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IR Reciever VS Photo diode or photo transistor

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jeyes56

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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..
 
A photo-diode is a diode who's leakage current gradually increases with the amount of IR that hits it.
It's used by placing it reverse-biased with a series resistor to measure the leakage current through the diode.
When forward-biased, it acts like a regular diode.

A photo-transistor is simply a transistor that "turns on" when IR hits it.
It's basically a normal transistor that has it's BE diode exposed to incoming light.

An IR receiver is an IC that reacts to IR signals that are pulsed at a certain frequency.
For example, TV remotes pulse their IR emitters as a set frequency then modulate the button commands over this frequency.
The receiver reacts only to IR light pulsed as this frequency to avoid interference from steady sources of IR.
 
A photo-diode is a diode who's leakage current gradually increases with the amount of IR that hits it.
It's used by placing it reverse-biased with a series resistor to measure the leakage current through the diode.
When forward-biased, it acts like a regular diode.

A photo-transistor is simply a transistor that "turns on" when IR hits it.
It's basically a normal transistor that has it's BE diode exposed to incoming light.

An IR receiver is an IC that reacts to IR signals that are pulsed at a certain frequency.
For example, TV remotes pulse their IR emitters as a set frequency then modulate the button commands over this frequency.
The receiver reacts only to IR light pulsed as this frequency to avoid interference from steady sources of IR.

Thanks for the reply, i have some question,

does it mean that photo diode is like an LDR, but it only reacts to IR light,,?
does it also mean that a photo diode has a variable voltage drop depending on the strength of the IR light it receives?

in photo transistor, does it mean that it has a fixed voltage drop when it receives a IR signal regardless of its strength?

in IR Receiver, does it mean that it only react to IR Light with certain frequency or IR Signal?
does it also mean that we can make an "IR Receiver" using a photo transistor together with frequency filter on it?
 
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
 
Wait a minute.
An IR photo-diode and IR photo-transistor respond to IR. Ordinary photo-diodes and photo-transistors respond to IR and ordinary visible light. Some photo-diodes and photo-transistors also respond to heat.

A photo-diode can be used with a reverse bias then its capacitance is reduced which makes it switch very fast. IR causes it to leak a small current.
It can also be used with no bias when it acts like a little solar cell and produces a small voltage and small current. But it has more capacitance which slows its switching speed.

An LDR is very slow. It is used to detect light like day light or night-time.
 
thanks for your reply,

sorry for my late reply,

in some cases, can you show me how to use an IR Receiver, because im searching in google but it seems that i don't understand them very much.
 
can you show me how to use an IR Receiver, because im searching in google but it seems that i don't understand them very much.
The datasheet shows and explains all the parts inside an IR receiver IC:
 

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A photo-diode is a diode who's leakage current gradually increases with the amount of IR that hits it.
It's used by placing it reverse-biased with a series resistor to measure the leakage current through the diode.
When forward-biased, it acts like a regular diode.

A photo-transistor is simply a transistor that "turns on" when IR hits it.
It's basically a normal transistor that has it's BE diode exposed to incoming light.

An IR receiver is an IC that reacts to IR signals that are pulsed at a certain frequency.
For example, TV remotes pulse their IR emitters as a set frequency then modulate the button commands over this frequency.
The receiver reacts only to IR light pulsed as this frequency to avoid interference from steady sources of IR.

thank you, for explaining
 
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