I tried to answer your questions. Keep in mind that
this is my way of doing you can find much easier ways.
> 1- why does the paper needed to be emulated... won't
the PCB tray act like paper?
On CX4200/CX4800 printers there is a paper sensor to
detect objects around the printing area and to find
the edge of the paper. Tray itself can not be used
like paper since you need to feed tray before starting
printing. You need to be sure that tray is aligned
properly before starting printing. Another issue is,
since tray is a metal part you can easily destroy
abrasive roller during feeding. In my solution tray
always exist below printing area. So you need to find
a method to emulate behavior of the paper otherwise
you will get paper jam error.
What I am doing is very easy, I am counting signals
coming from x and y axis optical encoders and
depending on position of head (x-axis) and y-axis
(tray/paper) I am sending high/low signal in parallel
to paper sensor. Both of paper end and paper sensor
have open collector/drain output so no problem to
drive for a short period of time.
> 2- which sensors will need to be emulated?
Paper sensor on inkjet head and paper end sensor need
to be emulated
> 3- Are there any more specifics on what needs to be
> monitored?
No.
> 4- how is the moved optical sensor used.
If you look at the behavior of the printer during
initial paper feeding, it takes the paper (checks
paper end sensor) and checks whether there is a
reflection from the paper in defined x/y axis range,
after then it moves the paper in reverse direction
(-y) slowly till finding edge of the paper by this way
printer sets it origin precisely.
I am using optical sensor to detect the slot on the
tray and control the paper sensor. Otherwise it is not
easy to minimize the y axis alignment errors in double
side PCB or solder resist printing. This method works
very well.
> Any other clarification would be helpful as well.
>
> I have the repair manual for this printer, but I'd
> like a little bit more on the theory behind the
> electronics modifications. If I can get
> a bit more information, I'd be interested in
> releasing a step-by-step
> how-to on the printer, complete w/ my own source
> code and
> schematics/pcb layout to help others create
> functioning PCB printers.
Having service manual that's great. I got it a few
weeks a go . I will also give the schematic and
program but I need to touch a little bit to the
schematic and code. There are so many unnecessary
things exist on schematic and in the code coming from
early tests.
If you are in USA or time difference in an acceptable
range we can communicate using messanger I will be
happy to help you during your modifications.
Good luck,
Volkan