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Range finder / altimeter ideas for a small model craft

Discussion in 'Electronic Basics' started by R C, Sep 10, 2003.

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  1. R C

    R C Guest

    I'm working on a hobby RPV (remote piloted vehicle) and we are trying
    to come up with an instrument loadout. Initial platform will be a 1/5
    scale model plane; working altitude 20-200 feet above ground, ground
    speed 10-40 mph. We'll be using an IMU from the autopilot project, but
    would like some sort of height-above-ground indication in addition to
    absolute altitude data we can gather via GPS/barometric sensors. I've
    looked into it, and found 3 basic approaches:

    1) Ultrasonic sensors, esp. polaroid sensors. Disadvantage to these
    seem to be low range, and low tolerance to flow noise. Cheap, light,
    fairly low-power.
    2) Radar. This seems like a fairly good application for an UWB radar,
    but information is scarce. Anyone have more specifics (price,
    availability in small quantities, power, design requirements, etc)
    than is available from www.time-domain.com?
    3) Lidar. Laser diodes are cheap, but I haven't seen many circuits for
    cheap lidar designs. I recall one design using a digital camera CCD
    for timing, but can't find it again. LIDAR does have the advantage of
    eventually allowing sweeping and amateur cartography, but I'm not sure
    if it's possible in our payload / price range. Commercial units seem
    fairly big (optics?).

    Anyone have suggestions, corrections, pointers to information I've
    missed?

    Thanks,
    R C
     
  2. happyhobit

    happyhobit Guest

  3. R C

    R C Guest

    Eh? I'm looking for a height-above-ground sensor to couple with
    absolute altitude provided by GPS and barometric sensors. I would
    _like_ to be able use LIDAR to generate topo maps, but it's likely out
    of budget.

    R C
     
  4. onestone

    onestone Guest

    Try www.shfmicro.com. They have cheap, and quite tiny DRO's. The 24GHz
    version is around 1" cubed, the 10GHz version is larger and flatter. The
    former uses a waveguide, the latter a patch antenna. Both come with a
    varactor diode for modulation. There output is the doppler frequency
    cuased by motion, however by modulating them you can also derive range
    quite simply. Both operate from 5V, although one has a high modulation
    voltage. Output is simply a lowish frequency sine wave into a typically
    2K load resistor. The patch antenna doesn't have huge range, but it may
    be simpler than building a squat horn. You could probably get away
    without the horn antenna, haven't tried that. Oh, yeah they work best
    when temperature stabilised. I used a very simple set up with an Analog
    Devices TMP01 and a 10R 20W TO220 resistor. M/A COM also sell these and
    pre built horns. There is a free horn design program via the web site.

    Al
     
  5. happyhobit

    happyhobit Guest

    Sorry, I misread and misunderstood. Double Bad Me. A real bad case of tunnel
    vision.

    Jay
     
  6. R C

    R C Guest

    No problem. I probably could've written a more descriptive subject, too.

    R C
     
  7. John Jardine

    John Jardine Guest

    Seemed OK to me?.
    The Hang gliding people use silicon, barometric pressure reading
    transducers to give altitude and rate of change.
    regards
    jhon
     
  8. happyhobit

    happyhobit Guest

    Hi John,

    RC is already using GPS and barometric sensors for altitude. I missed that.
    He's looking for something additional.

    Jay
     
  9. John Jardine

    John Jardine Guest

    Even worse, I managed to miss it *twice*.
    regards
    john
     
  10. R C

    R C Guest

    shfmicro has scaled back operations considerable, it seems. :(
    M/A-COM looks like they have a lot of useful building blocks. I was
    hoping to find a complete design somewhere; I haven't built anything
    anywhere near microwave frequencies.

    Thanks for the pointers, I'll have to see if I can find some reference
    works.

    R C
     
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