Hall Effect Sensor Test

I purchased five Hall Effect sensors (3144) and was able to test their operation by connecting an LED to the "output" pin...only the output actually goes low when in the presence of a magnet.  This means you connect the LED cathode to the output.  When I held a fridge magnet close to the sensor, in the proper orientation, the LED illuminated.  Simple test!

Servos and Interrupts

I got my daily fix of eBay parts in the mail so I hooked up my shiny new limit switch to D2 and attached a CHANGE interrupt to it.  The interrupt stopped a servo that was running Sweep.

#include  
 
Servo myservo;  // create servo object to control a servo 
                // a maximum of eight servo objects can be created 
 
int pos = 0;    // variable to store the servo position 
volatile int state = LOW;
 
void setup() 
{ 
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object
  attachInterrupt(0, pressed, CHANGE); 
} 
 
 
void loop() 
{ 
  for(pos = 0; pos < 180; pos += 1)  // goes from 0 degrees to 180 degrees 
  {                                  // in steps of 1 degree 
    myservo.write(pos);              // tell servo to go to position in variable 'pos' 
    delay(15);                       // waits 15ms for the servo to reach the position 
    while(state == HIGH) {
      delay(15);
    }
  } 
  for(pos = 180; pos>=1; pos-=1)     // goes from 180 degrees to 0 degrees 
  {                                
    myservo.write(pos);              // tell servo to go to position in variable 'pos' 
    delay(15);                       // waits 15ms for the servo to reach the position 
    while(state == HIGH) {
      delay(15);
    }
  } 
}

void pressed()
{
  state = !state;
}

Added PiR and MQ-2 to the Arduino

Last night we did some more component testing.  First up, testing the DS18B20 with 20' of Cat-5 cable to see if remote communications would be a problem.  Sensor "Tom" performed flawlessly.  After that I connected up the MQ-2 and watched it stabilize after a couple of minutes of heating.  I do wonder how much current draw it has.  Finally we experimented with a passive IR motion sensor and it was able to spot us moving 20' away!

Connecting Arduino Uno to Bluemix via MQTT

After some fits and starts, I was finally able to get my new Ethernet shield connected to the IBM Quickstart by using one of big blue's receipes.  I'm not sure why my Netgear router wouldn't work, but once I switch to my ISP's router, I was able to get on the network.

MQTT and the Big Blue IoT

I'm grateful to IBM for advertising on Google in the MQTT search results.  If they didn't, it might have taken far longer for me to discover their Bluemix offerings.  Following an IBM tut on getting an Arduino talking MQTT to their service.  So far I've only had time to setup the local Mosquito MQTT broker running.  Tomorrow, I hope to get my new Ethernet shield onto the network and providing temperature readings to the Bluemix service.

DS18B20 and The Internet of Things (IoT)

Step 1 of 98 was completed tonight.  I successfully communicated with 3 1-wire DS18B20 temperature sensors thanks to a great tutorial on Hacktronics.com.  Also, I think I finally understand the "pull-up resistor" concept, and with the Ohms law I learned earlier this week, I might even be able to calculate the current flowing (V/R = I ) to the 1-wire bus.

I can't wait for the Ethernet shield to get here so I can start working on the next phase of the Arduino project...connecting the house sensors to the Interwebs.

Working through the Make book

Tonight we attempted a couple of the primitive circuits in the Make: Electronics Learning Through Discovery book.  It was a little silly of us to try to make our own 6v power supply by taping 4AA batteries together then taping the solder onto the poles to create 6v of electrical potential.  It did work if you held it just right, but that was a pain.

The experiment involved measuring the amount of current flowing through the circuit while adjusting a potentiometer.  This was a demonstration of the Ohms Law that we learned about last night in a funny Make video.

This is a fun new hobby.