This is an interesting topic, its just about detecting a tolerant with UV sensors. Imagine cup 2013 Sri lanka local winners claimed that they did thing as the first people but my cousin was a too talented person and told me this simple idea (the secret is  Imagine cup 2013 Sri lanka local winners . My cousin was working for Siemens and was a higher national diploma holder in Electronic Engineering. While I was talking about this to him he smiled and told me this ‘UV sensing a tolerant surface’ is not a hard method and that’s just all about a simple but “costly” method.

This type of detection is very very useful while we develop some thing for blind people and using this they can easily identify “up stairs” (not down stairs), Tank like cylinder objects, Pyramid shaped objects and much more.


All we need is a(or more) 9V battery, 9 UV sensors and a card board

How to build

Get a 12” x 12” card board and put every next UV sensor in every 5.5”” gap and the angle moves on only 90, 180 and 270. just like below


How to detect

The detection is just like the below. Here I set to explain just a tolerant surface.


(Assume, the UV rays come back to the same sensors || Image the green object as stair case)

Simple UV detection is a matter with time, we measure the response time of UV sensor and calculate the distance in meters or centimeters or feet or inches. Its the same process that bats use to fly in night. 

Here we use 9 sensors get get all the responses. I name the sensors R1,R2,R3 (top three) like wise B1,B2,B3 (middle three) and Y1,Y2 and Y3 (bottom three).

Now say, after execute the device (or code) I get the following response times

R1 -> 9s

R2 -> 9s

R3 -> 9s

B1 -> 6s

B2 -> 6s

B3 -> 6s

Y1 -> 3s

Y2 -> 3s

Y3 -> 3s

That means if all R# sensors get the same response time (say it as R#s), all B# sensors get the same response  yime but differ from the R#s (say it as B#s) and all the Y# sensors get the same response  ime which differ from both R#s and B#s (say it as Y#s).

Simply this means its a bottom to top tolerant surface since R#s > B#s > Y#s

so the pattern comes like Y#s > B#s > R#s means that is a top to bottom tolerant surface.

Why 9 sensors, 3 are much enough nah??

This is a good question. but think about this scenario

What if I get response time like

R1 -> 9s

R2 -> 6s

R3 -> 3s

B1 -> 9s

B2 -> 6s

B3 -> 3s

Y1 -> 9s

Y2 -> 6s

Y3 -> 3s

yeah.. this is a left to right tolerant surface. So we cant sure whether the torent is top to bottom or left to right. and this is why use 9 sensors.

What are the problems

There are some very possible problems with this type of system, the main problem is battery life.

If we use a 9V battery for one sensor it will last for 3 hours and if we consider about using 9 sensors, the battery time is just 20 minutes. 

So just think about to

“build 9 sensors in a single sun glass with a 9V battery and its working for 6 hours perfectly..”

this is what we say