Month: July 2009

RFID shield for the Arduino

I at long last soldered the Arduino RFIDshield yesterday – and must admit that I am having a few problems, where it (very) occasionally recognises the supplied tag (and The Students Oyster card) – but most of the time it just sits there scanning with no results.

So I did a search – and have found others with the same problem :

Last week I ordered a RFID shield for Arduino via Marc Boon (who also organizes regular workshops on RFID here in the Netherlands). Friday evening I soldered it together, using the easy to follow instructions Marc sent with the kit.

The ready RFID shield mounted on to the Arduino.

Currently I am troubleshooting the RFIDuino. It seems to start up all right, as it nicely announces itself when connected to the serial monitor in the Arduino software. Green LED lights up as well, meaning it is scanning for RFID tags in the neighbourhood. However it does not see any, when I put a RFID tag on the antenna. Perhaps something wrong with the antenna. Or it may be a power issue (USB port not delivering enough power to the board), however that seems unlikely because the active part of the RFIDuino is working fine.

[From RFID Shield For Arduino – Interdependent Things ]

Arduino PWM

PWM (Pulse Width Modulation) is extremely easy to use on the Arduino – bit to use it there are some fundamentals you need to know – and the article pointed to below is a very good and thorough introduction to PWM on the Ardunio :

Secrets of Arduino PWM
Pulse-width modulation (PWM) can be implemented on the Arduino in several ways. This article explains simple PWM techniques, as well as how to use the PWM registers directly for more control over the duty cycle and frequency. This article focuses on the Arduino Diecimila and Duemilanove models, which use the ATmega168 or ATmega328.
If you’re unfamiliar with Pulse Width Modulation, see the tutorial. Briefly, a PWM signal is a digital square wave, where the frequency is constant, but that fraction of the time the signal is on (the duty cycle) can be varied between 0 and 100%.

PWM has several uses:

Dimming an LED
Providing an analog output; if the digital output is filtered, it will provide an analog voltage between 0% and 100% .
Generating audio signals.
Providing variable speed control for motors.
Generating a modulated signal, for example to drive an infrared LED for a remote control.

[From Arc Language Blog: Secrets of Arduino PWM]

Skype Apparently Threatens Russian National Security

Hm! Maybe this should be seen as a endorsment of SKype’s increased security over normal phone lines?

Mr.Bananas writes “Reuters reports that ‘Russia’s most powerful business lobby moved to clamp down on Skype and its peers this week, telling lawmakers that the Internet phone services are a threat to Russian businesses and to national security.’ The lobby, closely associated with Putin’s political party, cites concerns of ‘a likely and uncontrolled fall in profits for the core telecom operators,’ as well as a fear that law enforcement agencies have thus far been unable to listen in on Skype conversations due to its 256-bit encryption.”

Read more of this story at Slashdot.

[From Skype Apparently Threatens Russian National Security]

Ardunio Germination Station

A “greenhouse” controlled by a Arduino!

Germination Station Part I
I have been working on this project all spring, and I am finally getting around to posting about it. Unfortunately, it did not turn out to be as successful as I would have liked it to be. A couple of years ago, I created a PID controller that controlled the soil temperature of a Biodome. Now that we own a home, I was hoping to be able to add a bunch of other variables. The variables were the following: soil temperature, air temperature, light, and moisture. I also wanted to have Xbee units to relay the information back to a Webserver so that I could view the system’s status from the web.

[From Jerd King: Germination Station Part I]

Drupal Cache module errata

I have played around the the Drupal Cache module – and could not even get it started with the default (simplest comfiguration when used according to the documentation.

The original states:

Installation
1. Enable “Cache” (from “Cache” package) module on
Admininster -> Site building -> Modules page.

2. SETUP WEB-SITE’S settings.php CONFIGURATION FILE

Add the following lines to your settings.php:

    $conf[‘cache_inc’] = ‘./sites/all/modules/cache/cache.inc’;
    $conf[‘cache_settings’] = array(
      ‘engines’ => array(
        db-engine => array(
          ‘engine’ => ‘database’,
        ),
      ),
      ‘schemas’ => array(
        ‘db-schema’ => array(
          ‘db-engine’,
        )
      ),
      ‘bins’ => array(
        ‘default’ => ‘db-schema’,
      ),
    );
?>
“default” is for the default caching schema. All valid cache bins (tables)
can be added in addition, but you must have a “default” if you skip any bins.

[From Cache | drupal.org]

But it would not work until I started going through the source, and found that the default had to be :

   $conf[‘cache_settings’] = array(

   ‘engines’ => array(

   ‘database-engine’ => array(

   ‘engine’ => ‘database’,

   ),

   ),

   ‘schemas’ => array(

   ‘database-schema’ => array(

   ‘database-engine’,

   )

   ),

   ‘bins’ => array(

   ‘default’ => ‘database-schema’,

   ),

   );

Gas meter to Arduino

I will try this out at some stage, I really want to automatically record our gas usage vs. time :

Gas meter to CurrentCost to Arduino to Pachube up and running
Filed under: Arduino — john @ 7:35 pm
Built to circuit and connected it all up. Bluetacked reed switch to meter and board + cc dev board + 2 AA batteries into small container.

[From Gas meter to CurrentCost to Arduino to Pachube up and running « John’s Blog]