Sunday, April 20, 2014

Personal UV Sensor reboot

Back in 2011 one of my CFT projects was to develop a personal UV sensor for those who are a high risk for skin cancer.  Due to the limited availability of tuned UV sensors (i.e. a reliable source for UV Index rating values), I had to abandon the project. I produced one prototype, as outlined here: http://toddbot.blogspot.com/2011/08/uv-index-monitor-prototype-1.html but had to put further prototypes on hold due to  sensor procurement issues.

Well, apparently there is a rumor that the forthcoming Apple iWatch will include a UV sensor ( http://www.macrumors.com/2014/04/08/iwatch-uv-light-exposure-sensor/).  This is great if you have an iPhone, lots of money and want a new watch, but this isn't my target.

But, the new UV chip they are using, fits my budget: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si1132.pdf.

I want something small (and cheap) enough that you could clip it to a hat, a UV windbreaker, shirt or blouse. Oh, and it should be water resistant (wear it on the beach or by the side of the pool) or even water proof (go swimming with it on).  It should also allow you to set a timer (in hour increments) to remind you (via beeping) to apply more suntan lotion.

The only UI would be a capacitive touch sensor. Press to see (or hear through beeps) the current UV index. Press to set timer.  LEDs (matching UV Index official colors) and/or small buzzer would be the feedback mechanism.  It should cost under $20 and the battery should last a few years (at least 5) under moderate UI usage.

Why do this?  Well, why is every (new to market) useful sensor device required to work with RF and/or interface with your phone?  Why can't tech just "be there" when you need it, rather than be "gadgets" that work with other "gadgets".

Heck, give me a 10 year battery life and I'd say you just sew the thing into clothing.

Okay, I've said way too much.  Let's just say that I am working on it.... stay tuned.


2 comments:

Anonymous said...

I'd like to see how you work out the low power, minimal ui interface challenge ...

Todd Coram said...

Low power is easy. A low power MCU (like the SiLabs C8051 : http://www.silabs.com/products/mcu/capacitivesense/pages/c8051f8xx.aspx) combined with the UV sensor consumes next to nothing in sleep/idle and a combined 12-15mA during activity.

(The UV sensor reads well under a millisecond.)