PWM and speed

Thread Starter

braddy

Joined Dec 29, 2004
83
Hi,
I cannot figure out how to compute the speed of my robot knowing the pulse width modulation (PWM)? what other addition information do I need to have?
motor characteristics??

I am asking because I want to measure the width of a black line with a sensor(photo transistor) but I need to have a precise value of the speed.
The motor speed is controlled by the PWM.

thank you
C.
 

beenthere

Joined Apr 20, 2004
15,819
There are other variables involved. What rotational speed does the motor have at every percentage of PWM? What is the ratio of motor rotation to spacial displacement does you device have? what is the limit of accurate measurement your sensor has?
 

Thread Starter

braddy

Joined Dec 29, 2004
83
There are other variables involved. What rotational speed does the motor have at every percentage of PWM? What is the ratio of motor rotation to spacial displacement does you device have? what is the limit of accurate measurement your sensor has?
It is a DC motor, frankly beenthere, I cannot answer your questions about rotational speed or displacement. I dont have the specs with me I will check at school today.

The sensor is a photo transistor (GBR1134). I am using the freescale MC9S12c32 as MCU and I plan to use the input capture to determine the time the sensor is on( white surface) and off (black surface) or vice versa...So it is quite precise (nano second).
This time multiplied by the spped will give me the width of a line.


Thank you.
 
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