I am trying to build a DIY-esque turntable for a college project with Arduino.
I've read that trying to back-power servomotors can damage them and their gearing, let alone overheat, and I was wondering what could be a good alternative.
I am mounting vinyls on a platform rotated by a continuous servo, and I'd like to allow the users to "DJ scratch" to move the sound/song sample playback forward and backwards.
I need to be able to power the servomotor to spin, as the vinyl should spin on it's own, but I'd like to be able to interact with the spin and alter it aswell by rotating it by hand when desired.
What motor should I use? Are there continuous servomotors that would survive this treatment?
An ordinary DC motor, with no gears or only a simple gear with a very low gear ratio. Problem is, most of the DC motors you can buy are designed to spin at thousands of RPM. You can slow them down with PWM drive, but that often won't work reliably with very low duty cycles. Also, PWM signals can cause interference with the sound, unless you take steps to avoid.
So you need a DC motor with a very slow RPM, maybe with a very low ratio gearbox or a belt drive.
To get the RPM accurate, you need some kind of feedback from the turntable to allow the Arduino to adjust the motor speed in some way.
Use a smooth belt (on a smooth pulley, firmly affixed to the drive shaft) that slips when "scratching" but has a tension that can drive the turntable normally. The motor will feel negligible (near zero) "backwards" rotation. Beside "scratch" (back-and-forth) this allows the DJ to "pause" or "fastforward" the vinyl at the right moment.
Yeah, I've since read and had a conversation with someone who used to DJ at the time, and that on top of the plate there'd a slipmat between it and the vinyl, so that when pressed you wouldn't stop or back-power the motor, you'd stop the vinyl from rotating along with it.
I could implement this as a fail-safe for the time being, thanks!
