How Servo Work

koolguy · Nov 12, 2015

Hello Guys,
I remember i had used Servo last 2 year back with PIC ADC to Servo with some forum member code.
I have this Servo with me
hxxp://robokits.co.in/motors/standard-dual-ball-bearing-servo
data sheet
I want to know how it work, there are 3 pulses of different width , it it will rotate at small angle the data sheet show 90 and 60 degree of movement if i want to move 20/30 degree
How to move it?

kubeek · Nov 13, 2015

Maybe instead of typing your questions here, try google next time. https://bfy.tw/2lpQ

koolguy · Nov 13, 2015

How did you made that Google Page?
Can't we rotates it at 45*?

Ian Rogers · Nov 13, 2015

Servo's need a certain pulse width... 1.5mS will put the servo at 90° 1.0mS will put the servo at 0° and 2mS will put it at 180°

So 45° will be 1.25mS

Code:

while
   turn on servo pin
   delay uS 1250
   turn off servo pin
   delay rest of cycle

kubeek · Nov 13, 2015

koolguy said:
How did you made that Google Page?
Can't we rotates it at 45*?

lmgtfy.com
You can rotate it anything between 0° and 180°.

koolguy · Nov 13, 2015

So 45° will be 1.25mS
how to calculate ?

kubeek · Nov 13, 2015

koolguy said:
So 45° will be 1.25mS
how to calculate ?

Are you serious?
Look at the numbers again.
1ms - 0°
1.5ms- 90°
2ms - 180°

And now the hard part, just like in kindergarten, how many ms do we need to get 45°?

koolguy · Nov 13, 2015

I forgot how to calculate i dnt remember school calculation.
something like : 1500/90 =16.7 ........

Ian Rogers · Nov 13, 2015

Simple algebra!!!!

(1000 /180) * 45° + 1000 = 1250....

koolguy · Nov 13, 2015

Simple algebra!!!!
(1000 /180) * 45° + 1000 = 1250....

i am not getting

kubeek · Nov 13, 2015

Then I really think you should consider gardening or some other simpler hobby, because electronics is clearly not for you. This is not some advanced mathemathics, this is third grade stuff.

Ian Rogers · Nov 13, 2015

How many micro seconds in one milli second.... 1000... You need to specify micro seconds for accuracy!!

If there are 180 degrees spread over 1 milli second you need to divide it by 180 to get the size ( in microseconds ) of each degree!!!!

Therefore 1000 uS / 180 degree = 5.5micro seconds..... 45 degrees will be 45 * 5.5 micro seconds... That equals 250 micro seconds... Then you have to add in the 1000 micro seconds that represent 0 degrees.. Voila 1250 micro seconds...

koolguy · Nov 13, 2015

This is not some advanced mathemathics, this is third grade stuff.

Is this true Electronics is to high.
i do it because i can earn more money with this subject.

DerStrom8 · Nov 13, 2015

koolguy said:
Is this true Electronics is to high.
i do it because i can earn more money with this subject.

You won't earn any money if you can't do it!

koolguy · Nov 13, 2015

You won't earn any money if you can't do it!

i am now rising linearly.

koolguy · Nov 13, 2015

Ian Rogers said:
How many micro seconds in one milli second.... 1000... You need to specify micro seconds for accuracy!!

If there are 180 degrees spread over 1 milli second you need to divide it by 180 to get the size ( in microseconds ) of each degree!!!!

Therefore 1000 uS / 180 degree = 5.5micro seconds..... 45 degrees will be 45 * 5.5 micro seconds... That equals 250 micro seconds... Then you have to add in the 1000 micro seconds that represent 0 degrees.. Voila 1250 micro seconds...

Can't we have less than 1* degree movement in servo

koolguy · Nov 13, 2015

How many micro seconds in one milli second.... 1000... You need to specify micro seconds for accuracy!!

If there are 180 degrees spread over 1 milli second you need to divide it by 180 to get the size ( in microseconds ) of each degree!!!!

Therefore 1000 uS / 180 degree = 5.5micro seconds..... 45 degrees will be 45 * 5.5 micro seconds... That equals 250 micro seconds... Then you have to add in the 1000 micro seconds that represent 0 degrees.. Voila 1250 micro seconds..

yes you are right

Let see the Servo is at random position ........etc etc
i am thinking the internal circuit how it work i am not getting!

DerStrom8 · Nov 13, 2015

koolguy said:
i am now rising linearly.

Not from what I've seen.

Ian Rogers · Nov 13, 2015

In a cheap servo.... You'll be lucky to get ± 2°..

The other concern is there will be some noise.... Realistically you would need to use a hardware CCP to generate the PWM.... BUT!! there has to be an off time... most people use a 20hz pwm

EDIT*** Sorry I meant 200hz ( 5ms period )

koolguy · Nov 13, 2015

ok angular move depend on servo too.

How Servo Work

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