Circuit-less PCB Featured As Faceplate For A Digital Clock

August 17, 2022 by Dan Maloney 9 Comments

If there’s no circuitry on a printed circuit board, does it cease being a “PCB” and perhaps instead become just a “PB”?

Call them what you will, the fact that PCBs have become so cheap and easy to design and fabricate lends them to more creative uses than just acting as the wiring for a project. In this case, [Jeremy Cook] put one to work as the faceplate for his “742 Clock,” a name that plays on the fact that his seven-segment display is 42 mm tall, plus it’s “24/7” backward.

In addition to the actual circuit board that holds the Wemos ESP32 module and the LEDs, a circuit-less board was designed with gaps in the solder mask to act as light pipes. Sandwiched between the boards is a 3D printed mask, to control the light and direct it only through the light pipes. [Jeremy] went through a couple of iterations of diffuser and mask designs, finally coming up with a combination that works well and looks good. He mentions a possible redesign of the faceplate board to include a copper backplane for better opacity, which we think is a good idea. We’d also like to see how different substrates work; would boards of different thickness or using FR-4 with different glass transition temperatures work better? Check out the video below and see what you think.

We’re seeing more and more PCBs turn up as structural elements, from enclosures to control panels and even tools, and we approve of this trend. But what we really approve of is what [Jeremy] did here by making this clock just a dumb display that gets network time over NTP. Would that all three digital clocks in our kitchen did the same thing — maybe then they wouldn’t each be an infuriating minute out of sync with the others.

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Unique Seven-Segment Display Relies On FR-4 Fluorescence

October 16, 2021 by Dan Maloney 11 Comments

It’s interesting what you see when you train a black light on everyday objects. We strongly suggest not doing this in a hotel room, but if you shine UV light on, say, a printed circuit board, you might see what [Sam Ettinger] did, which led him to build these cool low-profile seven-segment fluorescent PCB displays.

As it turns out, at least some FR-4 PCBs fluoresce under UV light, giving off a ghostly blue-green glow. Seeing the possibilities, [Sam] designed a PCB with cutouts in the copper and solder mask in the shape of a traditional seven-segment display. The backside of the PCB has pads for UV LEDs and current-limiting resistors, which shine through the board and induce the segments to glow. Through-slots between the segments keep light from one segment from bleeding over into the next; while [Sam] left the slots unfilled, they could easily be filled with solder. The fluorescent property of FR-4, and therefore the brightness and tint of the segments, seems to vary by board thickness and PCB manufacturer, but it looks like most PCBs will show pretty good results.

We’d say the obvious first improvement might be to cover the back of the display with black epoxy, to keep stray light down, and to improve contrast. But they look pretty great just as they are. We can also see how displays with other shapes, like icons and simple symbols. Or maybe even alphanumeric characters — say, haven’t we seen something like that before?

Quadcopter Built From Recycled Motherboards

May 9, 2014 by Adam Fabio 18 Comments

A quadcopter built from a motherboard

[Eric] has figured out a great way to build quadcopters out of recycled computer motherboards. Multicopters come in all shapes and sizes these days. As we mentioned in the last issue of Droning On, they can be bought or built-in a multitude of materials as well. Drones have been built using materials as varied as wood, PVC pipe, carbon fiber, and aluminum.

One of the more common commercial materials is G10 fiberglass sheet. It’s stiff, strong, and relatively light. Printed circuit boards are generally made of FR-4 fiberglass, G10’s flame resistant cousin. It’s no wonder [Eric] had quadcopters in his eyes when he saw a pile of motherboards being thrown out at his university.

[Eric] used a heat gun and a lot of patience to get all the components off the motherboard. With a bit of care, most of the components can be saved for future hardware hacks. This is one step that’s best performed outside. Hot melting plastics, metals, and resin fumes aren’t the greatest things to inhale.

Computer motherboards being cut on a shopbot Clean PCBs in hand, [Eric] headed to his local TechShop. He drew his dead cat style frame in SolidWorks and cut it out on a ShopBot. While a high-end CNC cutter is nice, it’s not absolutely necessary. The fiberglass sheets could be cut with a rotary tool or a jigsaw. No matter how you cut it, be sure to wear a mask rated for fiberglass resins and some protective clothing. Fiberglass plate is nasty stuff to cut.

Once the upper and lower frame plates were cut, [Eric] completed his quad frame with some square wooden stock for arms. The final quad is a great flier, and spare parts are easy to source. Nice work on the recycling, [Eric]!

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