# With sending one pulse into a motor, does that make it move a step?

Discussion in 'Electronics Homework Help' started by aerozeppelin, Apr 19, 2014.

1. ### aerozeppelin

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Apr 19, 2014
Does changing the amplitude or width of these pulses do anything?

I'm trying to figure out how to increase a motors speed!

2. ### KMoffett

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Jan 21, 2009
What type of motor, voltage,current, speed?

Ken

3. ### aerozeppelin

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Apr 19, 2014
To be honest I'm not sure of the difference..!

720
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Jan 21, 2009

Ken

5. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Let's start with the basics. How many wires does the motor have?

6. ### aerozeppelin

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Apr 19, 2014
Sorry I should have specified that it isnt a physical motor Im talking about.
I'm trying to understand how a pulse effects a motors opperation.
I can't find any clear information about what the width/amplitude of a pulse actually does, specifically to a motors speed.

7. ### Harald KappModeratorModerator

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Nov 17, 2011
It all depends on the type of motor you use. There are many different types of electromotors, e.g.:
• DC motor
• Brushless DC motor
• AC two-phase motor
• AC three phase motor
• Stepper motor
• ...
Without knowing which type of motor were talking about, we can't say what a "pulse" does to the motor. Your talking of "pulses" sounds like you have heard about pulse width modulation. Read here how this is used to control DC motors.

8. ### aerozeppelin

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Apr 19, 2014
Sorry about the confusion! I'm a physics student in university taking a module on robotics so I'm pretty over my head with all of this! It came up in an exam like this:
How can the pulses be adjusted to increase the motor’s speed?
1. increase the pulse amplitude
2. decrease the pulse period
3. increase the pulse width
4. all of the above

And as the type of motor was not specified I assumed it was general.
Thanks for all of your help.

9. ### Harald KappModeratorModerator

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Nov 17, 2011
From that list it is most probable that the answer lies in PWM (pulse width modulation). Read the linked article or look up PWM in the wikipedia.

And by the way: I will move this thread to the homework section where it will find a far more comfortable home than in the general chat section.

Harald

10. ### Merlin3189

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Aug 4, 2011
As far as I can see, there are only two basic types of motor where the question would be relevant; stepper motors (most likely), which are designed to be pulse driven , or DC motors which are designed to be run on a constant DC, but could be driven by a suitable pulsed supply.

The whole point of stepper motors is that they move one step for each pulse (#), so you can control exactly how much and how fast they turn (within limits.) And that tells you what you need to answer the question.

(#Half stepping and other complications ignored for now.)

The pulse amplitude and duration affect the current, and thus the magnetic field, which affects the torque. Too little torque and the step does not happen, but extra torque does not move more steps.

If you *were* looking at a DC motor driven by a pulsed supply, you use an averaging process.
If the pulses are widely spaced, you can simply regard the motor as being repeatedly switched on and off. The changes to the pulses will do what you'd expect if you did the same with your DC supply (amplitude would be DC Voltage.)
When the pulses are closer together (many pulses per revolution) you can look at your your pulse train and work out the average DC equivalent. Any changes to the pulses will change this DC average and affect the motor accordingly.