Introduction: Car Seat Belt Reminder

Often I find that my wife get into our car and don't wear seat belt. I had to remind her to do so every time she steps in. Some time even I forget to tell her and once I was ticked because she was not wearing that. My car has a indicator LED in dashboard that tell if driver is not wearing a seat belt. There is no audio warning for not wearing seat belt. I thought of making a system that speaks and remind to wear seat belt if driver and/or pillion is not wearing seat belt. System should be smart enough to detect if pillion is on boarded or not and then if they are wearing seat belt or not. System should continue to remind until both driver and pillion (if sitting by driver side) wear seat belt. It should remind as soon as any of driver or pillion take seat belt off. I recorded reminder message in my sons sweets voice so that my wife won't mind when reminder system remind her! So lets make it.

Step 1: Components

1. Arduino UNO

2. HC-SR04 Ultrasonic Distance Measurement Transducer Module Sensor.

3. Magnetic Reed Switch.

4. ISD1820 Sound/Voice Board Recording Playback Module with Microphone.

5. USB Powered Mini Portable Speakers for Laptop & PC

6. Connecting wires

7. Hot Melt Glue Gun

8. Soldering iron and wire


10. Some free time

Lets Start!

Step 2: Connections and Arduino Sketch

Magnetic Reed Switch:

1. I have show how to connect Magnetic reed switch from seat car seat to Arduino pin. As an example I have shown connection to only one of the seat(Driver seat to pin 12 of arduino). We need to make another similar connection for pillion seat to pin 13 of arduino.

Ultrasonic Sensor

2. Connect Arduino pin 6 to Trigger pin of ultrasonic sensor

3. Connect Arduino pin 7 to Echo pin of ultrasonic sensor

4. Connect 5 V vcc and grn to respective pin in ultrasonic sensor

ISD1820 Sound board

5. Connect 3.3 volt and Gnd to ISD1820

6. Press and hold record button and record your message into the board. After you have recorded your message release record button. You may listen to your message by pressing PLAYE button

7. Connect P-E to pin 8 of arduino

8. Connect the SPI output to portable mini USB speaker for better sound effect and power the speaker from USB hub.

I have uploaded the Arduino sketch here. Upload this sketch to arduino. you may want to update the below variable from the sketch

int footMatDistance = 40;//Distance of foor mat from sensor

This variable is used to detect if pillion is sitting on seat or not (Driver is assumed to be seated in car all the time car's electric circuit is on).

I have placed ultra sonic sensor near pillion seat (Left side of car in my country). In some countries like US pillion seat is on right side. So based on where you connect your ultrasonic sensor adjust "footMatDistance" so that the distance returned by "getDistance" is less that "footMatDistance" when pillion is sitting on seat and more that "footMatDistance" when pillion is off seat. So that you capture pillion is sitting or not correctly. You may need to do hit and trial method to reach final value of "footMatDistance".

Power up every thing and see it working. If you have any question feel free to ask me on

Hope you like it.