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This project is an investigation into the effect of light intensity on the health of plants and people, or more specifically, gardens and gardeners.

I have spent my life moving back and forth between the north of the UK and the south, and even as far as France, and I have always been puzzled about the incredible effect that geographical location has on plant growth in my gardens, and on the physical health of myself and my friends.

As a child, I moved from Glasgow to Paris and back before the age of 9 and was acutely aware of the changes that I saw my own physiology and on the plant life around me. This same observation held every time I visited Scotland as an adult, through verious seasons and changes of weather, and then reversed as I returned to work in the south. In recent years, as my community and I have matured, I have become aware that certain more serious health problems are more common in the north, and that these are almost certainly brought on partly by lack of sun exposure. At the same time, I have now become a garden owner myself. I now struggle daily with very different gardening challenges in the south, from those of my garden-owning friends in the north.

Throughout this process, I have noticed that gardeners and dog walkers seem disproportionately insulated from the health problems associated with northern living. This is presumably because their hobbies force them outside every day, regardless of the weather.

I know that the difference in human health and plant life, between north and south, is almost certainly to do with light levels. However, I am constantly frustrated by my own inability to accurately measure light intensity with my own eyes. I feel that if I could properly judge how much sunlight I have had in each day, I could make sure to get enough, and teach others to do the same. I would then also be far better able to judge which spots would give a good home to which plant species in my garden. However, this is not an easy call to make.

The difficulty in judging light intensity is caused by the accommodation of the pupil of the eye. The pupils adjust naturally to light intensity. Therefore in any given situation, there seems to be just enough light. The very adaptability of the human being to living in any light intensity, makes it just a little harder for us to live really well, in any light intensity.

My hope in this project is to build a light meter that will enable me to accurately measure how much light there is in my environment in a range of different situations and at different times of day and year. My hope is that this will better enable me to manage my own physiology and also my own garden, with much less guesswork. I am living in Cambridge, but I am helped in the project by my life-long friend Catriona Ferris, who lives in the west of Scotland. She is going to take matching readings to investigate the light intensity in her own environment. Catriona and I are both keen gardeners and we have already investigated and compared most of the other growing conditions in our very different gardens, discussing every detail over facebook. This year we will investigate light conditions, to try to find insight into how light intensity affects not just our plants, but also our own lives and those of our communities.

The design that I have chosen for the light-meter is built from an Arduino and associated parts. My hope is that if we find really interesting results, then this could be turned into a population-level educational tool. It could perhaps be distributed via a magazine like Gardeners' World Magazine or via a tv program like Springwatch, underpinning a national study of light levels in lives and gardens. That way the keen maker-teenagers of the country could build these machines and educate everybody else around them about the nature of light, and its effect on their gardens and health.


Visit the hardware summary page to find out about the construction of the light meter.


Visit the software summary page to find the code that runs on the light meter.

Installation, Maintenance and Testing Guide

Using the machine is very easy. Just plug it all togehter. Plug into the computer with the Arduino's usb cable. Run the arduino software and past the code above into the code window. Then press the button (top left) to upload the code to the Arduino. Then unplud from the computer and plug in the battery and walk outside. The machine should automatically start displaying the light intensity on the lcd screen. The table below gives some example readings.

Some light meter readings

Maps of test areas


To see the results of our experiments please visit the following links:

August 2017

September 2017

October 2017

November 2017

December 2017

January 2018


I have no claim on this design. The parts are all commercially available, specifically to do this, and I am just using them for my own fun.