Hidden Bookshelf Door Shows Incredible Motion

Who didn’t dream of a hidden door or secret passage in the house when they were kids? Some of us still do! [SPECTREcat] had already built a secret door in a fully functioning bookcase with a unique opening mechanism. The intriguing mechanism allows the doors to start by sliding slightly away form one another before hinging into the hidden space. Their operation was, however, was manual. The next step was to automate the secret door opening mechanism with electronics.

The project brain is an off-the-shelf Arduino Uno paired with a MultiMoto Arduino shield to drive 4 Progressive Automations PA-14 linear actuators. These linear actuators have 50lb force, allowing the doors to fully open or close within 10 seconds and maintain a speed that wouldn’t throw the books off the bookcases.

Not wanting to drill a hole through the bookshelf for a switch or other opening mechanisms, [SPECTREcat] added a reed switch that is activated on the other side by a DVD cover with a magnet inside. In addition to that, there is a PIR sensor on the inside room to automatically close the doors if no motion is detected for 2 hours. Dont worry, there’s also a manual switch inside just in case.

Using one of the items on the shelf to trigger the secret passage is a classic move. He could also have used a secret knock code, like the Secret Attic Library Door we covered in the past. Check out the video below to see the hinge and slide movement in action.

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Illuminating New Take on Magnetic Switches

While there’s something to be said for dead-bug construction, hot glue, and other construction methods that simply get the job done, it’s inspiring to see other builds that are refined and intentional but that still hack together things for purposes other than their original intent. To that end, [Li Zanwen] has designed an interesting new lamp that uses magnets to turn itself on in a way that seems like a magnetic switch of sorts, but not like any we’ve ever seen before.

While the lamp does use a magnetic switch, it’s not a traditional switch at all. There are two magnetic balls on this lamp attached by strings. One hangs from the top of the circular lamp and the other is connected to the bottom. When this magnet is brought close to the hanging magnet, the magnetic force is enough to both levitate the lower magnet, and pull down on a switch that’s hidden inside the lamp which turns it on. The frame of the lamp is unique in itself, as the lights are arranged on the inside of the frame to illuminate the floating magnets.

While we don’t typically feature design hacks, it’s good to see interesting takes on common things. After all, you never know what’s going to inspire your next hackathon robot, or your next parts drawer build. All it takes is one spark of inspiration to get your imagination going!

Sentry Robot Turns Bad Cat to Good

The household of [James Watts] has cats, and those cats have decided that various spots of carpet are just great for digging up with their claws. After some efforts at training the cats, [James] enlisted a robotic cat trainer with remote wireless sensors. The automated trainer does only one job, but it does that one job reliably and tirelessly, which is just what is needed in this case. A task like “automate training the cats to stop clawing the carpet” is really made up of many smaller problems, and [James] implemented a number of clever ideas in his solution.

First of all, the need for an automated solution has a lot to do with how pets form associations, and the need to have the negative reinforcement be in the right place at the right time to be effective. A harmless spritz of water in this case is used for correction and needed to be applied immediately, consistently, and “from out of nowhere” (instead of coming from a person.) Otherwise, as [James] discovered, spraying water when the cats clawed the carpet simply meant that they stopped doing it when he was around.

There were a number of tricky problems to solve in the process. One was how to reliably detect cats actually clawing the carpet. Another was how to direct the harmless spray of water to only the spot in question, and how to rig and manage a water supply without creating another mess in the process. Finally, the whole thing needed to be clean and tidy; a hackjob with a mess of wires strung everywhere just wouldn’t do.

base_frontTo achieve all this, [James] created a main sprayer unit that is wirelessly connected to remote sensor units using NRF24L01+ serial packet radios. When a remote senses that a trouble spot is being clawed, the main unit uses an RC servo to swivel a spray nozzle in the correct direction and give the offending feline a watery reminder.

The self-contained remote sensors use an accelerometer to detect the slight lifting of the carpet when it’s being clawed. [James] programmed the MMA8452Q three axis accelerometer to trigger an external pin when motion is sensed above a certain threshold, and this event is sent over the wireless link.

For the main sprayer unit itself, [James] cleverly based it around an off-the-shelf replacement windshield washer tank. With an integrated pump, tubing, and assortment of nozzles there was no need to design any of those elements from scratch. If you want to give the project a shot, check out the github repository — probably worth it it since one night is all it took to change the cat behavior which explains the lack of any action video.

Pet projects usually center around automating the feeding process, but it’s nice to see other applications. For something on the positive-reinforcement end of training, check out this cat exercise wheel that integrates a treat dispenser to encourage an exercise regimen.

Garage Door Opener Logs to Google Drive

A garage door opener is a pretty classic hack around these parts. IR, Bluetooth, WiFi, smartphone controlled, web interfaces — we’ve seen it all.  But if you want to keep track of people going in and out, you need some way of logging what’s happening. You could go ahead and roll up your own SQL based solution, tied into a custom web page. But there’s an easier way; you can build a garage door opener that logs events to Google Drive.

[WhiskeyTangoHotel] was looking for an ESP8266 project, and a garage door opener seemed just the ticket. It’s simple enough to code up, and control over WiFi comes in handy. Interfacing with the garage door was simple enough — the existing opener uses a simple push button, which is easily controlled by wiring up a relay to do the job. Logging is as simple as having the ESP8266 send requests to IFTTT which is set up to make posts to a Google Sheet with status updates.

The project is fairly basic, but there’s room for expansion. By using separate Maker Channel triggers on IFTTT, different users of the garage door could be tracked. It would also be easy to add some limit switches or other sensors to detect the door’s position, so it can be determined whether the door was opened or closed.

There’s always another take on the garage door opener — check out this hack that opens the garage door in response to flashing headlights.

Raspberry Pi Home Automation for the Holidays

When you want to play around with a new technology, do you jump straight to production machinery? Nope. Nothing beats a simplified model as proof of concept. And the only thing better than a good proof of concept is an amusing proof of concept. In that spirit [Eric Tsai], alias [electronichamsters], built the world’s most complicated electronic gingerbread house this Christmas, because a home-automated gingerbread house is still simpler than a home-automated home.

fya59blixaq00y3-largeYeah, there are blinky lights and it’s all controlled by his smartphone. That’s just the basics. The crux of the demo, however, is the Bluetooth-to-MQTT gateway that he built along the way. A Raspberry Pi with a BTLE radio receives local data from BTLE sensors and pushes them off to an MQTT server, where they can in principle be read from anywhere in the world. If you’ve tried to network battery-powered ESP8266 nodes, you know that battery life is the Achilles heel. Swapping over to BTLE for the radio layer makes a lot of sense.

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IoT-ify All Things: LG Has Gone Overboard

If you been following Hackaday lately, you’ve surely noticed an increased number of articles about IoT-ifying stuff. It’s a cool project to take something old (or new) and improve its connectivity, usually via WiFi, making it part of the Internet of Things. Several easy to use modules, in particular the ESP8266, are making a huge contribution to this trend. It’s satisfactory to see our homes with an ESP8266 in every light switch and outlet or to control our old stereo with our iPhone. It gives us a warm fuzzy feeling. And that’s completely fine for one’s personal projects.

But what happens when this becomes mainstream? When literally all our appliances are ‘connected’ in the near future? The implications might be a lot harder to predict than expected. The near future, it seems, starts now.

This year, at CES, LG Electronics (LG) has introduced Smart InstaView™, a refrigerator that’s powered by webOS smart platform and integrated with Amazon’s Alexa Voice Service.

… with webOS, consumers can also explore a host of WiFi-enabled features directly on the refrigerator, creating a streamlined and powerful food management system all housed directly on the front of the fridge door. Amazon’s Alexa Voice Service gives users access to an intelligent personal assistant that, in addition to searching recipes, can play music, place Prime-eligible orders from Amazon.com…

This is ‘just’ a fridge. There are other WiFi-enabled appliances by now, so what?  Apparently, during the LG press conference last Wednesday, the company marketing VP David VanderWaal said that from 2017 on, all of LG’s home appliances will feature “advanced Wi-Fi connectivity”.

Notice the word advanced, we wonder what that means? Will ‘advanced’ mean complicated? Mesh? Secure? Intelligent? Will our toaster finally break the Internet and ruin it for everyone by the end of the year? Will the other big players in the home appliances market jump in the WiFi wagon? We bet the answer is yes.

Here be dragons.

[via Ars Technica]

Light Dimmer Shows How to Steal Power from AC Line

We see a lot of traffic on the tips line with projects that cover old ground but do so in an instructive way, giving us insight into the basics of electronics. Sure, commercial versions of this IR-controlled light dimmer have been available for decades. But seeing how one works might just help you design your Next Big Thing.

Like many electronic controls, the previous version of this hack required a connection to a neutral in addition to the hot. This version of the circuit relies on passing a small current through the light bulb the dimmer controls to avoid that extra connection. This design limits application to resistive loads like incandescent bulbs. But it’s still a cool circuit, and [Muris] goes into great detail explaining how it works.

We think the neatest bit is the power supply that actually shorts itself out to turn on the load. A PIC controls a triac connected across the supply by monitoring power line zero-crossing. The PIC controls dimming by delaying the time the triac fires, which trims the peaks off of the AC waveform. The PIC is powered by a large capacitor while the triac is conducting, preventing it from resetting until the circuit can start stealing power again. Pretty clever stuff, and a nice PCB design to boot.

Given the pace of technological and cultural change, it might be that [Muris]’ dimmer is already largely obsolete since it won’t work with CFLs or LEDs. But we can see other applications for non-switched mode transformerless power supplies. And then again, we reported on [Muris]’s original dimmer back in 2009, so the basic design has staying power.