Hello.Could be possible to use a lcd screen 16x2 to display voltage i/o from a circuit.It has a pot 4.7k?.The purpose is to reduce voltage in (12V) to adjustable value with pot(aprox.0v to 5v).
Thank you very much.
Yes, this seems possible. What have you done already? What specific help are you asking for?
Hello,thank you for your quick answer.What i am trying to do is to connect a photoelectric sensor(NPN - PNP outputs)Page Not Found | Pepperl+Fuchs with 12V i/o to Arduino Uno r3 but I need to reduce voltage from sensor(12V) to 0 - 5V(Analog or Digital Pin in Arduino).The final purpose is to get a counter when the sensor detect differences between High and Low.
Thanks.
Yes. You need to use two resistors connected in series, as a potential divider. If you Google that, you'll find lots of information.
In this case, you will need to connect 0V of the sensor (pin 3) to 0V of your Arduino. Next, conect a 1k resistor between 0V and the Arduino input you want to activate. By Ohm's Law, to get 5V across this resistor you will need 5mA to flow through it, (V = IR, so I = V/R = 5V/1000ohms = 0.005A = 5mA).
Next, connect a 1k5 resistor from the sensor output (pin 2 if you want the signal to go high when the beam is interrupted) to the Arduino input, where the 1k resistor is connected.
Now you have a series total of 2k5 (2500ohms) from the output to 0V. If you operate the sensor at 12V, you will have 12V at the sensor output pin 2 when the beam is interrupted. By Ohm's Law, (V = IR), you can find the current by solving for I, which gives I = V/R = 12V / 2500ohms = 0.0048A = 4.8mA. This is very close to the 5A we are looking for.
To check, we again use Ohm's Law to see that the voltage across the 1k resistor, which is the voltage at the Arduino input, is V = IR = 0.0048A * 1000ohms = 4.8V. The Arduino will see any voltage above 3.5V as a High signal, and anything less than 1V as a Low signal.
I hope this help you. 
Thanks for your answer.I have a potentiometer(4k7) and i would like to use it like a resistance and two 10k resistance,¿could be possible to use this pot to adjust v out(0-5v)?.
Yes, it is.
Replace the 1k resistor with the 4k7 potentiometer, leaving one end not connected. Replace the 1k5 resistor with the two 10k resistors, connected in parallel to give 5k.
Now, before you connect to the Arduino input, use a multimeter to measure the sensor output voltage and make sure it gives about 12V. Now measure the voltage across the potentiometer and adjust it until the voltage is about 4.5V. Now you can connect the 4.5V signal to the Arduino and test it.
With your information could practically finish the project.Now fighting with the code.
Thank you very much.