pe2950:
I'm working on a project where i need to detect if paper is waiting in the output tray of a printer.
The printer luckily output tray is a dark blue, with the paper being white; would something like this get the job done?
Reflective Infrared IR Optical Sensor with 470 and 10K Resistors : ID 2349 : $1.95 : Adafruit Industries, Unique & fun DIY electronics and kits
I know there are multiple ways to do this; is there anything that would be more reliable then this?
Any way to know HOW many papers are sitting in the tray?
The printer: https://www.google.com/search?q=xerox+3320&rlz=1C1GCEU_enUS821US821&source=lnms&tbm=isch&sa=X&ved=0ahUKEwigqfOCktLhAhUMj1kKHboJCHoQ_AUIDigB&biw=1920&bih=937
Hi! I'm new to my own embedded design, but I am an experienced photocopier tech.
I'm not a Xerox Brand printer tech, but the technology for paper movement and sensing is pretty standard.
I looked at that printer online from your links, but it is hard to tell what is in there.
It may already have an exit sensor, and you could put your own near that or possibly pointing down.
There are different types of sensors - flagged photointerruptors, or photoreflective sensors that reflect off the paper. The Adafruit looks like that, yes? Also another poster linked a similar sensor.
The sensor should detect white paper, and then you need to devise a way to count sheets.
A copier will read the leading edge of the page, count, then after the paper transport speed, and paper length are computed, then it can be determined that in the breaks between pages, the start and end of each sheet.
The copier CPU then clicks the billing meter, as well as decrements the copy count the user input.
Anyway, a flagged photointerruptor is a spring loaded, flag mounted in a frame with a photo-transistor on one end, and an iR LED on the other. The flag is designed to be hit by the paper, then the counter is started, then say after 11 inches (letter size paper) the flag is released, the spring returns the flag up, and the infra-red beam between the LED and transistor is broken, telling the controller that 1 letter size page has passed.
To be clear, you need a sensor for each function 1) knowing how many sheets, and 2) if paper is present on the exit tray.
Exit trays can have a cut-out in the bottom with a flagged photointerruptor, or a microswitch that is pressed by at least one sheet of paper, i.e. actuated by low weight. So if the flag is down, or if the switch is pressed, then there is paper in the exit tray. High or low tells CPU which.