Automatic door opener

Projects General Guidance
1

Hi,
First post here. My goal is to become better in electronic/electrical since i'm a programmer in industrial automation (sounds weird but heh).

Ok so i got a Arduino Uno with a 4xRelay board connected to. I'm living in appartment and right know i'm able to unlock my building door using one of the relay as a switch withing the 2 wire that come in the building buzzer but it's king of useless right know since i don't know when to open the door. I'll do a simple code that the user will need to enter on a single button to open the door.

I want to get the signal that the buzzer gets when someone press the button downstair and use it as an input to toogle the relay to open the door. This is the part that i need guidance in, will reducing the voltage from 12 to 5 and simply hook it to the Arduino input?

What would be the simpliest solution to achieve this ?

By the way keep it as simple as you can i'm a noob in electical systems :cold_sweat:

Thank you all ! :slight_smile:

2

Hi

The circuit you're looking for is called a potential divider, or voltage divider. It consists of two resistors so is very simple to construct. Because one resistor is connected to GND this will also pull the Arduino input pin down so it reads a solid 0 in between button presses.

The resistors will be in a ratio of 3.3 : 2 so for example you could use a 330R and a 200R resulting in an input voltage on your pin of just over 4.5V which is in the safe range, and would be read as a HIGH on a 5V Arduino.

There's lots of info online - googling "potential divider" should find you more than you'll ever hope to know :slight_smile:

All the best!
Geoff

3

Thank you ! Will definitely read about it :slight_smile: