An LDR module (Light Dependent Resistor module) is a device that uses a Light Dependent Resistor (LDR) sensor to measure the ambient light level. LDR is a type of resistor whose resistance changes depending on the amount of light that it receives.
An LDR module typically includes an LDR sensor and an amplifier circuit to amplify the weak signals generated by the LDR. The module also includes a voltage divider circuit, which is used to convert the change in resistance of the LDR into a change in voltage that can be read by a microcontroller or other electronic device.
The LDR module can be used in a variety of applications, such as light level sensing, brightness control, and daylight harvesting. They are commonly used in street lighting, security systems, lighting control systems, and other applications that require measurement of light level.
The LDR module can be interfaced with a microcontroller using an analog or digital input, and it can be connected to a power supply. Some LDR modules come with a potentiometer which can be used to adjust the sensitivity of the module.
It's important to note that LDRs are sensitive to the wavelength of light and thus have a spectral response that is not flat across the visible spectrum, which can affect the accuracy of the light level measurement. Also, LDRs have a low sensitivity to light and thus, require a pre-amplifier circuit to boost the signal generated by the LDR.