Hello everyone,
I'm trying to make a circuit to detect the variations in optical power from a source. I need very accurate results and the source I'm using is an array of about 36 high power LEDs. The Irradiance level (level of light power) in the area of illumination is about 700 Watts/meter squared. (That's nearly the intensity of sunlight.)
Here's what I have to do. I'm measuring the irradiance level (level of light power) of the light falling on the photodiode over an interval of 1 second. As the current output of the photodiode is proportional to light intensity, I'm hoping to pick up the variations in the output of the photodiode. To do this, I'm thinking of
1>Converting the photodiode current output to 0 to 5V voltage range.
2>Feed this voltage to a 16 bit ADC.
3>Interface the ADC with MATLAB
4>Store the readings of current in a variable in MATLAB
5>Find the minimum and maximum values in the variable and thus calculate light source instability. ((max-min)/(max+min))
I need help with step 1. I understand that photodiode current will be in microamperes range. I understand that a current to voltage conversion circuit (attached) is used for this.
I need help selecting an opamp for this circuit. As the application demands high accuracy, I need a low noise opamp with output range of 0 to 5 V so that I can feed it into a microcontroller. Can you help me by suggesting an opamp for my application? Will a regular 741 do?
Should I use a phototransistor instead of a photodiode? My light is in a spectral range of 400 to 1100 nm.
I'm trying to make a circuit to detect the variations in optical power from a source. I need very accurate results and the source I'm using is an array of about 36 high power LEDs. The Irradiance level (level of light power) in the area of illumination is about 700 Watts/meter squared. (That's nearly the intensity of sunlight.)
Here's what I have to do. I'm measuring the irradiance level (level of light power) of the light falling on the photodiode over an interval of 1 second. As the current output of the photodiode is proportional to light intensity, I'm hoping to pick up the variations in the output of the photodiode. To do this, I'm thinking of
1>Converting the photodiode current output to 0 to 5V voltage range.
2>Feed this voltage to a 16 bit ADC.
3>Interface the ADC with MATLAB
4>Store the readings of current in a variable in MATLAB
5>Find the minimum and maximum values in the variable and thus calculate light source instability. ((max-min)/(max+min))
I need help with step 1. I understand that photodiode current will be in microamperes range. I understand that a current to voltage conversion circuit (attached) is used for this.
I need help selecting an opamp for this circuit. As the application demands high accuracy, I need a low noise opamp with output range of 0 to 5 V so that I can feed it into a microcontroller. Can you help me by suggesting an opamp for my application? Will a regular 741 do?
Should I use a phototransistor instead of a photodiode? My light is in a spectral range of 400 to 1100 nm.
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