LDR - pull up / pull down

Other Hardware Sensors
1

Boa noite pessoal , meu nome é Emerson e sou iniciante no arduino.

Fazendo um projeto usando um ldr , vi que precisa se usar um resistor em pull up ou pull down para que o circuito funcione.

A minha duvida é: PORQUE?

eu ja entendi o porque de usar pull up e pull down em botões. Mas não me fez sentido nenhum usar junto no resistr ldr. alguem pode me ajudar?

// FOR ENGLISH SPEAKERS

Hello everybody, my name is Emerson and I'm a beginner on Arduino.

By doing a project using an ldr resistor like a ilumination sensor, I saw that you need to use a resistor in pull up or pull down for the circuit to work.

My question is: WHY?

I already understand why to use pull up and pull down on buttons. But it made no sense to me to use together in ldr. Can someone help me?

2

Pullup and pulldown do not apply in this case.

The resistor and the LDR make a voltage divider, which is used to calculate the resistance of the LDR. The LDR resistance is then an indication of the light level.

There are two ways to make the voltage divider, and the Arduino can be coded for either one. However, you must match the divider configuration to the code.

3

You may find this tutorial at adafruit helpful.