Over-engineering Ding Dong Ditch

One day, [Samy]’s best friend [Matt] mentioned he had a wireless doorbell. Astonishing. Even more amazing is the fact that anyone can buy a software defined radio for $20, a small radio module from eBay for $4, and a GSM breakout board for $40. Connect these pieces together, and you have a device that can ring [Matt]’s doorbell from anywhere on the planet. Yes, it’s the ultimate over-engineered ding dong ditch, and a great example of how far you can take practical jokes if you know which end of a soldering iron to pick up.

Simply knowing [Matt] has a wireless doorbell is not enough; [Samy] needed to know the frequency, the modulation scheme, and what the doorbell was sending. Some of this information can be found by looking up the FCC ID, but [Samy] found a better way. When [Matt] was out of his house, [Samy] simply rang the doorbell a bunch of times while looking at the waterfall plot with an RTL-SDR TV tuner. There are a few common frequencies tiny, cheap remote controls will commonly use – 315 MHz, 433 MHz, and 900 MHz. Eventually, [Samy] found the frequency the doorbell was transmitting at – 433.8 MHz.

After capturing the radio signal from the doorbell, [Samy] looked at the audio waveform in Audacity. It looked like this doorbell used On-Off Keying, or just turning the radio on for a binary ‘1’ and off for a binary ‘0’. In Audacity, everything the doorbell transmits becomes crystal clear, and with a $4 434 MHz transmitter from SparkFun, [Samy] can replicate the output of the doorbell.

For the rest of the build, [Samy] is using a mini GSM cellular breakout board from Adafruit. This module listens for any text message containing the word ‘doorbell’ and sends a signal to an Arduino. The Arduino then sends out the doorbell code with the transmitter. It’s evil, and extraordinarily over-engineered.

Right now, the ding dong ditch project is set up somewhere across the street from [Matt]’s house. The device reportedly works great, and hopefully hasn’t been abused too much. Video below.

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RasPiCommPlus, An Expansion Board For Expansion Boards

The easiest way to connect a GSM module to a Raspberry Pi would be to buy a breakout module, install some software, and connect to a mobile network with a Pi. Need GPS, too? That’s a whole other module, with different software. The guys behind RasPiCommPlus are working on a better solution – a breakout board for breakout boards that takes care of plugging a ton of modules into a Pi and sorts out the kernel drivers to make interfacing with these modules easy.

Right now, the team has a GPS and GSM module, digital in and out modules, an analog input module, and RS-232 and -485 modules. They’re working on some cool additions to the lineup, including a breakout for Sharp memory displays, a 9-axis IMU, a stepper motor driver, and a 1-wire breakout module.

Some of the RasPiCommPlus team showed up to the Hackaday Munich party and were kind enough to sit down for a demo video. You can check that out below.

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Arduino-Powered Alarm System Has All The Bells And Whistles

Put aside all of the projects that use an Arduino to blink a few LEDs or drive one servo motor. [IngGaro]’s latest project uses the full range of features available in this versatile microcontroller and has turned an Arduino Mega into a fully-functional home alarm system.

The alarm can read RFID cards for activation and control of the device. It communicates with the front panel via an I2C bus, and it can control the opening and closing of windows or blinds. There is also an integrated GSM antenna for communicating any emergencies over the cell network. The device also keeps track of temperature and humidity.

The entire system can be controlled via a web interface. The Arduino serves a web page that allows the user full control over the alarm. With all of that, it’s hard to think of any more functionality to get out of this tiny microcontroller, unless you wanted to add a frickin’ laser to REALLY trip up the burglars!

A GSM Base Station With Software Defined Radio

gsmIf you’re wondering how to get a better signal on your cellphone, or just want to set up your own private cell network, this one is for you. It’s a GSM base station made with a BeagleBone Black and a not too expensive software defined radio board.

The key component of this build is obviously the software defined radio. [Julian] is using a USRP B200 radio for this project. It’s not cheap, but it is a very nice piece of hardware capable of doing just about anything with GNU Radio. This board is controlled by a BeagleBone Black, a pretty cheap solution that puts the total cost of the hardware somewhere around $750.

The software side of the build is mostly handled by OpenBTS, the open source project for the software part of a cell station. This controls the transceiver, makes calls and SMS, and all the backend stuff every other cell station does. OpenBTS also includes support for Asterisk, the software of choice for PBX and VoIP setups. Running this allows you to make calls and send texts with your SDR-equipped, Internet-enabled BeagleBone Black anywhere on the planet.

Open your Hackerspace Door with a Phone Call

elabHackerspaceDoor

[Mário] sent us a tip detailing the access control system he and his friends built for the eLab Hackerspace in Faro, Portugal. The space is located in the University of Algarve’s Institute of Engineering, which meant the group couldn’t exactly bore some holes through campus property and needed a clever solution to provide 24/7 access to members.

[Mário] quickly ruled out more advanced Bluetooth or NFC options, because he didn’t want to leave out members who did not have a smartphone. Instead, after rummaging around in some junk boxes, the gang settled on hacking an old Siemens C55 phone to serve as a GSM modem and to receive calls from members. The incoming numbers are then compared against a list on the EEPROM of an attached PIC16F88 microcontroller, which directs a motor salvaged from a tobacco vending machine to open the push bar on the front door. They had to set up the motor to move an arm in a motion similar to that of a piston, thus providing the right leverage to both unlock and reset the bar’s position.

Check out [Mário’s] blog for more details and information on how they upload a log of callers to Google spreadsheets, and stick around for a quick video demonstration below. If you’d prefer a more step by step guide to the build, head over to the accompanying Instructables page. Just be careful if you try to reproduce this hack with the Arduino GSM shield.

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Arduino-based temp control via SMS

smsTempController

As connected as we are, reliable and affordable internet is still a luxury in the far reaches. [kohleick’s] country home is not just remote; with temperatures dropping to -30C in the winter, it’s practically Arctic. His solution for controlling the thermostat from afar was to take advantage of the GSM network and implement a SMS-based heater controller. The unit typically operates in “antifreeze mode,” but sending a simple text message prior to visiting causes the heater to kick it up to a more comfortable setting for your arrival. Daily logs report the system’s status, and an alert will trigger when temperatures fall below a set limit, thus indicating potential faults with the heater.

The build uses a Freeduino paired with an external GSM modem for communication and an LCD to display current status and menus, which users access via three buttons on the side of the picture frame. [kohleick] connected two temperature sensors: one directly to the Freeduino’s shield and a second outside the house. After the temperature sensors detect deviance from the set point, or upon SMS instruction, the Freeduino will crank up the heat through a 5V relay attached to the home’s boiler. Head over to the Instructables page linked above for a bill of materials, schematics, and the code. The Siemens GSM modem in this build is nothing to worry about, but be careful if you try to reproduce this project with an Arduino GSM shield, or your house might really heat up.

Safety warning: Arduino GSM shield may cause fires

Be careful with those Arduino GSM cards. As [James] reports, they may turn into fire starters. One person has reported a small explosion and fire already on the Arduino forums.
Now before we go any further – You may be asking yourself who the heck [James] is, and what gives him the ability to second guess the Arduino team. Well, here is [James’] blog disclaimer:  “James is a Senior Technical Expert for Technology and Applications at KEMET Electronics, a capacitor manufacturer. The content of this post are his and in no way reflects opinions of his employer.”

Senior Technical Expert?  That’s a good enough reason for us to believe him.

[James] states the problem is a tantalum capacitor used to decouple the GSM radio power supply from the main Arduino supply.
Tantalum capacitors are great for their low ESR properties. However, they have a well known downside of getting very hot, or even exploding when stressed. It’s not the Tantalum Anode that is burning. The Manganese Dioxide used as a cathode in some Tantalum capacitors is the culprit. Continue reading “Safety warning: Arduino GSM shield may cause fires”