A brick mailbox with a LIDAR sensor mounted inside

Using A LIDAR Sensor To Monitor Your Mailbox

June 6, 2022 by Robin Kearey 31 Comments

The inconvenience of having to walk to your mailbox to check for mail has inspired many hackers to install automated systems that let them know when the mail has been delivered. Mailbox monitors have been made based on several different mechanisms: some measure the weight of the items inside, some use cameras and machine vision, while others simply trigger whenever the mailbox’s door or flap is moved. When [Gary Watts] wanted to install a notification system for his 1940s brick letterbox, his options were limited: with no flap or door to monitor, and limited space to install mechanical contraptions, he decided to use a LIDAR sensor instead.

Probably best-known for their emerging application in self-driving cars, LIDAR systems send out a laser pulse and measure the time it takes for it to be reflected off a surface. In the case of [Gary]’s mailbox, that surface is either the brick wall or a letter leaning against it. Since letters are inserted through a vertical slot, they will usually be leaning upright against the wall, providing a clear target for the laser.

The LIDAR module, a VL53L0X made by ST, is hooked up to a Wemos D1 Mini Pro. The D1 communicates with [Gary]’s home WiFi through an external antenna, and is powered by an 18650 lithium battery charged through a solar panel. The whole system is housed inside a waterproof plastic case, with the LIDAR sensor attached to the inside of the mailbox through a 3D-printed mounting bracket. On the software side, the mailbox notifier is powered by Home Assistant and MQTT. The D1 spends most of its time in deep-sleep mode, only waking up every 25 seconds to read out the sensor and send a notification if needed.

We’ve seen quite a few fancy mailbox monitors over the years: some are extremely power efficient, some use multiple sensors to allow for different use-cases, and some others are simply beautifully designed.

Overengineering A Smart Doorbell

September 12, 2021 by Jenny List 19 Comments

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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Using MIDI To Solve A Keyboard Shortcut Problem

February 16, 2021 by Donald Papp 4 Comments

[Pete] admits that his MIDI-based slide advance alert system is definitely a niche solution to a niche problem, but it is a wonderful example of using available tools to serve a specific need. The issue was this: [Pete] is involved in numerous presentations streamed over video, and needed a simple and effective way for the Presenter to notify the Producer (the one responsible for the video streaming and camera switching) to discreetly advance slides on cue.

To most of us, this is a simple problem to solve. Provide the presenter with a USB macro keyboard to trigger the keyboard shortcuts for slide advancement, and the job’s done. But that didn’t quite cut it for [Pete]. In their situation, the Producer is managing more than just the slides as they switch between cameras, watch the chat window, and manage the video streaming itself. Triggering slide advancement via keyboard shortcuts only works if the presentation software is in focus when the buttons are pressed, which isn’t guaranteed.

[Pete’s] solution was to make a small two-button device (one button for next slide, one for previous slide) that uses MIDI to communicate with a small custom application on the producer’s machine, and doesn’t care about application focus. Pressing the slide advance button plays a distinct tone into the producer’s headphones, plus the custom application displays “Forward”, “Back”, or “Waiting” in a window, depending on the state of the Presenter’s buttons. The design is available on Instructables for anyone wanting a closer look.

[Pete] reports that it works and it’s far more discreet than saying “next slide, please” twenty or more times per presentation. You may notice from the photo that LEGO bricks play a prominent part in the device, and if you’d like to see more of that sort of thing, make sure to check out these other brick-mountable PCB designs.

Don’t Slack Off On Updating Your Status

September 2, 2020 by Kristina Panos 16 Comments

Displaying an accurate status in Slack (or whatever other employer-provided collaboration program you may be forced to run) is crucial in 2020. If you need to make a sandwich or take the dog out real quick, but you don’t update your status to show yourself as away, you might come back to a string of increasingly concerned or frustrated messages with lots of annoying question marks and the occasional interrobang.

[Becky Stern] decided that a physical interface would be a far more fun way to keep tabs on her status, and an excellent visual reminder to actually do it. We totally agree. Inside the box is a NodeMCU which is using [Brian Lough]’s Slack API library for Arduino. This made it easy for [Becky] to create a switch/case selector of statuses, and in each of these she can set the presence token as auto or away, and show a custom message with an appropriate emoji. These of course match the emoji semi-circling the selector, which is a rotary switch with a really nice knob.

While we’re on the subject of Slack notifiers, how about a companion cat to wave when you’ve been mentioned?

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The Easiest Way To Put Your Doorbell On The Internet

June 1, 2020 by Tom Nardi 39 Comments

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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IoT Cassette Scroller Never Needs A Pencil

March 10, 2020 by Kristina Panos 33 Comments

The see-through electronics craze of the ’80s and ’90s clearly had an effect on [MisterM], and we can totally relate. Those candy-colored components inside undoubtedly launched a few thousand kids in the direction of electronics, as we can attest.

Though the odds seemed very much against him, [MisterM] was able to fit all the necessary components for a scrolling IoT notifier inside a standard cassette tape. It took a bit of surgery on both the Raspberry Pi Zero W and the donor cassette in the name of getting all the components to fit in such a tight space. We’re glad he kept at it, because it looks amazing.

The Raspi uses Adafruit.IO and IFTTT to get all kinds of notifications — tweets, weather, soil moisture, you name it — and scrolls them across an 11×7 LED matrix. A vibrating disc motor gives a buzzing heads up first, so [MisterM] doesn’t miss anything. Hit the break button and flip this thing over, because the build video is all queued up on the B-side.

If you’d rather play around with cassette decks, add in some playback speed potentiometers to mess with the sound, or go all out and make a Mellotron.

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Hackaday Podcast 057: Dismantled LCD Panels, Unexpected Dynamometer, A Flappy POV, And Dastardly Encryption

March 6, 2020 by Mike Szczys 4 Comments

Hackaday editors Mike Szczys and Elliot Williams are onto an LCD and motors kick this week. Two different LCD screen teardowns caught our eye as one lets you stare into the void while using your iMac and the other tries to convince us to be not afraid of de-laminating the LCD stackup. On the motors front, it’s all about using magnets and coils in slightly different ways; there’s a bike generator that uses a planar alternator design, a dynamometer for testing motor power that itself is built from a motor, and a flex-PCB persistence of vision display that’s a motor/display hybrid. We round out the episode with talk of the newly revealed espionage saga that was Crypto AG, and riveting discussion of calculators, both real and virtual.

Take a look at the links below if you want to follow along, and as always tell us what you think about this episode in the comments!

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (60 MB or so.)