IR Sensor for Line Follower

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IR Sensor for Line Follower

• Characteristic of IR sensor
• - The emitter transmits IR light
• - The receiver receives the reflected IR light

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IR Sensor for Line Follower

• Characteristic of IR sensor
• - The current passing through the IR receiver is
  proportional to the IR light energy intensity
  received by it.

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IR Sensor for Line Follower

• IR sensor circuit used in CEG3430 robot
• More intensity of reflected IR light received by
  sensor, more voltage drop across the resistor in
  series with sensor.
• VR1 used to adjust the
• sensitivity of sensor circuit.

4
IR Sensor for Line Follower

• IR sensor circuit used in CEG3430 robot
• Modulated IR sensor circuit avoid interference by
  the ambient light.

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IR Sensor for Line Follower

• Differential IR sensor circuit proposed by Prof.
  K.H. Lee
• The basic idea of differential IR sensor circuit
  is to compare two adjacent IR sensors output
  value.
• - Only the difference between adjacent sensors
  value is used to detect the line.

v1gtv2 -gt high v1ltv2 -gt low
IR Emitter
v1
S2
S1

v2
-
Comparator
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IR Sensor for Line Follower

• Differential IR sensor circuit proposed by Prof.
  K.H. Lee
• Advantages of using differential IR sensor
  circuit
• Independent of ambient light.
• Independent of floor material and color.
• Avoid interference by fluctuation of light
  condition in surrounding environment. Such as
  camera flash etc.
• More reliable.

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IR Sensor for Line Follower

• Design of Differential IR sensor circuit
• Define ?v v1-v2.
• If ?v gt 0.6 volt then line is detected.
• Else if ?v lt 0.6 volt then no line is detected.

Comparator
v1
-
If v1-v2 gt 0.6 volt then output - gt low
v20.6

v2
-
If v2-v1 gt 0.6 volt then output -gt low
v10.6

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IR Sensor for Line Follower

• Design of Differential IR sensor circuit
• To achieve the previous rules, we have to use two
  comparators. One for determine v1-v2 gt 0.6 volt,
  another for determine v2-v1 gt 0.6 volt.
• The circuit can be further modified as follow

Comparator
v1
-
If v1-v2 gt 0.6 volt then output - gt low
v20.6

v20.6
-
If v2-v1 gt 0.6 volt then output -gt low
v11.2

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IR Sensor for Line Follower

• Implementation of Differential IR sensor circuit.
• The actual implemented circuit is as follow

VCC
VCC
Comparator
2K
10K
VCC
v1v2-0.6
s1
10K
s2
-
0.6 volt
LM339_1

Out
1N4148
v2v10.6
VCC
D1
-
D2
0.6 volt
10K
LM339_2
D3
v11.2

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IR Sensor for Line Follower

• Implementation of Differential IR sensor circuit.
• Diode 1N4148 D1, D2 and D3 provide 1.2 volt
  voltage difference between S1 output and negative
  terminal of LM339_2 .
• Initially, tune the 10K VR such that v1 lt v2 by
  0.6 volt (both s1 and s2 sensors are at the same
  condition).
• The voltage value at different points of the
  comparator should be as shown in the figure.
• Pull up resistors must be added at the outputs of
  LM339, because LM339 is an open collector output
  device.

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IR Sensor for Line Follower

• Differential IR sensor module circuit diagram.

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IR Sensor for Line Follower

• References
• Diode 1N4148 datasheet
• http//download.siliconexpert.com/pdfs/diode/hit/
  e208147_1n4148.pdf
• Comparator LM339 data sheet http//www.onsemi.com
  /pub/Collateral/LM339-D.PDF
• OR gate 74LS32 data sheet
• http//ece-www.colorado.edu/mcclurel/dm74ls32.pd
  f