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?

Junkbox Confidential

Thomas Edison famously quipped “To invent, you need a good imagination and a pile of junk.” Amen, brother. My personal junk pile (ahem, collection of pre-owned electromechanical curiosities) is certainly a source of spare parts, but also a source of surprise and wonder. Sometimes the junk itself spurs the imagination, but sometimes junk is just junk.

There are pieces of used gear that I bought for some particular plan, maybe a decade ago?, and totally forgot. While it’s fun to rediscover them — I bought six used super-soaker pump assemblies, and summer is just around the corner — the sad truth is often that the forgotten pieces were forgotten for a reason. Whatever kooky idea I had at the time has faded, and the parts are all that’s left.

But among these miserable creatures, there are some absolute gems. Parts that continually call out to be used. Bits that would fire even Thomas Edison’s imagination. Unforgetable junk.
Mostly, it’s their physicality that calls out to me. I have a stack of old 5″ hard drive platters, gutted, and converted into essentially a rotary encoder. For years, I used it as a USB scroll wheel on my desk, but most recently it has made reappearances in other goofy projects — a music box for my son that played notes in a row depending on how fast you spun it, and most recently a jog wheel for a one-meter linear motion project that hasn’t really found its full expression yet, but might become a camera slider. Anyway, when I needed a nice physical rotary encoder knob, the hard drive was just sitting there waiting to be used. Continue reading “Junkbox Confidential”

Rotary Dialer Becomes Numeric Keypad

Many laptops eschew the numeric keypad to free up space, and some desktop keyboards have taken on the trend, too. If you want a specialised numeric entry device and have absolutely no interest in speed or ease of use, [jp3141] has just the build for you.

The idea is to use the rotary dial from an old telephone to enter numbers into a computer. It’s slow and cumbersome, but it’s also pretty entertaining. The build uses an old AT&T Trimline dialer, though we’re sure most rotary phones would work. The pulses produced by the dialer are counted by a Teensy microcontroller, which emulates a USB HID keyboard device and enters the relevant keystroke into the computer. There’s also a USB serial interface for debugging, and an LED which flashes along with the pulses from the dialer circuit.

While it’s not the most efficient data entry method, it’s a semi-useful way to repurpose an old phone, and an amusing piece to take along to your next LAN party. We’ve featured a few… alternative… keyboards before, too. If you’ve cooked up a truly convoluted input device for your computer, be sure to let us know.

Rotary Phone Takes You Around The World And Through Time – With Music

Purposely choosing obsoleted technology combines all the joy of simpler times with the comfort of knowing you’re not actually stuck with outdated (and oftentimes inferior) technology. The rotary phone is a great example here, and while rarely anyone would want to go back to the lenghty, error-prone way of dialing a number on it on an everyday basis, it can definitely add a certain charm to a project. [Caroline Buttet] thought so as well, and turned her grandma’s old rotary phone into a time-traveling, globe-trotting web radio.

The main idea is fairly simple: a Raspberry Pi connects via browser to a web radio site that plays music throughout the decades from places all over the world. [Caroline]’s implementation has a few nice twists added though. First of all, the phone of course, which doesn’t only house the Raspberry Pi, but serves both as actual listening device via handset speaker, and as input device to select the decade with the rotary dial. For a headless setup, she wrote a Chromium extension that maps key events to virtual clicks on the corresponding DOM element of the web site — like the ones that change the decade — and a Python script that turns the rotary dial pulses into those key events.

However, the phone is only half the story here, and the country selection is just as fascinating — which involves an actual world map. An audio connector is attached to each selectable country and connected to an Arduino. If the matching jack is plugged into it, the Arduino informs the Raspberry Pi via serial line about the new selection, and the same Chromium extension then triggers the country change in the underlying web site. You can check all the code in the project’s GitHub repository, and watch a demo and brief explanation in the videos after the break.

Sure, listening radio through a telephone may not be the most convenient way — unless it’s the appropriate genre — but that clearly wasn’t the goal here anyway. It’s definitely an interesting concept, and we could easily see it transferred to some travel- or spy-themed escape room setting. And speaking of spying, if [Caroline]’s name sounds familiar to you, you may remember her virtual peephole from a few months back.

Continue reading “Rotary Phone Takes You Around The World And Through Time – With Music”

Old Rotary Phone Gets Called Into Action

The more glass we punch with our fingertips, the more we miss fun physical interfaces like the rotary phone. Sure, they took forever to dial, and you did not want to be one of those kids stuck with one during the transition to DTMF, especially if you were trying to be the 9th caller to a radio station, but the solidly electromechanical experience of it all was just cool, okay? The sound and the heft made them seem so adult.

[Tal O] gets it. He’s all but finished bringing this old girl into the 21st century without giving anything away on her surface. Inside are some things you’d expect, like a SIM800 GSM module for the telephony part, and an ESP32 to count the pulses from the dialer and communicate between it and the GSM module. But it also has a few things we haven’t seen before. The entire journey is outlined in a five-part video series, and we’ve got part one dialed in for you after the break.

Although [Tal] got the ringer working to prove it could be done, he didn’t want to have a separate 12V circuit just to run the bells. Also, the bells and their electromagnets take up a lot of space, so he compromised with an mp3 of a rotary ringer. [Tal] also wanted a way to have dialed-number feedback without cutting up the phone to add a screen, so he found a text-to-speech library and made the phone speak each number aloud as soon as it’s dialed. It uses the same internal speaker as the ringer, but we think it would be neat if the feedback came through the handset speaker.

If [Tal] is looking for another modern convenience to add to this phone, how about speed dial?

Continue reading “Old Rotary Phone Gets Called Into Action”

Finally, A Usable Rotary Phone From A Conference Badge

A few weeks ago we featured a project from [Dan], a work-in-progress in which he was attaching an EMF 2018 electronic conference badge to a rotary phone. At the time we looked forward to his progress, expecting maybe to see it in our travels round the field at EMF 2021. We have to say we did him a disservice then, because he’s made excellent progress and has now turned it into a fully functional cellular rotary phone.

When we left him he’d interfaced the dial to the badge and not a lot else, but it was enough to spark our interest because we think there should be more re-use of old electronic conference badges. Since then he’s reverse engineered the original bell with the help of a motor driver and a cheap DC-to-DC converter, and the handset with the guts of a Bluetooth headset because in experimenting he managed to kill the badge’s audio circuitry.

The result can be seen in the video below the break, and we have to admit it looks pretty good. Depending where you are in the world you’ll either love or hate the ringing sound, but that is of little consequence to the utility of the device. If you have a drawer full of conference badges gathering dust, perhaps it’s time to give them a second look.

Continue reading “Finally, A Usable Rotary Phone From A Conference Badge”

Finally, A Rotary Cell Phone With Speed Dial

If you’re reading this, chances are good that you’re the family IT department. We do what we can to help them, but there’s just no changing the fact that smartphones are difficult to operate with aging eyes and hands. When [sideburn’s] dad started complaining, he took a different approach. Instead of helping his dad adapt, [sideburn] stuffed modern cell phone guts into a 1970s rotary phone — if all you want to use it for is phone calls, why not reach for a battle-tested handset?

[sideburn] figured out the most important part first, which is getting the thing to ring. The bells in those old phones are driven by a huge relay that requires a lot of voltage, so he boosted a 3.2V rechargeable to 34V. Then it was just a matter of getting the GSM module to play nice with the microcontroller, and programming a MOSFET to trigger the boost module that makes the beast jingle.

The worst thing about rotary phones is that they were never meant to be dialed in a hurry. But [sideburn] took care of that. Once Rotocell was up and working, he added an SMS interface that makes the phone a lot more useful. Dad can add contacts to Rotocell by texting the name and number to it from a modern phone. Once it’s in there, he can dial by name, speeding up the process a tiny bit.

The SMS interface can also report back the signal strength and battery level, and will send battery low alerts when it’s under 20%. You can see Rotocell in action after the break.

Got an old rotary or two lying about? If modernizing the internals to make calls doesn’t light up your circuits, try turning it into a voice-controlled assistant instead.

Continue reading “Finally, A Rotary Cell Phone With Speed Dial”