Rotary Phone Lives On As Arduino Kitchen Timer

May 28, 2024 by Tom Nardi 5 Comments

It’s safe to say that few people still use rotary phones on a daily basis. Hell, most of us don’t even use landline telephones anymore. But just because these classic phones are no longer being used for their original purpose doesn’t necessarily mean they’re doomed to become e-waste.

[Scott-28] recently sent in a particularly well-documented project that turned an antique rotary phone into a digital kitchen timer using an internal Arduino. While we’re not sure practical is a word most folks would use to describe the resulting device, it’s certainly a conversation starter, and the details on how it was all implemented make for an interesting read.

As explained in the README, [Scott-28] first used an oscilloscope to figure out the pulses generated by the phone’s dial. From there, it was relatively easy to connect the dial to one of the pins on an Arduino Uno to determine which numbers the user had entered. The trickier part was getting the original bells to work — in North America, it takes up to 90 VAC to get a phone’s ringer going, which is quite a bit more than the lowly Arduino can handle.

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The Open Source Rotary Cell Phone, Two Years Later

September 10, 2022 by Tom Nardi 56 Comments

We know the pandemic has screwed with a lot of people’s sense of time, but we doubled checked, and it has indeed been more than two years since the Internet first laid eyes upon the incredible rotary cell phone put together by [Justine Haupt]. We’re happy to report that not only has she continued to develop and improve the phone since the last time it made the rounds, but that the kits for this open source marvel are currently available for preorder.

A lot has happened since this phone last graced the pages of Hackaday. For one thing, it’s now officially known as the Rotary Un-Smartphone. [Justine] has also spun up a small company for the express purposes of putting these kits into production, which clearly speaks to just how much attention the project picked up in mainstream circles.

The new rotary mechanism is based on modern components.

In terms of hardware, while the phone might look more or less the same externally, [Justine] says that there’s not a single unchanged component from the previous version. The 3D printed case has given way to a beautiful injection molded enclosure offered in several retro colors, and the rather incongruous rubber ducky antenna has been replaced with an articulated aerial that serves as a kickstand.

Speaking of reception, the original 3G cellular modem has been upgraded to a LTE-compatible model from uBlox, so it should still get a signal for a decade or so before your carrier kicks it off the network. When ordering the kit you can choose between a global version using the TOBY-R200 modem, or a North American variant with the TOBY-R202.

Even the user interface has been spruced up — while the previous model featured a simple LED indicator on the front to show when you were in a call, the new version features an OLED display that will show you the currently dialed number as well as status information such as battery life and signal strength. Some may be disappointed to hear that the authentic Western Electric model 10A rotary dial has been deleted in favor of a custom designed mechanism that uses all modern components, but we can certainly understand why the change had to be made from a production standpoint.

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The Case For Designer Landline Phones

June 9, 2022 by Kristina Panos 34 Comments

Long before the idea of hot dog-shaped iPhone cases, Otter Boxen, or even those swappable Nokia face plates, people were just as likely to express themselves with their landline phones. Growing up at my house in the 80s, the Slimline on the kitchen wall was hidden inside a magneto wall set from the early 1900s, the front of which swung out to reveal the modern equipment behind it. Back in my bedroom, I had the coolest phone ever, a see-through Unisonic with candy-colored guts. Down in the basement was my favorite extension, tactility-wise: a candy apple-red wall unit with dimly-lit circular push buttons that were springy and spongy and oh-so fun to dial.

Popular culture shows us that people were dreaming of cool telephone enclosures before they were even a thing. Obviously, TV secret agent Maxwell Smart’s shoe phone wasn’t plausible for the technology of that era, but it also wasn’t really feasible for aesthetic reasons. For decades, phone subscribers had to use whatever equipment Ma Bell had to offer, and you couldn’t just buy the things outright at the mall — you had to lease the hardware from her, and pay for the service.

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Rotary Phone MIDI Controller Still Makes Calls

March 15, 2022 by Kristina Panos 3 Comments

[Kevin] has long wanted to do something musical with a vintage rotary phone and an Arduino, and has finally done so and committed the first of several experiments to HTML in a five-part series. He found a nice old British Telecom number, but it had been converted to plug and socket wiring to work on the modern system. Because of this, [Kevin] wanted to keep it completely functional as a phone. After all, it ought to work fine until 2025, when pulse dialing will no longer be supported in [Kevin]’s locality.

As you can likely understand, [Kevin] was keen to interface with the phone from the outside and leave the inside untouched. He used a sacrificial ADSL filter’s PCB to break out the socket, and added a pull-up resistor between the pin and 5 V.

Pretty quickly, [Kevin] figured out that when the phone is on the hook, it gives a constant high signal, where as the picking up the phone presents as a high signal going low, and dialing each number results in pulses of that quantity that alternate between high and low. Continue reading “Rotary Phone MIDI Controller Still Makes Calls” →

Dial A For Arduino

October 9, 2021 by Al Williams 19 Comments

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?

Rotary Dialer Becomes Numeric Keypad

July 30, 2020 by Lewin Day 4 Comments

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.