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?
Best Answer
Belts or a gearbox are a good way to improve your resolution, but rather than relying on the stepper and a potentially sloppy coupling I suggest you include a rotary encoder (absolute or incremental, optical, hall, whatever). Couple that with a closed-loop position control algorithm (PID is easy enough in an MCU, or even an Arduino) and you can start to make some credible guarantees about turntable orientation.
Apart from the sloppiness inherent in soft couplings like belts, a good reason to do this is that steppers can jump steps, particularly if they're heavily loaded and having to fight a lot of inertia. Unless you have a way of detecting this, you have no way of knowing that it has happened, let alone compensating for it. otoh a closed-loop position controller will (if properly written & configured) compensate for any mechanical slop, in either direction.