitry just to do that. But the whole circuit provides an input button, haptic feedback, and the option of using the buzzer as a buzzer, so at least it is relatively economical if you need all of those features.

Continue reading “Buzzer Does Input And Output” →

Lenticular Lens Makes Things Invisible

January 25, 2021 by Al Williams 7 Comments

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.

Continue reading “Lenticular Lens Makes Things Invisible” →

Physically Huge SD Card Technically Has Some Benefits

January 24, 2021 by Lewin Day 27 Comments

SD cards were developed and released just before the turn of the millenium. Since then, we’ve seen smaller formats, miniSD and microSD, become popular for portable devices. However, sometimes bigger is better. [Useless Mod] dared to dream that dream, and put together a (physically) gigantic SD card.

In card is a full 10x scale reproduction of a SanDisk Extreme Pro SD card, complete with packaging, too. Built out of layers of laser cut MDF, it’s spray painted and given a high-quality label to complete the effect. The write protect slider instead serves in this case as a latch to open the assembly. Inside, there’s a simple regular SD card slot, wired up to the bigger card’s giant contacts made with copper tape. These interface with an huge 10x scale SD card slot, which acts as an adapter, allowing the giant SD to be used with regular hardware like cameras.

The giant SD might seem silly, but it has plenty of useful features. There’s flashing LEDs behind the label that make it easy to find if you drop it, along with an Apple Watch hidden inside that means it can be located using the Find My iPhone service. We’d have loved if it featured a RAID array full of 10 or more SD cards, as well, just to justify its enormous size. That said, [Useless Mod] points out that it’s big enough to keep a DSLR dry in a rainstorm when fitted to the hotshoe, so there’s that.

It’s a fun build, not a serious one, but one that we enjoyed on its merits. We suspect that, regardless of the card inside, you’ll have little luck recording at 4K with such long wire lengths in play. If you’ve ever had more normal compatability problems with the format, consider that it could be size causing your issues. Video after the break.

Continue reading “Physically Huge SD Card Technically Has Some Benefits” →

Collapsible Pattern Projector Is A Bright Idea

January 24, 2021 by Kristina Panos 13 Comments

It’s fantastic that we’re living in the age of downloadable PDF patterns, it really is. But printing out a bunch of sheets of paper and taping them together is a tedious and tiresome process that can introduce error right from the start. This goes for any type of pattern, from sewing to R/C planes.

[Quinn]’s quarantine project is designed to cover both of those and everything in between. It’s a pattern projector made from stuff already on hand — a couple of offset projectors to scavenge parts from, and a large, trapezoidal mylar mirror from an old rear projection TV. At maximum zoom it projects a 4′ x 3′ image onto the tabletop, which sounds perfect for a whole lot of sewing patterns. At minimum zoom, the projected image fits on a foam core board.

We love that this dreamy setup can be stowed away so easily on hooks in the ceiling. [Quinn] had to perform a few hacks to make it all work together, including fabricating a bracket and some adjustable ties to hold the mirror aloft at just the ~~right~~ correct angle.

Need something smaller? Check out this Pi-powered pocket projector. Want a cinema-quality setup? You just have to find the right auctions.

A Big Set Of Logic Gates For Teaching The Basics

January 24, 2021 by Lewin Day 22 Comments

Teaching students about logic gates is often done in two parts, once on the whiteboard for the theory, and again on the breadboard for the practice. [shurik179] wasn’t a fan of the abstraction between easy-to-understand symbols on the whiteboard, and small IC packages full of many gates in reality. Instead, he built a set of real-world logic gates that can be wired together as a teaching tool.

Each “gate’ consists of a PCB roughly the size of a business card that features LEDs to indicate the state of its inputs and outputs, and a silkscreen indicating the name and symbol of the gate in question. There’s also a master PCB, which features three seed values, A, B, and C, to feed into the system. Students can set these values to 1 or 0, and feed them into the gates, which are wired together with 3-conductor servo cables, and observe the input on the built-in LEDs.

It’s a great way to demonstrate logic gates in the classroom. The design also allows the PCBs to be flipped over to show the actual electronic components responsible for implementing the logic, serving as a great bridge towards better understanding of real electronic design. Of course, it’s not the only way to learn – even Fallout 4 has a fully fledged logic toolkit these days!

RGB Glasses Built From PCBs

January 16, 2021 by Lewin Day 8 Comments

Shutter shades were cool once upon a time, but if you really want to stand out, it’s hard to go past aggressively bright LEDs right in the middle of your face. A great way to achieve that is by building a pair of RGB glasses, as [Arnov Sharma] did.

The design intelligently makes use of PCBs to form the entire structure of the glasses. One PCB makes up the left arm of the glasses, carrying an ESP12F microcontroller and the requisite support circuitry. It’s fitted to the front PCB through a slot, and soldered in place. The V+, GND, and DATA connections for the WS2812B LEDs also serve as the mechanical connection. The right arm of the glasses is held on in the same way, being the same as the left arm PCB but simply left unpopulated. A little glue is also used to stiffen up the connection.

It’s a tidy build, and one that can be easily controlled from a smartphone as the ESP12F runs a basic webserver which allows the color of the glasses to be changed. It’s not the first time we’ve seen a flashy pair of LED shades either! Video after the break.

Continue reading “RGB Glasses Built From PCBs” →