Biosensor Array Body Temperature
The goal of this sensor is to provide regular measurement of the user's core body temperature. Work on this sensor has, primarily, been carried out by Shawn Blaszak.
- It has been decided to switch the sensor from the tmp102 to the DS18B20 (http://www.sparkfun.com/products/245). The reasons follow:
- Fewer Arduino channels needed.
- Fewer wires needed from the sensor to the base unit.
- Fewer external components.
- 1-wire library doesn't interfere with the present, interrupt driven, main Arduino sketch structure.
- We have selected a shielded, 5 conductor, cable from Newark Electronics (www.newark.com) to connect the sensor to the biosensor array base unit.
- Without a bare PCB requiring an enclosure, we have been able to shrink the sensor size and mount it, directly, onto the end of the multi-conductor cable. Heatshrink tubing is used to seal the connecton between the sensor and the cable.
- The other end of the sensor cable is connected to a four conductor, 3.5mm, audio plug which connects to a female, four conductor, panel mounted 3.5mm audio socket on the base biosensor array unit.
- Wiring color convention:
- Black wire - Ground
- Red wire - Power
- Yellow Wire - Data
Alternate/Cost Saving Modifications
The following are some changes that can be made to the design of this sensor to help lower the cost:
- Rather than using 3.5mm jacks, the sensor cable can be soldered directly onto the Arduino shield.
- Less expensive cables can be found. Cables with fewer conductors (only three are needed presently) and unshielded cables are both possibilities that might prove less expensive. Also, it may be possible to re-cycle existing wire from broke/out of use equipment.
- It has been decided to locate the sensor in the armpit of the user as placing it in the mouth presents a choking hazard during physical activities.
- The sensor chosen is the TMP102 breakout board available from Sparkfun Electronics: 
- Digital I/O means we can use flexible wires as opposed to more brittle thermocouple wire that can break if kinked.
- Sparkfun provides a link to pre-existing Arduino code for this sensor hosted on the Wiring website: 
- Small enough to fit under a person's armpit
- Reasonably fast response rate.
- Bare PCB requires some kind of enclosure or other potection from sweat and other moisture.
- 5/16/2011 - The DS18B20 sensor code has been added to the main Arduino sketch and is working. The physical sensor lead has been completed and the female plug on the main biosensor array unit has been mounted.
- 5/10/2011 - The decision has been made to switch from the tmp102 sensor to the DS18B20 1-wire sensor available from Sparkfun.com (http://www.sparkfun.com/products/245). This was done because it requires fewer external components; requires fewer Arduino channels; and we believe it won't interfere with our present interrupt driven Arduino sketch setup. This will represent version 2.0 of the body temperature sensor.
- 4/10/2011 - Communications testing complete - 4/10/2011 
To Be Completed
- Long-term durability/reliability testing
- Continued vigilence for a cheaper/easier alternative sensor and/or cable.