Photoelectric sensor fast switching circuit for Micro controller input

[dhanraj_kmr]

Hi,
I have purchased a photoelectric reflective sensor for detecting moving bottles.
Input is 24 volts and type is NPN.

I have a micro controller with 3.3v operating voltage. On that input by default voltage is always 3.3V. Interrupt is triggered on falling edge of that pin.
I would like to know how to build a circuit to pull down the voltage to 0 - 3.3 volt range. And support fast switching. I just reduced the voltage alone and check on multimeter, it was switching. But when i connected with input pin of controller, its not pulling controller input pin voltage to 0V when an object is detected.

Its appreciated to have some inputs.

 

[FvM]

I just reduced the voltage alone and check on multimeter, it was switching.

How did you "reduce the voltage"?

 

[karthickb3e]

Better to use the Opto-coupler as an isolator... through the Isolator u better to take the high to low transition at ur required voltage(3.3V)

 

[dhanraj_kmr]

Hi,
We have used the opto coupler. But voltage has been reduced to 0 - 1.5V while switching. We used 12Volt as input to sensor. I can apply 12-24 volt.

So we reduced the input voltage to sensor which is 12V. So sensor directly gave 3.5V while sensing. But this behavior was not expected and not referred in sensor datasheet. But it gave 3.5V when i applied 12V input.

 

[FvM]

A NPN output as I know it is an open collector transistor, usually equipped with a parallel zener diode and a series diode to protect against polarity reversal.

It's doesn't ouput a voltage on it's own and can drive a 3.3 or 5V logic input with suitable pull-up resistor directly. In so far I don't understand what you are doing. For clarity, you may want to tell the exact sensor type.