minn kota 12 volt trolling motor

Discussion in 'General Electronics Chat' started by voodie, Feb 1, 2007.

  1. voodie

    Thread Starter New Member

    Feb 1, 2007
    1
    0
    hi guys

    this 12 V trolling motor was under water for about 2 weeks. I basically found out that the electronic circuit board suffered irreparable damage.

    I have connected the pos motor lead directly to the pos battery lead and the motor works. [of course full speed.]

    I want to put a rheostat (potentiameter) in the system to be able to stop the motor and variable speed it up to full rpm. And I want to put a reversing polarity switch into the circuit to be able to go from forward to reverse.

    What kind of electronics will do the trick and how do I wire it up?

    Thanks a lot for your help!!!!
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    It would have to be a rheostat to do the controlling. The problem is that using such a device means you are sharing power. Whatever doesn't go into the motor shows up as heat in the rheostat. If the trolling motor draws 20 amps, the controller has to be able to dissipate 240 watts of heat. That is a large and expensive rheostat and lots of heat right under the knob.

    If you want to try this, hook up the battery again and measure the current draw. Then find a two pole double throw switch that will handle the current. You will also need the rheostat. Something like 500 - 1000 ohms should do, but it will have to handle the power figure you get by multiplying the current draw times the voltage. Go larger than the power you need so the poor rheostat won't burn up when you get into mud and lug the motor.
     
  3. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    Its a fair bet that the electronic circuit that was damaged provided a PWM output to the motor to vary the speed with a minimum of power loss and heat.
    There are plenty of kitset High power DC motor speed controllers out there, most using a MOSFET output stage.
    http://www.dse.co.nz/cgi-bin/dse.storefront/45c3108201273f72273fc0a87f3306b5/Product/View/K3072
    This one is available locally (for me) and is rated to 20 amps. Higher powers could probably be achieved by adding extra output devices.
    Another source would be electric Wheelchair speed controllers, electric scooter speed controllers etc.....
     
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