Validation

Fan Sound Test

In order for the mask to be as quiet as possible, the quietest fan needed to be determined. The sound (in dB) of each fan was measured at different voltages. The normal sound baseline is approximately 25 dB, and this value was subtracted from the recorded measurements of each fan's sound. The test determined that the medium and large fans are noisier and larger, thus being impractical choices for the mask. In contrast, sound was not detected from the small fan until it was measured at about 5V.

Flow Sensor Test

The relationship between flow (in slm, standard liter per minute) and the voltage applied to each fan was measured. To test the flow of each fan, a funnel was built according to the size of each fan and used so that the air would flow directly into the tube. Errors and noise in the data can be explained by the fitting of the funnels when performing the tests. The smaller fan had a more tightly fitted funnel than the other fans.

Flow Sensor Test - Funnel Set-Up

Flow Sensor Test - Results

From this test, similarities were found between the medium and large fans. Results from this test showed the minimum voltage the fans can run at while maintaining the recommended flow rate (3 L/min, 0.11 cfm).

Battery Life Test

To calculate the minimum battery life of the mask, the battery capacity (1250 mAH) was divided by the average current consuption due to the fan (90 mA), microcontroller (3 mA), single red LED (2.77 mA), and four green LEDs (2.34 mA each). When the mask is in use, the microcontroller and LEDs will be turned on periodically, so the fan will be the only device that is constantly drawing current. Thus, the battery life is expected to be longer than its calculated minimum value of approximately 11.9 hours.