This tiny spy robot can send audio and video and includes night vision
After building my two large video controlled robots (Oberon and Goober) as well as the small sized all terrain spy robot, I wanted to take the militarization process as far as I could using inexpensive components. A spy robot needs to have a rock solid video link that is good for at least 500 feet, crystal clear amplified sound pickup, silent motor operation and night vision, so that is a lot of stuff to pack into a small area. Also note that this project was built in 2004, when affordable miniature cameras and video transmitters were kind of a rare thing to find.
I decided to build this project when I finally found a source for an ultra tiny composite video camera with a low lux CCD element that would be good for night vision. I also had a tiny 250mw audio and video transmitter that was hacked from a security system into its absolute minimum size, so the project could finally come together. This version is just a simple proof of concept prototype and will eventually be made less than half the size and have the ability to survive a throw through a window into the target location for stealthy surveillance missions in a hostile environment. The final version will also have some onboard autonomous intelligence so once it is dropped or thrown into the target location it can quickly sneak into a dark hiding spot much like the way a fleeing insect.
Since I now had the small video camera and the tiny gearbox drive motors on order, I could experiment with some possible layouts and battery pack sizes using a computer CAD program. I originally planned to use very small lithium batteries, but it was found that the current draw from all of the subsystems made the video drop out when the motors were activated, so I decided to go with sub-AA sized rechargeable nickel batteries as these were commonly available for small RC aircraft use. The next version will use a custom made lithium ion battery pack similar to the ones used in cell phones for much smaller and extended run times, but for now the goal was cheap and simple.
I also intended to have a four wheel transmission system with possible a track drive, but in later experimentation it was found that only two wheels were needed as the little motors had more than enough power to just drag the back of the robot along. The final version will probably have a custom track drive though, as the two wheels would sometimes fail to pull the tiny robot over large carpet runners due to slipping easily on the smooth surfaces.
I originally made my own small video transmitter but it lacked audio and was very unstable as the robot moved around or when the batteries began to drain. This video transmitter is the output block of a small security camera reduced to its absolute minimal components, allowing it to send 900MHz audio and video back to a down converter. The small transmitter was very stable for several hundred feet, had very clear audio, and ran just fine from any DC power source from 6 volts to 12 volts. Having the video transmitter on a high frequency band will also help stop interference between it and the drive remote controller, which operates on the low 49MHz band.
It was very difficult to find a suitable micro video camera in 2004 for this project. The camera had to be black and white for use with the invisible infrared night vision LEDs, have a CCD imager rather than CMOS for clarity, and also output a standard NTSC composite signal rather than a serial bit stream. I eventually found this extremely small high resolution black and white composite camera and did a little hacking in order to remove the onboard power supply, which was 4x the size of the actual camera. This camera was perfect for this spybot now that it was reduces to only 1/4 inch square and able to run from 8 to 12 volts DC power.
Figure 3 - A micro sized NTSC composite video camera with low lux CCD
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