How to Calculate Resistance Values for a Phototransistor Circuit?

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To calculate resistance values for a phototransistor circuit, use the formula R = (V - Vf) / I, where R is the resistor, V is the supply voltage, Vf is the LED voltage drop, and I is the LED current. The necessary values for Vf and I can be found in the provided datasheet. Selecting the correct resistor is crucial to limit the current to the desired level. This approach ensures the circuit operates safely and effectively. Proper calculations will enhance the performance of the phototransistor circuit.
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I need help to calculate the resistance values for the attached circuit diagram. I have also attached the data sheets. Can you help me.
 

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hi there yaasir
welcome to PF :)

for the IR LED (or any LED for that matter), choose a resistor that will limit the current (I) to a chosen value at an assumed Vf. And we have both of these.

R = (V - Vf) / I

R = the resistor
V = The supply voltage
Vf = the LED voltage drop
I = the LED current

Vf and I can be obtained from the datasheet you posted

see how you go :)

Dave
 

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