Reverse Engineering Wireless Temperature Probes

[bhunting] lives right up against the Rockies, and for a while he’s wanted to measure the temperature variations against the inside of his house against the temperature swings outside. The sensible way to do this would be to put a few wireless temperature-logging probes around the house, and log all that data with a computer. A temperature sensor, microcontroller, wireless module, battery, case, and miscellaneous parts meant each node in the sensor grid would cost about $10. The other day, [bhunting] came across the exact same thing in the clearance bin of Walmart – $10 for a wireless temperature sensor, and the only thing he would have to do is reverse engineer the protocol.

These wireless temperature sensors are exactly what you would expect for a cheap piece of Chinese electronics found in the clearance bin at Walmart. There’s a small radio operating at 433MHz, a temperature sensor, and a microcontroller under a blob of epoxy. The microcontroller and transmitter board in the temperature sensor were only attached by a ribbon cable, and each of the lines were labeled. After finding power and ground, [bhunting] took a scope to the wires that provided the data to the radio and took a look at it with a logic analyzer.

After a bit of work, [bhunting] was able to figure out how the temperature sensor sent data back to the base station, and with a bit of surgery to one of these base stations, he had a way to read the temperature data with an Arduino. From there, it’s just a data logging problem that’s easily solved with Excel, and [bhunting] has exactly what he originally wanted, thanks to a find in the Walmart clearance bin.

Controlling Central Heating Via Wi-Fi

If you’ve ever lived in a building with manually controlled central heating, you’ll probably understand [Martin]’s motivation for this hack. These heating systems often have old fashioned valves to control the radiator. No Nest support, no thermostat, just a knob you turn.

To solve this problem, [Martin] built a Wi-Fi enabled thermostat. This impressive build brings together a custom PCB based on the ESP8266 Wi-Fi microcontroller and a mobile-friendly web UI based on the Open Thermostat Scheduler. The project’s web server is fully self-contained on the ESP8266.

To replace that manual value, [Martin] used a thermoelectric actuator from a Swiss company called HERZ. This is driven by a relay, which is controlled by the ESP8266 microcontroller. Based on the schedule and the measured temperature, the actuator lets fluid flow through the radiator and heat the room.

As a bonus, the device supports NTP for getting the time, MQTT for publishing real-time data, and ThingSpeak for logging and graphing historic data. The source code and design files are available under a Creative Commons license.

AES-CMAC on an ATtiny85

[Blancmange] built a custom door chime using an ATtiny85. Unlike most commercial products out there, this one actually tries to be secure, using AES-CMAC for message signing.

The hardware is pretty simple, and a protoboard layout is shown in the image above. It uses the ATtiny85 for control, with an LM380N audio amplifier, and a low cost 315 MHz receiver.

The more impressive part of the build is the firmware. Using AVR assembly, [Blancmange] managed to fit everything into the 8 Kbytes of flash on the ATtiny85. This includes an implementation of AES-CMAC, an AES cypher based message authentication code. The transmitting device signs the request with a key shared between both devices, and the receiver verifies that the message is from a trusted transmitter.

Fortunately, the assembly code is very well commented. If you’ve ever wanted to take a look into some complex ASM assembly, this is a great project to check out. The source code has been released into the public domain, so the rest of us can implement crypto on this cheap microcontroller with much less effort.

Automatic Garage Door Opener Works for Your Cat

Using an Arduino or Raspberry Pi to perform a task in the real world is certainly a project we’ve seen here before, and certainly most of these projects help to make up the nebulous “Internet of Things” that’s all the rage these days. Once in a while though, a project comes along that really catches our eye, as is the case with [Jamie’s] meticulously documented automatic garage door opener.

This garage door opener uses an ATMega328 to connect the internet to the garage door. A reed switch is installed which lets the device sense the position of the door, which is relayed back to the internet. [Jamie] wrote an Android app that can open and close the door and give the user the information on the door’s status. One really interesting feature is the ability to “crack” the garage door. This is done by triggering the garage door opener twice with a delay in between. From the video after the break we’d say this is how [Jamie’s] cat gets in and out.

We love seeing projects that are extremely well documented so that anyone who wants to make one can easily figure out how. Internet-connected garage door openers have been featured in other unique ways before too, but we’ve also seen ways to automatically open blinds or chicken coops!

A Raspberry Pi Garage Door Opener

We can never seem to get enough garage door hacks around here. [Tanner’s] project is the most recent entry into this category. He’s managed to hook up a Raspberry Pi to his garage door opener. This greatly extends his range to… well anywhere with an Internet connection.

His hack is relatively simple. He started with the garage door opener remote. He removed the momentary switch that was normally used to active the door. He bridged the electrical connection to create a circuit that was always closed. This meant that as long as the remote had power, the switch would be activated. Now all [Tanner] had to do was remove the battery and hook up the power connectors to his Raspberry Pi. Since the remote works on 3.3V and draws little current, he is able to power the remote directly from the Pi. The Pi just has to turn its pin high momentarily to activate the remote.

The ability to toggle the state of your garage door from anywhere in the world also comes with paranoia. [Tanner] wanted to be able to tell if the door is up, down, or stopped somewhere in the middle while he was away from home. He also wanted to use as little equipment as possible. Since he already had an IP camera in the garage, he decided to use computer vision to do the detection.

He printed off two large, black shapes onto ordinary white computer paper. One was taped to the top of the door and one to the bottom. A custom script runs on the Pi that grabs the latest image from the camera and uses OpenCV to detect the shapes. If both shapes are visible, then the script can assume the door is closed. Otherwise, it’s likely open. This makes it easier for [Tanner] to know if the door is opened or closed without having to check the camera himself.

Can’t get enough garage door hacks? Try these on for size. Continue reading “A Raspberry Pi Garage Door Opener”

Repurposing IOT Lightbulb Chip For Anything

Home automation products have hit critical mass in the world of consumerism, and now suddenly everyone has a product you can control using some protocol or other. Cree (the maker of LEDs) has a rather cheap IOT-enabled bulb available in Canada and the US for the low price of $15 — not bad considering regular LED bulbs can run you that much, without wireless connectivity!

So if you want to outfit your house in smart lights — great. But what about other things? Well, [Mac Alpine] decided to crack open one of the bulbs to see if he could re-purpose the IOT board. Turns out, you can.

In fact it’s almost too convenient. It’s a remarkably small chip, about half the size of a silver dollar. And it features a small ZigBee radio module. All you need is a 3V power supply, and boom — you have an IOT module that is capable of PWM output. It features an Atmel ATSAMR21E microprocessor which communicates over the radio to a Quirky Wink hub — it can also be triggered using IFTTT.

Continue reading “Repurposing IOT Lightbulb Chip For Anything”

Rock Climbing Wall Installed In Garage Doubles As Storage Space

Climbing enthusiast and human spider [Swighton] just couldn’t get enough climbing crammed into his day. If he couldn’t get out to the climbing spots, why not bring the climbing spot to him? So he did that by building a climbing wall in his garage.

The process started with determining the available space that can be allocated to the project. In [Swighton]’s case he could afford an 8×12 ft section of real estate. The garage ceilings were 8 ft high. A few days were spent sketching out ideas and designs. To suit his needs, the wall had to have a 45 degree overhang section, a small 90 section (think ceiling, not wall) and a pull-up bar. Once the design was finalized, it was time to pull some sheet rock off the walls and ceiling so that the 2×4 and 2×6 climbing wall framing could be securely fastened to the current garage structure.

Three-quarter inch plywood would cover the wooden frame. Before the plywood sheets were cut to size and installed, he drilled holes every 8 inches to accept t-nuts. These t-nuts allow hand holds to be installed and easily reconfigured. The quantity of t-nuts adds up quickly, an 8 inch square spacing results in 72 t-nuts per sheet of plywood.

[Swighton] also added a hatch to allow access to the inside of the climbing wall so that space would not go to waste. It is now a storage area but may become a kids’ fort in the future. After it was all said and done the wall only cost $400 which includes $180 for the hand holds.

If you’re like [Swighton] and can’t get enough climbing action, check out this wall with light up hand holds or this interactive wall.