[Dimitris] decided to build a homemade alarm system, but instead of triggering a siren, sending an SMS message, or Tweeting about an intrusion, he preferred that his system call him when there was trouble afoot. He says that he preferred a call over text messaging because there are no charges associated with the call if the recipient does not pick up the line, which is not the case with SMS.
The system is based around an off the shelf motion detector that was hacked to work with an old mobile phone. The motion detector originally triggered a siren, but he stripped out the speaker and wired it to a bare bones Arduino board he constructed. The Arduino was in turn connected to the serial port of an unused Ericssson T10s mobile phone. This allows the Arduino to call his mobile phone whenever the motion detector senses movement.
The system looks to be quite useful, and while [Dimitris] didn’t include all of the code he used, he says others should be able to replicate his work without too much trouble.
Open Electronics just released a neat little board that can place you on a map without using GPS.
The board works on the basic principles of a cellphone network – the ‘cell’ network is a series of towers that are placed more or less equidistant to each other. Save for the most desolate parts of the country, a cell tower usually communicates with a phone one or two miles away. Usually, several cell towers can be seen, so the position of a cellphone can be pinpointed to within 200-350 feet. Translating cell towers to latitude and longitude is easily done by querying a Google database that was created for the mobile version of Google Maps.
The board itself is a PIC18 microcontroller and a SIM900 GSM module. The firmware available at Open Electronics is pretty impressive – all communication to the board is handled through SMS and the phone can report it’s location to 8 other phones.
It’s pretty impressive to think the same technology that caught [Kevin Mitnick] is now available to the masses. We’re wondering what Hack a Day readers would use this for, so if you have an idea leave a comment.
This deathstar like ball is actually an autonomous surveillance camera. [Basil] wrote in to tell us about it. The body is custom designed for the project, then 3d printed. It can be dropped anywhere, as it is battery powered for up to a month, and communicates via cellar networks. It checks an email folder once an hour and responds to any requests with a snapshot of what is going on. In the video, which you can see after the break, he gets an immediate response. You can download the sourcecode as well as the files for the enclosure here.
If you wanted to reduce costs, that case could be done away with, but we suspect it helps with some moderate weather conditioning. We would also love to see a version that rotated around that equator on command for better pictures. Great job [Basil].
Continue reading “Send email, receive surveilance picture”
Here’s the scenario: you’re going to be traveling somewhere and you’ll be charged roaming fees if you use your cellphone. But there is free WiFi available in this place. You can save yourself money by leaving your SIM card at home and using a GSM-to-Skype bridge to take calls on your phone via WiFi.
[Trax] is using a USB GSM modem to take cellphone calls on a PC. He leaves his sim card in this modem so that it can make and receive calls and text messages through your normal telephone number. For some reason, the USB connection only provides control of this modem and doesn’t pass bi-directional audio. To make this happen, he built an audio interface cable using two transformers and a few passive components to connect the modem to the computer’s audio card.
On the software side of things, an application written in Delphi 7 manages the modem, the audio stream, and the Skype application. When a call is incoming it sets up a Skype connection with your handset via the Internet, passing along the caller ID data in the process. If you choose to answer the Skype session the application will pick up the GSM call and you’ll be connected. It works the same way when placing an outgoing call.
This seems easier to manage than a rig that physically pushes a cellphone’s buttons via the Internet.
[jayesh] wasn’t actually trying to solve any clever problems when we built his homebrew GPS tracker. He just had the hacker mentality and wanted to build something fun and useful while geeking out with electronics and software.
On the hardware side, he started with an Arduino, then added a GPS module for location detection and a GMS/GPRS module for the data uplink to his server over AT&T’s network. The Arduino uses several libraries and plenty of custom code. On the server, he worked up some wizardry with open-source packages and the Google Maps API. All of the source code and hardware details are well-documented. Put together, it’s a GPS tracker that can update a map in real-time. Sure, there are commercial products that do roughly the same thing, but where’s the fun in that? The principles here can also be put to good use in other microcontroller-based projects.
People love putting their Arduinos in interesting and remote places. while it may be possible, it may not be practical to run out and collect data from the devices. That is where this GSM / GPRS shield comes in handy.
Based around the SIMCom SIM900 that puts this device on the lower end of the price scale, (49 Euro for the module, ~60 Euro for the module mounted on a breakout board, or around 85 greenbacks) makes this module an interesting target for anyone wanting to add cell phone connectivity to a project.
To take this a step further [Boris] whipped up a nice shield PCB for the Arduino and Arduino like footprint users to make connections between the 900’s breakout board and the Arduino layout a snap. Electrically its just wires, and a LM317.
If you use the Google Maps Mobile function then the big G knows where you are even if your phone doesn’t have a GPS module in it. So the next time you want geolocation capabilities in a project consider building around GSM functionality which can also be used for Internet connectivity. That’s exactly what this module does and luckily the hard work has already been done for you.
The method really hinges on a couple of things. First of all, any GSM capable device knows the information about the cell it is currently communicating with. Secondly, Google knows the coordinates of radio towers used in the cellular mobile network. A little bit of data sniffing on Google Maps Mobile app communications confirms how and when cell information is transferred between the device and the maps server. Take a look at this series of write-ups which go into detail about hardware, software, cell network location data, and communication protocols which Google hasn’t publicly documented. Sure you’re not going to have the accuracy we’ve come to enjoy with GPS, but this can get you pretty close.