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Topic: Needing help deciding b/t servo and stepper for a project (Read 304 times) previous topic - next topic

eolvera1

Hi y'all,

I'm a researcher currently building and experiment from the ground up. I have nominal programming/electronics experience (a bit of python here and there). Apologies if this is the wrong place to ask but any input would be helpful.

The basic gist of it is I need a motor that can rotate a rectangular box (LxWxH 42cmx31cmx5cm) weighing between 3-3.5kg. I need to move the box from horizontal and then tilt it to 45degrees (at different increments) from the horizontal. I want to connect the motor to the box right at the bottom center.

It seems like a stepper NEMA 23/24 would be the right size motor BUT I was wondering whether a stepper or servo can be controlled with more precision on the Arduino? It is very important for the angle I rotate it to be constant and I have seen that steppers can miss a step but know next to nothing about a servo.

Any thoughts?

thank you in advance :)


eolvera1

I should also mention fast speed rotation is not necessary and in fact a slower rotation is preferred.

I am more concerned with accuracy and the motor being about to hold the 3-3.5 kg weight w/o slipping.

groundFungus

#2
Jun 06, 2019, 05:38 pm Last Edit: Jun 06, 2019, 05:39 pm by groundFungus
For accurate positioning I believe that a stepper is better than a servo (that you can afford).  Industrial servos that have the required torque and positional accuracy are expensive.  As for missing steps, a properly chosen stepper and mechanical arrangement will not miss steps.  You don't really say what sort of mechanical arrangement that you are using to cause the required motion.  It would help to know the mechanics to help choose a stepper.

eolvera1

You don't really say what sort of mechanical arrangement that you are using to cause the required motion.  It would help to know the mechanics to help choose a stepper.
Hi, thanks so much for your reply. By mechanical arrangement do you mean how I will be attaching the motor to the box?

If so, here are my plans:

The general idea is to use a shaft adapter like this https://www.pololu.com/product/1993 on which a piece of aluminum framing will be attached to (10cm long compared to the 42cm length of my box). That aluminum framing is attached to the box. I cannot screw the box straight into the shaft adapter bc its made of acrylic and it could crack.

jremington

The words don't convey much and this
Quote
I want to connect the motor to the box right at the bottom center
doesn't make much sense.

Please post a clear picture or drawing of the box, in its different proposed positions and your ideas about how to accomplish the proposed motion.

Note: "NEMA 23" tells us the dimensions of the motor mounting face plate, nothing more.

This drawing represents what I understood from the description, and calculate for the holding torque:


zwieblum

How fast should it move? I have this here on my bench, you can mount virtully anything on it - it's just not the fastest:

Paul_KD7HB

Hi y'all,

I'm a researcher currently building and experiment from the ground up. I have nominal programming/electronics experience (a bit of python here and there). Apologies if this is the wrong place to ask but any input would be helpful.

The basic gist of it is I need a motor that can rotate a rectangular box (LxWxH 42cmx31cmx5cm) weighing between 3-3.5kg. I need to move the box from horizontal and then tilt it to 45degrees (at different increments) from the horizontal. I want to connect the motor to the box right at the bottom center.

It seems like a stepper NEMA 23/24 would be the right size motor BUT I was wondering whether a stepper or servo can be controlled with more precision on the Arduino? It is very important for the angle I rotate it to be constant and I have seen that steppers can miss a step but know next to nothing about a servo.

Any thoughts?

thank you in advance :)


Yes, I have the thought that you are designing your thing ass backwards. Work on designing the mounting, rotating and box holding mechanics. When that is the way you want, then consider a simple DC motor and crank and connecting rod, can do exactly what you describe with no electronics, no programming, etc.

Paul

zwieblum

then consider a simple DC motor and crank and connecting rod, can do exactly what you describe with no electronics, no programming, etc.
Shoudn't an experiment be as complicated as possible to get at least a couple of papers from it?

Paul_KD7HB

Shoudn't an experiment be as complicated as possible to get at least a couple of papers from it?
Said like an academic! Probably right.

Paul

Robin2

Said like an academic! Probably right.
I came across a quote years back something like this "An engineer is a guy who can make something for $10 when anyone else can make it for $100"

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

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