Never Miss A Doorbell With This Notifier

March 1, 2020 by 14 Comments

[PatH] tells us that he tragically missed a craft beer delivery to his home, and vowed never to let this happen again. His problem was that he’d missed the doorbell, resulting in one of those annoying notes from the delivery guy. His solution? An ESP8266-driven doorbell detector, that both sends him an SMS and records each doorbell press to a Google Sheet.

The doorbell detection is surprising but simple and non-intrusive, instead of running a GPIO line through some kind of interface to the button itself he’s added a reed switch to his ESP8266 board and used that to detect the magnetic field of the bell solenoids. It’s a convenient method, but one that only works with an old-style bell.

When the bell rings the magnetic field triggers the reed switch, and in turn the sketch running on the ESP calls out to IFTTT which triggers both an SMS and a write to a Google Sheets document that records each doorbell activation.

The ESP8266 seems to be a popular choice with doorbell automatprs probably because of its built-in networking and low price, but it’s not the only option. This optocoupler-sensed effort for example uses a Particle Xenon.

Cable Operated Blast Door Needs No Power

February 17, 2020 by 34 Comments

Every well-equipped wood shop has a dust collection system, with blast gates at every tool to direct the suction power where you need it. If these gates are hard to reach they can be real pain to operate. [Cosmas Bauer] had this problem with his table saw, and created a convenient cable-operated mechanism.

The dust chute on table saw is on the back end, meaning he needs to walk around it to open it, and then walk back to the front to operate the machine. As we all know, laziness increased efficiency can be an excellent reason for projects. Electronics or pneumatics might get the job done, but [Cosmas] realised that a mechanical system might be simpler and more reliable.  Being a woodworker, he built most of the system out of wood.

The blast door itself is held in the closed position by a piece of elastic tubing. To pull it open, he attached a bicycle cable to the blast door, with the other side attached to a latching mechanism that is the star of the show. It’s a rotating disc, with the end of the cable and operating handle attached on the outer edge. A slot track is cut in the disc, in which a pin on the end of a short arm slides. It has a few sharp corners in the track, which forces the pin to only go around in one direction, and to latch in two possible positions when released. Check out the video after the break to see it in action.

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Binary Advent Calendar Does More With Fewer Doors

January 19, 2020 by 19 Comments

[John] sent this one in to us a little bit after Christmas, but we’ll give him a pass because it’s so beautiful. Think of it this way: now you have almost a full year to make a binary advent calendar of your own before December 1st rolls around again.

Normal advent calendars are pretty cool, especially when there is chocolate behind all 24 doors. But is it really a representational ramp-up if you never get more than one chocolate each day? [John] doesn’t think so. The economics of his binary advent calendar are a bit magical, much like the holiday season itself. Most days you’ll get two pieces of chocolate instead of one, and many days you’ll get three. That is, as long as you opened the right doors.

A momentary switch hidden behind the hinge of each door tells the Arduino clone when it’s been opened. The Arduino checks your binary counting abilities, and if you’re right, a servo moves a gate forward and dispenses one chocolate ball per opened door. We love the simplicity of the dispensing mechanism — the doors are designed with a ceiling that keeps non-qualifying chocolates in their channels until their flag comes up.

[John] is working out the kinks before he releases this into the wild. For now, you can get a taste in the demo video featuring a bite-sized explanation. If you don’t like chocolate, maybe this blinky advent calendar will light you up inside.

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A Simple App Controlled Door Lock

January 16, 2020 by 9 Comments

[Adnan.R.Khan] had a sliding door latch plus an Arduino, and hacked together this cool but simple app controlled door lock.

Mechanically the lock consists of a Solarbotics GM3 motor, some Meccano, and a servo arm. A string is tied between two pulleys and looped around the slide of a barrel latch. When the motor moves back and forth it’s enough to slide the lock in and out. Electronically an Arduino and a Bluetooth module provide the electronics. The system runs from a 9V battery, and we’re interested to know whether there were any tricks pulled to make the battery last.

The system’s software is a simple program built in MIT App Inventor. Still, it’s pretty cool that you can get functionally close to a production product with parts that are very much lying around. It also makes us think of maybe keeping our childhood Meccano sets a little closer to the bench!

In Soviet Russia, Doorbell Rings You

January 13, 2020 by 11 Comments

We can imagine that the origin of the doorbell is truly ancient. if you lived in a cave, you probably had a stick and a rock nearby for people to get your attention without invading your cave. In 1817 a Scot named William Murdoch had a bell in the house that visitors rang via a compressed air system, but the electric doorbell had to wait until 1831. Since then, little has changed with the basic idea. [Erientes] — who lives in the Netherlands, not Russia — wanted a smarter doorbell. In particular, he’s read about older people being victimized by people who ring the doorbell for entry. So [Erientes] used a Raspberry Pi to make a doorbell that supports facial recognition.

The exercise is really more of an operations challenge than a technical one thanks to a high-quality Python library for face recognition powered by DLib. However, we did like the user interface aimed at non-technical users. The metaphor is a traffic light in which a red light means do not allow entry. The lights are buttons, so you can use them to whitelist or blacklist a particular person.

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Behind Amazon’s Doors Is A Library

December 6, 2019 by 7 Comments

Some people love Amazon, while others think it has become too big and invasive. But you have to admit, they build gigantic and apparently reliable systems. Interestingly, they recently released a library of white papers from their senior staff called the Builder’s Library.

According to their blog post:

The Amazon Builders’ Library is a collection of living articles that take readers under the hood of how Amazon architects, releases, and operates the software underpinning Amazon.com and AWS. The Builders’ Library articles are written by Amazon’s senior technical leaders and engineers, covering topics across architecture, software delivery, and operations. For example, readers can see how Amazon automates software delivery to achieve over 150 million deployments a year or how Amazon’s engineers implement principles such as shuffle sharding to build resilient systems that are highly available and fault tolerant.

The Amazon Builders’ Library will continue to be updated with new content going forward.

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Improved Outdoor Solar Harvester Now Handles All The Parts

November 19, 2019 by 6 Comments

[Vadim Panov]’s 3D printed solar harvester is in effect a rechargeable outdoor battery, and the real challenge he faced when designing it was having it handle the outdoors reliably. The good news is that part is solved, and his newest design is now also flexible enough to handle a variety of common and economical components such as different battery connectors, charge controllers, and solar panel sizes. All that’s left is to set it up using the GoPro-style mounting clamp and let it soak up those solar rays.

We saw his first version earlier this year, which uses inventive and low-cost solutions for weatherproofing like coating the 3D print with epoxy (the new version makes this easier and less messy, by the way.) It was a fine design, but only worked with one specific solar panel size and one specific configuration of parts. His newest version makes a few mechanical improvements and accommodates a wide variety of different components and solar panel sizes. The CAD files are all available on the GitHub repository but he’s conveniently provided STL files for about a dozen common sizes.

When it comes to harvesting light, staying indoors offers less power but requires a far less rugged setup. If that interests you, be sure to check out the Tiny Solar Energy Module (TSEM) which can scrape up even indoor light.