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Sensors Presentation

2. Types of Sensors Tested. Voltage Regulator acting as a temperature sensor (Models LM234, LM 235)Manufactured by ST (www.st.com)Photo transistor acting as a light sensor (Model LM135)Manufactured by Fairchild Semiconductors (www.fairchildsemi.com). 3. Applications of Sensors. Voltage Regulator

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Sensors Presentation

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    1. Sensors Presentation October 7, 2003 Scott Chao Allison Douglas Kristin Lee

    2. 2 Types of Sensors Tested Voltage Regulator acting as a temperature sensor (Models LM234, LM 235) Manufactured by ST (www.st.com) Photo transistor acting as a light sensor (Model LM135) Manufactured by Fairchild Semiconductors (www.fairchildsemi.com)

    3. 3 Applications of Sensors Voltage Regulators Used in Hi-Fi systems, TVs, VCRs, and other electronic equipment Photo Transistor Emitter/detector pair is used in sensing motion. e.g. If you needed to measure how fast something was going and/or its position the emitter and detector could sense the motion and output to a logic system

    4. 4 Information on Fairchild Infrared Sensors Range for detecting an object by reflection can be from 0 mm to 400 mm Dust, however, can impair this range All are constructed using silicon chips, which can detect the entire visible spectrum The photosensors are built with a daylight filter that prevents most visible light in the environment from reaching the detector chip Response to light sources may be noticeable.

    5. 5 Temperature Sensor Information The circuit output (calibrated or not) can be given by the equation: V_ot + (VO_to * T/T_o) where T is the unknown temperature and T_o is the reference temperature (in °K). Nominally the output is calibrated at 10mV/°K.

    6. 6 Experimental Results – LM235 Temperature sensor LM235 960.7 ohm resistor V+=5.00 V DC output = 2.5282 V DC at room temp If we blew hot air on it or held it the voltage increased

    7. 7 Experimental Results – LM235

    8. 8 Experimental Results – LM123 Used two orientations of the LED; straight up, parallel with the transistor and bent toward the transistor Measured output with and without a box to block ambient light. R_transistor = 4.6 Ohms R_LED = 992 Ohms Vcc = 5v LED and transistor parallel: Without box: Vout = 4.95 V With box: Vout = 4.778 V Separated without box – Vout = 4.97 V Separated with box – Vout = 4.99 V LED bent towards transistor: Without box – Vout = 4.77 V With box – Vout = 4.6 V

    9. 9 Experimental Results – LM135

    10. 10 Experimental Results – LM234 Temperature sensor LM234 R1= 231.97 ohms R2 = 9.94 kohms R3 = 661.37 ohms with C1=1.5 nF, Vo = 4.33 V with C1=3.05 nF, Vo = 4.33 V Most likely faulty values

    11. 11 Experimental Results – LM234

    12. 12 Next Steps Relate analysis of outputs to ozone sensors outputs Will test ozone sensors when we receive them Will take apart existing cell phones to determine size, power limitations

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