In a few days I will start to build a hand railing for my stairs out of bamboo with a built in LED strip. I want to be able to indicate the position of a person standing on the staircase by illuminating an LED at the corresponding distance along the length of the hand railing. Of course I will be needing an individually addressable LED strip for this but that is not the issue, neither is the micro controller I will be using (I figured an ESP8266-01 would do nicely, hoping to also being able to switch the led strip wirelessly).
I am kinda stuck on the measuring distances part. The best case scenario would be that the measuring sensor(s?) would be integrated in the railing itself, which would mean sensing from the side. I don't know if this is possible other than using multiple ultrasonic sensors but this would mean that components will be visible through holes in the bamboo and that kind of takes away the magic. It also means that the code will be more complex since I have to check how close the person is to one sensor compared to the other to get a more precise distance. I am looking for the most elegant solution here.
Another option is to measure from the top or bottom of the staircase but the only sensors I came across were either the ones that couldn't measure more than a few feet or this really expensive one:
My questions are: What is the best way to approach this? What sensor(s) do I need in order to keep costs at a minimum?
This is my first post and my drawings are awful so, please be gentle :).