The Final Project: How Our Device Works

Block Diagram of the Device:

           

As seen in the block diagram, the device is broken into two main parts. The first is what actually detects the pulse. This is accomplished through the transmission of infrared light from the IR LED to the IR receiver. As the infrared light passes through the person’s finger, changes in the transmission of light are caused by the person’s pulse. These changes in transmission are then detected by the IR sensor. The IR sensor is connected to the analog pin. The numbers relating to the transmission of the infrared light to the receiver are then taken in by the Arduino board and are the same numbers that are displayed on the Serial Monitor. The Serial Monitor in our program displays the raw value as well as a corrected value meant to smooth the function if the values were to be graphed. As seen in the block diagram, this occurs after the program (documented in the Appendix) detects changes in the numbers transmitted from the receiver by defining specific variables each time the loop is run; this is the second box on the left side of the block diagram. When a change is detected in these variables, the Red LED in serial pin 4 will blink. If there is no change detected in the variables, the program is coded using the “digitalWrite” function so that the Red LED will remain constantly lit.

The timer loop runs separately from the rest of the device.  By defining a clock, and setting up the Arduino so that it records time, it was capable to make a timer. As seen in the block diagram, the time at which most functions of the timing portion of the device are defined is 30 seconds. Once the timer hits 30 seconds, this triggers the buzzer to go off and the Green LED to light up. The device is also programmed to reset itself once 60 seconds have passed. The loop thus causes the device to go through the cycle all over again and the buzzer and light to activate again at time equals 30 seconds.