At present, the single chip photodiode based on IC is one of the best way to realize light sensor. Photodiodes are made from monocrystalline silicon. A typical sensor application component consists of a photodiode, a current amplifier and a passive low-pass filter. For end users, it is important to integrate all these devices into a small package.
Six indicators for visible light sensors.
When selecting the visible light sensor, the most important point is to understand which specification parameters are the most critical. In general, when choosing a visible light sensor, need to consider factors including spectral response inhibition, the maximum number of lux/IR, light sensitivity, integration of signal regulating function, power consumption and packaging size, and so on six important specifications. The detailed description of these 6 specifications is as follows:
1. Spectral response /IR inhibition: ambient light sensor should only be sensitive to the range of 400nm to 700nm spectrum.
2. Max lux number: most applications are 10,000 lux.
3. Light sensitivity: according to the lens category of light sensor, light attenuation can be between 25% and 50% after passing through the lens. Low light sensitivity is critical (<5 lux), and light sensors that can work within this range must be selected.
4, integration of signal conditioning functions (i.e., amplifier and ADC) : some sensors can provide a very small package, but it requires an external amplifier or passive components to obtain the desired output signal. Optical sensors with a higher degree of integration eliminate external components (ADC, amplifiers, resistors, capacitors, etc.) and have more advantages.
5. Power consumption: it is better to use nonlinear analog output or digital output for light sensors that are to be subjected to the high lux (BBB 0. 1 million lux).
Once the above important specification parameters are identified, the next question to consider is which type of output signal is helpful for the implementation of the target application.
1. The system products using ambient light sensor can provide more comfortable display quality. This is important for some applications. For example, car dashboards require a clear display in all ambient light conditions. During the day, the user needs the maximum brightness to achieve the best visibility, but the brightness is too harsh at night.
2. Light sensors have brought many benefits to portable applications. The system with light sensor can automatically detect the condition change and adjust the setting of the monitor to ensure that the display is in the best brightness, thus reducing the overall power consumption. Mobile phones, laptops, and digital cameras, for example, can extend battery life by using ambient light sensors that automatically control the brightness of the display.
3. In the use of light sensor, the incident wavelength is 520nm of visible light, and the output current is linearly varying with the light intensity, and the near-infrared is automatically attenuated, and the spectral response is close to the curve of the human eye. In LED induction lamp use, according to the environmental light intensity into electricity, gives the electric energy consumption of secondary energy saving effect, or through external resistance value adjustment visible through the valve to control the lamps and lanterns is switched on or off, achieve more intelligent environmental protection office and living environment.