Troubleshooting Optical endstops

Hi, I've had an optical endstop for free from a company to try out and see if I like it. However, the endstop would not trigger on many occasions. However, I did manage to get it working about half of the time.

Measured all cables, checked out all the PCB traces, nothing wrong, connector was working fine too.

Now I have ordered these:
[www.reprapsource.com]

from this webshop:
[www.ebay.nl]

I suspect that the free one I got (was another design than the one I bought now) had a problem of noise somehow. But maybe I was doing something wrong.

For example, I had printed 'flags' to enter inside the optical sensor. They would sometimes and sometimes not trigger it, but they were completely in there, so I could not find a reason why.
Are there known cases of digital/electronical noise generated by the machine that can distort the function of such a optical sensor?

And is there a place known where I can troubleshoot the optical sensors if something goes wrong with the new ones I ordered?

Wish you all a happy easter!
- Marinus

If you tested endstops with printed flags, not all materials block IR well and perhaps the printed flags dont do a good job at blocking either. Can you clarify if you tested with multiple materials, specifically if you see any difference between metal flags and plastic printed ones.

With opto end stops:

One side of the opto is the emitter, and the other side is the sensor. Make sure the emitter side is toward the floor or away from any light source.

Any other light source can trigger optos if it contains the right light frequencies that the sensor is sensitive to. Many of the sensors are sensitive to Infrared, which means sunlight can set it off of the sensor gets exposed to sunlight.

As regards to the opto flags themselves, I recommend painting them with an IR absorbing paint. If you don't, the flag itself can reflect outside light back into the sensor. I've used spray-on cans of "Kettle black" for this purpose, as it tends to absorb IR and it's usually a matt black (so no reflections).

Thanks for your tip, I've designed a small shield that can be placed over the optical sensor, that allows in the endstop flag, and at the same time block all outside light.

Let's hope this is sufficient I never knew that other light sources could influence the continuity of these sensors.