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PC-controlled underwater robot

Discussion in 'Robotics & Mechatronics' started by vopap, Apr 6, 2003.

  1. pebe

    pebe Member

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    Location:
    Ellon - Scotland
    Not really. You haven't said why you needed 32 sensors. Or if the depth information supplied by the sonar is to be automatically dealt with by the tethered sub itself, or by the controlling sub, or handled by you with a control stick at the PC.

    In other words, I cannot see the overall picture.
     
  2. vopap

    vopap New Member

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    Location:
    ON, Canada
    :D :oops: :cry:
    So what happened I was first gonna use infrared detectors (a great variety of them around 32 all around the ship) I also mistakengly thought that infrared gives a digital output. Now I found that IR phototransistors are analog output an that they do not work in water, so my 32 phototransistors flew out of the window.

    To satisfy myself with some other sensors, I decided to use one sonic meter to measure to distance to the bottom of the river. So now I do not need any 32 bits of data for the sensors but less.


    Now my electrical design is so far:

    1. Use a OOPic Microcontroller.

    2. OOPic has TTL circuits, they are being converted onboard into CMOS of the computer by a IC like SN75188 or the MAX203.

    3. Connected to the microcontroller, I have:

    OUTPUT FROM THE OOPIC
    a. 4 H-bridges for each pump to enable the sub go up or down i.e. change its buyancy.
    b. Another H-bridge for the propultion motor.
    c. Servo control (one line) for the controll of the ruder.
    d. ???Some circuit (probably another H-bridge till I find something more apropiate) to control the on/off of a lamp to iluminate the path underwater.

    INPUT TO THE OOPIC
    a. double-axis tilt sensor (one of the ANALOG products). Two digital lines (PWM), plus self-test line
    b. sonar meter to measure the distance to the bottom of the river (this circuit is something I have to find.

    4.Totally independent from the microcontroller, I have a webcam, connected straight to the computer via USB port. Mounted on the front of the sub. Gonna use it to take pictures and know where I am going.

    5. Ideally, this should be made remote control, however there must be a two receivers and two transmitters on the sub and connected to the computer (serial output transmitter, usb output transmitter, serial input receiver and usb input receiver) I believe it would be possible to interface the OOPic to the usb output of webcam and so reduce the number of receiver-transmitter pairs, however, I would need about ~6mb/s transmittion for the camera, plus I would have to play around with the webcam driver i guess to be able to interpret the data. So for now, my solution is to make the robot tethered

    6. Since the robot is tethered, I will a have power supply outside, something like an old car battery (probably will have to reduce the power for the servo, transformer wont work so I better find a servo with 10 v of voltage suply)

    7. The frame is made of PVC, sealed hermetically but with possible access inside to acomplish required changes (hopefully none)

    8. I would make my own PC program to control the robot, and hopefully with a screen in it showing the output from the camera

    So I have two questions:

    1. URGENT. How can I interface the transducers to the OOPic to measure the distance to the botom of the lake. Analog or PWM output would be perfect. If you can give me the circuit, that would be exceptional
    2. Optional, but a nice thing to have: How can I make the thing wireless (In here I am very dumb: how to interface the usb to pic? how to make the wireless transmission to the receiver/transmitter on shore? How to isolate the camera output so I can use camera drivers on the PC?) This is closer to science fiction :cry:



    Hope that is enough info pebe :) :? :( :oops:
     
  3. pebe

    pebe Member

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    Location:
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    Yes, that's a very good description.

    I have never designed or built a circuit for a depth sounder, but I believe they use a ceramic disc with a resonant frequency of about 150KHz. A transmitter hits the disc with a single high power pulse which sends a sonic signal to the seabed and is reflected. The returned pulse is picked up, amplified, detected, and compared in time with the transmitted pulse. The distance is calculated from the elapsed time.

    I have searched for suitable circuits on google but without much success. These are the only ones which may be relevant.

    http://www.riccibitti.com/sonar.htm.
    http://groups.yahoo.com/group/aus-electronics/messages/74

    It may be that you may have to purchase a used one.

    About the radio link. I assume you intend to have some sort of floating station with cable from your sub to the station and radio link(s) from there.

    It seems you only want to send data one way - from your PC. That should be fairly easy.

    For the video, I wouldn't attempt to go via the controller - if the camera wants 6Mbs then most controllers won't be able to handle it. I think it better to take the output from the camera as it is (USB) and modulate that straight on to a radio carrier. You can get radio links that work on 2.4GHz and so have adequate bandwidth. When received, change the demodulated levels to suit the PC USB interface.

    On the question of carrying signals through the water, it would be possible to use low frequency radio to keep attenuation low, but there is no way you could bring up the video signal except through a cable.

    Hope that helps a bit.
     

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