Sniffed Transformer Puts Wired Doorbell Online

August 6, 2019 by 30 Comments

There’s certainly no shortage of “smart” gadgets out there that will provide you with a notification, or even a live audiovisual stream, whenever somebody is at your door. But as we’ve seen countless times before, not everyone is thrilled with the terms that most of these products operate under. Getting a notification on your phone when the pizza guy shows up shouldn’t require an email address, credit card number, or DNA sample.

For [Nick Touran], half the work was already done. There was already a traditional wired doorbell in his home, he just had to come up with a minimally invasive way to link it with Home Assistant. He reasoned that he could tap into the low-voltage side of the doorbell transformer and watch for the telltale fluctuations that would indicate the bell was doing its thing. The ESP8266 has an ADC to measure voltage and WiFi to connect to Home Assistant, so it seemed like the perfect bridge between old and new.

Transformer voltage before and after

Of course, as with any worthwhile project, it ended up being a bit more complicated. Wired doorbells generally operate on 16-24 VAC, and [Nick] knew if he tried to put his Wemos D1 across the line he’d release the critical Magic Smoke. What he needed was a voltage divider circuit that would take low-voltage AC and drop it to an even lower DC voltage that the microcontroller could cope with.

The simple circuit [Nick] comes up with cuts the voltage way down and removes the negative component completely. So what was originally 18.75 VAC turned into a series of 60 Hz blips at 2.4 VDC; perfect for feeding into a microcontroller ADC. With a baseline to work from, he could then write some code that would watch for variations in this signal to determine when the bell was ringing.

Or at least, that was the idea. While the setup worked well enough on the bench, its performance in the real-world left something to be desired. If his house guest had a heavy hand, it worked great. But a quick tap of the doorbell button would tend to go undetected. After investigating the issue, [Nick] found that he needed to use some software trickery to ensure the ESP8266 was able to keep up with the speedy signal. Once he was able to reliably detect short and long button presses, the rest was just a simple matter of sending an MQTT message to his automation system.

Compared to the hoops we’ve seen other hackers have to jump through to smarten up their doorbells, we think [Nick] got off fairly easy. This project is also an excellent example of how learning about circuit design and passive components can still come in handy in the Arduino Era.

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Hold 3500 Volts Up To Your Eye

August 6, 2019 by 15 Comments

Old military equipment can sometimes be found in places like flea markets and eBay for pennies, often because people don’t always know what they have. While [tsbrownie] knew exactly what he was getting when he ordered this mystery device, we’re not sure we could say the same thing if we stumbled upon it ourselves. What looks like a vacuum tube of some sort turns out to be an infrared sensor from an old submarine periscope that was repurposed as a night vision device. (Video, embedded below.)

Of course, getting a tube like this to work requires high voltage. This one specifically needs 3500V in order to work properly, but this was taken care of with a small circuit housed in a PVC-like enclosure. The enclosure houses the tube in the center, with an eye piece at one end and a camera lens at the other, attached presumably by a 3D-printed mount. The electronics are housed in the “grip” and the whole thing looks like a small sightglass with a handle. Once powered up, the device is able to show a classic green night vision scene.

Old analog equipment like this is pretty rare, as are people with the expertise to find these devices and get them working again in some capacity. This is a great video for anyone with an interest in tubes, old military gear, or even if you already built a more modern night vision system a while back.

Thanks to [Zzp100] for the tip!

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CB Radio + Arduino = 6 Meter Ham Band

August 5, 2019 by 13 Comments

Somehow [hvde] wound up with a CB radio that does AM and SSB on the 11 meter band. The problem was that the radio isn’t legal where he lives. So he decided to change the radio over to work on the 6 meter band, instead.

We were a little surprised to hear this at first. Most radio circuits are tuned to pretty close tolerances and going from 27 MHz to 50 MHz seemed like quite a leap. The answer? An Arduino and a few other choice pieces of circuitry.

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A SuperCap UPS

August 5, 2019 by 61 Comments

If you treat your Pi as a wearable or a tablet, you will already have a battery. If you treat your Pi as a desktop you will already have a plug-in power supply, but how about if you live where mains power is unreliable? Like [jwhart1], you may consider building an uninterruptible power supply into a USB cable. UPSs became a staple of office workers when one-too-many IT headaches were traced back to power outages. The idea is that a battery will keep your computer running while the power gets its legs back. In the case of a commercial UPS, most generate an AC waveform which your computer’s power supply converts it back to DC, but if you can create the right DC voltage right to the board, you skip the inverting and converting steps.

Cheap batteries develop a memory if they’re drained often, but if you have enough space consider supercapacitors which can take that abuse. They have a lower energy density rating than lithium batteries, but that should not be an issue for short power losses. According to [jwhart1], this quick-and-dirty approach will power a full-sized Pi, keyboard, and mouse for over a minute. If power is restored, you get to keep on trucking. If your power doesn’t come back, you have time to save your work and shut down. Spending an afternoon on a power cable could save a weekend’s worth of work, not a bad time-gamble.

We see what a supercap UPS looks like, but what about one built into a lightbulb or a feature-rich programmable UPS?

Cat Feeder Adds Metrics To Meow Mix

August 5, 2019 by 16 Comments

If there’s one thing any cat will work for, it’s food. Usually, this just consists of meowing and/or standing on your chest until you give up the goods. [DynamicallyInvokable] has a beautiful cat, Emma, who meows loudly for food at obscene hours of the morning. As she ages, it’s getting harder and more important to control her weight. Clearly, it was time to build the ultimate automatic cat feeder—one that allows him to get lazy while at the same time getting smart about Emma’s weight.

After a year and a half of work, the feeder is complete. Not only does it deliver the goods several times a day, it sends a heap of data to the cloud about Emma’s eating habits. There’s a scale built into the platform, and another in the food bowl. Together, they provide metrics galore that get automatically uploaded to AWS. Everything is controlled with an ESP32 Arduino, including a rainbow of WS2812s that chases its tail around the base of the feeder. The faster it goes, the closer it is to feeding time.

The best part about this unique feeder is that nearly every piece is 3D printed, including the gears. Be sure to check out the build gallery, where you can watch it come together piece by piece. Oh, and claw your way past the break to see Emma get fed.

Emma doesn’t have to worry about sharing her food. If she did, maybe [DynamicallyInvokable] could use facial recognition to meet the needs of multiple cats.

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Kickstarter Hack Chat

August 5, 2019 by No comments

Join us on Wednesday, August 7th at noon Pacific for the Kickstarter Hack Chat with Beau Ambur and Clarissa Redwine!

For many of us, magic things happen on our benches. We mix a little of this, one of those, and a couple of the other things, and suddenly the world has the Next Big Thing. Or does it? Will it ever see the light of day? Will you ever build a community around your project so that the magic can escape the shop and survive the harsh light of the marketplace? And perhaps most importantly, will you be able to afford to bring your project to market?

Crowdfunding is often the answer to these questions and more, and Kickstarter is one of the places where hackers can turn their project into a product. Beau and Clarissa, both outreach leads for the crowdfunding company, will stop by the Hack Chat to answer all your questions about getting your project off the bench and into the marketplace. Join us as we discuss everything from building a community that’s passionate enough about your idea to fund it, to the right way to share your design story.

join-hack-chatOur Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, August 7 at 12:00 PM Pacific time. If time zones have got you down, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io. You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.