Sensors Presentation

1
Sensors Presentation

• October 7, 2003
• Scott Chao
• Allison Douglas
• Kristin Lee

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 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
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
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
Experimental Results LM235

• Temperature sensor LM235960.7 ohm
  resistorV5.00 V DCoutput 2.5282 V DC at
  room temp
• If we blew hot air on it or held it the voltage
  increased

7
Experimental Results LM235
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 OhmsR_LED 992 Ohms Vcc
  5v
• LED and transistor parallelWithout box Vout
  4.95 VWith box Vout 4.778 V
• Separated without box Vout 4.97 VSeparated
  with box Vout 4.99 V
• LED bent towards transistorWithout box Vout
  4.77 VWith box Vout 4.6 V

9
Experimental Results LM135
10
Experimental Results LM234

• Temperature sensor LM234R1 231.97 ohmsR2
  9.94 kohmsR3 661.37 ohmswith C11.5 nF, Vo
  4.33 Vwith C13.05 nF, Vo 4.33 V
• Most likely faulty values

11
Experimental Results LM234
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