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Ultrasonic Distance Sensor/Alarm

Discussion in 'Sensors and Actuators' started by bsides, Feb 18, 2011.

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  1. bsides


    Feb 18, 2011
    Looking to build a circuit system which is made up of two components, a emitter and sensor. The emitter neets to be able to emit ultrasonic soundwaves at 360degrees or close to it. The sensor needs to be able to pick up the signal at 15 ft and trigger an alarm.

    Imagine an electronic Grenade and a victim that is effected when the grenade explodes at 15ft or closer. (Easiest way to explain this).

    First of all wondering if this is even possible to do.


  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Getting an accurate measure of 15 feet will be an issue without some active feedback (e.g. one unit sends a signal, the other responds. The time between sending one signal and receiving the other will be directly related to distance (plus a constant))
  3. shrtrnd


    Jan 15, 2010
    I suppose there might be somethng out there, but I don't recall ever seeing a 360 degree coverage device. You might be having to use at least two or three emitters, to GET 360 degree coverage. There are a lot of relatively simple circuits out there (not 360 degrees alone). Check into the ones for home security electronic 'ultrasonic' alarm detectors. I know you said you want to build it, but it'd help to check some of the cirucits already existing (I hate reinventing the wheel). Like I said though, I think you'll need two or three individual circuits, to get the 360 degree coverage. Maybe somebody else will add a reply later, if they know of something like that.
  4. duke37


    Jan 9, 2011
    I have a vague recollection that some loud speakers were made with the driver facing upwards. Above the driver was a 45 degree cone pointing towards the driver. This was supposed to distribute the sound over 360 degrees. I never heard or saw one so don't know its effectiveness
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    I have seen a similar thing done with an IR LED to make a beacon that prevents the approach of a robot.

    In this case both the beacon and the robot have "smarts".

    The same concept might work with an ultrasonic source, but very likely NOT if you're going to rely on passive echo location.

    The easiest way that I see is having the device with the alarm send out periodic "ping"s. The other end simply sends a "pong" as soon as it hears a "ping". The alarm measures the time delay between sending the "ping" and receiving the "pong". If this delay gets small enough it triggers the alarm.
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