Testing a stepper motor driven belt loop

 Everything seems to be coming along quite nicely already.
We managed to get a stepper driver up and running (relatively) easily. Sure, it needs its own power rather than being driven off the puny usb port supply, but other than that simply swapping out some LEDs for a motor and everything worked as it should! So now it's time to try it out with the actual belt drive....

Oh dear.
Nothing. Or that's how it seemed at first. There was the tiniest little hum of activity coming from the motor, suggesting it was trying to do something. So I moved the belt(s) out of the way.

And, sure enough, the motor was trying to spin - it just didn't have enough power to push the belt around the track. Despite using low-friction bearings and trying to minimise the load on the motor, running it at 5V (off a phone charger power supply) just wasn't quite enough to get things moving.

So we tried bumping the power up and supplied (just the motor) with 9V from a power adapter (being careful to isolate the power to/from the Arduino and keep that separate - in the fullness of time we'd probably have a single power supply and run the Arduino off a step-down converter, but for now we'll keep things simple by keeping the two power supplies separate).

It looks like our motor is getting enough power now and preventing it from stalling. But the extra power isn't pushing the belt around - it's just causing the teeth to slip. So we need some kind of spring or something to help push the belt against the gear, to prevent it slipping.
There's no guarantee that will work - it's still possible that the belt will slip. But it's quite obvious that without something to hold the belt against the gear, this thing is never going to spin around!

As for the short video length?
Well, that's because when I tried to squeeze the belt against the gear (to simulate it being held by a spring) this happened.....

D'oh!