Small transmitter for guided camera system

Discussion in 'The Projects Forum' started by vane, Jan 15, 2008.

  1. vane

    Thread Starter Active Member

    Feb 28, 2007
    181
    0
    I was wondering if i could make a motorised tripod with 5 directional aerials pointed in a + shape mounted on the moveable bit on the tripod, and make a tiny circuit that transmits a signal to the directional aerials, so that when the transmitter is stationary the signal is going into the centre aerial, however when you move it the transmitter to the right the signal goes down the right side directional aerial, what i want is that when the signal is detected in the right aerial, it engages the motor which swings the tripod to the right and vise versa with left, up and down. what i want is the transmitter to be as light as possible but still be able to transmit atleast 300ft(including the transmition range from the directional aerials) and be as light as possible. i was thinking i could program a PIC chip and write a program that says when signal in left aerial is strongest move left etc, thanks, vane
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Do you mean a Yagi-type antenna?
    http://www.hamuniverse.com/yagibasics.html

    Or perhaps a corner reflector type?
    http://www.northcountryradio.com/Articles/crfl.htm

    A pair of either would make it fairly easy to detect which had the strongest signal, and rotate the antenna in that direction until the signal is of equal amplitude.

    But then you'd either need two receivers, or a method to switch between antennas at a rapid rate.

    Low-frequency antennas would be VERY large. CB radios operating in the vicinity of 29-30 MHz have a wavelength of 36 feet.

    However, you could do some research on QRP transmitters/receivers. These are VERY low powered transmitters that operate in various bands.
     
  3. vane

    Thread Starter Active Member

    Feb 28, 2007
    181
    0
    all looks a bit too complicated for me :(
     
  4. vane

    Thread Starter Active Member

    Feb 28, 2007
    181
    0
    my dad suggested having lasers and sensors instead of transmitters and recievers then putting a band of highly reflective tape on the subject and program the movable tripod around it
     
  5. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    To do what you want with radio is extremely difficult, since you need to exploit antenna directivity. The best possible method would be light, but your 300ft requirement makes that quite hard. You would obviously need a 'line of sight' to accomplish this.

    Lasers, since coherent, have great directivity, which might be good for range. The beam divergence of standard ~670nM laser pointers might be sufficient at such a great distance, but not up close. You would want to shine the light over the entire assembly so that it can make decisions. Spreading the light to an appropriate radius and maintaining proper collimation would be too daunting for a simple project.

    I cannot think of a simple way to do this! The only good way would be radio-based, but that's also quite hard. Good luck!

    Steve
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The WWII high frequency direction finders used loop antennas mounted at right angles. The signals received drove the trace on a CRT to generate a trace that pointed at the origin of the signal. By using two receivers, you might be able to rotate until one signal was at a maximum and the other effectively zero. That would have the plane of one loop pointed at the signal source. But it would be a tad hard to decide beforehand which loop would do the pointing. Guess you could arrange for a LED to indicate which antenna was at the null.
     
  7. vane

    Thread Starter Active Member

    Feb 28, 2007
    181
    0
    the reason i wanted this is because none of my family are any good at recording my rc planes and helis so i though a computer system could :)
     
  8. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    When I was in the Navy, I had the um, er, "privilege" of working on a 1950's vintage weather balloon tracker. It was a big dish mounted on horizontal and vertical gimbals and driven by servos. The receiving antenna at the focus of the dish was off-center and spun by a motor. The sine wave produced by the spinning receiver was used to control the servos.

    It was twitchy as all get-out and needed lots of TLC, but when it was tuned up it worked well enough.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Oh, I think I see ... you want to mount a videocamera on this thing, and have it track your model R/C aircraft around the sky, eh? :)

    That could be do-able using audio frequencies; have the tracker seek the racket your model's engine is making ;) Since the plane will be travelling at relatively low speeds and fairly close to the receiver, there won't be too much "lag."

    It will still be a complex project, and require much tinkering - though you could learn quite a bit from doing it.

    You'd need a parabolic reflector, perhaps a leftover satellite antenna.
    You'd need to build a gimbal for it so that it could move freely up and down as well as left and right; and some strong motors, DC or stepper, to move the thing. You'd need to counterbalance it very well.

    You will also need a microphone mounted at the reflector's focal point, but it would need to be moveable by motor as thingmaker3 mentioned. The sound receiver would have to know where the microphone was in it's travel around the center of the focal point, and also have to compensate for the variations in sound levels produced by the individual firings of the engine, while still differentiating between the levels of volume around the mic's orbit in order to steer the antenna.
     
  10. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Bet it's electric. And it won't take too much wind and distance to have the camera pointed way off the airplane if it has a fuel engine.
     
Loading...