Newbie from NZ

[rjsutton]

cool
so i wouldnt need an encoder to check the revs moved if i just use the gear you show above?
bloody marvelous if thats the case ( can you please confirm my reasoning )
ive just ordered

https://www.ebay.com/itm/120W-High-T...97.m4902.l9144

with a ratio of 1:7.5 which should give me 3.21 NM as far as i can see
its a 120w motor so will be heaps better than the little ones
I hope im reading everything as i should be.
appreciate all your help.
Richard

[Doddy]

The purpose of the encoder is to allow the control system to determine where the sled physically is (actually, where it thinks it is, based on the number of [partial] revolutions and a knowledge of the screw pitch). That's one way of skinning the cat. The other is to simply think of what your actual use-case is - which is to understand when the sled is fully opened, and when it's fully closed - which the two proximity sensors will allow you to determine.

This simpler solution offers fewer bells and whistles (e.g. stall detection and acceleration/deceleration around limits), but also fewer things to go wrong - potentially higher reliability. You could introduce stall detection with a suitably rated circuit breaker. You'll have to tune the system with the actual position of the sense vane but it should be robust enough for your simple use-case.

I'm not a motors man - a bigger number looks better than a smaller number to me.

[Doddy]

...and one other thing - with heavy duty motors (or rather, heavy current draw on a low voltage supply) - remember Ohm's law. I'd personally slave a lead-acid battery close-by and trickle-charge it from the vehicle battery. Then use the shortest, beefiest cable runs to the controller and to the motor, maybe even bi/tri wiring it to reduce the power loss in the cable.