One of the main reasons I wanted to learn microcontrollers was that I wanted to make my own energy consumption monitor. I live in the US, and I have an Itron digital electric meter on my house. On the top of the meter is a plastic optical conduit that goes to an IR LED that flashes once for each watt-hour used. I was hoping to use an IR transistor to read the meter flashes with an MSP430, and pass the info to a host computer (probably an old junk laptop I have). Once I had the meter-reading done, I could start considering weather sensors and appliance sensors to see how they affect the electricity usage.
So, I tried wiring up an IR sensor (one side of a dual-IR phototransistor salvaged from an old ball mouse) and hooking it up as I would a switch on an input pin.
I ran a test program, aimed an old VCR remote at it, and voila! It worked! While still jazzed about this, I took the LaunchPad outside with a battery pack, and taped the IR phototransistor over where the IR flash should be… nothing. I turned on the air conditioning to be sure I was using a decent amount of energy… nothing.
I finally broke out my cell phone camera and tried to see the flashes. At first, I thought my meter didn’t flash. Then, I put the camera up close. It wouldn’t focus, but I could see the flashes (please excuse the noise from the A/C unit):
Too dim for my set-up. I need to either find a more sensitive sensor, change the circuit to amplify the signal (an o-scope would be nice!), or can this idea.
Any ideas? I would love your comments.