WEEK 5 & 6

OBJECTIVE :

1.      Finalize sensor probe design

PROCEDURE :

•        Below is the back side of SMT package LED. this package quite difficult to solder because of the size but it its excel in-term of  performance and for sensor placement.

       

•   Then technique to solder SMT package is, first to put a bit of solder iron to make it easy to stick later on

•            This is where the LED will be placed 

       

• Below shows the connection of RED and INFRARED LED. The red wire soldered to red led and the green wire is ground while the orange wire soldered to infrared led

• Below is Light to Frequency sensor TSL235R 

• As usual the red for VCC, green for ground and  orange wire is the output of the sensor to be connected to DSPIC30F2012 later

•  By using a velcro tape. Two hole is made using puncher, one for sensor TRL235R and the other for red and infrared LED

• There are 5 wire all together (LED+SENSOR). by using DB9 connector it is more durable and easy to connect to the main board

CONCLUSION

• SMT LED package need more practice to solder. The overall process took two weeks to finished 

WEEK 4

OBJECTIVE :

1.      Find oxygen saturation formula

PROCEDURE :

• 1.         The oxygen saturation is defined, as SaO2 (SPO2) and s a function of the concentration of the two forms  of hemoglobin in the blood: 

•         The peak follower algorithm uses the differentiated Lowpass output sequence from    the IR sensor as its input. The idea is to allow the Peak variable to follow these differentiated peaks and decay at a very slow rate. It works much like a filter capacitor in a power supply. It attempts to follow the peaks and decays very slowly producing an envelope that can be used to time the heartwave that is produce by the IR signal. This IR signal was chosen because its amplitude is greater that that of the RED source and it doesn’t vary as much as the RED sensor does.

•       The peak follower is used to time the period of the heart wave and also set up a period for the RMS calculation of the AC portion of the signal. In the T1 handler, the AC signal is calculated by taking the difference between the Filtered Sensor output and the DC level (from the DC tracking algorithm). For example, the AC signal from the RED sensor is:

      

              Rdiff = Rfilt – R_DC;

The RMS value is calculated for each sample of the Rdiff and accumulated using the statement:

                Rsum = RDiff*RDiff + Rsum;

               After the period is detected, the RMS value is calculated and Rsum set back to 0:

     

                Rms = sqrt(Rsum/period);

           
                Rsum = 0;

       

                 Once the RMS value is calculated, the SPO2 is calculated by finding the ratio R;

                  R = Rrms/RDC / Irrms/IRDC

                  Then,