doubledragon
Junior Member level 3
Infra red
How to determine the resistance for IR circuit diagram? any formula?
How to determine the resistance for IR circuit diagram? any formula?
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leotim said:Your Photodiode is in wronge direction, you must reverse the diode direction.
leotim said:You want to use this circuit as a switch (Light Detector) or as an intensity meter?
Switch
In this mode, the transistor is in saturated state when there is no light and in the off state (Ic = 0) when the light is present.
Intensity meter
In this mode, the transistor never saturates and output voltage (Collector voltage) is always greater than 0 and less than VCC.
Which mode matches your needs?
leotim said:If:
VCC = 12V
I_dark = 1 nA
I_Light = 100uA
β = 200;
V_BE(ON) = 0.6V
V_CE(SAT) = 0.2
R1 = 120 kΩ
R2 = 5.6 kΩ
R3 = 1 MΩ