Blaze UV Key

I put together the electronics and software for a mobile FSK UV Sensor.

04 July 2014

This post has been migrated from its original home to here. It originally lived at this location.


The Blaze UV Key is an ultraviolet (UV) sensor that connects to an iPhone to display an accurate UV Index reading wherever you are. The UV Index, is an international standard measurement of the strength of ultraviolet radiation from the sun at a particular place in time.

How it works

We’ve combined the UV sensor into a concise electronic circuit that communicates with an iPhone through the audio jack.


Using a technique called frequency-shift keying (FSK) we can transmit data through tone. Connecting devices with the headphone jack is nothing new, if you cast your mind back to the era of the Sinclair ZX81, loading a program was done with an audio cassette that had a program stored on it with FSK. By playing the audio tape to the Sinclair, you were loading the program into the device.

The iPhone app we’ve designed visualises the current UV index reading as well as providing timers and alerts for the user to apply more sunscreen or seek shade.

Here’s a short video of our prototype in action.

Next steps

At the minute, our circuitry sits inside a host iPhone case mounted to the back of the iPhone in use. In the future, we see this being shrunk down further to fit inside a key fob, so you’d always have reliable and accurate UV index information at hand to stay safe in the sun.


Links & resources

Project page: BLAZE UV Key
Project code: GitHub

BIMA awards finalist 2015: Phone app & portable sensor category
Wirehive awards winner: Best use of tech