Light Sensor Project Design & Technology James Persico 09JY
Fire exit lights often contain a light sensor unit that activates the light when electricity fails, and people need to find an exit. Power cut light backups
Fire exit lights These light up when there is not enough light to show them clearly enough.
Amount of light reaching crops
Photographerâ€™s light meter
Environmentalists can measure the amount of light pollution caused by streetlights/floodlight shining into the sky.
A farmer could work out how much light his crops are Photographers use light sensors receiving. If they are placed in a to measure the average amount shaded location, he can see if of light in an environment to help there is still enough light reaching them decide shutter speed, ISO the crops. speed and aperture.
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)
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 overcurved 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
Have a logo – To improve appearance Include accessories – To aid in using the device
Sunrise, indicative of light
Light detecting resistor
LEDs, indicate level of darkness.
Robust cylindrical design.
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 â€˜Delta Techâ€™. 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.