Positional vs Continuous Rotation Servo Motors

What's the difference between a positional and a continuous rotation servo motor? How do you control them with the Arduino servo library? Which one do you need for your project? Get all your questions answered in this video! For an example of a fun project that uses a continuous rotation servo motor, see this project on the Science Buddies website: www.sciencebuddies.org/scienc...
Want to learn more about electronics? Check out our electronics tutorials! • Electronics Tutorials
0:00 introduction
0:25 positional servo
0:48 arduino servo library
1:42 continuous rotation servo
3:42 potentiometer control
4:48 pulse width modulation
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[@nowhereman5956]

I am a DIY beginner and I purchased mg90s for my mearm project. My servo motors do not indicate "360" on the label and it took me a half day to figure it out! Thank you for your video, it is a nice lesson for me.

[@pinsetter1991]

huge props to you my good sir. spent 2 days trying to figure out why my servo wouldnt stop spinning hahah

[@picknikbasket]

Very useful, thanks for this clear and concise video covering a tricky topic.

[@Bubu567]

It's worth pointing out that you cannot short the pwm pin to ground or VCC and expect it to work, even though it technically qualifies for PWM at 0% and PWM at 100%, respectfully. The PWM range must be between 1% and 99% so that the controller in the servo can sync with the pwm frequency and calculate the on/off ratio.
However, if it's a 360 servo, it SHOULD work by shorting the PWM pin to ground or VCC to control the direction, but you will not be able to make the motor stop without a 50/50 duty cycle PWM signal.

[@smcgrady3537]

Brilliantly effective demonstration - thanks

[@latifatbelle7950]

Helpful. Thanks 👍

[@rowantan2520]

thanks for the tip .Thought i got the right motor untill i wondered why it was spinning at 130 degrees and stopped at 90. Bought a sg90 thinking it was a positional and ended up with a continuous rotation servo motor

[@justinmallaiz4549]

Thankyou!.. I'm interested in the opposite. (As a mini esc and motor setup, I want to reduce the sensitivity/range of motion). I prefer to keep the potentiometer to set the trim. I Should be able to connect 2 resisters in parallel (outter to inner). Has anyone tried, or can confirm?

[@dailypetvideos26]

I am subscribed

[@obadaaltabaa1179]

Thanks for clearing things, i was using a positional 180 degree servo then i switched to a 360 degree rotation servo and it went crazy i thought it was broken😅

[@DannyMaes]

Hello,
I have a question about a positional servo, which could be used to move a pencil up or down on a sheet of paper.
In my view, the use of myServo.Write() is very straightforward, you need only 2 different values, to select one of the 2
servo positions (up or down).
In Arduino Nano code, I have seen this implemented by using a Timer2 (to generate a pulse width of 1ms/2ms and fixed
period of 20ms), addressing the registers OCR2A and OCR2B, loading it with value 156 or 148).
Why would one choose the second implementation for positioning the servo motor?
Thanks for this clear explanation about positional and rotational servos.

[@Science.Buddies]

A more general answer - the Arduino language provides a bunch of really convenient commands and libraries that do the under the hood/behind the scenes work of setting register values for you. There are advantages and disadvantages to each approach. The Arduino libraries are human-readable and easy to learn, but you don't know exactly what they're doing and which registers they're using unless you dig into the source code. This can sometimes lead to conflicts with certain libraries or commands trying to use the same registers, meaning you can't use them simultaneously. Setting registers manually can be a pain, but then you know exactly what's going on and which registers you're using. In the specific case of the servo library, you can read more about it under "Usage" here: www.arduino.cc/reference/en/libraries/servo/. It's pretty convenient to easily control 12 servos with only a single timer - doing that yourself would be a hassle for multiple servos! The price you pay is disabling analog write functionality on pins 9 and 10, since analogWrite on those pins uses timer 2. So if you don't need analogWrite on pins 9 and 10 or need timer 2 for something else, you should be able to use the library.

[@user-rx6jc9bg3c]

thanks for the simple explanation. one more curious point is that do both servo has the same torque or not?

[@Science.Buddies]

We're not sure, you'd have to look up the datasheets to check.

[@Zer0kx]

Seems like I ordered the right ones on accident. Lucky!

[@coryhernandez8824]

can you program two servos to rotate continuously controlled by a joystick?

[@Science.Buddies]

Yes, you may find our Arduino joystick tutorial helpful: th-cam.com/video/vo7SbVhW3pE/w-d-xo.html

[@priyammascharak8400]

But how do i set the angle for the continuous rotation one is there a library for it or do i just have to fiddle with speed and timing?

[@Science.Buddies]

You can't directly control the angle of a continuous rotation servo like this, if you want to control the angle you need a positional servo.

[@rykonvolta6554]

The SG90 positional servo lasted on a continuous process for about 24 hours until it burned out, and now whenever I try to run it then it always gets really hot and doesn't respond to the program on my microcontroller. Is this short lifespan normal? Should I get a different brand or one not made of plastic? I saw a chatroom somewhere that implied metal gears are better quality servos that can last a lot longer.

[@Science.Buddies]

We've never tried running one of these servos for 24 hours straight so we can't say for sure, but they're definitely on the cheaper end of the servo spectrum. They're popular in hobby projects because they're so cheap and widely available, but you may want to invest in a more expensive heavier-duty servo (including metal gears, which won't strip as easily as plastic gears - although that's a different issue than burning the motor out).

[@Lennings82]

If the servo is not moving. is it still draining power?? in that case, it may not be good to use a servo in an application where it will be on for days. it may damage the servo?

[@Science.Buddies]

It depends on whether there is a load on the servo. If it is just sitting there then the DC motor inside should not need to draw any current (although the control circuitry might). If there is a torque on the servo horn that it must oppose in order to stay in one place, then it will draw more current. As long as you stay below the current rating it should not damage the servo though.

[@ramosdanwendellb.7531]

Is there a positional 630 servo motor?

[@Science.Buddies]

There are more expensive servos that have a 4th wire and allow for 360 degree position control, like this: www.adafruit.com/product/3614. For 360 degree position control you can also look into stepper motors, or using a DC motor with an encoder. We do not have our own tutorials on these topics (for now), but you should be able to find them on TH-cam.

[@predator_x3]

Hi, can i use 360 servo for a arduino robot arm (potentiometer arm)?

[@mustaqeem_]

Pls tell me if U got the answer

[@predator_x3]

@@mustaqeem_ well i had to find that the hard way. The answer is.....
No. No you can't. Now i got 3 useless 360° servos

[@luisserranolaguna1610]

can u do PID with continuous servos???

[@Science.Buddies]

For these hobby servos with the Arduino library, the feedback is "built in" so there's no need for additional PID control.

[@arbaazkhan326]

hi can someone help me with a system where i want 180 degree motion with 2 different speeds using a battery and button to operate

[@ShanuShamsudeen-lp5xf]

Why not, its possible

[@ganggamers9335]

sir can i make a continuous rotation servo to rotate 90 degree rotation ?

[@Science.Buddies]

Not if you are just using the servo on its own and the Arduino servo library. The Arduino library will control the speed of the continuous rotation servo, not its position. We recommend looking up a tutorial on "motor encoder" (unfortunately we do not have our own yet).

[@sigitberkaryaa]

You have a code program servo 2:15 ? Please i want it 🙏

[@Science.Buddies]

Please see this tutorial in our Arduino series: th-cam.com/video/qJC1nt_eJZs/w-d-xo.htmlsi=JdVztoeY4pArqOQ7

[@user-ru2gj1pi5y]

Hi, beginner here, Can I ask for the code?

[@Science.Buddies]

You can find code on the Arduino website: docs.arduino.cc/learn/electronics/servo-motors/

[@dailypetvideos26]

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