I have laser transmitterers and laser sensor modules for some time, and I am excited on the high performance of Arduino Due (that outperforms all other Arduino models including the new ones clearly).
My first thoughts on the current topic were these:
- light takes 3.3ns to travel 1m
- Arduino Due clock frequency is 84MHz
- one clock cycle is therefore 1000/84=11.9ns
- therefore light travels 3.6m in one Arduino clock cycle
That is a challenge. Our living room is 7m long, when opening kitchen door that can be increased to 9m, and with a mirror on the other side I can get 18m measurement distance at home -- which translates to 5 Arduino Due clock cycles.
I searched this forum for "speed of light" and found some threads and discussions, but no solution. Searching the web I found that speed of light typically gets measured with rotating mirrors or rotating gear wheels. I liked the idea to "just measure the time" for the light "to travel a given distance". I wanted to do it without moving parts, and I wanted to try it with Arduinos.
The laser transmitter has some delay, as well as the laser sensor modules. I wanted to cancel out these delays by delta measurements. So I came up with this experiment setup:
Of course (30+34.5) cm is by far too low, light travels less than 0.2 Arduino clock cycles for that distance, later the 2nd mirror would be placed 7m or 9m away from the laser.
Short description of the experiment:
- laser transmitter sends a beam
- half of the beam gets reflected at edge of mirror 1 (N) and goes to sensor 1
- the other half does not hit mirror 1, gets reflected at mirror 2 and reaches sensor 2
I have a lot to write and photos to show, so my plan is to not write one monster posting but start this thread with several postings, the last one being on discussion of the results, discussions I had with colleagues at work, next steps, questions.
But before submitting this posting and starting this new thread, let me summarize the results obtained sofar:
- speed of light c=299792.458 km/s
- the order of magnitude of measurements is correct !
- the 14m measurement calculation gives 56313 km/s (18.7% of c)
- combining different measurements calculation gives 67355 km/s (22.5% of c)
- bill of material for the whole experiment is 30$ only (2 Arduino Due, 1 Arduino Uno, ...)
The pictures/diagrams/photos that will be shown in the next postings are displayed not that big. You will get much better resolution by right clicking them and open in original size.