proximity and direction measurement

Discussion in 'The Projects Forum' started by thebiggestbangtheory, Aug 13, 2009.

  1. thebiggestbangtheory

    Thread Starter New Member

    Aug 13, 2009
    Hello all,
    I am a newbie to this board and hands-on electronics in general. I am trying to identify a kit which can help me build a system which can do proximity measurement along with direction.

    I have gone through some of the offerings from various manufacturers who sell ultrasonic proximity sensors and the like (ping). I am looking for something which will be able to measure distance as well as relative direction.

    Can someone please point me in the right direction? My requirements are as below:

    1) Need a sensor to measure how far another sensor is and in what relative direction (maybe an answer in terms of degrees..)

    2) Want a reliable technology

    3) Must be interfaceable with a PC

    Thanks in advance,
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    What are the parameters? How much distance and what accuracy as to bearing?

    Is this what you want to do -
    Or do you want
    It would help to know that requirement as well.
  3. jj_alukkas

    Distinguished Member

    Jan 8, 2009
    You must use a microcontroller.

    Sensor to sensor distance on not-so-close situations requires ultrasonics.

    Well I donno how you are going to measure degrees. You will require more than one sensor and some CPU.
  4. thebiggestbangtheory

    Thread Starter New Member

    Aug 13, 2009
    Hello all :)

    First of all, great comments, my post was not well worded.

    Parameters: A sensor system which when deployed can measure the distance between a mother node and children nodes and the relative direction of the children nodes with respect to mother node.

    should be able to work with distances of 5-20 ft, accuracy ~90+%

    technology: ultrasonic, bluetooth, zigbee, ir, ...

    I was looking at Senix ultrasonic products, but the problem I can't seem to get my mind wrapped around is how to figure out relative orientation.

    example:I can have 4 ultrasonic sensors, 3 placed like the ends of a triangle and one in the centroid. Then I make each one of the sensors placed at the vertices, emit a pulse which will be picked up by the one in the centroid, but I can't figure out how to determine relative direction.

    any ideas/comments/pointers are greatly appreciated.

    PS: a wild thought .. I have heard about directional antennae arrays..can anyone suggest if this is a decent possibility or a wild goose chase

    Thanks again
  5. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    Imagine two transmitters, each giving a pulse in turn.
    Assuming you are in a room, locate one at eg. the center of the north wall and one at the center of the east wall.

    Pulse the North one & measure the time (ie. distance) to the reciever. Imagine drawing a circle around the transmitter at that distance radius.

    Do the same with the East one, get another circle at the RX radius.

    The Rx is where the two arcs cross in the room.

    You can add more transmitters to get more 'arcs' and a better estimate if there are obstacles that confuse the signal.

    You can also do it using a mobile transmitter and two or more receivers, still the same idea. Trigger a pulse and measure the delay to each receiver (and the 'distance arcs' can still be drawn from the fixed - now receiver - locations).

    If you don't want the mobile part tethered, you could use eg. an infrared pulse to control the mobile ultrasonic transmitter.

    For multiple mobile sensors, have a different IR selection code for each mobile.
  6. jj_alukkas

    Distinguished Member

    Jan 8, 2009
    Directional antenna arrays will give you direction if used in large numbers , but it wont be accurate. Your project seems like it will need some tech like bluetooth or wifi and complex CPU.
  7. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Mechanically more complicated but gives accurate bearing: A rotating array of two US receivers, 30 cM apart with small parabolic reflectors and a central transmitter. 360 rotation untill a return is detected, switch to short sweep, compare phase difference, when = you are dead on.