LineBlock

Theory

The LineBlock uses an Infrared LED and photodiode to detect how reflective a surface is. 

The LED emits infrared light, which then bounces off a surface, if the surface is reflective (like white paper) then lots of light is reflected back to the photodiode that detects how much IR light it is receiving.  When the sensor is placed near a dark or black object (or black line), then less light is reflected, and the photodiode reports a lower value.

The sensor can also be used as a distance sensor, since the further away an object is, the less light it reflects back to the sensor.

The part number of the sensor we will be using is TCRT5000, here is the datasheet for that part:

 

Assembly

1. Required Materials

   
   IR Sensor
   Cable 3 Wire
   Connector 3 Pin
   Block 2x2
   Resistor 100 ohm
   Resistor 4.7k ohm
   
   
2. 
   It is very important not to mix up the
   Photodiode (black on the left)
   with the
   IR LED (blue on the right)
3. 
   Cut or break off the 2 little black plastic legs in the middle
   
4. 
   With the IR LED (blue) on the right
   Bend the two legs closest to you so they overlap
5. 
   Wrap the 100 ohm resistor
   Stripes = Brown Black Black Black Brown
   Around the IR LED's (the blue one) leg
6. 
   Wrap the 4.7k ohm resistor
   Stripes = Yellow Purple Red Gold
   Around the Photodiode's leg
7. 
   It should now look like this
8. 
   Twist the resistors together
9. 
   Cut the connectors off one end of the cable
10. 
    Strip about 10mm off the end of each wire
11. 
    Hook the middle wire around the 2 legs that are bent together
12. 
    Wrap the left wire around where the resistors are twisted together
    (Take note that this wire will be your 'G' Ground wire)
13. 
    Wrap the right wire around the photodiode's leg
    (the one with the 4.7k resistor also attached)
14. 
    Solder all 3 wires and the resistors in place
    
15. 
    Cut off the extra leg length
    Be careful not to cut too close and cut the wire off
16. 
    
    Use a pin to bend the latch that holds the black connector housing on
    
17. 
    Pull the housing off each wire
18. 
    Place the cable into the block
19. 
    Pull the cable until the sensor is almost in the block
    
20. 
    Place the 3 pin housing on the ends of the wires
    Make sure the metal ends are the right way up so the plastic latch can click into place
21. 
    Place a silver strip on the side of the connector
    Make sure it is the wire that goes to where the two resistors are twisted together
22. 
    Check with Mr. Dash before continuing
23. 
    Push the sensor down into the block until it fits in the slot
    You must be very careful that none of the 4 wires touch each other.
24. 
    Push the wires and resistors down into the block
    until another block can easily fit onto the bottom of the LineBlock.
    You must be very careful that none of the 4 wires touch each other.
25. 
    The sensor should just be poking out of the slot in the top
26. 
    Check with Mr. Dash before continuing
27. 
    Fill the block with hot glue
28. 
    Place wax paper on top of the LineBlock
    Then place a block on top and squeeze firmly together
29. 
    You're Done!
    Your line block should look like this.

 

 

Connection Diagrams

• 
• 
  The LineBlock can be connected to any Analog Pin (A0 - A7)
  (Silver stripe always goes to G (GND))
  

 

Hints

 

This sample program draws a live graph of the input from the analog sensor: