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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Overengineering A Smart Doorbell

Fresh from the mediaeval splendour of the Belgian city of Gent, we bring you more from the Newline hacker conference organised by Hackerspace Gent. [Victor Sonck] works at the top of his house, and thus needed a doorbell notifier. His solution was unexpected, and as he admits over engineered, using machine learning on an audio stream from a microphone to detect the doorbell’s sound.

Having established that selling his soul to Amazon with a Ring doorbell wasn’t an appropriate solution, he next looked at his existing doorbell. Some of us might connect directly to its power to sense when the button was pressed, but we’re kinda glad he went for the overengineered route because it means we are treated to a run-down how machine learning works and how it can be applied to audio. The end result can sometimes be triggered by a spoon hitting a cereal plate, but since he was able to demonstrate it working we think it can be called a success. Should you wish to dive in further you can find more in his GitHub repository.

How would you overengineer a doorbell? Use GNU radio and filters? Or maybe a Rube Goldberg machine involving string and pulleys? As always, the comments are open.

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Door Mutes Microphone To Prevent Remote Learning Humiliation

In a kind of reverse twist on the doorbell, [TheStaticTurtle] whipped up a system to mute his computer’s microphone whenever someone opens the door to his room. He lives in France, where the government announced a strict lockdown last Friday. Like many university students around the world these days, he is now forced to take online classes. Even though he has his own room, occasionally someone will barge in and announce something, often to [TheStaticTurtle]’s embarrassment.  When his classmates suddenly heard “Do you want some pie?” the other day, it was the last straw.

His first decision was to sense the door opening with a magnet and sensor, which he stuck to the door and frame with hot glue. He then ran a long cable to his desk, where it connected to an ATTiny 85 with a DigiSpark boot-loader. He wrote firmware to simulate special key combinations, which were then registered with his audio routing software Voicemeeter Potato. We presume he isn’t using an external mic, in which case muting might have been easier to accomplish with a hardware switch. All in all, this is a pretty clever and timely hack. Should you be in a similar predicament and want to try this out, he’s published the source code on GitHub.

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Pop Open Your Neighbor’s Front Door With 12 Volts

Many in the community are skeptical about the security of commercial smart home devices, and for good reason. It’s not like you have to look far to find examples of poorly implemented systems, or products that are abandoned by their manufacturers and left without critical security updates. But the design flaw in this video doorbell really drives home how little thought some companies give to their customer’s security.

As explained by [Savvas], and demonstrated in the video after the break, all you need to do if you want to get into a home equipped with one of these vulnerable door bells is pop the unit off the wall and hit it with 12 volts DC.

Incredibly, the terminals that connect to the electronic lock inside the house are completely accessible on the back of the unit. They even labeled them, on the off-chance the robber forgets which wire is which. It’s not even as though the thing is held on with some kind of weird security screws, it’s just a garden variety Phillips.

In the video, [Savvas] even shows he used a little gadget attached to a QuickCharge USB battery bank to get a portable 12 VDC source suitable for tripping these locks. Which, interestingly enough, is based on a trick he read about in the Hackaday comments. Something to consider while penning your next comment on these storied pages.

[Savvas] says he’s reached out to the company to get their side of the story, but so far, hasn’t received a response. We aren’t surprised, this is a fundamental flaw in the product’s execution. Clearly they wanted to make an easy to install device that doesn’t require any additional electronics in the house, and this is the inevitable end result of that oversimplification. All the more reason to roll your own smart doorbell.

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Contactless Doorbell Built To Avoid Coronavirus

It’s often said that necessity breeds creativity, and during a global pandemic such words have proved truer than ever. Realising the common doorbell could be a potential surface transmission point for coronavirus, [CasperHuang] whipped up a quick build.

The build eschews the typical pushbutton we’re all familiar with. Instead, it relies on an ultrasonic distance sensor to detect a hand (or foot) waved in front of the door. An Arduino Leonardo runs the show, sounding a buzzer when the ultrasonic sensor is triggered. In order to avoid modifying the apartment door, the build is housed in a pair of cardboard boxes, taped to the base of the door, with wires passing underneath.

It’s a tidy way to handle contactless deliveries. We imagine little touches like this may become far more common in future design, as the world learns lessons from the COVID-19 pandemic. Every little bit helps, after all. Video after the break.

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The Easiest Way To Put Your Doorbell On The Internet

Thanks to low-cost WiFi enabled microcontrollers such as the ESP8266 and ESP32, it’s never been a better time to roll your own smart home system. But that doesn’t mean it isn’t daunting for new players. If you’re looking for an easy first project, putting your old school doorbell on the Internet of Things is a great start, but even here there’s some debate about how to proceed.

Most people stumble when they get to the point where they have to connect their low-voltage microcontroller up to the relatively beefy transformer that drives a standard doorbell. We’ve seen a number of clever methods to make this connection safely, but this tip from [AnotherMaker] is probably the easiest and safest way you’re likely to come across.

His solution only requires an inductive current sensor, which can be had for less than $1 from the usual overseas suppliers. One leg of the doorbell circuit is passed through the center of this sensor, and the sensor itself is connected up to your microcontroller of choice (here, and ESP32). The rest is software, which [AnotherMaker] explains in the video after the break. With the addition of a little debounce code, your microcontroller can reliably determine when somebody is out there jabbing the bell button; what you do with this information after that is up to you.

If you’re worried this method is too easy you could always try it with an optocoupler, or maybe convert the low-voltage AC to something your microcontroller can handle.

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A Raspberry Pi Video Intercom System

When it comes to hacks, we’re always amazed by the aesthetic of the design as much as we are by the intricacies of the circuit or the cleverness of the software. We think it’s always fun to assemble projects that were just sort of rigged up in our shop really quickly and made to just work, without worrying about much else. But, when you really invest time in the aesthetics and marry form with function, the results are always one to marvel at.

That’s what the engineers over at [Hacker Shack] did with their Raspberry Pi-based video intercom system over on Hackster. Now we’ve seen RPi doorbell projects here on Hackaday before, but it’s the implementation of a full-duplex video intercom system that makes [Hacker Shack’s] project really stand out. (Unless you want to be a bit more secretive). They used a Raspberry Pi 3 Model B with an off-brand Pi camera, but the R Pi branded camera will also work just fine. Couple the camera with a very crisp LCD display, microphone, and speaker and you’re good to go! Continue reading “A Raspberry Pi Video Intercom System”