Contactless Digital Tachometer using PIC Microcontroller

Hey friends, I should have posted this project last month itself but there was some problem with the circuit. [link], author of this project did an exellent job. I have been watching him learning on this website. He came as a total noob but now he is well versed with 8051 and PIC microcontroller. earlier he has submitted Microcontroller Based Home Security System

This project is about A Contactless Digital Tachometer. As per defination from wikipedia

A tachometer (revolution-counter, Tach, rev-counter, RPM gauge) is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays the revolutions per minute (RPM) on a calibrated analogue dial, but digital displays are increasingly common. The word comes from Greek Ταχος, tachos, "speed", and metron, "to measure".


Following diagram explains the logic of this project.

The infra red reflective object sensor work by simply emitting the infra red beam and when it encounter the white object surface than the infra red beam will be reflected back to the phototransistor; next the phototransistor and the 2N3904 transistor which formed the Darlington pair will start to conduct and will generate enough voltage across the 470 Ohm resistor to be considered by the PIC16f690 microcontroller build in Capture Compare Pulse width modulation(CCP )module input port as the logical "1". When the infra red beam encounters the black tire surface than both of the phototransistor and 2N3904 transistor will turn off; and the voltage across 470 Ohm resistor will drop to 3.5 volt (logical "0").

Therefore by timing the generated pulse period by the infra red reflective object sensor we could easily calculate the RPM using this following formula:

Frequency = 1/T Hz; T is the generated pulse period in second.

RPM (Rotation per Minute) = Frequency x 60

Here is a sample video of working project:

You can download project related files here:

Download Contactless Digital Tachometer project

Thank you Romel for this contribution. If anyone has doubts regarding this project, please use forum.
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Tue Apr 15 2014, 04:12 PM
Tue Apr 15 2014, 11:21 AM
Mon Apr 14 2014, 10:00 PM
Sun Apr 13 2014, 02:59 PM
Sun Apr 13 2014, 12:41 PM
Sun Apr 13 2014, 09:00 AM
Sun Apr 13 2014, 01:54 AM
Sat Apr 12 2014, 07:33 PM


Mon Apr 14 2014, 01:00 PM
@Haranadh,bipin chandra etc. Create threads for your questions.
Sun Apr 13 2014, 04:05 AM
we bought HC 06 Bluetooth modem instead of Module ,Can any one help me of using it as bluetooth module since i am doing this project?
Sun Apr 13 2014, 03:58 AM
Hi,Actually we bought Bluetooth modem instead of Bluetooth Module
Sat Apr 12 2014, 02:55 PM
Please use forum if you want to ask a question.
Sat Apr 12 2014, 01:06 PM
Hi Ahana,I can Help you on this
Sat Apr 12 2014, 03:51 AM
bipin chandra
can anybody help me. we are making a project to control the position of dc motor. so there we need to interface lcd screen and the 4X3 memberane keypad and a dc motor driver chip. can anybody please give me the complete circuit diagram connection of these components with the 8051.and alse help in the programming. my email id is
Fri Apr 11 2014, 01:10 PM
will anybody tell me why do we need comma positions to be considered to know about latitude and longitude from gps?
Thu Apr 10 2014, 01:31 PM
sayed awad
how do i interface energy meter with msp430 kit microcontroller ??
Wed Apr 09 2014, 03:29 PM
In a section the forum you mean?
Wed Apr 09 2014, 02:10 PM
how to create threads for ourself?
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