Hi all,
im confused with IR Receiver, photo diode and photo transistor,
i know that all of this can pass a IR light,
but i don't know if what are there differences to each other?
please give me a reason when to use them..
All of those devices are photo (light) detectors. All three use different material compositions for their intended applications. We choose a detector, any detector, for its intended application.
i know that all of this can pass a IR light
The devices do not "pass" IR light. They respond in different ways to different wave lengths of light, be it in the visible or invisible light spectrum.
Since you mentioned the term IR Receiver, DemonicSandwich gave you a good description of an IR Receiver but at the heart of that is the IR Detector. IR detectors can be broken down into a few types such as thermal as used in those IR temperature detectors and photo types which respond to the IR spectrum (invisible) of light. Well invisible to us anyway. When we say IR receiver it sort of implies an IR detector bundled with other associated circuitry for example as DemonicSandwich mentioned a TV remote control. So an Infrared detector is just a detector that reacts or responds in light in the IR (Infra Red) spectrum or IR radiation.
A photo diode is actually a photovoltaic device. Think of a small solar cell. When light strikes it it produces a small photovoltaic voltage. A LED can actually do this. Take an everyday generic LED and connect your DMM to it. Connect the negative lead to the cathode and positive lead to the anode. Set the DMM to measure milli volts and shine a flashlight on the LED. You will see a voltage that increases as more light strikes the LED. The LED is acting as a photo diode. So we can say a photo diode is a type of light or photo detector capable of converting light into a voltage or current.
What if we were to take that photo diode and use it to drive a small transistor base? How about we place it all in a single small package? This would be a photo transistor. Because it is a transistor it gives us gain and in many cases plenty of gain. We have combined a photo diode with a transistor and made a photo transistor.
There is also the LDR (Light Dependent Resistor) in the family of light sensors which is simply a resistor whose resistance changes based on the light striking it.
Each of these sensors has some good and bad points. When we design a circuit that requires a light sensor we choose the sensor based on our requirements. Things like response time, and size are a few examples of the many we need to consider. There is no best or worst sensor.
Hope that helps....
Ron