This is my first post here, so hello all. I really hope I can learn a lot from you guys.

I am trying to build a robotic arm to carry an object and put it inside of different boxes that are placed in different fixed locations.

I found a few robotic arms that can do it, but I am still trying to find the right motor for the job. I read a lot on-line about the different motors, but I am not sure which on to pick. Since the boxes are located in fixed places, the motors have to move in a precise way, so, according to my research, Servo motors are the ones I should use.

Since it is a low budget project (I am college student), I wasn't sure which motor to choose (there are a lot of servo motors out there). I found several Servo motors on-line, for example , Analog Feedback Servo, and I was wondering what is the best servo motor I can buy for a really low cost project? I think I can spend about 10-20$ per motor (I need 5 motors).

I already have an Rpi and I know that pin 18 is the PWM pin that controls the motor's precision movement, but before I purchase a PWM controller and additional motors I need to run some testing to find how precise the motor is.

By the way, how can I calculate the amount of weight the motor can handle?

Any ideas and information will be greatly appreciated.

Thank you

  • 1
    $\begingroup$ Don't rule out stepper motors for that application. A stepper has quantifiable and repeatable accuracy, whereas those model-airplane servos are all over the place in terms of both accuracy and repeatability. $\endgroup$
    – Mark
    Jun 9, 2016 at 23:42

1 Answer 1


The choice of motors is a trade off between cost/power/ease of implementation/etc. that only you can make. But hobby servos like you linked to are a common choice for low-cost, low-power, hobby arms.

Simple max-torque calculations for a robot arm are pretty straight forward. (This is a simple tutorial). But there are a few online calculators to help: [1], [2].

You might also benefit from this robot arm tutorial.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.