Design a depth finder circuit

Discussion in 'The Projects Forum' started by snail71, May 19, 2017.

  1. snail71

    Thread Starter New Member

    May 19, 2017
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    This is a project I want to do purely for the learning experience. I want to use a standard off the shelf transducer like the Lowrance HDI dual 83/200 KHZ depth and temperature sensor. Here is an info page for it. The sensor basically has a ground and +/- pins for the depth transducer. If I understand correctly it uses the same ceramic for both transmit and receive. I have no problem with just selecting one of the two frequencies (83 KHZ gives better depth and wider beam, 200 KHZ more detail).

    I will utilize a microcontroller to generate the signal, receive the signal, and display the results. I will power the circuit from a 12V battery. I know I'll need an amplifier to drive the transducer and a filter / amplifier to receive and condition the signal for the A/D on the micro. One area I am not sure how to handle is decoupling the transmitter to transducer verses the receiver.
     
  2. debe

    Senior Member

    Sep 21, 2010
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    May be these circuits of older echo sounders will be of some help. The transducer coupling is still relavent to modern sounders. FURUNO FG-200.1.jpg FURUNO FG-200.2.jpg FUSO MF_25A.1.jpg FUSO MF_25A.2.jpg
     
  3. debe

    Senior Member

    Sep 21, 2010
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    A.1.jpg A.2.jpg A.3.jpg A bit more info for your consideration. There is also a National IC, LM1812 sounder on a chip. Heres a page from the data sheet. & a Furuno sounder based on it. Also a project from a electronics magazine back in 1982 Electronics Australia.
     
  4. snail71

    Thread Starter New Member

    May 19, 2017
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    Thanks for the circuits above.

    I'm also looking at this sonar ranging IC. Looks like it could be adapted to create a solution.

    [​IMG]
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    I've made ultrasonic ranging circuits with just two chips: a Micro that generates the "ping" pulse, and an amplifier to convert the very low lever echo to a logic level to feed back into the micro.

    This device was measuring fluid columns of a foot or two. To measure to much greater depths you would need to drive the transducer harder, and perhaps up the gain of the receiver, but the basic concept of measuring the time of flight between the ping and the return echo as a measure of depth will remain the same.
     
  6. snail71

    Thread Starter New Member

    May 19, 2017
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    I have located schematics from a service manual from an existing depth finder. They seem to be close to what I'm looking for. I have started reworking the schematic for the TX part of the analog circuit. The part that I'm stuck on (not being an analog guy) is the transformer in the TX circuit. It lists a part number but I haven't found anything for it. I assume it is custom wound for the circuit. Can anyone help me determine what I need? The TX circuit says it works with either 50 KHz or 200 KHz. The manual also states that the measured voltage with an oscilloscope across the output should 400-600vpp.

    Here is the TX circuit:
    [​IMG]

    And here is a pic of the transformer on the PCB:
    [​IMG]
     
    Last edited: Jun 12, 2017
  7. debe

    Senior Member

    Sep 21, 2010
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    I would just find an old discarded Sounder & remove the transformer & use it for your project, so long as its the right frequency. Theres plenty of old discarded paper style sounders thrown out these days.
     
  8. #12

    Expert

    Nov 30, 2010
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    Don't even pretend I can prove this with math but, a transformer out of a SMPS designed for about 28 volts (or less) of output, and connected backwards might work. They operate in the hundred KHz range and the other thing to discover is the turns ratio you need. If you have all week to mess around, you might try extracting some 6 lead transformers out of some old power supplies.
     
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