Living with polar bears


Well, the polar bears have begun their migration back north to the loft. It was my first experiment with an ambient device and the Christmas tree was certainly hard to ignore, especially when Jo complained the bears had gone off again! As a result, I updated the arduino sketch a bit to just briefly flash the bears off every three minutes when our energy use was high instead of turning them off completely. Still annoying apparently (kind of the point!) but the bears did manage to stay under arduino control all Christmas with only a few breaks on manual! A few observations now that the experiment is over:

  • I don’t think having a display like CurrentCost’s in the house makes a huge difference after the initial discovery phase. That’s not to say that the display is pointless: it is much easier than checking the meter, and the cost estimate is great, but after I found out what wastes the most energy, I rarely look at it. Is that the same for most people?
  • On the other hand, having a Christmas tree flashing when a lot of energy is being used is much harder to ignore! Not really an all year round solution but I’m sold on the idea of ambient devices. I hope to have a more compact one soon. It would be nice to have a simple indication near the front door as well for quick checks that everything is off before going out.
  • Energy use alone wasn’t enough information to tell whether the house was occupied or not. I had planned to leave the lights on automatic all the time, so they would turn on when we arrived home and off when we were out. A daft idea with hind sight because the fridge and central heating were enough to confuse the poor polar bears.
  • The arduino does a great job controlling Home Easy devices. I had it set up to send ‘reminders’ on a regular basis, which seems like a good way to make sure things are in the right state without any acknowledgements from the Home Easy receivers. (Also quite entertaining when the lights pop back on after someone turns them off with the normal Home Easy remote! I’m easily amused!)
  • This was the first project I ‘completed’ with the the arduino, and it was almost useful! Well, I enjoyed it at least, and it’s got me thinking more about the next project: the ambient orbs if Farnell ever ship the TLC5940 I ordered, or a wireless programmable thermostat.

Arduino Home Easy controller library


I’ve been having another look at controlling Home Easy devices recently, after some encouraging successes from other people on twitter and the Home Easy page on the Arduino wiki. There was already a class for receiving Home Easy signals but I’m plotting some techno polar bears at the moment so wanted a simple Arduino library for sending Home Easy signals.

After digging out an ancient C++ book I’ve now got working library, complete with example. I kept it very simple to start with so there are a few more bits still to add, like setting a specific controller id or sending a specific device code, but I’m quite pleased with the result. Here’s the sample for using the library…

#include <HomeEasyCtrl.h>

// This is the Home Easy controller
// This example will use a 433AM transmitter on
// pin 4 and will flash an LED on pin 13 when
// transmitting
HomeEasyCtrl easy(4,13);

// This is just a pin which has a push button
// connected, to trigger a Home Easy device
const int buttonPin = 6;

int buttonState = 0;

void setup()
{
 pinMode(buttonPin, INPUT);
}

void loop()
{
 buttonState = digitalRead(buttonPin);

 if (buttonState == LOW) {
 easy.deviceOn();    // turn on device 0
 delay(3000);        // wait 3 sec
 easy.deviceOff();   // turn it off again
 }
}

Just get in touch if you want the library.

Updated: managed to upload the library to the Arduino Home Easy wiki page.

Home Easy page on Arduino Playground


Largely thanks to @barnybug, the Home Easy Arduino hacking has been going really well. Making an LED blink is one thing, but making it blink by pressing a button the other side of the house is quite another! I’ve currently just been receiving signals, but when I’ve got the transmitter going as well, I want to do things like only relaying an on command to the socket if the current energy use isn’t too high. (Would be nice to have that working in time for Home Camp, but no promises.)

Should anyone else want to get going with some Home Easy hacking as well, I’ve created a Home Easy page on the Arduino wiki. So far it’s mostly just the sketches from Barnaby but I’m working on using interrupts instead, with the eventual aim of creating a Home Easy library for the Arduino. (There’s a Google code project for many RF protocols at once, but I just have Home Easy.)

Here’s what I have for receiving a Home Easy message with interupts so far which, with some even messier code, seems to do the trick. I would like to be able to register functions to call for specified controller/device codes, but not looked in to how that would work yet.

ISR(TIMER1_CAPT_vect) {
unsigned int pulse_width = ICR1;

if( !bit_is_set(TCCR1B ,ICES1)) { // falling edge was detected
// start over if the high pulse was out of range
if(pulse_width < min_high_width || pulse_width > max_high_width)
{
pulse_count = 0;
}
// don’t need to do anything with high pulses as long
// as they’re ok; should all be the same width
}
else { // raising edge was detected
// start over if the low pulse was out of range
if(pulse_width < min_low_width || pulse_width > max_low_width)
{
pulse_count = 0;
} else {
if(pulse_count < max_low_pulses) {
rx_wire_bits[pulse_count++] = pulse_width > bit1_low_detect ? 1 : 0;

if(pulse_count == max_low_pulses) {
message_received = receiveMsg();
pulse_count = 0;
}
}
}
}

// reset the counter
TCNT1 = 0;

// toggle bit value to trigger on the other edge
TCCR1B ^= _BV(ICES1);
}