Day: February 15, 2022

First Days With A New Microscope

February 15, 2022 by 35 Comments

For big-ticket purchases, I tend to do a lot of research before I open my wallet. I like to at least have the illusion that when I send my money off to a far-away stranger, I’m likely to get back something of equal value in a reasonable timeframe that does what I want it to do. So I tend more toward the “analysis paralysis” end of the spectrum, where I pore over so many specs and reviews that I end up buying nothing.

While that sounds like a bad thing, and sometimes is, I find that it tends to help me avoid rashly spending money on things that aren’t going to work for me. This is especially true in the area of tools, where while I’m trapped in my analysis loop, I often find a workaround or substitute that’s good enough to get the job done.

For some things, though, there is no substitute, and when you start working with SMD components that you’d have a hard time telling from a grain of salt, you’re probably going to need a microscope. I recently determined that this was where I was in my electronics journey, and now that I’ve worked my way through the analysis and procurement phase of the process, I thought I’d share my first impressions of my microscope, and what it’s like to get used to working with one.

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A handheld printer printing "CHI 2022 and a capacitor symbol

Print-a-Sketch Turns Any Surface Into A Printed Circuit Board

February 15, 2022 by 33 Comments

Although powerful design software and cheap manufacturing services have made rolling your own PCBs easier than ever, there are some situations where a piece of FR-4 just doesn’t cut it: think art projects with hidden LEDs or biomedical applications that need to attach to the human body. For such occasions, [Narjes Pourjafarian] and her team at Saarland University in Germany developed Print-a-Sketch: a handheld device that lets you print electric circuits on almost any surface using conductive ink.  Also check out their academic paper (PDF).

The heart of the device is a piezoelectric print head, as used in some types of inkjet printer. It dispenses tiny droplets of silver nanoparticle ink, which is conductive enough to make useful electronic circuits by simply printing a schematic. Lines can be drawn to connect components, while customized footprints can hold LEDs, capacitors or even integrated circuits.

As demonstrated in the video embedded below, the Print-a-Sketch can be used in various different modes. In freehand mode, you can draw whatever you like just by moving the device around. But it also has several assisted sketching modes, where it can straighten out wobbly lines, draw multiple lines in parallel, or even print complete predefined shapes. Especially satisfying is the way it can draw resistors by literally printing zig-zagging lines.

Thanks to an optical motion sensor, similar to the ones used in gaming mice, the device knows at all times where it is and how fast it’s going. That enables the control circuitry to compensate for unsteady movement; the authors claim a printing precision of less than 0.5 mm. In addition, an RGB camera is used to detect the material underneath and adjust the amount of ink dispensed, depending on how absorbent the surface is: rough paper needs more ink to obtain a conductive trace than a ceramic tile.

The number of potential applications seems limitless: how about a yoga mat with integrated touch buttons to control the video player on your iPad? A piece of kinesiology tape with an integrated stretch sensor to measure the exact motion of your arm? Or a floor tile with a printed moisture sensor? All of these are demonstrated by the team, but we’re sure our readers can come up with many more ideas.

Of course, drawing circuits using conductive ink is not a new idea: previous projects either relied on drawing the entire thing by hand, or used traditional inkjet printers. But the Print-a-Sketch’s sophisticated hardware and software really put it in a league of its own. And since the entire design is open-source, you can simply build one and bring your ideas to life.

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Accurately Track Your Mains Frequency

February 15, 2022 by 27 Comments

Depending upon where in the world you live, AC mains frequency is either 50Hz or 60Hz, and that frequency is maintained accurately enough over time that it can be used as a time reference for a clock. Oddly it’s rarely exactly that figure though, instead it varies slightly with load on the network and the operators will adjust it to keep a constant frequency over a longer period. These small variations in frequency can easily be measured, and [jp3141] has created a circuit that does exactly that.

It’s a surprisingly straightforward device, in which a Teensy takes its power supply from a very conventional if now a little old-school mains transformer, rectifier, and regulator. A sample of the AC from the transformer passes through a low-pass filer and a clamp, and thence to the Teensy where it is fed into one of the on-board comparators from which its period is measured using one of the timers. Even then the on-board crystal isn’t considered accurate enough, so it is in turn disciplined by a 1 pulse per second (PPS) signal from a GPS receiver.

The Teensy then reports its readings over a serial line every five seconds to a Raspberry Pi, which collates and graphs the data. In case you are wondering what the effect of mains frequency variations might be, we once covered the story of how an entire continent lost six minutes.