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.

PIC Mesh, Accessible Distributed Networking

Wireless networks have been reduced to a component, for most of us. We fit a device, maybe an ESP8266 module or similar, and as if by magic a network exists. The underlying technology has been abstracted into the firmware of the device, and we never encounter it directly. This is no bad thing, because using wireless communication without having to worry about its mechanics gives us the freedom to get on with the rest of our work.

It is however interesting once in a while to take a look at the operation of a real wireless network, and [Alex Wong], [Brian Clark], and [Raghava Kumar] have given us a project with the opportunity to do just that. Their PIC Mesh university project is a distributed wireless mesh network using 2.4GHz NRF24L01 transceiver modules and PIC32 microcontrollers. They have it configured for demonstration purposes with a home automation system at the application layer, however it could be applied to many other applications.

The real value in this project is in its comprehensive but easy to read write-up of the kind you’d expect from a university project. The front page linked above has an overview of how the mesh works, but there are also pages taking us through the hardware, the networking software layer, and the home automation application layer. If you have ever wanted to understand a simple mesh networking system, this is a good place to start.

We’ve covered quite a few mesh networks over the years, but sadly we can only link you to a few of them. We’ve had a mesh network using the Raspberry Pi, Project Byzantium’s “ad-hoc wireless mesh networking for the zombie apocalypse“, and a 1000-node Xbee network for testing purposes.

Cheap Toy Airboat Gets a Cheap R/C Upgrade

[Markus Gritsch] and his son had a fun Sunday putting together a little toy airboat from a kit. They fired it up and it occurred to [Markus] that it was pretty lame. It went forward and sometimes sideward when a stray current influenced its trajectory, but it had no will of its own.

The boat was extracted from water before it could wander off and find itself lost forever. [Markus] did a mental inventory of his hacker bench and decided this was a quickly rectified design shortcoming. He applied a cheap knock-off arduino, equally cheap nRF24L01+ chip of dubious parentage, and their equivalent hobby servo to the problem.

Some quick coding later, assisted by prior work from other RC enthusiasts, the little boat was significantly upgraded. Now the boat could be brought back to shore using any R/C controller that supported the, “Bayang,” protocol. He wouldn’t have to face the future in which he’d have to explain to his son that the boat, like treacherous helium balloons, was just gone. Video after the break.

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Hackaday Prize Entry: Shakelet

A person who is deaf can’t hear sound, but that doesn’t mean they can’t feel vibrations. For his Hackaday Prize entry, [Alex Hunt] is developing the Shakelet, a vibrating wristband for that notifies hearing impaired people about telephones, doorbells, and other sound alerts.

To tackle the difficulty of discriminating between the different sounds from different sources, [Alex’s] wants to attach little sound sensors directly to the sound emitting devices. The sensors wirelessly communicate with the wristband. If the wristband receives a trigger signal from one of the sensors, it alerts the wearer by vibrating. It also shows which device triggered the alert by flashing an RGB LED in a certain color. A first breadboard prototype of his idea confirmed the feasibility of the concept.

After solving a few minor problems with the sensitivity of the sensors, [Alex] now has a working prototype. The wristband features a pager motor and is controlled by an ATMEGA168. Two NRF24L01+ 2.4 GHz wireless transceiver modules take care of the communication. The sound sensors run on the smaller ATTiny85 and use a piezo disc as microphone. Check out the video below, where Alex demonstrates his build:

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Hackaday Prize Entry: Dtto Modular Robot

A robot to explore the unknown and automate tomorrow’s tasks and the ones after them needs to be extremely versatile. Ideally, it was capable of being any size, any shape, and any functionality, shapeless like water, flexible and smart. For his Hackaday Prize entry, [Alberto] is building such a modular, self-reconfiguring robot: Dtto.

ditto_family To achieve the highest possible reconfigurability, [Alberto’s] robot is designed to be the building block of a larger, mechanical organism. Inspired by the similar MTRAN III, individual robots feature two actuated hinges that give them flexibility and the ability to move on their own. A coupling mechanism on both ends of the robot allows the little crawlers to self-assemble in various configurations and carry out complex tasks together. They can chain together to form a snake, turn into a wheel and even become four (or more) legged walkers. With six coupling faces on each robot, that allow for connections in four orientations, virtually any topology is possible.

Each robot contains two strong servos for the hinges and three smaller ones for the coupling mechanism. Alignment magnets help the robots to index against each other before a latch locks them in place. The clever mechanism doubles as an ejector, so connections can be undone against the force of the alignment magnets. Most of the electronics, including an Arduino Nano, a Bluetooth and a NRF24L01+ module, are densely mounted inside one end of the robot, while the other end can be used to add additional features, such as a camera module, an accelerometer and more. The following video shows four Dtto robots in a snake configuration crawling through a tube.

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Hackaday Prize Entry: BLE Beacon Library

While faking BLE advertising beacons using an nRF24L01+ module is nothing new, it’s become a heck of a lot easier now that [Pranav Gulati] has written some library code and a few examples for it.

[Pranav]’s work is based on [Dmitry Grinberg]’s epic bit-banging BLE research that we featured way back in 2013. And while the advertisement channel in BLE is limited in the amount of data it can send, a $1 nRF24 module and a power-thrifty microcontroller would be great for a battery-powered device that needs to send small amount of data infrequently for a really long time.

We’re not 100% sure where [Pranav] is going to take this project. Honestly, the library looks like it’s ready to use right now. If you’ve been holding off on making your own BLE-enabled flock of birds, or even if you just want to mess around with the protocol, your life has gotten a lot easier.

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Fixing the Terrible Range of your Cheap NRF24L01+ PA/LNA Module

nRF24L01+ PA/LNA module specs look great on paper. Wireless communication up to 1000m in a small package readily available from a variety of cheap sources in China? The hard work of software connectivity already done by a variety of open source projects? Sounds great! But if you mashed BUY and are getting maybe 1% of that range, don’t worry because thanks to these clear directions, they can be fixed.

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