Thursday 9 February 2017
Contact less IR tachometer using PIC16F628A
Tachometer is a device that gives the information about the rotational speed of any shaft or disc. It usually measures the speed in revolutions per minute (RPM).
I want it to measure the speed of motor so for this i searched the net and found various design but unfortunately they don't worked for me, don't know why?. So i decided to make my own tachometer using PIC16F628A micro-controller and LCD.
Today i am going to make a simple tachometer that could measure the rotation speed of a PC power supply fan without making any physical contact (that's why it is contact less) with the rotating object. The range of this tachometer is 0 - 9999 RPM and displays the RPM on a 16x2 LCD.
Working operation is simple; IR LED start transmitting and the receiver only receives them when they reflect back. So just count the pulses received and multiply it with 60 to get rpm. For pulse counter, i am using timer 0 in counter mode.
Receiver part is build around the receiver LED (photo diode), transistor, and resistor etc. normal condition, the photo diode offers high impedance (as usually used in reversed biased) and so the voltage across it will make the BC557 transistor in the receiver part cut off. The output Pulse will be at logic low. When there is a reflected pulse, the resistance of the photo diode will drop down and allow BC557 transistor to saturate. This gives a logic high Pulse output. The PIC 16F628A will count the pulses within the 1 sec interval to determine the RPM.
Download: The schematic and code here.
Schematics:
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| Contact less IR tachometer using PIC16F628A |
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| Snapshot of IR tachometer |
Components Required:
U1-------------------------PIC16F628A
R1-------------------------100 ohm
R2-------------------------1.7K ohm
R3-------------------------1K ohm
R4-------------------------10K ohm
D1------------------------- IR LED
D2-------------------------photo diode
D3-------------------------1N4148
Q1--------------------------BC557
Mics:
16x2 LCD
4MHz crystal
22pF ceramic capacitor (2)
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