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Interface Continuous Rotation Servo with STM32 || PART 1
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Jul 20, 2024
Purchase the Products shown in this video from :: https://controllerstech.store ________________________________________________________________________________________ Continuous Servo PART2 :::: https://youtu.be/rofpd2UvWFQ Interface Regular Servo Motor with STM32 :::: https://youtu.be/WMS0t9WGqVw Regular Servo Angle Control in STM32 :::: https://youtu.be/GQdz5RxIyqo STM32 Playlist :::: https://www.youtube.com/playlist?list=PLfIJKC1ud8gga7xeUUJ-bRUbeChfTOOBd DOWNLOAD THIS PROJECT FROM :::: https://controllerstech.com/interface-continuous-servo-with-stm32/ ________________________________________________________________________________________ ******* SUPPORT US BY DONATING****** https://paypal.me/controllertech *******Join the Membership******* https://www.youtube.com/channel/UCkdqtSMnhYuMsJkyHOxiPZQ/join
View Video Transcript
0:01
[Music]
0:09
hello and welcome to controller Tech few
0:12
months ago I covered a video explaining
0:15
how to interface a Servo motor with SDM
0:18
32 the motor I used in that video was a
0:22
180° servo motor which rotates between 0
0:25
to
0:26
180° based on the pulse of the input PW
0:30
M signal today I have with me another
0:33
kind of Servo motor a continuous
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rotation
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Servo as the name itself suggests This
0:40
Server rotates continuously throughout
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360° and we can control its RPM by
0:46
varying the width of the input pwm
0:49
signal here I have both kinds of Servo
0:52
motors with me you can purchase these
0:55
from the controller's teex
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store both the motors look identical
1:00
with literally no difference from a
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visual point of view you have to rely on
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sellers information about which one is
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180° and which one is
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continuous some of these motors do come
1:14
with the label on them but not all have
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it here I have a Servo tester which will
1:20
be used to test these Servo
1:23
Motors the tester has three different
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modes available to test the servo motor
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this select button can be used to switch
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between the
1:32
modes I will use the manual mode as it
1:36
is used to vary the width of the pwm
1:39
signal this Servo tester can be used to
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test up to three Servo Motors
1:46
simultaneously this is the output end of
1:48
the tester and we will connect the motor
1:51
here the motor has three wires red is
1:54
the VCC Brown is the ground and yellow
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is the signal let's connect the wires to
2:01
the tester output
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pins I am connecting the second Servo
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also and we will see how both these
2:08
servos behave with the pwm signal
2:12
towards the input of the tester I have
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connected the VCC pin to the 5vt battery
2:18
and ground to ground of the battery
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let's rotate the knob to vary the width
2:23
of the pwm signal you can clearly see
2:27
the behavior of both servos when they
2:29
are provided with same signal the
2:33
180° Servo changes its position based on
2:36
the width of the pwm signal whereas The
2:39
Continuous rotation Servo changes the
2:42
RPM also note the direction of rotation
2:45
of the continuous rotation
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Servo when the knob is at extreme end
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the continuous Servo is rotating at high
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RPM in clockwise
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Direction when the knob is rotated the
2:57
RPM starts decreasing and and the motor
3:00
stops when the knob is at the center at
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this moment the
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180° Servo is also rotated through
3:09
90° and now when the knob continues to
3:12
rotate the RPM of the continuous Servo
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is increasing again also the
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180° Servo rotates through another 90°
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completing the full
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180°
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rotation as I mentioned there are other
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modes available on the Tester the
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neutral mode sends a pulse with the
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width of 1 milliseconds whereas the auto
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mode changes the width very fast and we
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see an output like this let's see the
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pulse output on the
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analyzer here I have a logic analyzer
3:47
and I will connect the signal pin from
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the tester output to the channel one of
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this
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analyzer let's rotate the knob to one
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extreme end and check the pulse on the
3:58
analyzer
4:04
the frequency of the signal is 50 htz
4:07
which is standard for any Servo motor
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note that the pulse width is 880
4:13
micros now I am rotating the knob
4:16
towards the middle till the point where
4:18
the servo stops rotating the pulse width
4:21
is 1.5 milliseconds at this point now I
4:25
am rotating it to the other end
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here we have the width of 2.1
4:34
milliseconds so we saw the RPM and
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direction of the motor varied by varying
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the width of the pwm signal between 0.9
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milliseconds to 2.1
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milliseconds actually this goes even
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more extreme than this and I will show
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it when we write the code so let's start
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the cube ID and create a new
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project I am using STM 32 f13
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C8 give some name to the project and
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click
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finish let's start with the clock setup
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first I am selecting the external
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Crystal to provide the clock the blue
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pill board has 8 MHz Crystal on it and
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we will run the system at 60
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MHz I am choosing 60 because most of the
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SDM 32 MCU can run at this clock
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frequency so if you have some confusion
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you can set the clock as for this
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video note that both apb1 and two timer
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clocks are running at 60
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MHz the timer will use this clock to
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generate the output signal each timer is
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either connected to apb1 or apb2 bus you
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can check the data sheet of your MCU to
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confirm which bus it is connected to I
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have already made a video explaining the
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pwm generation in SDM 32 you can check
6:00
it out in case of any doubt since both
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the APB timer clocks are at the same
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frequency I don't need to worry about
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the timer's
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Source now go to CIS debug and enable
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serial wire let's configure the timer
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now I am using the timer one to generate
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the pwm signal set the clock source to
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internal clock now enable the pwm
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generation for channel 1
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you can see the pin pa8 got configured
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as the pwm output we will connect this
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pin to the signal pin of the
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servo let's configure the parameters now
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we need to generate a signal with a
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frequency of 50
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HZ here is the formula to calculate the
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frequency of the pwm signal we have the
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timer clock of the same frequency as the
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apb2 which is 60
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MHz if if I set the prescaler to
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1,200 and the auto reload value of 1,000
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the output frequency will be 50
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HZ the ARR value plays an important role
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as the width of the signal is calculated
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with respect to this value I will
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explain in a while why I chose to input
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the ARR value of
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1,000 let's set the prescaler value to
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1,200 also set the a value to
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1,000 whenever you are setting these
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values the value should be one lower
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than the desired value this is because
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the code at the register level adds a
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one to this value click save to generate
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the
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project we know that the servo motor
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uses the signal width from 1 millisecond
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to 2
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milliseconds this is a standard for any
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Servo but when I was testing it I found
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that the motor was responding from 0.5
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milliseconds to 2.5 milliseconds so I
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will consider these
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values the pulse has a frequency of 50
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Herz which implies that the period is of
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20
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milliseconds a width of 0.5 milliseconds
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out of 20 milliseconds is equivalent to
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2.5% duty cycle and a width of 2.5
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milliseconds is equivalent to 12.5% duty
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cycle now let's assume that we set the
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auto reload value to
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100 in order to vary the signal between
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two extreme ends we only have a
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difference of 10 steps between them so
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each step would have a major change in
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the pulse width on the other hand if we
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use the auto reload value of 1,000 the
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duty values will change to 25 and
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125 this will result in a total of 100
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steps between the extreme values and so
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are outputs signal will have more
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variations all right let's write our
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code now inside the main function start
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the timer in the pwm
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mode I am using the timer one channel
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one for the pwm
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generation the compare register is where
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we set our pulse value for the duty
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cycle here I am setting the value to 25
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basically one of the extreme
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ends let's build and flat the project to
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the
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[Music]
9:35
board you can see the servo motor is
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rotating with very high
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RPM if we check the output on the logic
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analyzer we can see the pulse has a
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width of 0.5
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milliseconds the frequency of the output
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signal is almost 50
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HZ now I am setting the pulse value to
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50 which will result in the sign with a
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width of 1
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milliseconds you can hear the sound of
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the motor to note the difference between
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their
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speeds the speed has been reduced
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compared to the previous
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value now we will set it to 75 which
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will result in a pulse of width 1.5
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milliseconds and this will stop the
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motor just like it was stopping when the
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knob was in the middle setting the value
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to 100 will result in a pulse of width 2
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milliseconds the motor is now rotating
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in the counterclockwise
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Direction you can see the pulse width is
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2
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milliseconds and in the end we will set
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it to
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125 which will result in a pulse of
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width 2.5
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milliseconds note the sound of the motor
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the speed has been increased to maximum
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so we can see the motor is responding
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for the pulse of width between 0.5
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milliseconds to 2.5
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milliseconds we will write our code with
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respect to these values let's define a
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pulse variable to store the pulse value
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which we will set to the compare
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register I am setting the initial value
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of 75 this is where the motor stops now
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I want to gradually increase the RPM of
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the motor in One Direction and then in
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the other direction so our pulse value
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is at 75 right now and we will increase
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it until we reach
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125 with each step the value will be
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passed to the compare register let's
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give a delay of 250 milliseconds between
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each step when the pulse reaches 125 the
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motor will be at the maximum RPM in the
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counterclockwise Direction and this one
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while loop will exit then we will start
12:02
reducing the pulse value and we will
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keep doing it until the value reaches to
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25 when the pulse is reducing the motor
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will start slowing down and it will stop
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when the pulse is around
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75 then with the further reduction in
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the pulse value the motor will start
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rotating in the clockwise Direction and
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its speed will keep
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increasing when the pulse value is near
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25 the motor will rotate at maximum RPM
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in the clockwise
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Direction at this point this while loop
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will exit and the first one will run the
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pulse will start increasing again and
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the motor will start slowing down the
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motor will stop when the pulse value is
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near
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75 the pulse continues to increase and
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the motor will start rotating in the
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counterclockwise
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Direction the entire Loop will continue
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forever
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let's build and Flash the project to the
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board hear the sound of the motor to get
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the idea about the speed and please
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ignore the background noise
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[Music]
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[Music]
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[Music]
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[Music]
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you saw the motor was responding how we
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programmed it to do
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we were able to control the RPM of the
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continuous Servo motor using the pwm
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signal in the next video we will see how
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to use the potentiometer and a button to
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control the RPM and direction of this
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servo
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motor this is it for the video you can
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download the code from the link in the
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description leave comments in case of
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any doubt keep watching and have a nice
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day ahead