Self powered LED pulse counter using photovoltaic optocoupler. Possible?

[trisk3ll]

Hi there,

I'd like to count pulses from the LED on my electricity meter. Pretty easy if I had a good power supply but I want to run on a coin cell battery. The tricky bit is I can't find a photo diode with a lower enough power consumption. I'm trying to work with a budget of 10-20uA (aiming for more than a year battery life). Lowest photo-diode I can find is 800uA which isn't going to work for me.

So I had the idea to use a photovoltaic light detector instead. ie. Use a sensor that converts the LED output into a tiny DC current without draining the battery.

Is this going to be possible? Does an LED emit enough light to activate a photovoltaic cell? If I could find a photo-cell that could register a LED pulse then I'd feed those pulses into an PIC interrupt and that would be my counter.

Any pointers appreciated.

Cheers,
D.

 

[Diver300]

Forget it. Photocells will need a lot more light than that.

It's an electricity meter. How can you not have power?

 

[trisk3ll]

I don't want to pull the meter apart to get at the powered parts. So battery operation is what I have to work with.

I was afraid a photocell might take a bit more to trigger than an LED blink. Can you suggest any advance on 800uA continuous draw for monitoring blinks then?

 

[crutschow]

A photo-diode generates only a small leakage current in the nA region when dark (where did you get the 800µA value?). Do you have a way to block ambient light from the diode so that it only sees the LED light?

If so you should be able to use a photo-diode with a micropower op amp to amplify the signal.