People use the keys every day, but sometimes, we will forget to put or take the keys while we go out or back to home. Therefore, I made an Arduino project to help us remember to take the keys. This project is very simple, the ultrasonic sensor will sensing if someone passed or not. If the ultrasonic sensed someone passed it, the liquid-crystal display (LCD 16by2 12C) will show "Please put/take the key", and the speaker will sound a warning.

Supplies

Supplies for the decoration

1. Carton (aleast 20cm x 15cm x 10cm)

2. Ruler

3. Utility knife

4. Pen (for cutting)

5. Tape (for fixing)

Supplies for the machine

1. Breadboard

2. Arduino Leonardo, Uno, etc. (x1)

2. Ultrasonic sensor (x1)

3. Liquid-crystal display 16by2 12C (x1)

4. Speaker (x1)

5. Wires (few)

6. Power bank

Step 1: Step 1: Assemble Ultrasonic Sensor

First, stick two wires from the positive and negative electrode on the breadboard to 5V and GND. Get the ultrasonic sensor and the breadboard. Stick the ultrasonic sensor on the bottom row of the breadboard, and stick four wires from VCC to the positive electrode on the breadboard; Trig to D5; Echo to D4; GND to the negative electrode on the breadboard.

Step 2: Step 2: Assemble Speaker

Second, stick the black wire(negative) of the speaker on the negative electrode on the breadboard, and stick the red wire(positive) on D7.

Step 3: Step 3: Assemble Liquid-Crystal Display

At last, get the LCD(Liquid-Crystal Display) and four Male-female plug connecting wires. Stick the wire from GND to the negative electrode on the breadboard; VCC to the positive electrode on the breadboard; SDA to the SDA on the Ardunio board; SCL to the SCL on the Ardunio board (Incorrect connection of the positive and negative poles will cause the Arduino to burn).

Step 4: Final Circuit Diagram

Step 5: Step 4: Decoration "Carton"

Get a carton, at least 20cm x 15cm x 10cm (the bigger the carton is, the more convenient you have to put the project in it). Cut a hole using the utility knife on the front of the box, the hole should be 5 x 2.5 so that the ultrasonic sensor can work successfully. Cut another hole with 7.5 x 2.5 cm. Put the LCD display in the hole and use the tape to fix it. Same as the ultrasonic sensor.

Step 6: Code and Ardublock Here

https://create.arduino.cc/editor/kerry_fan/d702bfde-e6e4-46c4-bfb0-a8e7e7fd3fd3/preview

Step 7: Completion !!!

Now, you finish an easy and useful Arduino project with the above steps, you can also make this project with your friends and family. At last, if you like this project, please share it to others, thank you.