Hello,
I have 10 LEDs with different colors: blue, red, green, orange, yellow and each LED has a different Imax: 2mA, 5mA, 10mA, etc... up to 120mA (the last one). The task is to get them at the same luminosity, by changing the current through the LED. This is the part when the photodiode comes in. I`ve searched all datasheets of the LEDs and the whole light spectrum is between 420 and 675 nm. This is why i chose this photodiode: BPW21R.
I need a circuit, that uses this photodiode and provides me a maximum of 3v3 output (the analog pins i`m using are 3v3 tollerant), but he whole circuit is powered by 5V. This is what i`ve found: https://www.circuitlab.com/circuit/g7t4a9/transimpedance-amp/ (I need a 3v3 maximum output)
So by applying 3v3 at the VCC of the OpAmp, the maximum output should be arround 3v3, right? Or... i can apply 5V to the VCC and make a voltage divider at the output to have a maximum of 3v3. The output of this circuit will be connected to an Analog Pin of a Teensy3.5 uC.
I will place the photodiode above 1 LED (it doesn`t matter which) and i will save the value i read on the pin. Then i`ll move the photodiode above the rest of the LEDs and increase/decrease the current untill i get the same value on the pin (an error of 5-7% is okay). The only problem is that this photodiode, doesn`t have the same Spectral Sensitivity vs. Wavelength. I need to measure the intensity of the light of different LEDs (red / blue / green / orange).
I know that this will need to be calibrated, but i don`t know how. If you have other ideas, involving a photodiode, feel free to post.
PS: the LEDs are separated by walls + ceiling, so the light from one LED or the ambiental light won`t affect the measurement on an other LED.
Thanks in advance!
I have 10 LEDs with different colors: blue, red, green, orange, yellow and each LED has a different Imax: 2mA, 5mA, 10mA, etc... up to 120mA (the last one). The task is to get them at the same luminosity, by changing the current through the LED. This is the part when the photodiode comes in. I`ve searched all datasheets of the LEDs and the whole light spectrum is between 420 and 675 nm. This is why i chose this photodiode: BPW21R.
I need a circuit, that uses this photodiode and provides me a maximum of 3v3 output (the analog pins i`m using are 3v3 tollerant), but he whole circuit is powered by 5V. This is what i`ve found: https://www.circuitlab.com/circuit/g7t4a9/transimpedance-amp/ (I need a 3v3 maximum output)
So by applying 3v3 at the VCC of the OpAmp, the maximum output should be arround 3v3, right? Or... i can apply 5V to the VCC and make a voltage divider at the output to have a maximum of 3v3. The output of this circuit will be connected to an Analog Pin of a Teensy3.5 uC.
I will place the photodiode above 1 LED (it doesn`t matter which) and i will save the value i read on the pin. Then i`ll move the photodiode above the rest of the LEDs and increase/decrease the current untill i get the same value on the pin (an error of 5-7% is okay). The only problem is that this photodiode, doesn`t have the same Spectral Sensitivity vs. Wavelength. I need to measure the intensity of the light of different LEDs (red / blue / green / orange).
I know that this will need to be calibrated, but i don`t know how. If you have other ideas, involving a photodiode, feel free to post.
PS: the LEDs are separated by walls + ceiling, so the light from one LED or the ambiental light won`t affect the measurement on an other LED.
Thanks in advance!