# Airbag Protection and Alerting System for Elderly People
## 4 Results and Discussion
The proposed system has a relatively low cost (JOD 113.25), very quick response time (only 150 ms delay from electrical grid), low power consumption (11.1 Wh), and very good accuracy (90%). Thus, increasing the applicability of our system. All of our components are function-safety critical. They were selected to achieve a long operating life with the smallest size, lightest weight, highest quality, greatest reliability, and with a minimum cost, thus increasing system efficiency. Components were purchased from trusted manufacturers who use proven manufacturing methods. Duplicating electrical components to achieve redundancy will not be cost effective nor provide a suitable size. The average life span (useful life) of the system consists of three phases, where each phase is critical to a certain kind of component:  
* Phase I (wear in, infant): This phase is critical for software programs as most failures in this phase occur due to design flaws or wrong assembly, for example: Arduino Nano microcontroller. * Phase II (useful life): This is the longest phase and the most predictable, as most errors or failures are random. Electronics experience this phase the most, for example: Boost converter. * Phase III (wear out): This phase occurs due to stress, fatigue, and aging which applies to most well assembled and designed mechanical components, for example: Solenoid air valve. Table 1 illustrates our system's average life span criticality on a scale from 0-3, where 0 is least critical to 3 which is most critical. Figure 17: Accelerometer’s accuracy under various thresholds. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Component** & **Life Span** & **Maintenance Type** & **Justification** \\ \hline \multirow{4}{*}{Arduino Nano} & Around 2–3 years (hot environment), up to 10–15 years (cool environment) & Scheduled maintenance (let a technician test it, if it functions store it for emergencies, if not salvage) & Checkups are not possible, we must take a short yet suitable period both financially and practically because our system is a safety system, so we need to have a safety factor or margin \\ \hline \multirow{4}{*}{Gravity sensor (ADXL345)} & \multirow{2}{*}{\(\infty\)} & Condition-based maintenance (let a technician test it, if it functions reuse it, if not salvage) & There is no specified expiry or life span \\ \hline \multirow{4}{*}{Solenoid air valve} & Approximately 5 million cycles & Condition-based maintenance (let a technician test it, if it functions reuse it, if not salvage) & There is almost no need for maintenance since it can run so many times while our application does not logically require even a close number of cycles, but we still do it for extra safety \\ \hline \multirow{4}{*}{MOSFET IRF520} & \multirow{2}{*}{\(\infty\)} & Condition-based maintenance (let a technician test it, if it functions reuse it, if not salvage) & There is no specified expiry or life span \\ \hline \multirow{4}{*}{Bluetooth BLE module (HC-06)} & \multirow{2}{*}{\(\infty\)} & Condition-based maintenance (let a technician test it, if it functions reuse it, if not salvage) & There is no specified expiry or life span \\ \hline \multirow{4}{*}{Lithium-ion battery 3.7 v, 3A (charge)} & \multirow{2}{*}{A minimum of 8 h} & Scheduled maintenance (check every 8 h for battery percentage and recharge regularly) & There is no specified expiry or life span \\ \hline \multirow{4}{*}{Lithium-ion battery 3.7 v, 3A (life span)} & \multirow{2}{*}{Around 2–3 years or 300–500 charge cycles} & \multirow{2}{*}{Scheduled maintenance (change just before the 2-year mark)} & Checkups are difficult, so we must take a short yet suitable period both financially and practically because our system is a safety system, so we need to have a safety factor or margin \\ \hline \end{tabular}
\end{table} 
Table 1: Average life span criticality.