Project: Car Speed Detector Using Arduino

Car speed Detector Project

In this project I am going to show you how to measure the speed of running car (or man) from outside. Police department uses this type of system to prevent over speed of vehicles. Our project is a little different from the system used by police but the overall car speed detector concept is same.

In this project, two IR sensors are placed apart on one side of road. When any vehicle crosses the sensors, the internal timer of Arduino counts the time between activation of sensor. Now speed is measured by using simple distance time relationship.

Project Car Speed Detector Using Arduino


Both IR sensors are connected to the interrupt pin of Arduino, and they detect the falling wave. The purpose of using interrupt is that, it improves the efficiency of system. A LCD is connected to Arduino and measured speed is shown on LCD.

When car moves in front of the first sensor, it gives the output signal to Arduino, Arduino detects the falling wave, now internal timer of Arduino is started and when car moves in front of second sensor timer is stopped.

Now Arduino measures the speed of car which is measured by distance time relationship

                          Speed = Distance ÷ Time 
  • Speed: Car’s speed
  • Distance: Distance between sensors
  • Time measured by Arduino

IR Sensor:

The IR sensor includes an IR LED and a phototransistor. When an object passes between the sensors, light reflects from the object and falls on the phototransistor. An operational amplifier IC (LM358) is used and the phototransistor is connected to it. When object come in front of sensor, it sends a logical HIGH signal to Arduino.

READ  DIY Arduino Unit Converter: How to use LCD


An Arduino Nano is used as the controlling unit, You may use any other Arduino variants according to your choice.

Components Used

Component Specification Quantity
Arduino Nano 1
IR Sensor 2
LCD 16X2 1
Power Adaptor 12 Volt 1
Switch DPDT 1

Car Speed Detector Circuit

Circuit diagram is shown in the figure below. If you are going to make circuit on breadboard or general purpose PCB (or Zero PCB), the figure below is useful.

For PCB etching,

In the Arduino pins D2 and D3 are interrupt, where D2 is INT0 and D3 is INT1. Output pins of the IR sensors are connected to these pins.

Project Car Speed Detector Using Arduino schematics

LCD is connected to Arduino’s D4 to D9 pins, where D4 is connected to EN, D5 is connected to RS and D6 to D9 of Arduino are connected to D4 to D7 pin of Arduino. A preset is connected to third pin of LCD, which is contrast control. Pin 15 and 16 are used for backlight of LCD.

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