After years of hoping and wishing [Dave] finally took the plunge and installed solar panels on the roof of his house. He’s got twelve panels that are each rated at 240 Watts! But just having them sitting there and pumping power back to the grid isn’t enough. Understandably, he decided to add his own solar array monitor so that he could see just what those babies are bringing to the party.
The solar array has an inverter which takes the DC from the cells and converts it to mains voltage AC for use on the grid. The system includes a panel meter which you’d normally find on the supply to the house. All he needed to do is find a way to grab the data from that device. It’s an Elster meter, and offers two types of feedback: a blinking LED that corresponds to each Watt-hour passing through the meter, and an IrDA port which provides a more error-proof method of reading data. Monitoring the 1 Wh pulse is quite a popular method for keeping track of your electric meter, but if your hardware misses a pulse the data will be off. [Dave] chose to use a light sensor to monitor the IrDA output, which is encoded data. As long as you can read the protocol, which has been published by Elster, a transmission can be missed now and again without disturbing the overall power consumption data.
After seeing our communications via light post , reader [Chris] dropped this handy little link in our inbox. A very good tutorial about using infrared to enable communications between 2 pic micro controllers.
The tutorial covers all the parts you will need, physical wiring and schematics with notes detailing each section of the circuit. It then goes on into basic IR theory, and a simplified push button circuit you can make to see that it is, in fact, working. Once you get the exercise built on some breadboards, he does some software and get some results from it all.
Now in the end this little device was hitting in the neighborhood of 9600 baud, but had to be pretty darn close to each other with a direct line of sight. These are often accepted as a couple of drawbacks to IR technologies. IR, which has never really vanished, is in use on a lot of devices though. The more you know the better off you are.
Join us after the break for a quick video!
Continue reading “IR communications tutorial”
[Mario Mauerer] and friends were commissioned to build this 2m persistence of vision display (translated) for a party (in a hight-voltage lab no less). Dubbed “Display from Hell”, it uses 100 blue SMD LEDs to generate the POV images. They’re connected to an ATMega64 via shift registers. Their target speed is 600rpm for a flicker free image, which means the propeller tips are moving at 140mph. The board can be updated wirelessly via IRDA and plans for adding SD storage are in place. You have to see and HEAR this thing in the video embedded below. Continue reading “Stupidly huge POV display”