Week 9

This week we focused on testing various aspects of our bandage starting with the illuminance of the LED matrix.  We used a dark closet along with a light meter, as shown in figure 9.1, to take the measurements displayed in table 9.2 below.

Figure 9.1 - Light meter being used on the PDT device (dark room not visible)

Table 9.2 - Illuminance of LED matrix in lux

As is shown in table 9.2, reading were taken directly on top of the matrix as well as 1mm above the lights.  Interestingly, the illuminance was greater when flat on the matrix meaning a final product must have the LEDs as close to the patients skin as possible.  

In addition to how much light the matrix gives off, we testing two different batteries with the matrix.  Figure 9.3 below shows both batteries next to the PDT device.

Figure 9.3 - 6v camera battery (bottom), 6v lamp battery (top)

We plan on using the larger battery for sustained tests while the smaller one will be used for demonstrations as it is close to the size a battery on the finished product would be.  

The reason the large battery was selected was for its capacity.  The LED matrix requires 1.7 volts and draws a current of approximately 2 amps overall.  As stated above, this capacity allows for sustained testing of the matrix.  Because lamp batteries predominantly come in 6 volts, a smaller battery that has a 6 volt drop was selected for ease of use when changing batteries.  In order to supply the proper voltage to the matrix, ohm's law (V=IR) was used to determine that a 172 ohm resistor was needed between the 6 volts supply and LEDs so as to not blow the diodes.

We are working hard on our presentation and final report and look forward to sharing our design next week!

-The team