Ultrasonic Sensor Helps You Enforce Social Distancing

If you’re going outside (only for essential grocery runs, we hope) and you’re having trouble measuring the whole six feet apart from other people deal by eye, then [Guido Bonelli] has a solution for you. With a standard old HC-SR04 ultrasonic sensor, an audio module and a servo to drive a custom gauge needle he’s made a device which can warn people around you if they’re too close for comfort.

As simple as this project may sound like for anyone who has a bunch of these little Arduino-compatible modules lying around and has probably made something similar to this in their spare time, there’s one key component that gives it an extra bit of polish. [Guido] found out how intermittent the reliability of the ultrasonic sensor was and came up with a clever way to smooth out its output in order to get more accurate readings from it, using a bubble sort algorithm with a twist. Thirteen data points are collected from the sensor, then they are sorted in order to find a temporal middle point, and the three data points at the center of that sort get averaged into the final output. Maybe not necessarily something with scientific accuracy, but exactly the kind of workaround we expect around these parts!

Projects like these to help us enforce measures to slow the spread of the virus are probably a good bet to keep ourselves busy tinkering in our labs, like these sunglasses which help you remember not to touch your face. Make sure to check out this one in action after the break!

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Magnets Turn Flexible PCB Into Electric Grasshopper

Just because something doesn’t seem to have an apparent purpose, that doesn’t mean we shouldn’t try making it anyway. As flexible PCBs become cheaper and easier to order from low-scale fab houses, we’re seeing hobbyists experiment with new uses for them such as [Carl Bugeja]’s jumping circuit.

The circuit is based a coil printed on the flexible PCB itself acting as an electromagnet, but unlike other designs which use the same trick, in this one the coil is made to be the static side of an actuator. Attached to the circuit with folding arms is a stack of two permanent magnets, which work as the moving part. Since the magnets make up most of the mass of the circuit, as they’re pushed down and sprung back up, it causes the whole thing to leap around just under one centimeter off the table like a little electric grasshopper.

This is far from [Carl]’s first appearance here on Hackaday, and he’s been clearly busy exploring new uses for flexible PCBs with their properties as electromagnets, from making POV displays with them to small robots that move around through vibration. We’re excited to see what else he can come up with, and you can see this one in action after the break.

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Inverse Kinematics Robot Arm Magna-Doodles The Time For You

Following a surge of creativity fueled by the current lockdown, [Diglo] writes in with his tabletop clock driven by a robotic arm drawing on a Magna Doodle tablet. And if you have one of those still lying around with some old toys and don’t mind cannibalizing it for the project, you too can follow along the source files to build your own.

The clock works by exploiting the principle that Magna Doodle tablets work by being drawn on with a magnetic stylus. That way, to draw on one of them you don’t need to add a point of articulation to bring the pen up and down, [Diglo] simply attached a controllable electromagnet to the end of a two-dimensional SCARA arm. In total, the whole build uses three stepper motors, two to control the movement of the arm, and one on the back of the tablet to sweep a magnetic bar which “erases” it.

This clock is similar to another we’ve featured a few years ago, which also used a Magna Doodle, but greatly improves on the idea. If a Magna Doodle seems too childish to build a magnetic clock however, there’s always ferrofluidic displays to try to dip your fingers into, but we really think you should watch this one in action after the break first.

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New Part Day: Battery-Less NFC E-Paper Display

Waveshare, known for e-ink components aimed at hobbyists among other cool parts, has recently released a very interesting addition to their product line. This is an enclosed e-ink display which gets updated over a wireless NFC connection. By that description, nothing head-turning, but the kicker is that there is no battery inside the device at all, as it harvests the energy needed from the wireless communication itself.

Just like wireless induction charging in certain smartphones, the communication waves involved in NFC can generate a small current when passing through a coil, located on this device’s PCB. Since microcontrollers and e-ink displays consume a very small amount of current compared to other components such as a backlit LCD or OLED display, this harvested passive energy is enough to allow the display to update. And because e-paper requires no power at all to retain its image, once the connection is ended, no further battery backup is needed.

The innovation here doesn’t come from Waveshare however, as in 2013 Intel had already demoed a very similar device to promising results. There’s some more details about the project, but it never left the proof of concept stage despite being awarded two best paper awards. We wonder why it hadn’t been made into a commercial product for 5 years, but we’re glad it’s finally here for us to tinker with it.

E-paper is notorious for having very low refresh rates when compared to more conventional screens, much more so when driven in this method, but there are ways to speed them up a bit. Nevertheless, even when used as designed, they’re perfectly suited for being used in clocks which are easy on the eyes without a glaring backlight.

[Thanks Steveww for the tip!]

Wood-Turning A Bladeless Fan

It’s a simple enough premise: to make a Dyson-style bladeless fan out of wood. The execution of the finished fan, done and filmed by [Neil] from Pask Makes on YouTube, is however spectacular. Using nothing but scrap wood from a chopping board business local to him, he’s made the entire body of the fan using some interesting fabrication methods.

To plan the circular design of the body, [Neil] used an online calculator to measure the specific cuts of wood he needed in order to form cylinders out of trapezoidal sections glued together. Once the rough shape is made, he then used a profile template to turn the air channel with precision out of the two main parts of the fan body. Then, he uses SketchUp in order to figure out what shape needs to be cut from the base in order for the top to fit on it. From there, it’s just a matter of drilling out slots for the air intake, which he does so with an ingenious custom jig, and fitting the internals of a standard fan into the new wooden body.

The video, which you should definitely watch after the break if you have a spare half hour, might not be detailed enough to be used as a tutorial, but it certainly outlines his methods and the tools used well enough to impress us. And the finished build is beautiful to look at, too! If you’re looking for more impressive woodworking, we’ve covered this gorgeous recreation of a Commodore 64 case in wood. But if the hand-built nature of that doesn’t satisfy you, here’s a professional-looking custom caliper case made with CNC and laser engraving.

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Z80 Computer Is Both Arduino And Shield

There have been plenty of Z80 computer builds here on Hackaday, but what sets them apart is what you do with them. [Andrew] writes in with his Z80 single-board computer made from scratch, using the Arduino standard headers for its I/O. In turn, since he needed an easy way to program the flash memory which holds the software to run on the Z80, he used an Arduino Mega as a debugger, making the SBC an Arduino shield itself.

Using such a common header pinout for the Z80 computer allows it to be used with a variety of readily-available Arduino shields. This compatibility is achieved with an analog-digital converter and a 3.3 V regulator, mimicking the pins found in an Arduino Uno. The code, available on GitHub, includes an extensive explanation and walkthrough over the process in which the Mega takes over the bus from the Z80 to function as a fully-featured debugger. Programs can be loaded through embedding an assembly listing into the Mega’s sketch, or, once the debugger is up you can also upload a compiled hex file through the serial connection.

This isn’t the first time [Andrew] has been featured here, and his past projects are just as interesting. If you need to translate a Soviet-era calculator’s buttons into English, hack a metallurgical microscope or even investigate what’s that Clacking Clanking Scraping Sound, he’s the one you should call.

Parking Meters That Were A Bit Too Smart For Their Own Good

A common sight in automobile-congested cities such as New York are parking meters lining the curbs next to parking spots. They’re an autonomous way for the city to charge for the space taken by cars parked along the sidewalk near high-traffic commercial areas, incentivizing people to wrap up their business and move their vehicle out of a costly or time-limited parking space.

The parking meter is such a mundane device most people wouldn’t look at them twice, but on the inside it’s fascinating to see how they’re engineered, how that’s changed through the years, and how a software bug handicapped thousands of digital meters at the start of 2020.

The Origin Of The Parking Meter

One of Carl C. Magee’s earliest parking meter designs, filed for patent in 1932.

Parking meters were originally commissioned in the 1930s by the government of Oklahoma City, due to the rapidly increasing number of automobiles, and therefore demand for parking space. Up until then, the city used patrolling policemen to regulate parking space, but they couldn’t keep up with the pace of the increased traffic and the lack of available parking space made business drop around downtown shops.

The first widely-adopted parking meter was dubbed “Black Maria”, a machine patented in 1935 by Carl C. Magee and Gerald Hale and first installed in the city in July of that year. This was a completely automated mechanical device made to solve the problem of regulating the time a driver can park their car in a given spot. It would take a nickel as payment, inserted into the mechanism by rotating a handle which also served to wind a clock spring. This clock would then tick down the remaining time the user could remain parked there, which could range from 15 minutes to an hour depending on the location.

An early Black Maria design, circa 1933.

Within days store owners noticed a positive effect in their profits thanks to the increase in customers with the regulated parking. What’s more, the coins collected from the meters also generated revenue for the city, and so, parking meters started spreading throughout the city. And as decades went, the mechanics were improved upon. A window was added into which a patrolling officer could easily look to check if the right amount of money (or money at all) was inserted. Separate panels for the coins to be easily collected without risking damage to the rest of the internal clockwork were also added.

The evolution of parking meters eventually passed through meters that could take care of parking spaces on either side of it, halving the amount of necessary poles per sidewalk. Electronic models starting appearing in the 1990s and eventually connectivity added. With meters all hooked up to the same network, the symbiotic connection between the parking meter and your spot was severed. It didn’t matter where your car was parked anymore; you could simply take your printed ticket and put it on your dashboard to be legally parked. Further advancements led to numbers spots that can be paid from any kiosk in the city, or though a smartphone app. But those digital advancements don’t always translate into reliability…

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