Friday, October 12, 2012

FPV System

FPV camera on ArduCopter

I built an ArduCopter for a research project I am working on.  One requirement is the ability to pilot the copter remotely.  To do that I need a powerful FPV (First Person View) system.  An FPV system gives you a view from the remote vehicle you are piloting.  That way you can fly the copter beyond your line of sight (although it's not actually legal to fly a remote vehicle out of sight...yet).

HobbyKing FPV system

I was on a tight budget so for our first prototype we went with a complete system from HobbyKing.  It's a pretty basic system with a 900Mhz 1.5W transmitter with a Sony 520 TV line color CCD camera.  The camera is a bit large compared to more expensive models and the camera circuitry is completely exposed.  The transmitter is probably larger and heavier than it needs to be.  And the transmitter antenna is way too big to be practical on a vehicle.  But with relatively high resolution and a powerful transmitter, it should do the trick.  It came without any instructions but luckily it wasn't too hard to figure out how to wire it up.

The system was pretty easy to set up.  The receiver power supply came with a foreign power plug so I cut it off and spliced in a US plug from an old power cord.  Just plug the camera and transmitter into the included wiring harness and add 12v DC.  I used a 11.1v LiPo battery.  On the receiver side, just plug in the 12v DC power supply and attach the RCA cable to your monitor.  Make sure the transmitter and receiver are on the same channel, and you should see an image on the monitor.  I tried it out using my television and it worked.  The picture was actually quite good.

camera image wirelessly transmitted to a TV

Getting it to work with the TV is easy.  The signal from the receiver is analog and so is my old TV.  The real trick is getting the receiver to work with my laptop.  For that you need to convert the analog signal to a digital signal that your computer can use.  Based on some online recommendations, I used an EasyCap 2.0 to import the image to my laptop.  The EasyCap plugs into your USB port and has RCA and S-video cables to import analog signals.  I installed the drivers and software, plugged it into my laptop and attached the receiver.  Using the software, I was able to see the image from the camera.

EasyCap and receiver attached to laptop sending a live wireless image of my mill

With that hurdle crossed, the next step was to see if I could get the image imported into the Mission Planner software.  The Mission Planner software displays all of the gauges and coordinates while flying the ArduCopter.  Incorporating the FPV image into the software allows you to see all of the flight information and the view from the ArduCopter all on the same screen.  I was able to easily import the image by changing a few settings in the Configuration tab following these instructions.

live camera image successfully imported into the Mission Planner software

To mount the camera to the ArduCopter I used this mount from Hobby King.  I didn't need the pan function so I only used one servo to control the camera tilt.  The mount is a bit flimsy, especially the servo linkage, but it works fine for our prototype.  I mounted it between the front motor arms with some scrap aluminum.  It is clamped to the arms so I didn't have to drill any holes which might weaken the arms.  The servo plugs into an extra channel on my receiver and I use the pit trim pot on my radio to control the tilt of the camera.  I soldered a male JST battery pigtail to the power distribution board to supply 11.1v to the camera and transmitter.

camera and mount

The final step was testing the range of the wireless video signal.  I mounted the transmitter to the roof of my car.  I set up the base station, running the laptop and the receiver off of AC power with the receiver up about 15 feet on a pole.  Then I proceeded to drive away maintaining cell phone contact with someone at the base station.  We lost the image about 1400 feet from the base station in a dense urban environment.  Given the 1.5 W power of the transmitter, I expected slightly better distance.  I believe that with a signal tracking directional antenna on the base station, elevated above the roof lines giving line of sight to the arducopter, distance will be greatly improved.

This set up was just a proof of concept for our prototype.  I intend to upgrade to a smaller sealed HD camera, a smaller and lighter transmitter, better receiver, and an antenna tracking system on the receiver to prevent signal loss.  I'll keep you posted.

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