Light Level Meter [1], is a Firefox OS app developed by myself to demonstrate the use of Mozilla WebAPI [2]. The app measures the ambient light level in lux [3] and present in realtime. It records the max and min values and plots the variation of the light level over time.

I've made use of DeviceLightEvent [4] to get the current ambient light level from the light level detector in the device (I have tested it with Keon [5]). The real time chart is implemented using Smoothie Charts [6] which is a simple, easy to use javascript charting library for streaming data.

Measurement of ambient light level has many uses. One is that it could be used to adjust the light level of electronic visual displays that are there in many of the devices we use today such as mobile phones and tablets. By such adjustments based on the ambient light level, we could save energy while delivering a comfortable reading experience to the user.

Another use of measuring ambient light level is in electrical lighting design. For example, the light level recommended for reading is different from that is recommended for hand tailoring. Recommended light levels in building designing in Sri Lanka can be found in page 38 of "Code of Practice for Energy Efficient Buildings in Sri Lanka" [7].

Source code of Light Level Meter [8].

[1] https://marketplace.firefox.com/app/light-level-meter
[2] https://wiki.mozilla.org/WebAPI
[3] http://en.wikipedia.org/wiki/Lux
[4] https://developer.mozilla.org/en-US/docs/Web/API/DeviceLightEvent
[5] http://en.wikipedia.org/wiki/GeeksPhone_Keon
[6] http://smoothiecharts.org/
[7] http://www.energy.gov.lk/pdf/Building%20CODE.pdf
[8] https://github.com/callkalpa/callkalpa.github.io/tree/master/LightLevelMeter