Good clocks are generally those that keep time well. But we think the mark of a great clock is one that can lure the observer into watching time pass. It doesn’t really matter how technical a timepiece is — watching sand shimmy through an hourglass has its merits, too. But just when we were sure that there was nothing new to be done in the realm of 7-segment clocks, [thediylife] said ‘hold my beer’ and produced this beauty.
A total of 28 servos are used to independently control four displays’ worth of 3D-printed segments. The servos pivot each segment back and forth 90° between two points: upward and flat-faced to display the time when called upon, and then down on its side to rest while its not needed.
Circuit-wise, the clock’s not all that complicated, though it certainly looks like a time-consuming build. The servos are controlled by an Arduino through a pair of 16-channel servo drivers, divided up by HH and MM segments. The Arduino fetches the time from a DS1302 RTC module and splits the result up into four-digit time. Code-wise, each digit gets its own array, which stores the active and inactive positions for each servo. Demo and full explanation of the build and code are waiting after the break.
Experts on cognition tell us that most people think they know more than they really do. One particular indicator for that is if someone is an expert in one field and they feel like all other fields relate to theirs (everything boils down to math or chemistry or physics, for example). This causes them to be overconfident on things they don’t actually know about. When it became clear that the current virus crisis might lead to a shortage of ventilators, many electronic experts set about to design low-cost easy to replicate ventilators. How hard is it, after all, to squeeze a bag once every few seconds? But it turns out, there are a lot of details you need to know to do it right. [Real Engineering] and [Real Science] joined to create an excellent video that covers a lot of what you need to know. You can see the video below. The video shows a few designs that — while motivated by altruism — would probably do more harm than good if used on real patients.
The video’s creator is a biomedical engineer who worked in the past for Medtronic — a maker of ventilators who, by the way, recently open-sourced one of their designs. They also had [Dr. Rohin Francis], who has a medical YouTube channel, fact check the video. and provide some on-screen background We learned a few new medical terms and found that a high-end ventilator made in one factory gets built at about 225 per week. They think they can increase to 500.
What do potato chips and lost car keys have in common? On the surface, it would seem not much, unless you somehow managed to lose your keys in a bag of chips, which would be embarrassing enough that you’d likely never speak of it. But there is a surprising link between the two, and Samy Kamkar makes the association in his newly published 2019 Superconference talk, which he called “FPGA Glitching and Side-Channel Attacks.”
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.
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…
We’re used to our domestic appliances being completely automated in 2020, but not so long ago they were much simpler affairs. Not everything required a human to run it though, an unexpected piece of electromechanical automation could be found in British bedrooms. This is the story of the Goblin Teasmade, an alarm clock with a little bit extra.
When you read “Arduino wristwatch”, you fall into the trap of envisioning an Arduino UNO clumsily strapped to someone’s wrist. [Marijo Blažević’s] creation is much more polished than that. A round circuit board holds two surface mount ICs and 12 LEDs. The whole thing looks nice fit snugly inside of a watch body. It isn’t a Rolex, but it does have considerable geek cred without being unwearable in polite company.
One IC is an AVR micro, of course. The other is a DS3231 real time clock with built-in crystal. A CR2032 keeps it all running. The main body, the outer ring, the bottom, and the buttons are 3D printed in PLA. The crystal and the band are the only mechanical parts not printed. The bill of materials shows a 36mm crystal and even provides links for all the parts.
You don’t want to run LEDs all the time because it is bad on the battery. When you press the button once, you get one of the LEDs to light to show the hours. Another press reads the minutes in units of 5 minutes. A third press shows you one of five LEDs to show how many minutes to add. For example, if the time is 9:26 you’d get LED 9 (hours), LED 5 for 25 minutes, and the third press would show LED 1 for 1 extra minute. If either of the minute indicators show 12 o’clock, that indicates zero minutes.
The exciting thing, of course, is that you can program it beyond the code on GitHub. Already it can tell time and display the temperature. You don’t have a lot of I/O, but you ought to be able to get some more options and maybe some flashy LED blinking patterns in if you try.
The race for chemical engineering is quite literally on. Every year, the American Institute of Chemical Engineers (AlChE) brings together hundreds of university students to face-off to design the fastest car using techniques they’ve learned from chemical engineering courses.
The Chem-E-Car competition races cars which are only powered by chemical reactions. The goal is to come up with an elegant solution – you can’t simply jettison matter out the back as the method of locomotion. In particular, the rules don’t allow the use of liquid or obnoxious odor discharge, commercial batteries, brakes, or electrical/mechanical timing devices. However, this doesn’t mean that electronics are absent from these designs. Many teams must gather data in order to design a control system to improve the performance of their car.
Students have to build a power system, stopping mechanism, circuitry, and mechanical assembly for the body of the car, all to fit in a size constraint not much bigger than a shoebox. The competition primarily judges the accuracy of the chemical reaction for stopping the car more so than speed or power. Given that the load the car must carry is typically unknown until the day of the competition, this is a significant challenge, allowing teams to find a way to design a flexible reaction that can accommodate a range of loads and distances.
For example, this 2015 entry from the Rice University team (PDF) uses a fuel cell for locomotion and an iodine clock reaction as a timer for braking. The fuel cell powers an Arduino which monitors a light-dependent resistor. In between the LED and that LDR, the clock reaction turns opaque at a predictable time and triggers the motors to stop turning.
While many schools choose not to disclose their designs in order to gain a competitive edge, we applaud the teams who have shared the story of their builds. Kudos to the Rice team mentioned above, to the 2014 Rutger’s team whose white paper outlines the construction of aluminum air batteries worthy of Walter White, to the car from the Universitas Negeri Semarang, Indonesia powered by a thermoelectric generator (PDF), the UC Berkeley team for outlining numerous approaches to developing their power system, and the two Ohio State team’s entries seen winning the regional competition in the video below.
