Setting up
As I played around with the photocell to familiarize myself with its sensitivity, I had the thought of using this very simple set up to capture the light level changes of a sunset. I had no idea how long sunsets last since it changes by the season. This would be a chance to enjoy it fully.
Since I don’t have a lot of experience in using Arduinos and writing code in the IDE, I asked my best friend Claude to help me set up a simple code that helps me capture a light reading every 60secs and print out the results with the corresponding timestamp and sensor reading. While setting up the photo cell with a 10Kohm resistor, I realized that the size of the resistor affects the photocell’s sensitivity to darkness and the output values. I decided to bring both a 10K and 1K resistor to test the sensitivity I need on site.
Finding a site
I got to the park around 6pm. Sunset officially begins around 6:40pm so I had some time to find a site. As I walked around, I noticed the golden glow hitting on the trees that are directly next to the river and the running path and decided to station at one of the trees so that the sensor can pick up the sunlight fully.
I changed the timer interval to 10 secs and tested out both 10K and 1K resistors. I realized that they decrease in value in around the same magnitude – around 4 ~ 8. The 10K resistor results in an output starting from 956, very close to the full reading of 1023. Where as the 1K resistor began with a reading around 580. If the difference is the same – does it matter which one I choose? What would these numbers mean without a frame of reference?
The sky darkened and the sun angled lower. I had no time to waste and went with the 1K resistor, feeling as if the lower numerical value is a more ‘accurate’ representation of the light I was experiencing through my body.
Reading the sunset
I sat and watched the sunset with my photo sensor. It was very surprising to read the values coming from the sensor every 10 secs. 485, 478, 475, 469… I could barely see the light change before it really gets dark – maybe every 5 minutes at best? I watched the sun, and then watched the numbers, feeling every moment of the light change. Numbers validating my senses.
At one point when the sensor hit around 220, I felt the temperature drop! Was it the effect of seeing the numbers? Was it heightening my own awareness?
Wrapping up
As the sun disappears, the street lamps started kicking in. The sensor was outputting values around 140 at this point so I decided to leave since I was concerned that the sensor would pick up the light coming from the lamps.
Findings
I didn’t know how to output the values from the serial monitor so I was only able to capture values over a 5minute period. In a CSV, I then plotted the values on a line chart with indicators of each reading. It’s very interesting to see the pattern of a decrease in magnitude (around 10 – 13) every minute.
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What to try next
