LED vs Light sensor
Usually light dependent resistors ( LDR s) and photodiodes are used as light sensors to activate or deactivate circuits based on the presence or absence of light. But a common transparent LED can also be used in the place of an LDR or a photodiode. Here is a simple circuit that uses a transparent red LED as the light sensor that switches on a white LED when the red LED is in dark. Ordinary transparent LEDs function as light emitters and light detectors. These detect a narrow band of wavelengths of light and their p-n junction forward biases to generate around 1V voltage with a minute current of 0.030mA when exposed to bright sunlight. So a transparent LED can also be used as a light sensor like a photodiode. LEDs detect a much narrower band of light having peak sensitivity at a wavelength slightly lower than the wavelength these emit. For example, a transparent red LED emits around 660nm light and responds better to orange light at 610nm. Buy Top Branded...