Current to voltage converter

[kam123]

Hi to all

I want to build a current to voltage converter to measure the variations of sunlight using a solar cell calculator. I've done some research on solar cell and found that the voltage generated by the solar cell does not vary linearly with increasing frequency of light, but its current does vary linearly. so i want to monitor the variation of light intensities during the day using the current generated by the solar cell. The current generated by the solar cell is of order of micro amper (200 :mu:A at noon on a sunny day)Can any one suggest me a schematic or explain to me how to proceed with it.

I have LM324 op amp available.

Thanks

 

[Nigel Goodwin]

You simply pass the current through a resistor, and measure the voltage drop across it - simple ohms law.

 

[cdstahl]

i'd use a transresistance amplifier -- basically an inverting opamp without the input resistor.

This is done to keep the solar panel voltage at 0V.

with a simple resistor, the solar panel's V-I curve comes back into play. eg, for lots of light, current would be high, but that would imply a voltage that exceeds the open-circuit voltage.

 

[Roff]

i'd use a transresistance amplifier -- basically an inverting opamp without the input resistor.

This is done to keep the solar panel voltage at 0V.

with a simple resistor, the solar panel's V-I curve comes back into play. eg, for lots of light, current would be high, but that would imply a voltage that exceeds the open-circuit voltage.

A small series resistor (100 ohms or so) might be necessary to isolate the op amp from the solar cell capacitance. Capacitance from the inverting input to ground can make the op amp oscillate.

 

[cdstahl]

yeah, maybe a cap across the feedback resistor instead / as well to give some filtering. from the "throughout the day" comment, i'm guessing this isn't going to be high bandwidth!