In my earlier post titled “Designing a Sensor Helmet” I defined the groups that the helmet is comprised of.   Since the main purpose of the helmet was to detect telemetry, this post I will go into more details on the sensor group.

The electronic sensors supplied fall into to types, analog (A) and digital (D).  This will determine how the micro controller will read them.  The sensors that will be incorporated into the helmet fall into 4 use categories, these are:

1. Spactial – GPS Receiver(D-TTL-UART), 3-Axis Tilt Accelerometer – Compass(D-I2C)
2. Meteorological – Temperature – Humidity(D-1wire), Light(A), and Barometric Pressure(D-I2C)
3. Environmental – Dust Particle(A), Sound(A), CO1(A), CO2(D), and Methane(A)
4. Biometric – Heart Rate(A)

There were 3 significant factors in deciding which sensors to use.  The choices were made based on low power consumption, size, and cost.  Here is a table listing the sensors based on costs.

Sensor	Retail Cost
CO2 Sensor	$56.00
GPS Receiver	$39.95
Tilt-Compass	$29.95
Pulse Sensor	$24.95
Dust Sensor	$11.95
Humidity-Temp	$9.95
Barometer	$9.95
Sound MEMS	$9.95
Carbon Mono	$7.25
Methane CNG	$4.95
Ambient Light	$4.95
Total	$209.80

One of the key functions of the helmet will be to plot the data with points from the GPS receiver.  This will allow data to be layered on maps for route analysis. The steps on how to do this has yet to be refined.  The GPS receiver and CO2 sensor I sourced will put me over budget.  I also held back purchasing the Tilt-Compass and Pulse Sensor.  The Dust Sensor was out of stock and didn’t include the connection cable.  I was able to find the Dust Sensor on eBay so I’ll need to make a determination.  The item is key but the function can be offset using the GPS functions of a smart phone.

The imaging system, described in the next post, will record 1280p 30fps video.  The sensor data points can be overlaid on this video for visual analysis.  This will be done with Dashware and was demonstrated in my QuickFire video.