Design an infrared pulse monitor

Challenge: Create an infrared (IR) monitor to detect the human pulse in a finger.
Materials: circuit components, breadboard, plastic tube, and foam pieces.
Performance evaluation: Measure student’s heart rate.
What is the need or problem that this product addresses? What are the design criteria?
Write your answers in your report. Read the text aloud
An oximeter that measures the oxygen content of blood using visible and infrared lightHuman flesh is partially translucent at IR wavelengths. A pulse monitor has an IR LED that radiates light across the fingertip and a photodetector on the other side that detects light passing through the fingertip. As the heart beats, arterial blood vessels expand and contract, blocking varying amounts of the IR light. Read the text aloud Show Pulse oximeter
Circuit design for the infrared pulse monitor
  1. Build the LED lamp and switch portion of the circuit. Test it by verifying that the LED goes on and off when the switch is pressed.
  2. Build the QED (IR-emitting diode) portion of the circuit and the second LED lamp (and other 100 Ω resistor) portion of the circuit. The LED should be illuminated.
  3. Build the QSD (IR-sensing diode) portion of the circuit. The QSD should be detecting light overhead, which will cause the LED to turn off.
  4. Add series resistors and adjust the potentiometer so that the LED illuminates when you cover the sensor with your hand.
  5. Point the QED and QSD at each other. Modify the resistance (series resistors and potentiometer) so that pressing the switch turns the sensor’s lamp on and off. Read the text aloud Show About these electronic devices
Place your finger between the emitter and sensor and optimize the circuit performance to detect your pulse. (Hint: Add one or more resistors in series and adjust the potentiometer.) Read the text aloud
Create a design based on this circuit for an IR pulse monitor using the tube, foam, duct tape, and/or other common materials. Read the text aloud
Construct the prototype of your IR pulse monitor using the equipment. Read the text aloud
Measure your pulse. Is your measurement reasonable and easy to take? Read the text aloud
How well did your design work? Evaluate its performance. Read the text aloud
Based on your evaluation, improve your design. Prototype and test it. Read the text aloud

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