Originally Posted by Andy238
From what I gather the best and most accurate control system uses a stepper motor, a stepper motor controller, and an optical encoder. I understand how a stepper motor works (is controlled by voltage pulses th rotate a specific amount per pulse). I understand what the encoder does (creates a pulse based on a rotating disk with light/dark bands). The part I don't know enough about is how these things work together, or rather how they are connected together, to make a complete control system. I'm just not an electronics whiz. Does anybody know how this stuff should be integrated that can help us out? I know Don does but he's working on his commercial version and I'm not sure if he is willing to share his secrets - which I totally understand, btw.
There are two different approaches to accurate position control - you could use a stepper motor, which as the name suggests rotates in a number of steps, managed by a controller. Therefore, absolute positioning can be achieved by use of a 'home' position sensor, then telling the motor to rotate the correct number of steps needed to get the motor to a specific position.
Alternatively, you could use a standard motor coupled with an encoder, so you drive the motor and count the pulses received which allows you to get to a known position.
One of my previous projects from a couple of years ago was designing an automated curtain controller, and at that time I had decided a stepper motor was the best way forward. I documented some of the system here: http://willcoxonline.com/Curtain/
which may give you a little insight into steppers and how they work. I abandoned the project as I moved on to other things, I decided it was a bit over-engineered for a curtain controller, and the problem is that the control system used to drive a stepper is more complex than a conventional motor.
For somebody who has some basic electronics knowledge, it really is not that hard to design a system that can do everything that is needed to build an automatic masking system.
I've already posted a link to my site which shows a schematic of a microcontroller based system with encoder feedback and RS232 interface. Adding IR control is not a big deal, but it's not something that I'm particularly interested in at this stage, which is why I haven't got that on my control system.
BUT, as GetGray says, it's one thing for an electronics hobbyist to build a system for their own use, but a completely different kettle of fish to build, sell and support a system commercially!
So as far as I can see there are three ways to achieve a motorised masking system:
1) Buy an off the shelf complete screen/masking package for $$$$$
2) Buy a kit that will allow you to construct a masking system from a set of 'black-box' parts
3) Build a system from scratch including electronics etc
Option 1 and 3 already exist (and I've already provided an example schematic and source code for option 3, which shows how the various parts are interconnected, which seems to be the main question at the moment), and it sounds like Don has a system in the works that will satisfy option 2, which would be the most suitable solution for those d-i-y'ers that don't have any electronics knowledge.
So, those that are asking how all these components fit together, I've already shown you an example. But, unless you know how to build it, and by it's very nature it needs technical electronics knowledge to understand, then it's not going to be much help.
To use an analogy, although you can learn how a car works, and can buy wheels, chassis and an engine, unless you have some mechanical knowledge and the tools to put them together, you can't just build a car. (but you might be able to build a kit-car ;-))