AGSB

2011

Light Sensor Project Design & Technology

James Persico 09JY

Brainstorm

Light Sensor

Fire exit lights

Emergency lighting

Power cut light backups

Amount of light

reaching crops

Photographer’s light meter

Light Pollution

These light up when

there is not enough

light to show them

clearly enough.

Fire exit lights often

contain a light sensor

unit that activates the

light when electricity

fails, and people need

to find an exit.

Environmentalists can

measure the amount

of light pollution

caused by

streetlights/floodlight

shining into the sky.

Photographers use light sensors

to measure the average amount

of light in an environment to help

them decide shutter speed, ISO

speed and aperture.

A farmer could work out how

much light his crops are

receiving. If they are placed in a

shaded location, he can see if

there is still enough light reaching

the crops.

Problem I believe my local area contains levels of light pollution well above those necessary for safety. I want

to conduct a science experiment to measure levels of light pollution in urban, sub urban and rural

locations, to see if there is a noticeable difference. Light pollution can ruin health, as clinical studies

have shown that the body needs an extended period of darkness to be able to sleep well, and

damages nighttime views of the Milky Way, now invisible in most of the UK.

Brief I need a light sensor capable of detecting light and indicating the level of light by giving a reading in

some way. I need it to be robust, portable, and reliable, for the purposes of my experiment.

Example of light pollution (source: moblog.com)

Specifications

MUST

It must detect light - Crucial to the entire project

It must be fully functional – No parts must be faulty or irregular.

It must use a 9V battery – This is what the circuit runs on

It must have an on/off switch – To save battery power

It must have all components enclosed and secure inside the case – To keep everything

together

The case must have no convex corners <20mm or concave corners <80mm – To avoid over-

curved or over-sharpened edges.

The base must be secure – To avoid the contents falling out.

The product must be finished well – To ensure a professional look and maximum safety

The 4 LEDs must be in a sensible order or colour – Easy to understand colours help the user

operate the sensor better without having read the manual

All wires must be secured using securing holes – To ensure safety and rigidity

Have a moulded top – To provide an aesthetically pleasing design

SHOULD

Be portable – To expand the device’s uses

Be durable – To withstand the small knocks of daily use

Have easy access to the battery – So the user can replace a dead battery with ease

COULD

Have a logo – To improve appearance

Include accessories – To aid in using the device

Final Idea

Sunrise, indicative

of light

LEDs, indicate

level of darkness.

Robust cylindrical

design.

Switch

Light detecting

resistor

Finished Product

The product also comes with a free gadget to open the back of the device, allowing the user to

change the battery when the one supplied is exhausted.

Testing the device

In a dark location (cupboard)

Testing the device under a standard sodium streetlight. The LEDs show that the lighting level is

above reasonable darkness, and that light pollution is taking place. A satisfactory level of lighting

would mean all lights would be lit up, while the red one is clearly out in this picture.

Evaluation

Mould Design I think the mould design was one of the best aspects of the product, reflecting its intended purpose

while not looking loud or messy. The black colour I chose helps the user distinguish between the

lights and the plastic when the product is in use.

The circuit I improved on the work I had done with the PICAXE project in Year 8, and my soldering was, overall,

much tidier. I only had one overflow of solder, and this was easily fixed inside a minute. In future I

could start to concentrate on my speed, as this became a small issue towards the end of the project.

The logo I used the skills I learnt from the Clinometer project to help me produce a Sticka logo for the

product, again in the name ‘Delta Tech’. I could have improved by increasing the size of the font,

this would have wasted less material, as I had to scrap some messy and badly cut Stickas, simply

because the machine was finding my drawings too small.

The back removal panel The panel hole used to remove the back to replace the battery can also be used to hang the light

sensor on a wall, so as to measure general room lighting, which is an added bonus. However, the

back could be finished better, so there is room for improvement.

Conclusion Over the course of the project I have used many skills acquired from the previous project, and

revised ones from projects I did several months ago, like vacuum-forming and PCB drilling. I finished

the product in time, and it is in full working order, as shown in the pictures. I have also managed to

solve my problem of testing light pollution, and may use the results as evidence if I decide to follow

up the matter with my local authority.

The product has met its specifications and has shown it can be used flexibly in other scenarios too.