Arduino Energy Meter Interface

I like to measure stuff. I also like to trend my energy use in the hoouse. I have been thinkin about an interface to my house's energy meter for some time, and how to read it. I also have an Arduino Uno in my drawer that i never have powered up. So this is actually my first Arduino project :-)

Here is my energy meter:

On the left side it says 1000imp/kWh. So i looked at the Infra Red LED in the metal ring using the camera of my phone:



It turns out that in the magnet cicle ther is an IR LED that emit one pulse for each Wh or 1000 pulses per kWh. Of course i must try to read these pulses and calculate the Power :-)

Inside and old ball type computer mouse i found an IR phototransistor:

The photo transistor is the black one reading the rotary encoder pulses. It is a dual device to read quaderature signals so i only need to use the middel one wich is the collector and one of the sides that is an emitter. I noticed that the middle pin of the IR transistors was connected to + on the Electrolytic capacitor and assumed it was Vcc. The other two pins went to the IC in the mouse.

I connected it up with a 5V from the Arduino on the collector and 100k pulldown on the emitter to ground. Used an old USB wire and placed the transistor on the meter:

 

Here is the schematic:

  

And the real world :)

  Then measured the emitter to ground using my prehistoric oscilloscope:

Scope is set at 1ms/div so the pulse is about 1.5ms long.

Actually it seems pretty imune to the other light sources around.. except remote controls :-o


Calculation:
The energy consumed between each blink is 1[Wh] = 3600 [J] = 3600[Ws]
The power is then P[W]= 3600[J] / t[s]


So i only need to measure the time and then calulate power.

Here is the quick and dirty Arduino sketch to measure time using timer:

I really like the Arduino platform. It really can not be easier.

Result from the in the IDEs built in serial console:

Playing with some halogen lamps and it looks good :)


Next i might try to collect the data some how.