Home Forums SPICE Simple 4 pixel camera sensor circuit design

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      liu yalan
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      In the following I describe a simple 4 pixel camera sensor, which can be versatilely used in robotics.

      The sensor consists in general of four pin photo diodes with a relatively large photo sensitive area, arranged in a square, and an according collimator lens. Every photo diode can be thought of a quadrant of a two dimensional graph. We can use the sensor to measure the intensity of light, detect motions, track a light source in two dimensions or do basic 2-D optical flow calculations.

      I am using a MCP6041-I/P op amp(datasheet:<a href=”http://www.kynix.com/uploadfiles/pdf9675/MCP6041-I2fP_911970.pdf”>http://www.kynix.com/uploadfiles/pdf9675/MCP6041-I2fP_911970.pdf</a&gt;) to convert the signal from the photo diode that produces an output current into a voltage (called transimpedance amplifier). This is implemented with a single resistor (R1) in the feedback loop of the amplifiers shown in schematic below. The capacitor (C1) provides stability for this circuits.

      https://www.robotshop.com/letsmakerobots/files/userpics/u11554/Optical_flow_sensor_schematic.jpg
      The output voltage is given by:
      http://www.kynix.com/BlogImage/1.3.1.png

      Light sensitivity and linearity are maximized in this photovoltaic mode.

      I started to build the prototype, positioning and glueing the four pin photo diodes on a 14 x 14 mm black colored piece of carton:
      https://www.robotshop.com/letsmakerobots/files/userpics/u11554/Optical_flow_sensor_1.jpg

      Then I bended the photo diode leads and placed the sensor array in a 45 degrees angle in the middle of a 4 x 6 cm double side perf board:

      https://www.robotshop.com/letsmakerobots/files/userpics/u11554/Optical_flow_sensor_2.jpg
      Next I assembled the PCB mount lens holder and soldered the photo diode leads:

      Finally I populated the board on the backside, using 1206 SMD capacitors and resistors and wrap wire. Only the MCP604 is a PDIP version.

      https://www.robotshop.com/letsmakerobots/files/userpics/u11554/Optical_flow_sensor_3.jpg

      Now I have to wait that the op amp arrives to test the sensor and write according programs:
      https://www.robotshop.com/letsmakerobots/files/userpics/u11554/Optical_flow_sensor_5.jpg

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