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question of IR sensors

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Advanced Member level 4
Apr 11, 2009
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ir tx and rx schematic

I have an Infrared project that in this project must be two infrared LED (emitter/detector).when an object go between emitter and detector an speaker to sound but this sound's volume must change according to type of object (viewpoint of opacity percentage).
1-how can I distinguish emitter and collector in detector(black LED) ?
2-how must I drive detector better(pullup or pulldown) resistor connect to emitter or collector?
3-how can I convert DC output of detector to variable sound(direct with Op-Amp or with MCU) ?
I am new to electronic.
thanks for your answers.
Best Regards.

ir rx diode

can you post the picture of the ir? does it have 2 or 3 legs is one shorter than the other? use pull up resistor to collector.
to get ac you need an oscillator if you want to do it without mcu a 555 is good else you can generate a sound isng the mcu.

is this what you want?
put an ir tx and a rx the signal from the tx will reach in a diff concentration depending on the object for certain objects there will be diff sounds.
so the voltage at the rx will vary from now on will you use a mcu or not? make your choice.

by the way are you obliged to use the ir?
if not give me the application so to tell you if there are better options like ultrasonic
good luck

connecting two infrared sensors

It have 2 leg that one is shorter than other and its glass are black.
the DC output of rx change according to turbidity of object with this change I want the speaker or buzzer output an different sound .when the operator man hear the correct and higher sound press a key and then the MCU's ADC record the voltage to it's flash memory.
the rx IR must connect to the MCU only for ADC reading.

ir diode one leg longer

I want make this device to measure sludge level of my pool. If I use ultrasonic, the frequency of ultrasonic must be at range of 550-750 KHz and I can't make this frequency. but IR is easy to use(the IR must be about 950nm), I have problem with amplification of IR rx output and distinguish emitter & collector leg of rx(detector IR). I don't know why I use 555 (when I drive two IR without any additional component,in rx side if resistor with -Vcc connect to shorter leg and +Vcc connect to long leg output of shorter leg will decrease from 2.5 to 0.1 v and in reverse mode resistor with +Vcc connect to long leg and -Vcc connect to short leg and output is long leg, output increase from 2.5 to 5 v, I don't know which one is better?)and how to amplify the poor output to drive an speaker ?

how to connect infrared collector

as you are describing the ir tx is a diode the short is the cathode
what is the dc voltage using?
here are a pic of the sensor and a schematic that might be useful.

so you will use a mcu.
does it accept analog inputs?

will a design like the following work?
the voltage at the rx will change. SO you can put a comparator circuit which has a predefined level. Whenever it exceeds that level a buzzer will turn on.
so what you need is tx, rx, opamp transistor and buzzer.


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can you connect ir sensors together

yes. the pic that you attached is my IRs .I bias the tx and rx with 5v .thanks for schematic .what is the "HB analog input port" in the schematic in output of rx IR ??
is that an H-Bridge ?
the PIC16F877 MCU have internal analog to digital converter and accept analog inputs.
the output voltage of rx, in normal mode and withno external component can't run anything even buzzzer and only have voltage without current.
the schematic you sent is true but is base, what opamp and transistor is best and can drive a buzzer ??
Best Regards.

ir sensor 3 legs

right it wont.
If you will not use a mcu for accurate results I advice you to use a comparator like lm 393 0r 339 then connect the output to buzer via transistor

here is a simple schem.

**broken link removed**

just use an npn 2222 at the output and a buzzer

good luck
Do not hesitate to ask further details if needed

Pushing THe HELPED ME button is a good way to say thank you

I go to design and test your recomendations. If have problem, trouble to you again. Very Thanks sir.
good luck
Best Regards.

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