Lab Report 2 - ECE-342 Lab 2: Photodiode Light Detector...

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ECE-342 Lab 2: Photodiode Light Detector Stephanie Duy, Robert England Lab Group 4 October 15, 2007 Abstract This report describes the design and test of a photodiode light detector. The detector uses an LF351 operational amplifier and a PNZ334 photodiode, and is tested with infrared, red, and blue light-emitting diodes. The detector requires ±12 V power supplies, and outputs -1 V when it detects an infrared LED, driven with 15 mA, 2.5 mm away. Component selection and test procedures are described. 1
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Contents 1 Introduction 3 2 Circuit Design and Preliminary Analysis 4 2.1 Detector Circuit Design 5 2.2 Test Circuit Design 6 3 Experimental Implementation 7 3.1 LED Modeling ______ 8 3.2 Diode sensitivity_____ 11 3.3 Sensitivity with a Reverse-Bias Voltage_____ 14 3.4 Sensitivity to Distance 16 4 Discussion 19 5 Conclusion 20 A Data Tables 21 B Calculating a Best-Fit Line______________________________26 2
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1. Introduction This report describes the design and implementation of a photodiode detector using an LF351 operational amplifier and a PNZ334 photodiode. The detector was used to test the performance of infrared (UT188X-81-940), red (ETG-5WB630-30), and blue (LC307PBL1-30Q-A3-MT) light-emitting diodes. The exponential model of each LED was derived from measurements of the v-i characteristics of each diode. The sensitivity of the detector to each LED at a fixed distance and setup was then tested. The LED that the photodiode was most sensitive to was then used to test the response of the detector to different reverse- bias voltages. A bandpass filter constructed in a previous laboratory experiment was then used to filter noise from ambient light sources, so that the detector could detect the LED more accurately. The detector output was then measured with varying distances between the photodiode and the LED to investigate its response to changing light intensity. Section 2 details the process of designing the detector circuit and the circuit used to test the detector, including the calculation of component values. Section 3 presents experimental measurements taken on the detector and test circuits, and describes the process of finding experimental models for the LEDs used. Section 4 summarizes the results of the detector system. Appendix A contains seven supplementary data tables used to create the plots in the report. Appendix B details the process of finding the best-fit linear approximation of a series of data points. 3
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2. Circuit Design and Preliminary Analysis A schematic of the detector circuit and the test circuit is shown in Figure 1 below. There were two required specifications for the circuit: The test current through the LED must be 15 mA. The output voltage of the detector must have a magnitude of 1 V when the
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This lab report was uploaded on 04/19/2008 for the course ECE 342 taught by Professor Hummels during the Fall '07 term at University of Maine Orono .

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Lab Report 2 - ECE-342 Lab 2: Photodiode Light Detector...

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