Solder In The Veins

Simple Power Loss Detector with SMS Notification

Peter — Mon, 28 Jun 2010 21:40:26 +0000

After having a few un-expected power outages this year, it got me thinking about how I could easily (and cheaply) be alerted (preferably via SMS) should one occur. With a laptop running Linux, a little bit of Python and some easily obtainable hardware and software, I come up with a simple method of doing just that. Read on for the code and set-up instructions.

What You’ll Need

A Laptop or netbook running Linux (This won’t work with a Desktop PC)
Gammu (a management application for cellular devices)
The acpi system utility.
The Python Interpreter (Version 2.6.)
The commands, time and datetime Python modules
The Python bindings for Gammu.
A GSM modem or Phone that is compatible with Gammu (in my case, I’m using a Huawei E160 HSDPA USB modem with a Prepaid SIM card on the O2 network in the UK.)

Installing and Configuring the Software

Ubuntu/Debian users can install Gammu, the Gammu Python bindings and the acpi utility using the following command:

apt-get install gammu python-gammu acpi

The only configuration we’ll have to do here is to Gammu. First, determine what serial port device your GSM modem is connected to by running the dmesg command. If your using a USB dongle like me, the serial port device will be prefixed with /dev/ttyUSB

Once you’ve found the serial port device, enter the command gammu-config into the terminal to configure Gammu for use with your modem. You should be presented with something similar to the screenshot below:

gammu-config Configuration Menu Screen (Click on the image for a full-sized version.)

The only thing you need to worry about here is the Port option. Just replace the value in this option with the serial port device that corresponds to your GSM modem, then select the Save option to save the new configuration.

The Code

The Python script (pwralarm.py) which handles the job of detecting mains power outages and sending notifications can be found on the Software page. You will need to extract the script from the zip archive and configure it for your own use before it can be used. To configure the script for your own use, just set the variable mobileno at the top of the script to the Mobile/Cellular number you would like SMS notifications to be sent to by entering the number between the quotes.

Everything should now be good to go. To use the script,, make sure you have your GSM modem connected and your laptop/netbook plugged into the mains first, then type the command ./pwralarm.py to execute the script.

The script will run in an infinite loop and If the mains power source is disconnected (which is determined by the script running the acpi -a command and looking at the output) this will be detected by the script and an SMS notification message sent using the SendSMS() method of the Gammu module. To stop the script, just hold down the CTRL and C keys in the terminal you’re running the script in.

In Conclusion…

Ok, so this is a very, very, very ugly hack, but if you’re like me and you use a laptop as your main PC, which spends most of it’s time anchored to a desk and connected to the mains, you should find this useful as a way to alert you to possible power cuts or if your laptop is disconnected from the mains for any reason, for that matter (theft detection device, anyone?)

Hope it’s useful to someone. Feel free to leave any feedback in the comments or you can always get in touch with me via the Contact page on this site.

Handy Link: Bitwise Operator Video Tutorial

Peter — Mon, 21 Jun 2010 19:48:28 +0000

OK, so I haven’t posted anything here for a while but hopefully this should make up for it. Searching for a tutorial on Bitwise Operators in C brought up the little gem embedded below… Hope it’s useful.

From HPR: Python Roundtable Discussion

Peter — Thu, 11 Feb 2010 06:55:20 +0000

This may be old news to some of you but I thought it was interesting enough to warrant a blog post.

The Podcast site Hacker Public Radio has a rather interesting episode about the current and future plans for the development of Python. Hope it’s useful to someone.

Back up again!

Peter — Fri, 05 Feb 2010 12:36:58 +0000

The great hosting provider migration is finally over! Good riddence fasthosts (or should I say farsehosts) and hello Cyberhostpro!

No related posts.

From TehnikService: Quick PCB Etching

Peter — Mon, 11 Jan 2010 00:47:37 +0000

TehnikService has an interesting article about PCB etching using the “Sponge Method” This seems like a good way for beginners to get started making their own PCB’s.

Has any one tried this?

Handy Link From tehnikservice: TV EEPROM Dumps

New Development Board Offering from Protostack

Peter — Sat, 09 Jan 2010 19:03:14 +0000

Protostack has released a new and improved version of it’s 28-pin development board. It’s priced at $9.60 and includes a number of welcome changes from the one I reviewed here in a previous post.

Read on to see what’s changed….

Ok, so what’s changed? Well, have a look at the image of the board below.

Bare View of Board (No Components Soldered.) Click image to view a full sized version of this image.

One welcome revision is the clearer labelling of the positive and negative power rails. They are now labeled with the more intuitive + and – symbols for positive and negative, respectively.

Also, the 6-pin ISP connector has changed from a single 6 row arrangement to a 3×2 arrangement (as shown in Image 2, below.)

Image2: ISP 6 pin Header Revisions. Click on the image to view a full-sized version

There’s also space on this revision of the board for an integrated, voltage-regulated power supply circuit. So if you need a built-in 5v or 3.3v power supply you won’t have to mess about building one of your own and finding somewhere to attach it to the power rails! The only criticism I can think of with this feature is that there’s no space for a diode. This would offer more protection against damaging the Microcontroller (and other sensitive components) if you accidentally mixed up your positive and negative by, for example, connecting up a battery the wrong way round.

As far as connecting a power supply to the board is concerned, you have two options: either a normal 2-pin connector, or a barrel connector (which allows you to use any run-of-the-mill power adaptor as a power source) can be used in order to supply power to the board. You can see where both types of connector can be fitted to the board in images 3 and 4, below.

Image 3: Power Supply Circuit (Without Barrel Connector) Click on image for a full-sized version.

Image 4: Power Supply circuit (With Barrel Connector) Click on image for a full-sized version

Overall, this revision of the board looks a lot more beginner friendly that the one I previously reviewed here in July. The clearly marked power rails (with the familiar + and - symbols) and the integrated power supply make it one of the best prototyping boards out there for a beginner hobbyist in my opinion.

If you need more info on this development board then a datasheet and users’ guide are available from Protostack, in PDF format.

Handy Link: Programing an AVR with a Bus Pirate

Peter — Thu, 07 Jan 2010 17:12:31 +0000

The guys over at HintShop have published a tutorial on using a bus pirate as an In-Circuit Programmer to flash firmware to an AVR Microcontroller using SPI.

As if that wasn’t cool enough, they also include instructions showing how multiple Mircocontrollers can be flashed by one Bus Pirate on the same board, in their tutorial! Is there anything this little gadget can’t do?

Handy link: Arduino Ethernet Bumper Pack

Peter — Thu, 07 Jan 2010 16:24:21 +0000

Georg Kaindl, over at gkaindl.com has developed a collection of libraries for the Arduino environment which allows developers to make use of the DHCP, DNS and Bonjour (Apple Computers’ implementation of Zeroconf) protocols in their network-enabled Arduino projects. Documentation for each individual library (including installation instructions) can be found on Georg’s site.

If anyone is using these libraries in their own projects already, then feel free to share you experiences in the comments section. I’d love to hear about some of the cool stuff other people have made with them.

Handy Link From tehnikservice: TV EEPROM Dumps

Peter — Wed, 06 Jan 2010 17:42:15 +0000

Ever wondered what was contained in the EEPROM memory of your TV? Well, you may find the answer here. This page on tehnikservice.net has EEPROM dumps from a variety of TV models available for download. Hope this is useful to someone.

Handy Link: bpython

Peter — Thu, 31 Dec 2009 18:56:32 +0000

bpython is a Python interpreter interface on steroids! It’s main features are:

Syntax Highlighting
A save function (to save code you’ve entered to a file)
Auto-intending (we all know how important correct indenting is when you’re writing python scripts!)
Auto-Completion which displays suggestions for any built-in functions, helping you to get the syntax for a statement spot-on without having to dig through reference manuals. The auto-completion feature also helps with import declarations, showing you a list of available modules as you type.

Installation in Ubuntu is as painless as typing sudo apt-get install bpython Other packages are available for Debian, Fedora and OpenSUSE as well. You can also obtain the source code from here and compile it yourself if need be.

If you need any help with using bpython, then check out the project’s webpage. Hope this is useful to someone.