How to construct a sliding door on box

I have a small box that is around 11 inches tall and 8 inches wide. In it I’ve cut a window in one of the sides.

Ideally I want to build a sort of roll up door of fabric that I can open and close to show and hide the contents inside. I’m struggling however to come up with a mechanism and find the right parts. I thought about using a stepper motor with a rod to lower and raise the fabric but I’m worried about the position getting lost between power cycles. Ideally I would want some sort of solution with gears that is powered by a servo so that I have exact control over position. Making a simple servo powered door that opens outward would be easy but I’m trying to avoid that solution.

The problem I’m having is I’m not sure where to get these sorts of parts. I’ve never constructed a track or used gears with servos and am lost at where to even go looking for parts. Any advise on hardware or build techniques would be greatly appreciated.

For reference, here is the box. Eventually it will be made of wood:

A starting point:

https://www.servocity.com/

https://traxxas.com/search?keyword=steering

For knowing start and end positions a sensor of some kind, actuated when part X is in position Y, is commonly used.

A sail winch servo can do about 3 full turns with position control - I think some can do 6 turns.

A servo would be by far the easiest way to motorize the system as they have position control and power electronics all in a neat package.

If you make a fabric panel with a weight sewn into the lower hem to keep it taught it should slide up and down nicely onto a roller at the top - like roller shutters on a shop. Choose the diameter of the roller so that the rotation of the servo is sufficient to wind up the fabric as far as you want it.

Another option is to pull the fabric over a roller at the top and then horizontally just beneath the roof. I believe some domestic garage door mechanisms work like that.

You could have the fabric slide in tracks on either side of the opening to keep everything neat. The weight would need to be sufficient to overcome any friction.

...R

It would be a lot easier to start with a roll top box, something like this (of many similar designs).

Have a look at how blinds work - roller or Roman blinds

I would offer that by picking the drive and then picking the applicaion you are very close to an X/Y problem
If I had to do this, I would use a simple DC motor and a two sensors. one for full open, one for full closed.
your project would also adapt to a grey scale encoder on the blind.

dave-in-nj:
If I had to do this, I would use a simple DC motor and a two sensors. one for full open, one for full closed.
your project would also adapt to a grey scale encoder on the blind.

I know that would work, But if a servo is suitable it would be a great deal easier to implement.

A DC motor needs a motor driver and the sensors need to be fitted in place and wired up. And then all the programming has to be done to detect the sensors - not difficult but not as simple as a couple of servo.write() instructions.

...R

Robin2:
I know that would work, But if a servo is suitable it would be a great deal easier to implement.

A DC motor needs a motor driver and the sensors need to be fitted in place and wired up. And then all the programming has to be done to detect the sensors - not difficult but not as simple as a couple of servo.write() instructions.

...R

You are absolutely correct and the servo is a much better fit on a hobby project like this than a stepper.
The blind does not have to overcome power found in cutting tools, like on a CNC table.
Using wild guesses, the blind is to cover a distance of about 10 inch or 25 cm
a 1/2 inch rod has a circumference of 1.5 inches. so would need to rotate about 7 times.
a 1 inch dia spool would have a circumference of 3.15 inches and would need to rotate just over 3 times.
the larger the diameter, the greater the torque needed, the larger the motor.
I am summing that a constant rotation servo would not have position feedback ?
the 3 rotation servo would ?
in any case, two switches, wired in parallel, both normally open could be the end switches. you retract until the switch is made. then drive until the other switch is made. lots of assuming, but would only need 1 pin.

for a DC motor, you can use an h-bridge like the L298 (which. IMHO is a good use of this device for a new design)
and a simple power supply.
If the curtain is to go anything other than full open and full closed, then toss out the DC motor, use the servo and Bob's your uncle !
in whatever the OP does, this is a beginner project as far as the motor goes.

Seems to me you are always going to need at least one close sensor, whatever motor you use. As you point out, if someone pulls out the plug when the door's half open, the program won't remember what position it was in unless you update a ROM with the value every step, which'll wear out the ROM pretty quickly.

So, whenever the box is powered up, if the 'closed' sensor is not activated, roll the door shut until it is. Then call that position 0 for the stepper motor. You'll already have calculated the motor position for fully open.

As to the mechanical aspects, I'm not sure what kind of torque these tiny stepper motors can handle. You'd probably be best to use a thin roll-up rod. Fabric? I'm not sure about. You don't want any flexibility in the material, or it'll derail and jam. The material used for commercial blinds would probably be best, as they have the same potential problem.

crudpuppy:
if someone pulls out the plug when the door’s half open, the program won’t remember what position it was in

A sail-winch servo would.

…R

If you have cords on both sides attached to both ends of the blind, you can pull it in either direction.

As used to drive the dial pointer on radios, the "winch" drum has a tension spring for the cord.

Paul__B:
If you have cords on both ...

This is an old Thread.

...R

Doesn’'t hurt to mention. :grinning:

Paul__B:
Doesn''t hurt to mention. :grinning:

I thought Reply #10 (which re-awakened the corpse) was particularly helpful :slight_smile:

...R

Robin2:
I thought Reply #10 (which re-awakened the corpse) was particularly helpful :slight_smile:

Ah, yes, indeed! :cold_sweat: