Bicycle speed-o-meter using AT89C51
Nowadays you will see digital speedometer (odometer) in most of the bikes and scooters. They are having analog cum digital speedometer consol. In such consol speed is displayed in digits on LCD as well as by pointer. What if such kind of digital speedometer is attached to your bicycle? Won't it look nice if your bicycle speed is shown on LCD? The given project does exactly the same thing.The project given here displays bicycle speed on LCD. It uses micro controller AT89C51 and 16x2 LCD.
The speed measurement of any vehicle depends upon number of wheel rotations. Because the distance travelled is calculated in terms of number of wheel rotations. So number of wheel rotations in unit time will directly give us the speed of vehicle. Now the main thing is to count number of wheel rotations. Here I have used reed switch and a magnet to count wheel rotations. See the figure given below for the arrangement.
The bicycle wheel is mounted on wooden mounting stand using iron pipe, bolt and boll Barings. A reed switch is placed near wheel onto iron pipe as shown. One magnet is attached to one of the wheel arrows as shown. Now as the wheel rotates the magnet passes nearby reed switch. So reed switch makes contact. So, on every rotation of wheel the reed switch makes contact and if we connect supply with the switch it will generate one pulse. And we can count the pulse as number of wheel rotations.
The micro controller counts number of pulses (as number of wheel rotations) per unit time (for 1 sec) and calculates speed in km/hr. Then it displays the speed on LCD with two digits after decimal point resolution.