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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Wed Oct 19 2016, 03:30 PM
can you provide an explanation for the inverter 8051 code and how it works
Sat Oct 15 2016, 12:15 AM
@snaya. Create a thread in the 8051 forum for your questions
Fri Oct 14 2016, 10:00 AM
i m going to make a project with 8051and the name is scrolling led message display .now i wanna ask so many of questions.may be u can help me .so help me out
Fri Sep 30 2016, 10:40 AM
plz I want code for adc interfacing with8051
Sun Sep 25 2016, 04:41 AM
hi sir, could you help me regarding simple multiplication calculator?it should be include with buzzer. i use dragonplus. please
Sat Sep 24 2016, 05:49 PM
@Rus Ans .. what project ?
Sat Sep 24 2016, 05:48 PM
@engr1931 depends on type of scanner
Sat Sep 24 2016, 03:07 PM
Is it possible to send data from 2 barcode scanner to pc using serial port using 8051?
Wed Sep 21 2016, 02:22 AM
Rus Ana
can anyone help me for my project? T.T
Fri Sep 09 2016, 02:54 PM
Sarath babu
8051 a/c motor speed control



[email protected]
Fri Oct 21 2016, 10:35 PM
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Forum Activity
Pratik_Suthar Avatar
Posted By Pratik_Suthar
Thu Oct 13 2016, 12:39 PM
@martin the HEX file provided in the project is no...
ajay_bhargav Avatar
Posted By ajay_bhargav
Thu Oct 06 2016, 06:15 AM
Hi Phil, Do you want to add this to existing proje...
ajay_bhargav Avatar
Posted By ajay_bhargav
Thu Oct 06 2016, 06:13 AM
CE should be high when you go for reading mode/wai...
ajay_bhargav Avatar
Posted By ajay_bhargav
Thu Oct 06 2016, 06:03 AM
You can also use ESP8266 with its SDK to write app...
ExperimenterUK Avatar
Posted By ExperimenterUK
Mon Oct 03 2016, 11:15 PM
This is an old thread and the links no longer work...
martinsnc115877 Avatar
Posted By martinsnc115877
Wed Sep 14 2016, 12:51 PM
sir, i did your led scrolling mass display, and it...
ExperimenterUK Avatar
Posted By ExperimenterUK
Fri Sep 09 2016, 11:45 PM
The Hex file for this project is a bit too big for...
rajavarmanslr Avatar
Posted By rajavarmanslr
Thu Aug 18 2016, 01:40 PM
I have two 8051 that interfaces with nRF24l01. One...