A Maker has developed a UV monitor based around an ambient light sensor, an ATmega168 and a 3V battery.
Summer is quickly approaching. That means weekends at the beach, all day picnics and more time doing chores around the house. This also means more time spent outdoors and the inevitable bout with sunburn. Sure, those rays and extra vitamin D always make us feel and look good in the short, but that love isn’t a two-way street. Aside from painful, bright red arm and face, long-term unprotected exposure to sun can cause wrinkles, age spots, and potentially lead to benign and cancerous skin lesions down the road. As a way to keep us all a bit more mindful of potential epidermis damage, one Maker by the name “matrixwide” has developed a UV monitor based around an SI1132 light sensor, an ATmega168 MCU and a 3V CR2032 battery.
A recent entry in this year’s Hackaday Prize, the aptly named Sunburn Monitor employs a sound-based interface that emits beeping signal settings indicating skin types (ranging from pale white to dark brown) and the use of sunscreen (none to SPF 45). As the Maker notes, this is to save power and reduce the cost of a display, especially since the monitor will often be outdoors in bright sunlight where only reflective displays would be usable.
“SI1132 was chosen as it produces a ‘calibrated’ UV index and takes up very little space. The ATmega168 was chosen as a cheap uC with hardware I2C support which is supported by the Arduino environment,” matrixwide writes. This, of course, enables a broad range of users to easily modify the code as they see fit in the IDE.
As for power management, the system relies primarily on either deep sleep via hardware interrupt or watchdog timer interrupt for sleep-wake-sleep monitoring cycles. One of the Sunburn Monitor’s P-MOSFETS is tasked with controlling the power to the UV sensor, while another handles reverse-polarity protection.
Though the board’s current form factor (1.95” x 2.02”) represents a balance between ease of assembly and wearability, future iterations will be shrunken down to allow for remote sensor. For that version, the Maker says that he plans on implementing an UV photodiode and a tinyAVR instead.