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Michael Karas
12/09/11 14:20
  12/09/11 16:56

Read: 545 times
Beaverton Or

Msg Score: +1
 +1 Good Answer/Helpful
#185057 - Controlling Speed
Responding to: Andy Neil's previous message
Andy Neil said:
Kai Klaas said:
I think he means to set the speed by PWM, not to control it.

But still, PWM only sets the power - it does not directly set the speed.

Andy has a good point. Yes, you can setup the motor to receive a PWM drive at a certain duty cycle and the motor will go to a particular speed. Change the duty cycle and the speed will increase or decrease accordingly. However if the load on the motor is not constant then the speed attained will be dependant on the amount of the load, amount of friction in the system, the duty cycle and the supplied voltage.

In the scenario of actually "controlling the speed" of the motor it would be necessary to add a tachometer to the motor where the control system can then read the actual speed. It would then compare the detected speed to the desired speed and then control the generated PWM signal in a servo manner to bring the speed to within the expected range.

Michael Karas

List of 15 messages in thread
speed control of 12v dc motor      Tarun Patel      12/08/11 22:47      
   Google      Per Westermark      12/09/11 01:42      
   That doesn't make sense!      Andy Neil      12/09/11 03:46      
   Which Motor ?      Michael Karas      12/09/11 05:41      
      RE: Which Motor ?      Andy Neil      12/09/11 10:48      
   reply      Tarun Patel      12/09/11 05:45      
      I suppose you mean...      Daniel Contarino      12/09/11 07:27      
      RTFM      Erik Malund      12/09/11 07:29      
   PWM is done via the enable input      Kai Klaas      12/09/11 09:31      
   PWM != speed control      Andy Neil      12/09/11 10:47      
      Setting speed...      Kai Klaas      12/09/11 11:42      
         But still...      Andy Neil      12/09/11 13:15      
            Controlling Speed        Michael Karas      12/09/11 14:20      
               Analogy      Andy Neil      12/10/11 04:51      
   Direction and Speed Control      Satish S Munot      01/07/12 03:27      

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