Clock Runs Computer In Slow-Motion

At the heart of all computers is a clock, a dedicated timepiece ensuring that all of the parts of the computer are synchronized and can work together to execute the instructions that the computer receives. Clock speeds for most modern off-the-shelf computers and smartphones operate around a billion cycles per second, and even clocks that tick at a human-dizzying speed of a million times per second have been around since at least the 1970s. But there’s no reason a computer can’t run at a much slower speed, as [Greg] demonstrates in this video where he slows down a 6502 processor to a single clock cycle per second.

To reduce the clock speed from the megahertz range down to a single hertz or single clock cycle per second, [Greg] is using the pendulum from an actual clock. He attaches a small magnet to the bottom of the pendulum which is counted by a sensor as it swings past. Feeding that pulse into a monostable conditioner yields a clock signal which is usable for one of his 6502-based computers, and at this extremely slow rate, it’s possible to see the operation of a lot of the computers’ inner workings a step at a time. In fact, he optimized the computer’s operation as this slow speed let him see some inefficiencies in the program he was running.

It helps if your processor is static, of course. Older CPUs with dynamic storage for registers and some with limited-range PLLs would not work with this technique. The 8080A, for example, required a clock of at least 500 kHz.

Not only can this computer use a pendulum clock as the basis for its internal clock, but [Greg] also rigged up a mechanism to use a heartbeat. Getting in a little bit of exercise to increase his heart rate first will noticeably increase the computer’s speed. And, if you’re looking to get a deeper glimpse into the inner workings of a computer, we’d recommend looking at one which forgoes transistors in favor of relays.

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An Atomic Pendulum Clock Accurate Enough For CERN

That big grandfather clock in the library might be an impressive piece of mechanical ingenuity, and an even better example of fine cabinetry, but we’d expect that the accuracy of a pendulum timepiece would be limited to a sizable fraction of a minute per day. Unless, of course, you work at CERN and built  “the most accurate pendulum clock on the planet.”

While we’re in no position to judge [Daniel Valuch]’s claim, we’re certainly inclined to believe him, mainly because the 1950s-era Czechoslovakian pendulum clock his project was based on, the Elektročas HH3, was built specifically as a master clock for labs, power plants, and broadcast use. The pendulum of this mid-century beauty is made of the alloy invar, selected for its exceptionally low coefficient of thermal expansion. This ensures the pendulum doesn’t change length with temperature, but it still only brings the clock into the 0.1 second/day range.

Clearly that’s not good enough for a clock at CERN, the European Laboratory for Nuclear Research, where [Daniel] works as an RF engineer. With access to a 10-MHz timebase from a cesium fountain atomic clock — no less a clock than the one that’s used to define the SI second, by the way — [Daniel] looked for ways to sync the clock up to it. Now, we know what you’re thinking — he must have used some kind of PLL to give an electromagnetic “kick” to the bob to trim the pendulum’s period. Good guess on the PLL, but the trimming method is a little cruder — [Daniel] uses a stepper motor attached to the clock’s frame to pay out or retract a length of fine chain into a cardboard dish attached to the pendulum’s rod. The change in mass changes the pendulum’s center of gravity, which changes its effective length, and allows the clock to be tuned a couple of seconds per day.

It seems like [Daniel] is claiming that his chain-corrected clock won’t drift more than a second from the cesium clock for 158 million years. Again, we’ll take his word for it, but it’s a wonderfully ad hoc approach to tuning the clock, and we appreciate its simplicity.

Building Reaction Wheels With Python And LEGO

Reaction wheels are useful things, typically used by satellites to keep themselves oriented the right way up in space. Turning the reaction wheel creates an equal and opposite torque in the spacecraft, allowing it to point and rotate itself accurately. The same technique also works here on Earth, and [Brick Experiment Channel] decided to build one out of LEGO to control an inverted pendulum.

The initial design using a small LEGO wheel on an inverted pendulum was only able to work reliably over a 4-degree angle from the vertical. Upgrading the wheel to a larger, heavier one enabled the wheel to instead work over a 28-degree range instead.

A MPU9250 inertial measurement unit was pressed into service for control of the reaction wheel, fitted to the base of the pendulum and read by a Raspberry Pi. The Pi takes accelerometer and gyroscope readings, and then controls the motor on the pendulum with a PID controller to keep the inverted pendulum upright.

The video goes into a great deal of detail on what it takes to make the pendulum run smoothly. From changes to the control coefficients to measuring the motor’s back EMF, [Brick Experiment Channel] demonstrates everything required to make the pendulum robust to outside perturbances.

The inverted pendulum is a great way to learn about control theory, as we’ve seen time and again.

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PendulumSynth Ties Music And Physics Together

Many musicians will be familiar with the metronome, a pendulum charged with generating a rhythmic tick to keep one’s performance in regular time. With PendulumSynth, [mrezanvari] takes the same basic pendulum but uses it in an altogether different musical way.

The build relies on a 10-inch plastic ball to serve as the weighted end of the pendulum, stuffed with a STM32F411CE BlackPill board, a BNO085 IMU, and an nRF radio module for sending out data for external processing. The pendulum’s motion is turned into MIDI data or CV for output to musical hardware which handles actually generating the output sounds.

The system operates in a variety of modes. Gravity mode outputs continuous MIDI data and CV relative to the continuous motion of the pendulum, while DIV3 mode tracks the pendulum’s motion and outputs 3 regular trigger points that correspond as such.

The combination of the intuitive physical nature of the pendulum and its sheer large size makes for an enticing musical exhibit. We’ve seen some other great musical installation pieces before, too. Video after the break.

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This POV Clock Combines A Nixie With A Pendulum

Talk about your mixed timekeeping metaphors: there are clocks, and pendulum clocks, and there are Nixie clocks, and persistence of vision clocks. But this is a Nixie pendulum POV clock, and we think it’s pretty cool.

We first spied this on Twitter and were subsequently pleased to learn that [Jayzon Oeve] has posted a more detailed build log over on Rather than a moving array of dots to create the characters to display, this uses a single IN-12b Nixie tube at the end of a pendulum. The pendulum is kept moving by a small nudge created by a pulse through a fixed hard drive voice coil acting on a magnet affixed to the bottom of the pendulum — we’ve seen a similar approach used before.

Pretty much all of the electronics are mounted on the pendulum arm, including a Nano, an RTC, and an accelerometer to figure out where in the swing the bob is and when to flash a number on the display. There’s a video below that shows it at work both at full speed and in slow-motion; as always with POV clocks, these things probably look better in person than on video. And while swinging Nixies around like that seems a little dicey, we like the way this turned out.

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Double Pendulum Uses Custom Slip Rings

Rotating mechanisms can be a headache when it becomes necessary to deliver power through them. [Igor Brkic] faced just such a challenge when creating his double-pendulum build, and solved it with a little DIY.

The project is known as KLAATNO, inspired by the Croatian word for pendulum, klatno. It’s a mechanical installation piece, consisting of a power-assisted pendulum, with a second pendulum fitted at the end of the swinging arm. A 24 volt geared motor is used to drive the assembly. It’s controlled by an Arduino Pro Mini, which measures the back EMF from the motor terminals to determine the speed and direction of the motor’s movement.

To make the installation more visually striking, EL wire was installed on the swinging arms of the twin pendulums. This required the transfer of power to the rotating assembly, which was achieved through the use of custom made slip rings. Copper sheet is used in combination with a flexible metal wire sourced from a guitar string. It’s not as low-friction as [Igor] would like, but it gets the job done.

It’s a fun installation that would be perfectly at home in the common area of any university engineering building. Of course, our favorite pendulums are of the siege weapon variety. Video after the break.

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Gesture Control Without Fancy Sensors, Just Pots And Weights

[Dennis] aims to make robotic control a more intuitive affair by ditching joysticks and buttons, and using wireless gesture controls in their place. What’s curious is that there isn’t an accelerometer or gyro anywhere to be seen in his Palm Power! project.

The gesture sensing consists not of a fancy IMU, but of two potentiometers (one for each axis) with offset weights attached to the shafts. When the hand tilts, the weights turn the shafts of the pots, and the resulting readings are turned into motion commands and sent over Bluetooth. The design certainly has a what-you-see-is-what-you-get aspect to it, and as a whole it works much like an inverted, weighted joystick hanging from one’s palm.

It’s an economical way to play with the idea of motion sensing, and when it comes to prototyping, being able to test a concept while keeping costs to a minimum is a good skill to have.