Introduction of photosensitive sensor and its software application

NwindyHe 2022-01-15 01:37:24

1. Definition of photosensitive sensor : Photosensitive sensor is also called photoelectric sensor , It uses photoelectric devices to convert optical signals into electrical signals ( voltage , electric current , Resistance, etc ) A kind of sensor .

2. Photosensitive resistor : It is a kind of photoelectric device made of semiconductor material, which has no polarity and is sensitive to light .

        2.1 Main parameters of photoresist :

                A Dark resistance and dark current : Generally, the resistance value of photoresist when it is not irradiated by light is called dark resistance , The current flowing at this time is called dark current .

                B Bright resistance and bright current : Generally, the resistance value of photoresist when exposed to light is called bright resistance , The current flowing at this time is called bright current , The difference between the bright current and the dark current is called photocurrent .

        2.2 The main characteristics of bright resistance :

                A Volt ampere characteristics : Under certain light intensity , The voltage applied at both ends of the photoresist is positive to the current , The resistance value is only related to the incident light intensity of irradiation , It has nothing to do with adding current or voltage at both ends .

                B Spectral characteristics : Photoresistors are sensitive to light of different wavelengths , Its sensitivity is different , That is, the same photoresist has different frequency response to incident light of different wavelengths .

                C Temperature characteristics : The photoresist is greatly affected by temperature , When the temperature rises , His dark resistance and sensitivity decreased .

        2.3 Working principle of photoresist : The photoresist is connected in series into the circuit , Add appropriate voltage at both ends , When there is no light , The resistance is infinite , Proximity circuit breaker , When there is light, the resistance decreases , Current increase , Sufficient light intensity is equivalent to short circuit .

3. Photodiodes , The principle of photosensitive triode is similar : There is light conduction , There is no light .     

4. Simple application :

        4.1ADC Relationship with actual voltage value :

                A First determine ADC Use several digits to express , What is the maximum value . For example, a 8 Bit ADC, The maximum is 0xFF, Namely 255.

                B Then determine the reference voltage value corresponding to the maximum value . Generally speaking, the maximum value corresponds to 3.3V.

                C To calculate the voltage , Just take your ADC Divide the value by the maximum value just determined and multiply by the reference voltage value , for example

ADC The value is 0x80, The actual value is 0x80/(0xFF+1)*3.3V = 1.65V.

        4.2 Software reading : Judge directly in the software ADC Value read , for example ADC The maximum is 4000, Can be ADC Divide 400, Equal scale down to 0~10, stay 10 When reading ADC The maximum means that the greater the partial voltage at both ends of the photodiode , The darker the luminosity , Different gears can be classified between different ratios .

        


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