Let's Make Robots!


Tracks human faces using a webcamera and two servo motors to pan and tilt

This is my first time using OpenCV, an open source computer vision library developed by Intel Corporation.  It wasn't too hard to get setup or use OpenCV in Microsoft Visual Studio 2008 Professional (I haven't tried it with the free Express version of Visual Studio).  I used this link to get started with OpenCV 2.1 (I had problems configuring OpenCV2.2).


  • LynxMotion pan and tilt kit with Hitec HS-422 servo motors
  • Creative USB webcamera, stripped from its case
  • Atmel AVR ATmega328P microcontroller programmed using AVR Studio 4, AVR GCC, and programmed with an AVRISP MKII
  • A very cheap USB to serial converter (shown in the last image) bought from dealextreme.com.  This actually turned out to be a USB to inverted UART converter.  I inverted the signal using a transistor inverter circuit as shown on the breadboard near where the ribbon cable connects.

The basic operation goes something like this:

  1. Computer fetches an image frame from the USB webcam
  2. Program rotates the image 90 degrees (I mounted the camera sideways)
  3. A face recognition algorithm is applied to the image using OpenCV libraries
  4. When a face is found the pixel coordinates of its center are subtracted from the pixel coordinates of the center of the image.  This results in x and y difference values that can be either negative, positive, or zero if equal.
  5. Serial commands are sent from the computer COM port to the AVR microcontroller corresponding to the direction (sign of x and y difference values) and magnitude of the x and y difference values.
  6. The AVR microcontroller recieves the serial commands from the computer which changes the servo position(s).

My goal is to eventually deploy this on a mobile robot with a WiFi webcam to replace the USB webcam and a Bluetooth serial link to replace the wired serial connection, but first I have to drop the cash on a WiFi webcam.  Otherwise I may go down the road of using a full blown computer on the robot itself.

Code can be found at my sourceforge page under the folder Face Tracker.

Will update with a video in the near future!

*Click to enlarge

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raspberry pi is better and simpler and cheaper than the beagle.. i will post a tutorial asap but the modifide code of this project was lost when the sd card of pi died..
now starting from scratch and bit for problems than the initial case....

Sorry to hear the SD died, always good to back up often.  I haven't used a rasperry pi yet, mainly because of the long lead times but for a couple of other reasons.  Have you used a beagleboard or beaglebone or pandaboard?

This is a really cool project.

Hey Rogue i am tying to make this project agiain for my laptop but i couldnt get this work on my windows 7 x64 pc. and tiried this on virtual pc only works on win XP any ideas bout that..

Nothing comes to mind as to what is a likely problem, I've got it to work on both win 7 x64 and x32 machines without much trouble.  I don't know what version of open CV you are using (I used 2.1 if I remember correctly), if you have compiler errors, etc.