What’s The Time? It’s Casino’clock!

As the saying goes, nothing can be said to be certain, except death, taxes, and the never-ending inventiveness of clock hacks. No matter how tried and proven a concept is, someone will always find a new twist for it. Case in point: notorious clock builder [Shinsaku Hiura] took the good old split-flap display approach, and mixed things up by using a deck of playing cards to actually represent the time.

Technically, the clock works just like a regular flip clock, except that only the upper half of the split-flap is used to display the digits, while the lower half is showing the cards’ backsides. Other than that, the mechanics are the same: a set of hinges holding the cards are arranged on a rotor that’s moved by a stepper motor until the correct digit is shown (STLs available on Thingiverse). Aces low, Jokers are zeroes, and the queen strikes at noon.

At the center of it is an ESP32 that controls each digit’s motor driver, and retrieves the time via WiFi, keeping the general component count conveniently low. Of course, one option is to arrange the cards in their order to keep rotations at a minimum, but let’s be real, the flapping sound is half the fun here. So instead, [Shinsaku Hiura] arranged the cards randomly and mapped it in the code accordingly. You can see it all in action, along with some additional design information, in the video after the break.

For some more of his clock creations, check out this different flip clock approach and the Hollow Clock. But if the future is of more interest to you than the present, here’s a matching Tarot deck.

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Automated Blinds Can Be A Cheap And Easy Build

Blinds are great for blocking out the sun, but having to get up to open and close them grows tiresome in this computationally-advanced age. [The Hook Up] decided to automate his home blinds instead, hooking them up to the Internet of Things with some common off-the-shelf parts.

The basic idea was to use stepper motors to turn the tilt rod which opens and closes the blinds. An early attempt to open blinds with unipolar stepper motors proved unsuccessful, when the weak motors weren’t capable of fully closing the blinds when running on 5 volts. Not wanting to throw out the hardware on hand, the motors were instead converted to bipolar operation. They were then hooked up to DRV8825 driver boards and run at 12 volts to provide more torque.

With the electromechanical side of things sorted out, it was simple to hook up the motor drivers to a NodeMCU, based on the ESP8266. The IoT-ready device makes it easy to control the motors remotely via the web.

The build came in at a low cost of around $10 per blind. That’s a good saving over commercial options which can cost hundreds of dollars in comparison. We’ve seen other work from [The Hook Up] before too, like his creative Flex Seal screen build. Video after the break.

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The circuit, assembled on a purple PCB, with a large capacitor and a sizeable white resistor, wires soldered to holes in the PCB

Protect Your Drivers When The Motor Stalls

[Mark Rehorst] tells us about a tragic incident involving an untimely demise of $200 worth of motor driving hardware, and shares a simple circuit so that we can prevent such tragedies in the future. His Arrakis sand table project has quite a few motors involved, and having forgotten to add limits into the software, he slammed a motor-driven mechanism into a well-fixed part of the table. The back EMF of the motor created a burst of energy, taking out the motor driver, the controller board, and the power supply.

With the postmortem done, he had to prevent this from happening again – preferably, in hardware. Based on a small appnote from Gecko Drives, he designed a simple PCB that shunts the motor with a high-power resistor, as soon as the current starts flowing into a direction it’s not supposed to flow into. He goes in depth about the way that the circuit works and the reasoning behind parts selection, as well as shows an LTSpice simulation and shares the PCB files. This was his first time designing PCBs in KiCad, and we believe he’s done a great job! This worklog is certainly worth reading if you’d like to understand how such circuits work and what goes into building one.

He dubs this a “bank account protection” circuit, and we can absolutely relate. It’s not just CNC tables that need such protections of course – we’ve seen a solution for small hacky makeshift electric vehicles, for instance. A motor’s generative properties aren’t always a problem, however – here’s just one example of a hacker trying to put them to good use.

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A camera slider made from wood and recycled parts

Turning Old Plotter Parts Into A Smooth Camera Slider

Taking apart old stuff and re-using the parts to make something new is how many hackers first got started in the world of mechanical and electronic engineering. But even after years working in industry we still get that tinge of excitement whenever someone offers us an old device “for parts”, and immediately begin to imagine the things we could build with the components inside.

A GoPro mounted on a moving platform made from recycled partsSo when [Victor Frost] was offered an old Cricut cutting plotter, he realized he could use its parts to create the camera slider he’d been planning to build. The plotter’s X stage, controlled by a stepper motor, was ideal for moving a camera platform back and forth. [Victor] wanted to build the entire thing in a “freehand” way, without making a detailed design or purchasing any new parts. So he dived into his parts bin and dug up an Arduino, a 16×2 LCD, some wires and buttons, and a few pieces of MDF.

The camera mount is simply a piece of steel that a GoPro’s magnetic mount can latch onto, but [Victor] keeps open the possibility of mounting a proper tripod ball head. The Arduino drives the stepper motor through an Adafruit Motor Shield, with a simple user interface running on the LCD. The user can set the desired end points and speed, and then run the camera back and forth as often as needed. In this way, the software follows the same “keep it simple” philosophy as the hardware design.

If you’re planning to build your own camera slider, [Victor]’s design should be easy to copy, if you happen to have an old cutting plotter. If not, you can try this simple yet well-engineered model. Want even more? Then check out this fancy multi-axis camera motion control rig.

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Don’t Tune Your 3D Printer To Middle ‘C’ After All

Layer shift caused by the belt being way too loose.

3D printer belt tension seems like a simple thing to deal with — you set the tension and then check it’s good now and then. If it gets really loose, then the teeth can slip and you’ll get some shifts in the print, ruining it, but its an easy fix. But, we hear you ask, how do you determine what the correct tension is? Well, here’s [Lost in Tech] with a video showing some measurement techniques and analysis of a typical 3D printer, (video, embedded below) using nothing more special than a set of luggage scales. A simple theory suggested was that a tighter belt tension would result in increased radial load on the stepper motor bearings, which in turn, due to friction, would result in an increase in temperature of the motor.  After setting a few tension values on one of the belts, it was noted that tension values at the upper end of the range, resulted in a measured increased in temperature of two degrees celcius, and a large increase in noise. This can’t be good for the motor.

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An electromechanical wall clock on a workbench, showing "8888"

Silent Stepper Motors Make Electromechanical Clock Fit For A Living Room

Large mechanical seven-segment displays have a certain presence that you just don’t get in electronic screens. Part of this comes from the rather satisfying click-click-clack sound they make at every transition. Unfortunately, such a noise quickly becomes annoying in your living room; [David McDaid] therefore designed a silent electromechanical seven-segment clock that has all the presence of a mechanical display without the accompanying sound.

As [David] describes in a very comprehensive blog post, the key to this silent operation is to use stepper motors instead of servos, and to drive them using a TMC2208 stepper motor driver. This chip has a unique method of regulating the current that does not introduce mechanical vibrations inside the motor. A drawback compared to servos is the number of control wires required: with four wires going to each motor, cable management becomes a bit of an issue when you try to assemble four seven-segment displays.

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A doorblell made from a stepper motor and a hard drive

Minimalistic Doorbell Doesn’t Need An Internet Connection – Or Even A Power Supply

Doorbells are among those everyday objects that started out simple but picked up an immense amount of complexity over the years. What began as a mechanism to bang two pieces of metal together evolved into all kinds of wired and wireless electric bells, finally culminating in today’s smart doorbells that beam a live video feed to their owners even if they’re half a world away.

But sometimes, less is more. [Low tech obsession] built a doorbell out of spare components that doesn’t require Internet connectivity or even a power supply. But it’s not a purely mechanical device either: the visitor turns a knob mounted on a stepper motor, generating pulses of alternating current. These pulses are then fed into the voice coil of an old hard drive, causing its arm to vibrate and strike a bell, mounted where the platters used to be.

Besides being a great piece of minimalistic design, the doorbell is also a neat demonstration of Faraday’s law of induction. The stepper motor is apparently robust enough to withstand vandalism, although we can imagine that the doorbell’s odd shape might confuse some well-meaning visitors too. If you’re into unusual doorbells, you might want to check out this one made from an old wall phone, as well as this electromechanical contraption.

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