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.

Continue reading “Over-engineering Ding Dong Ditch”

Sniffing pH Sensor RF Signals for Feedback Re: Your Esophagus

For about a week [Justin] had a wireless acidity level sensor in his esophagus and a pager-looking RF receiver in his pocket. So he naturally decided to use an RTL-SDR dongle to sniff the signals coming out of him. As most of our Hackaday readers know, these cheap RTL2382U-based DVB-T receivers are very handy when it comes to listening to anything between 50MHz and 1800MHz. [Justin] actually did a great job at listing all the things these receivers can be used for (aircraft traffic monitoring, weather images download, electric meter reading, pacemaker monitoring…).

After some Googling he managed to find his Bravo pH sensor user’s guide and therefore discovered its main frequency and modulation scheme (433.92MHz / ASK). [Justin] then used gqrx and Audacity to manually decode the packets before writing a browser-based tool which uses an audio file. Finally, a few additional hours of thinking allowed him to extract his dear esophagus’ pH value.

Super Serious Garage Door Opener

Tired of cheap plastic garage door openers? [Yetifrisstlama]’s is probably the most serious garage door opener that we’ve seen. The case is an old emergency stop switch, which has plenty of space for the circuitry and features a big red button.

This build log starts with details on reverse engineering the original door opener’s protocol. It’s an amplitude-shift keying (ASK) signal that sends a 10 bit code to authenticate. The main components inside are a PIC16LF819 microcontroller, a MAX7057 ASK/FSK transmitter, and some RF circuitry needed to filter the signal. There’s a mix of through hole and surface mount components mounted on a prototyping board, requiring some crafty soldering.

[Yetifrisstlama] says that the next step is to add a power amplifier to increase the range. The code and project files are also provided for anyone interested in working with ASK. While the hack looks awesome, it might make bystanders think you’re doing something more sinister than opening a garage door.

Ask HackADay: Organization?!

Several people have been asking a similar question to,

“How do you at Hackaday keep track of and organize all your equipment?”
-[Jeff Allen] and others.

We have a variety of resources to help you keep track of your tools, equipment, parts, and supplies! Follow us after the jump for some tips for keeping your workspace clean and tidy. Continue reading “Ask HackADay: Organization?!”

Ask HackADay: Network Security Camera

Today we received the question,

“How to control a web cam via internet,
i want to use it for security reasons, always out of the house and my PC connected want to open the cam from time to time to checkout if something wrong!!”

- [Mohamed Saleh]

What a fun project we thought! And so many different ways of tackling it. Find out what we suggested to [Mohamed] after the break. Continue reading “Ask HackADay: Network Security Camera”