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Author Topic: pwm and servo motors  (Read 1405 times)

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Offline urshiva239Topic starter

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pwm and servo motors
« on: March 06, 2012, 06:06:26 AM »
I am new to robotics
i want to send a pwm signal to a servo motor
please guide me the steps how to give a pwm signal from atmega168 controller

Offline joe61

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Re: pwm and servo motors
« Reply #1 on: March 06, 2012, 07:03:31 AM »
Take a look at the tutorial section of this site, there are some just about that. Take a look at this one to start, you may have to make some adjustments for the 168 but if you have the data sheet they should be pretty straightforward.

Feel free to ask here with specific questions.

Joe

Offline urshiva239Topic starter

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Re: pwm and servo motors
« Reply #2 on: March 12, 2012, 01:02:33 AM »
Thank you for your reply joe

I have doubt that does PWM signal works only for servo motors or also to DC motors?

Offline newInRobotics

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Re: pwm and servo motors
« Reply #3 on: March 12, 2012, 04:24:31 AM »
PWM is PWM, it so happens that it can be used for many things including motor and servo speed/position control  :)
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Offline urshiva239Topic starter

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Re: pwm and servo motors
« Reply #4 on: March 12, 2012, 05:39:51 AM »
hmmm okay dude ..
but i was asking that do need any extra circuits for different types of motors?
I have a Double horse 9053 RC Helicopter ( http://www.hobby-estore.com/3-CH-Volitation-9053-Helicopter-Gyro-p/eh-dh9053.htm )
I am not able to understand which type of motors does it have.. Please help me out of this

Offline joe61

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Re: pwm and servo motors
« Reply #5 on: March 12, 2012, 06:24:05 AM »
I would think the vendor could answer a question like that. You might try emailing them. I didn't see any specs on the web page.

Joe

Offline jkerns

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Re: pwm and servo motors
« Reply #6 on: March 12, 2012, 08:51:29 AM »
hmmm okay dude ..
but i was asking that do need any extra circuits for different types of motors?
I have a Double horse 9053 RC Helicopter ( http://www.hobby-estore.com/3-CH-Volitation-9053-Helicopter-Gyro-p/eh-dh9053.htm )
I am not able to understand which type of motors does it have.. Please help me out of this


A servo motor controls to a position. You send it a pulse and the internal feedback sets the output to a position that is proportional to the width of the pulse. The pulse is repeated at regular intervals - but what matters is the width of the individual pulse, not the percent of the time that it is on. Servos typically move 180 degrees (or 90 or 360).

DC motors can run continuously. The motor power will be correlated to the power sent to the motor - this can be controlled by pulse modulation - you turn Thorn the power on for 10% of the time and off for 90% and you get about 10% of the available power. 50%/50% gets you half, etc. The exact pulsewidth is not that important - what is important is teh percent of the time that it is on.

From the description, you have three motors - each turns a rotor. Likely they are all three DC motors that are controlled by pulse modulation.  In a RC car or RC fixed wing airplane typically servos are used to steer the front wheels or move control surfaces back and forth, and DC motors are used for the main propulsion.
I get paid to play with robots - can't beat that with a stick.

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Offline newInRobotics

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Re: pwm and servo motors
« Reply #7 on: March 12, 2012, 02:41:30 PM »
hmmm okay dude ..
but i was asking that do need any extra circuits for different types of motors?
No, dude, what You were asking was whether PWM works for DC motors as well as for servos. What You had in mind while asking your question is as different matter  :P

I am not able to understand which type of motors does it have..
Not servos, that's for sure. Most likely brushless DC motors, although might be brushed ones as well.
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W

Offline urshiva239Topic starter

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Re: pwm and servo motors
« Reply #8 on: March 13, 2012, 03:32:48 AM »
heheheheh  ;)  :D
whatever ... but is there any way to find which type of motors are that?
i even mailed to vendor but there is no reply from him...

Offline newInRobotics

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Re: pwm and servo motors
« Reply #9 on: March 13, 2012, 04:09:04 AM »
You can take toy apart and have a look at the motor Yourself, if it has two terminals, then it is brushed motor, if it has more than two - it's brushless  :)
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W

Offline urshiva239Topic starter

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Re: pwm and servo motors
« Reply #10 on: March 19, 2012, 12:48:29 AM »
Thanks dude  :) :)
it has only two terminals .. i think that means it is a brushed motor?
and does it have any changes to give pwm signal for a brushed and brushless motors?

Offline newInRobotics

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Re: pwm and servo motors
« Reply #11 on: March 19, 2012, 01:41:10 AM »
Thanks dude  :) :)
No problems dude  ;D

it has only two terminals .. i think that means it is a brushed motor?
You think correct.

and does it have any changes to give pwm signal for a brushed and brushless motors?
PWM stays the same, as it simply is modulated width pulse, hence Pulse Width Modulation, what changes is control algorithm (the way You apply PWM to do something) and hardware (motor driver). Just look around and find out how brushless motors work, this will help You understand what is needed to drive one.
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W

 


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