Dial A For Arduino

A lot of phrases surrounding phones don’t make sense anymore. With a modern cellphone, you don’t really “hang up” and there’s certainly no “dial” to be had. However, with [jakeofalltrades’] project, you can read an old-fashioned phone dial using an Arduino.

The idea behind a phone dial is actually pretty simple. When you pull the dial back to the stop using one of the numbered holes and release it, it causes a switch to open and close the same number of times as the hole you selected. That is, if you pull back the 5 hole, you should get 5 switch closures. The duration of each switch event and the time between switch events is a function of the speed the dial moves because of its internal spring. The zero hole actually produces ten pulses.

There are standards for how precise the timing has to be, but — honestly — it’s pretty loose since these were not made to be read by precise microcontroller timers. In the United States, for example, the dial was supposed to produce between 9.5 and 10.5 pulses per second, but the equipment on the other end would tolerate anything from 8 to 11.

Even if you don’t want a rotary dial in your next project, the code has some good examples of using ATmega328 timers that you might find useful in another context. However, a dial would add a nice retro touch to any numeric input you might happen to need.

If you need project inspiration, how about a volume control? Or, why not a numeric keypad?

Simplify Your Life With This Pocket Rotary Cellphone

With its constant siren song of distraction and endless opportunity for dopamine hits, a smartphone can cause more problems than it solves. The simple solution would be a no-nonsense flip phone, but that offers zero points for style. So why not build your own rotary dial pocket cellphone?

Of course, what style points accrue to [Justine Haupt] take a hit in terms of practicality, but that was never really the point of this build. And even then, the phone appears to be surprisingly useful. It’s based on the rotary dial from a Trimline phone, which itself was an epic hack back in 1965 when it was introduced. The 3D-printed case contains an ATmega2560V microcontroller and an Adafruit FONA 3G cell module, while a flexible mono eInk display adorns the outside. Some buttons, a folding SMA antenna, and some LEDs for signal strength and battery level complete the build, which easily slips into a pocket. The dial can be used not only to dial the phone but to control the speaker volume; in practice, [Justine] mainly uses the speed dial buttons to make calls, though.

We’ve seen rotary phones converted to cell before, but this one is a next-level integration of the retro and the modern. It’s simple, intuitive, and distraction-free, and best of all, it’s a great excuse not to return a text.

Thanks to [J. Peterson] for the tip.

Rotary Dial Becomes USB Keyboard

[Max] had a rotary dial from an old telephone and — unsurprisingly — had nothing in particular to do with it. The simple answer? Use an Arduino Leonardo to turn it into a USB keyboard device.

Of course, the Leonardo can easily impersonate a USB keyboard, so that’s the easy part of the project. Interfacing to the dial requires an understanding of how the phone system works.

While today, TouchTone phones are most common, they were quite uncommon for many years. Early phones required you to have an operator connect your circuit to another person’s circuit. Unfortunately for the operators, the system was inherently unscalable and also cost prohibitive.

There were a variety of schemes tried and — supposedly — an undertaker who was angry that the operator was connecting his customers to her husband’s competing mortuary invented the dial telephone.

The details are pretty simple. A typical dial has two contacts. There’s a normally open contact that closes when you spin the dial to any position. It says closed until the spring returns the dial to the home position.

The other contact is normally closed and makes or breaks the phone line. Each time the dial rewinds past a position, the contact opens briefly. Of course, this is a mechanical system, so the software has to debounce the inputs, but that’s easy enough.

If you don’t have access to a dial, you could always print one. Sort of.

Control Your Web Browser Like It’s 1969

Imagine for a moment that you’ve been tasked with developing a device for interfacing with a global network of interconnected devices. Would you purposely design a spring-loaded dial that can do nothing but switch a single set of contacts on and off from 1 to 10 times? What kind of crazy world would we have to live in where something like that was the pinnacle of technology?

Obviously, such a world once existed, and now that we’ve rolled the calendar ahead a half-century or so, both our networks and our interfaces have gotten more complex, if arguably better. But [Jan Derogee] thinks a step backward is on order, and so he built this rotary phone web browser. The idea is simple: pick up the handset and dial the IP address of the server you want to connect to. DNS? Bah, who needs it?

Of course there is the teensy issue that most websites can’t be directly accessed via IP address anymore, but fear not – [Jan] has an incredibly obfuscated solution to that. It relies on the fact that many numbers sound like common phrases when sounded out in Chinese, so there end up being a lot of websites that have number-based URLs. He provides an example using the number 517, which sounds a bit like “I want to eat,” to access the Chinese website of McDonald’s. How the number seven sounding like both “eat” and “wife” is resolved is left as an exercise to the reader.

And here we thought [Jan]’s rotary number pad was of questionable value. Still, we appreciate this build, and putting old phones back into service in any capacity is always appreciated.

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Better Simulators With Homemade Potentiometers

Perhaps you’ve played a flight simulator before, using something like a mouse and keyboard. That’s a fine experience, but like any other activity you can get a lot more out of it if you put a little more effort into the experience. Some will upgrade to a joystick for a modest improvement, and others will build incredible accurate cockpit replicas down to the smallest detail. The builders of these “pits” are always looking for ways of improving their setups, and it’s from this world that we find a method of building specialized, inexpensive hall-effect sensors.

A hall-effect sensor is a circuit that outputs a voltage based on the presence of an external magnetic field. These can be used to make compasses, but with a permanent magnet in close proximity can also be used to create a potentiometer-like device at lower cost and with higher precision than a similarly-priced pot. There was a method of building these in the simulator world using the housing of a Bic pen and some strong glue, but [LocNar] has improved on this method as well. He repurposed some bearings and some stock metal tubing in order to fabricate a professional-level sensor at a fraction of the cost.

This build is essentially a solution for anyone needing a potentiometer that’s easier to build, less expensive, has higher precision, and interacts with a digital input in a much more predictable (and programmable) way. Certainly this has applications in the simulator world, but will work for many other applications. If you’ve never thought about the intricacies (and shortcomings) of potentiometers, some other folks have taken a deep dive into that as well.

Thanks to [Keith O] for the tip!

Robot Arms Nudge The Hands Of Time In The Strangest Clock

We see a lot of clocks here at Hackaday. Digital clocks, retro clocks, lots of Nixie clocks, binary clocks, and clocks that appear to be designed specifically to be unreadable. But this dual-servo kinematic clock is something we haven’t seen yet, and it’s certainly worth a mention.

[mircemk]’s idea is simple and hearkens back to grammar school days when [Teacher] put a large cardboard clock dial on the blackboard and went through the “big hand, little hand” drill. In this case, the static cardboard clock has been replaced by a 3D-printed dial and hands, while a pair of servos linked together by two arms takes the place of the teacher. The video below shows it in action; the joint in the linkage between the two servos has a screw sticking out that can be maneuvered across the clock face to reposition the hands. It’s a little jittery, though; [mircemk] might want to tune the servo loops up a bit or tighten the linkage joints to make things a little smoother.

Even with the shakes, we find it wonderfully weird and hard to stop watching. It reminds us a bit of this luminous plotting clock from a while back – same linkage, different display.

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Make The Surface Dial Do More Things, Such As MIDI

The Surface Dial is a $100+ rotary control. You can turn it, and it’ll make some basic stuff happen on your Microsoft Surface. It’s silver and sleek and elegant but fundamentally, it just works via emulated keyboard shortcuts. This doesn’t really do much for translating analog rotational motion into digital feedback in a nice way, so [SaveTheHuman5] created Elephant to fix this issue.

As standard, there are two ways to work with the Surface Dial as an end-user. The easiest way is to use existing utilities to map dial actions to shortcut keys. However, for interfacing with knobs and sliders in user interfaces, this is clunky. Instead, [SaveTheHuman5] drilled down and created their own utility using the Surface Dial API provided by Microsoft. This allows raw data to be captured from the dial and processed into whatever interactions your heart desires – as long as you’ve got the coding muscles to do it!

The Elephant software allows the knob to be used in two distinct modes – mouse capture, and MIDI. Mouse capture allows one to use a regular mouse to select UI objects, such as knobs in a music application, and then turn the Surface Dial to adjust the control. Anyone that’s struggled with tiny emulated rotary controls on a VST synth before would instantly know the value of this. In MIDI mode, however, the knob simply presents itself as a MIDI device outputting commands directly which would be more useful in performance environments in particular.

Overall, it’s a tidy hack of an otherwise quite limited piece of hardware – the only thing we’d like to see is more detail on how it was done. If you’ve got a good idea on how this could work, throw it down in the comments. And, if your thirst for rotary controls is still not satiated, check out this media controller. Video after the break.

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