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Can a phototransistor receive light from an LED?
An LED and a phototransistor are sealed in a light-proof plastic package, so that light from the LED is received by the phototransistor. When the LED is turned on by a current supplied from an external source, the phototransistor is turned on. If the phototransistor is wired as a switch, this can turn on other devices.
Can I use LED as photodiode?
In addition to emitting light, an LED can be used as a photodiode light sensor / detector. As a photodiode, an LED is sensitive to wavelengths equal to or shorter than the predominant wavelength it emits. A green LED would be sensitive to blue light and to some green light, but not to yellow or red light.
What does a phototransistor measure?
The phototransistor is a semiconductor device that is able to sense light levels and alter the current flowing between emitter and collector according to the level of light it receives.
Can a LED detect light?
LEDs can both emit and detect light. This means an optical data link can be established with only a single LED at each end, since separate transmitting and receiving LEDs aren’t needed.
What is the principle of phototransistor?
A phototransistor is similar to a regular BJT except that the base current is produced and controlled by light instead of a voltage source. The phototransistor effectively converts light energy to an electrical signal.
What can a phototransistor be used to detect?
Infrared phototransistors are rated on the wavelengths of the infrared light so they should match up with a phototransistor that detects their specific wavelength. It can be used to detect the presence of IR signals from any electronic source in its vicinity like IR remote control or infrared burglar alarm system.
Which is the most common phototransistor circuit configuration?
The common emitter phototransistor circuit configuration is possibly the most widely used, like its more conventional straight transistor circuit. The collector is taken to the supply voltage via a collector load resistor, and the output is taken from the collector connection on the phototransistor.
How is a phototransistor used in coin counting?
Coin counters – phototransistor can be used in coin and other counting applications. A beam of light is interrupted each time a coin or other item passes a given point. The number of times the beam is interrupted equals the number of coins or objects to be counted.
What happens when infrared light falls on a phototransistor?
When infrared light falls onto the surface of the phototransistor which is made-up of infrared light-sensitive material. It responds to this infrared light and conducts. This will give the required voltage to the LED and it lights up.