Concept Selection

The variable inductance strap concept was chosen to be the sensing method of the final design for four reasons. First, it produced a 17.8% change in inductance when subject to full stretching. This considerable amount of change can compensate for the lesser amount of stretching expected from the infants' chest. Refined wiring techniques can also increase this inductance change.

Secondly, even though the sensitivity of this sensor option is comparable to the aforementioned weight scale option, the cost of manufacturing the variable inductance strap would be significantly cheaper than buying "x" number of weight sensors to implement in a sensing grid. The chosen sensor could be integrated into an infant sleepwear shirt and manufactured cheaply using pre-existing technologies for fabricating clothing and embedding wire into fabric.

An additional economic advantage of this design is the component separation aspect. The transmitter circuitry attached to the variable inductance sensor can be contained in a space roughly the size of a quarter with the thickness of a watch battery. The electronics can be connected to the shirt by a button snap and therefore easily removable by an adult. The sleep wear shirt can be expected to become soiled and require washing or replacement. The freedom to remove the electronic component from the shirt will allow parents to safely wash the shirt or replace it completely for an estimated 10 to15 dollars. The original transmitter circuitry can then be saved and attached to the replacement shirt. Overall, the chosen sensor would greatly boost the marketability of the monitor.

Third, this sensing method will be completely safe for the infant. Circuitry on the infant will operate on current limited to three milliamps and will provide secondary current paths in case of a break somewhere in the circuit. These two precautionary measures will nearly eliminate the risk of electric shock during the lifetime of the device. Furthermore, the variable inductance strap requires elastic that is no more difficult to stretch than elastics used in existing infant sleep wear. So there will be no risk of impeding the chest movement. The signal transmitted from the circuitry on the infant will be transmitted at a very low power and will cause no adverse effects to the infant. According to the Federal Communications Commission (FCC), electromagnetic waves used in any type of wireless communication are not found to cause adverse health effects on humans unless they are in proximity to high power broadcasting equipment such as in a radio station.

Lastly, this sensing method was chosen for its innovative qualities. Although the team has discovered existing SIDS monitors. None have been found that utilize a more cost effective method of sensing that is both safe and reliable. The market price for the Sleep Sound package is estimated to be 100$.