This example uses an LM358 dual-operational amplifier IC. Here’s a circuit diagram that can be switched as the light and dark sensor… Regardless of which way the voltage divider network is paired with the OP-AMP, the output logic can be used to make light or the dark sensor. The reference voltage can be adjusted using a pot or variable resistance. If it’s light, the output voltage from the LDR network will be greater than the reference voltage and the output of the OPAMP will be LOW.If it’s dark, the output voltage from the LDR network will be lower than the reference voltage and the output of OPAMP will be HIGH.Apply the reference voltage to the non-inverting input. Next, try connecting the output of the LDR-resistor voltage divider to the inverting input of an OPAMP. If it’s light, the output voltage from the LDR network will be greater than the reference voltage and the output of the OPAMP will be HIGH.If it’s dark, the output voltage from the LDR network will be lower than the reference voltage, and the output of OPAMP will be LOW.Apply the reference voltage to the inverting input. First, connect the output of the LDR-resistor voltage divider to the non-inverting input of an OPAMP. The voltage divider can be paired with an operational amplifier to design the ideal light or dark sensor. The output from the voltage divider network is analog. As a result, a higher voltage will be obtained at the output of the voltage divider. There will be much less of a voltage drop in the LDR in the light because of its drop resistance in the light. As a result, a low voltage will be obtained at the output of the voltage divider. There will be a high voltage drop in the LDR because of its high resistance to the dark.An LDR can typically gauge the light or dark because of its specially tuned spectral response.Ī light or dark sensor can be designed by using an LDR that’s connected to a voltage-divider circuit. However, this tuning to pure green light makes LDR particularly sensitive to the spectrum of light visible to human eyes. Additionally, its spectral response is tuned to a maximum of 540 nm wavelength of light. An LDR’s response to illumination has a sharp fall in resistance. Practically, light-dependent resistors (LDRs) are poor at measuring light intensity. If in the light, the sensor’s resistance drops to a few hundred ohms. If in the dark, the sensor has a high resistance - think several thousand ohms or mega ohms. It offers pure resistance although this is dependent on the ambient light. Despite a long response time, this sensor is inexpensive and useful in several applications.Ī photoresistor consists of a zigzag track of photo-sensitive semiconductors. The most common one used is a photoresistor or light-dependent resistor. Light sensors are widely used in electronic applications.
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