Unformatted text preview:

IR transmission and detection. IR diodes and phototransistorMASSACHUSETTS INSTITUTE OF TECHNOLOGY 6.071 Introduction to Electronics, Signals and Measurement Spring 2006 IR transmission and detection. IR diodes and phototransistors InfraRed (IR) signals are used extensively for short range communication. Devices ranging from entertainment systems to transportation and security systems use some sort of IR signals for “remote communication”. In this lab we will explore the characteristics of these signals from generation to detection and will also design and construct support circuits for the detection of such signals. The lab is designed to assist us with your final project: the heart rate lab. Experiment 1. We will explore a few concepts that you are likely to encounter in your heart rate project laboratory. You will use the IR diode QED123 and the phototransistor QSD124 to transmit through the air and detect a certain signal. The signal is provided by the instrument called IR_Laboratory.vi. This instrument generates a signal with the following properties: DC offset Slow varying DC value Small amplitude pulse with a frequency of 1 Hz 60 Hz noise signal Your task is to use this signal to power your IR diode, use your phototransistor to detect the signal transmitted by the IR diode and process the signal so that only the pulse signal remains. The block diagram of the experiment is shown below: QDPhototransistorinterface circuitinpout signalfrom DAC0IR diode powercircuitprocessed signalto ACH0 The first step in the design of the IR diode power circuit and the phototransistor interface circuit is to look at the data sheets of these devices. The data sheets are available on the class web site. 6.071 Spring 2005. Chaniotakis and Cory Page1Show your designs and your observations on this page. 6.071 Spring 2005. Chaniotakis and Cory Page2Experiment 2 You may now be able to actually see some rudimentary form of a signal that corresponds to your heart pulse. Here is the idea: Use again the IR_Laboratory instrument to generate the desired DC voltage to power your IR diode. Set the amplitude of the Pulse Signal to be zero. You may want to test the performance of your circuit with and without the noise. By placing your finger between the diode and the phototransistor, the fluctuations of the blood volume in your finger will result in fluctuations of the transmitted IR through the finger and thus in fluctuations of the energy seen at the base of the phototransistor. This will in turn produce fluctuations of the phototransistor output signal which you should be able to see. QFingerDPhototransistorinterface circuitDC inpout signalfrom DAC0IR diode powercircuitprocessed signalto ACH0 Observations: 6.071 Spring 2005. Chaniotakis and Cory


View Full Document

MIT 6 071J - IR transmission and detection

Download IR transmission and detection
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view IR transmission and detection and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view IR transmission and detection 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?