High torque servo/stepper setup

Question

This is a bit of a general question. I have a project I want to put together similar to the 'sentry gun' projects seen on youtube. I've gathered an SSC-32 servo controller and couple of small servos - i think they're around 76oz-in - and I made a little brace so they are attached at right angles. This basically works as a pan-n-tilt mechanism, and I've plugged the controller board into my serial port, and it all works nicely. The problem is that it's a bit too dainty.

I need way more muscle, and so my question is in several parts.

1. Where is a good place to get hefty servos for a good price? I need something that can easily swing a 2x4 around (around 2')
2. Can someone point me at a tutorial for hooking this up? I assume the SSC-32 board and it's 4 AAs won't cut it as I'll need more power for those bigger servos. So How do I control the servos with the board but power them separately?
3. Would there be an advantage to using stepper motors instead? Like, more torque/$? I've never dealt with steppers, but I heard they were similar.

Thanks for any advice!

Answer 1

1. The Dynamixel servos are quite popular for their precision, high torque, and nice controls. Unfortunately, you'll be paying for all those features. I recommend Trossen Robotics: Dynamixel servos Trossen also sells a full pan/tilt setup for the Dynamixel servos: Trossen Robotics pan/tilt They have a whole range of sizes and torques. ServoCity.com also sells some pan/tilt setups: ServoCity pan/tilt

2. Trossen provides a nice controller and software. I believe Pololu.com also sells servo controllers with information.

3. Servos will be much easier to interface with, while a stepper motor will provide greater angular resolution. How precise does your pointing need to be? The nicer Dynamixel servos will do steps of 0.3 degrees, while a stepper motor will get you much smaller incremets if you do the "micro stepping" method. Try looking at Sparkfun for a stepper/stepper driver: Sparkfun.com

PS. When you're done with your project, how about adding it to RobotBox :)

Answer 2

1. a few examples of heavy duty servos here and here, these will easily swing a 2x4 around.

2. Depending on the servo you can just connect the Control line to your servo control and connect the power of the servo to the recommended power source. for the ones linked i would use a lead-acid battery(car battery) or a good power supply.

3. Depending on your design a stepper motor probably will not work, and servos are much easier to interface and drive then steppers.

on a side note a diagram of your design and the estimated weight of the load its moving would help.