Pan tilt system help

Help & Support Robot Parts
1

Hello,

First of all sorry for the absence of knowledge, I’ve only recently started learning about microcontrollers and robotics.

So, I want to make a pan&tilt (and roll if within budget and ability to do so) system that can move a load of 2-3 kg.

Motors
One requirement is extreme accuracy with repeatability to finite angles. That’s why I think stepper motors are the way to go and specifically I’m thinking of robotshop.com/eu/geared-bipolar-stepper-motor-3v-555-oz-in.html.

Motor Controller
Next I need motor controller for those steppers and the manufacturer of the mentioned stepper motor has two bipolar stepper motor controllers (1, 2) but both of them handle only 1 motor (they offer another controller but for unipolar motors that handles up to 4 motors). Ideally I would like a single controller that will hook up with a Raspberry Pi or an Arduino, but I had no luck finding a multi-bipolar stepper motor controller and I’m not sure if they are compatible with the motor I’ll be using.

Structure
Now comes the even harder part for me. I have almost no idea how to connect all those motors to make a pan&tilt system. Someone I asked told me that the load should never be on top of the motor and I should use gears etc. to move the real load. How can I use the mentioned motor to connect it to another same motor and then that motor to move the load?

Thanks and I really appreciate any help.

2

I want it as accurate as possible, the requirement is <=0.1 °.

I’ve looked into existing pan/tilt(/roll) systems and couldn’t find one with the accuracy I need.

One thing that could help me move a bit forward is if you could tell me what components/gears are compatible with the stepper motor I’m going after.

Thanks

3

Stepper motors don’t provide absolute positioning - only relative positioning. If there is a power outage and the controller loses power, it won’t know its last position. The accuracy depends on the controller and the motor.

4

That system is servo-based; you would get exact positioning. You would need a servo controller though. The accuracy is theoretically about 0.09 degrees, but closer to 1 degree when you factor in static friction and inertia.

5

What’s the accuracy you want vs. the accuracy you’ll live with? Take a look at an existing pan/tilt/roll system for ideas. It is correct that you should not subject a motor shaft directly to a heavy load and instead offset the force using gears or pulleys. Unfortunately we don’t have a huge selection of such products at this time. If you cannot find a single stepper controller capable of controlling three stepper motors, then you’ll need to buy three individual controllers. Design the mechanics in CAD first.

6

Consider a Cytron 3-40V, 2A Unipolar / Bipolar Stepper Motor Controller for each motor and an Arduino to control them all. The motor’s shaft is 8mm, and unfortunately we don’t have a lot of 8mm accessories such as gears or timing pulleys with 8mm bores.

7

Hi again,
Getting really close finally, just another question though about the controller and the motor. With this combination will I have precise reproducability of position? This will be software controlled - no manual joysticks etc. - in a remote location. If there is a power outage, will I be able to reproduce past positions or the starting position of the motor/controller will be the last position before the outage?

Thanks

8

Thanks, I’m thinking of having higher step degrees in exchange for being able to visit exact past positions, do you know if Servocity’s PT785 can provide that?