calculate RPM of a DC motor

ChArLyZzZ

New Member

• Dec 5, 2005

• #1

hey guys
I'm using PIC16F877a...i'm connecting a DC motor on pin RC2/CCP1 (PWM) and getting the speed back from an optical interrupter on pin RC1/CCP2 (capture mode)...I'm using a 4 MHz crystal
I'm letting CCP2 generating an interrupt every 16th rising edge, then i display the values of CCPR1L and CCPR1H on LCD
I want to know how can i calculate this value to be the RPM of the motor??
I know how to calculate the period of the signal,but what next??
Thank you guys for ur help

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Dec 5, 2005

• #2

It's simple maths, dividing 1 by the time taken per revolution gives you revs per second, you then multiply that by 60 to give RPM. I've shown that as two steps, but in practice you would do it in a single step.

Presume one revolution takes 10mS (0.01 seconds), you simply divide 60 by 0.01 to give 6000 RPM.

If you have more than one pulse per revolution, you just alter the top value accordingly - so if you had two pulses per revolution then you would divide into 30 instead of 60.

 

L

lovely89

New Member

• Jul 15, 2009

• #3

requse for the rpm programm

hey bro i have to write the same programm using the 16f877a and the opto interrupter. can u please send me this programm on my e mail opr post it here .jaksaranjeet@hotmail.com


thankx.

 

L

lovely89

New Member

• Jul 16, 2009

• #4

ok sorry its jaskaranjeet@hotmail.com

 

AtomSoft

Well-Known Member

• Jul 16, 2009

• #5

Nigel i never knew that. Thanks for the code even tho it wasnt for me heh...

Ill make sure i save this page.

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Jul 16, 2009

• #6

AtomSoft said:

Nigel i never knew that. Thanks for the code even tho it wasnt for me heh...

Click to expand...

If you check the date, my post was from 2005

 

AtomSoft

Well-Known Member

• Jul 16, 2009

• #7

wow!!! never noticed cool!!! Isnt it nice to know your info is still usefull

 

N

nassjazz

New Member

• Apr 4, 2014

• #8

sir! i have to write the same programm using the 16f877a and the opto interrupter. can u please send me this programm on my e mail or post it here
my email is , I would be very thankful to you if u send me the code

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Last edited by a moderator: Apr 5, 2014