# Precision 0.5 degree Stepper needed for Turntable

Basically our project brief is to design a turn table, an object weighing around 10kg which will be placed off centre (but allowing around 20kg in case) to rotate in 0.5 degree increments, pausing for a few seconds to have a photo taken and continue through to 180 degrees. We're currently using Arduino.

We thought of having the turn table on a lazy Susan bearing to distribute weight. From research we've figured we want a stepper motor with high torque and possibly a worm shaft to prevent the table from continuing motion on the bearing once stopped. Our concern is the specific increments of movement as most stepper motors move in 1.8 degree steps. We've looked at micro-stepper motors but we haven't found one which can carry the load desired/ hasn't got enough torque. We're not super experienced in this but we'd like to play around with a prototype given reasonable suggestions.

Could anyone provide any advice about how we could set our system up for precision and efficiency?

• How about a timing belt reduction setup? It will also tolerate inevitable small misalignments in your mechanical setup. Nov 27, 2014 at 3:14
• I was going to suggest a gearbox, but yeah, that could work. Nov 27, 2014 at 3:25
• Unfortunately recommendations for specific products are off-topic. Nov 27, 2014 at 4:36
• A worm turns once per revolution of the motor. 1.8 deg motors are 200 steps per revolution. Pick a drive gear with the nice integer ratio like 180 teeth and use 100 steps or 60 teeth and run 300 steps, etc. The belt and cog pulleys gives better motor position and the M4 size is all over eBay to work with 5mm (typical stepper) and 8mm (typical rod from printer/scanner) shaft. Often sold as a couple pulleys and 2 meters of belt. Nov 27, 2014 at 7:34
• One thing I learned from programming the robots that assemble airplanes is that for precise position control you always need to have a way to actually measure the position of the object you want to move, as for so small movements one step of the motor relates to anything but that exact amount of movement of the object. Nov 27, 2014 at 10:22