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 Oct 06 2015, 08:22 AM
HI you looking for ideas or you have solution
Fri Oct 02 2015, 03:39 PM
poojitha: projects on wireless communication between two microcontrollers
Thu Oct 01 2015, 04:38 PM
hey! i wanted to simulate my circit using proteus. i have a sugar cube relay in my circuit....but i dont know which one is that in the device libraries of the software. any help? thankyou.
Tue Sep 29 2015, 09:40 PM
@Michal, that rocket is too heavy for itself and trust is not enough unless afterburners are fed with fuel properly.
Sat Sep 26 2015, 08:19 PM
Hello, its possible to make a amateur rocket with this engine, or something simillar, which be able to flight?
Thu Sep 24 2015, 10:38 AM
Ir Switch sir.
Wed Sep 23 2015, 01:10 AM
@engr1931 which project ?
Tue Sep 22 2015, 11:57 AM
Hello sir, is it ok to use 12.000MHz oscillator in IRswitch, because the requirement written in the post is 11.059MHz. And i use PIC1018 as an Ir receiver
Mon Sep 21 2015, 04:15 PM
Hello sir, your blog is kind of helpful for us especially students. May I know do you have the coding for decimal to binary using proteus 8. My mini project is about to convert decimal to binary just like a calculator. The output is LCD. A bit confusing is the decimal to binary coding on proteus 8. pls help thanks.
Sun Sep 20 2015, 09:08 PM
Have you searched our Embedded GSM Development and GSM and CDMA Discussion forums ?



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praveenraoms Avatar
Posted By praveenraoms
Tue Oct 06 2015, 01:06 PM
hi i want to know the code to access the geographi...
sachinmm Avatar
Posted By sachinmm
Wed Sep 30 2015, 08:54 AM
how to used polling method in this?? my code is co...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Sep 29 2015, 09:39 PM
__irq is just compiler directive to wrap IRQ routi...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Sep 29 2015, 09:36 PM
The comment does say the time values as per the th...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Sep 29 2015, 09:33 PM
are you testing this on Proteus? or MplabX simulat...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Sep 29 2015, 09:31 PM
[Topic moved to ARM Development Forum]
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Sep 29 2015, 09:29 PM
start with reading datasheet. SPI interface on LPC...
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Posted By ajay_bhargav
Tue Sep 29 2015, 09:27 PM
I am not sure you've solved it or not but "USARTRe...
ExperimenterUK Avatar
Posted By ExperimenterUK
Tue Sep 29 2015, 06:31 PM
i am confused in "__irq" it is uesd??sachin...
sachinmm Avatar
Posted By sachinmm
Tue Sep 29 2015, 11:11 AM
my I2C.c file=>>/*********************************...