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Constructing a Low Cost Mobile Eye Tracker

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Constructing a Low-Cost Mobile Eye Tracker is designed for use by individuals with limited use of their upper extremities to interact with items in their environment. This is brief overview of instructions on how to build a low-cost mobile eye-tracking system from off-the-shelf components. Below is a list of parts needed for the system, necessary tools, and a step-by-step construction guide.

For a complete list of the directions, please visit:  http://thirtysixthspan.com/openEyes/openEyes_ConstructingaLow-CostMobileEyeTracker.pdf.

Technical Specifications: 

Introduction: This is a detailed set of instructions on how to build a low-cost mobile eye-tracking system from off-the-shelf components. Below is a list of the parts needed for the system, a list of necessary tools, and a step-by-step construction guide. If you have any questions please e-mail dwinfiel@iastate.edu.

Important safety information: You should always wear a grounding wrist strap when handling electronic components to protect them from electrostatic discharge. You should always wear safety glasses when cutting material such as plastic or metal, when cutting or stripping wire, and when soldering.

Parts List

  1. Aluminum Wire 14 gauge
  2. Aluminum Wire 9 gauge
  3. 2 10' DB15 Male to Female cable
  4. 2 Aluminum Project Enclosures(13.3 x 7.6 x5.4cm)
  5. .2 DB15 connectors
  6. Fire-I Board Camera (black and white)
  7. Fire-I Digital Camera (color)
  8. 5.7mm lens OR 12.0mm telephoto lens (eye lenses)
  9. 1.9mm wide angle lens OR 3.6mm medium angle lens (scene lenses)
  10. 17mm M12x0.5 Lens holder
  11. 13.5mm M12x0.5 Lens holder 13.5mm
  12. 940nm Infrared LED
  13. 4 14 pin dip sockets (do not use low profile sockets)
  14. 33 Ohm Resistor (0.75W or greater)
  15. Safety Glasses
  16. USB connector
  17. Zip Ties
  18. Standard Rosin-Core Solder
  19. Electrical Tape
  20. Plastic CD case
  21. Nylon Spacers
  22. 8 Screws 2-56 x ½
  23. Wratten IR Filter
  24. Shrink wrap tubbing
  25. 2 DB9 connectors

 

This is the detailed parts listed for the mobile eye tracker. The following may be purchased from Radio Shack.

  1. 33 Ohm Resistor
  2. 14 pin dip socket
  3. IR LED
  4. Aluminum Project Enclosures
  5. Electrical Tape
  6. Solder
  7. Heat Shring Tubbing
  8. Zip Ties
  9. 10' Cable, DB15 Male to Female
  10. Aluminum Wire (14 gauge, 1/4 pounds coil)
  11. Aluminum Wire (9 gauge, 1/4 pounds coil)
  12. DB15 Female Connectors (package of 6)
  13. DB9 male Connectors (package of 6)
  14. Fire-I Board Camera B/W
  15. Fire-I Digital Camera
  16. 12.0mm Zoom Lens
  17. Eye camera lens (5.7 millimeters, 38 deg)
  18. Wide Angle Lens (1.9 millimeters)
  19. Medium Lens (3.6 millimeters)
  20. Lens Holder (17 millimeters)
  21. Lens Holder (13.5 millimeters)
  22. 2-56 x 1/2 Stainless Steel Screws
  23. Nylon Spacers (1/4 long)
  24. Nylon Washers
  25. FILTER WRATTEN IR #87

 

Required Tools

  1. Drill
  2. Soldering iron (temperature adjustable to 700 degrees Fahrenheit)
  3. Dremel rotary tool (with cutting disk)
  4. Set of small screwdrivers.
  5. Xacto knife
  6. Locking forceps
  7. 3/32 inch drill bit
  8. Sandpaper
  9. Wire cutters
  10. Wire strippers

 

Scene Camera Case

Step 1: Open the case of the color camera.

  • First, it is necessary to find all of the screws (two of the screws are hidden behind the label at the top of the camera).
  • Remove the 4 screws on the back of the camera.
  • Pull the back of the camera case off. The camera board should remain attached to to the front of the camera case.
  • There is a small secondary board that is attached to the main camera board. This secondary board plugs into the main board and holds the main camera board to the front of the case. Remove the main camera board by carefully pulling it straight up (away from the front of the camera case).

 

Step 2: Remove the lens mount

  • On the back of the main camera board there are two screws that go through the board. These screws hold the lens mount to the board. Remove these screws. Remove the lens mount.

 

Extract the CCD sensor

Note:

  • The sensor is cut from the board because it is heat sensitive and will be damaged if it is desoldered from the board.
  • This is a delicate process. It is important to be very careful when using the knife because it can easily slip off of the sensor. This could result in damaging the camera board and/ or personal injury.
  • When doing this you should wear a grounding wrist strap and safety glasses

 

Step 1: Cut the Pins

  • First put some tape over the top surface of the sensor. This will help prevent it from accidental damage.
  • Cut all the way through the pins on one side of the sensor using the Xacto knife. Cut the pins as close as possible to the camera board (it will take awhile to cut all the way through the sensor pins and you must be careful to only cut the pins and not cut the camera board).

 

Step 2: Remove the sensor

  • Score the pins on the other side of the sensor a few times with the knife, as close to the camera board as possible without cutting the board.
  • Lift the free side up and down (make sure that the pins bend at the score line) until the pins on the other side break off. They should break on the score line.

 

Step 3: Remove the pins from the board.

  • First turn on the soldering iron and set the temperature to 700 degrees Fahrenheit. (If you do not have a variable temperature iron use an iron that is 30 Watts).
  • Clamp the locking forceps onto one of the pins (it is easiest to clamp onto the pins from the back of the camera board).
  • Touch the tip of the soldering iron to the pin and pull the pin out with the forceps (make sure not to touch anything else on the board with the soldering iron).
  • Repeat steps 2 and 3 until all of the pins are removed.

 

Camera Enclosure

Note: Wear safety glasses when cutting with the Dremel rotary tool. Wear safety glasses when drilling.

Step 1: Mark the locations for cutting

  • Mark one of the sides of the enclosure as shown in the picture bellow:

 

Step 2: Cut the holes for the connectors.

  • Cut out the holes, marked in step 1, using a Dremal Rotary Tool.

 

Step 3: Mark the locations for screw holes.

  • Place the camera board in the enclosure.
  • Align the connectors on the camera board to the holes in the enclosure.
  • Mark the locations of the camera screw holes on the enclosure.

 

Step 4: Drill the holes

  • Install a 3/32 inch drill bit into the drill.
  • Drill the holes, marked in step 3.

 

Install the Camera Board in the Enclosure

Step 1: Connect wire to the camera board

  • Measure and cut 14 pieces of solid 24 AWG wire, each approximately 5 inches in length.
  • Strip the end of each wire to about 1/8 inch.
  • Turn on the soldering iron and set the temperature to 700 degrees Fahrenheit.
  • Hold the stripped end of the wire against the hole in the board (where one of the pins was removed).
  • Touch the tip of the soldering iron to the wire. 6. When the wire gets hot enough to melt the solder, push end of the wire all the way through the board (be careful not to burn your fingers when the wire gets hot).
  • Inspect the connection on the back of the board. There should be enough solder left on the board to hold the wire. However, it might require additional solder.
  • Cut off any excess wire that sticks out from the back of the board.
  • Repeat this process for the remaining wires.
  • Check the back of the board to make sure that none of the contacts are shorted together. This can be done easily with a mult-imeter. (Many multi-meters have a continuity checker that will beep if the contacts are connected).

 

Step 2: Connect the wire to the DB15 pin connector

  • Strip the ends of each of the wires from the camera board
  • Attach each wire to the correct pin on the DB15 pin connector, except for the ground pins (The order is important).
  • The ground pins (pins 6 and 9) should be connected to the enclosure.

 

Please visit http://thirtysixthspan.com/openEyes/openEyes_ConstructingaLow-CostMobileEyeTracker.pdf for directions in its entirety.  

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Constructing a Low Cost Mobile Eye Tracker