12 volt trolling motor switch

Discussion in 'General Electronics Chat' started by mattkinz, Mar 1, 2009.

  1. mattkinz

    Thread Starter Member

    Mar 1, 2009
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    I am pretty stupid in electronics.

    I have an underwater scooter missing a reed switch and a control box that turns the unit full on or off when a magnet nears the switch. The propulsive motor is like a trolling motor and uses a 12 volt, 26 AH battery.

    The orig manufacturer went out of business and cannot be contacted or even found. I will have to find appropriate parts to replace. The original control box is sealed and waterproof with no markings. Just 3 wires, one to battery, one to trolling motor and one to broken reed switch. I have one working scooter but bought two other fixer-uppers.

    Any help would be appreciated on where to find the replacement parts or how to make a red switch motor controller with simple on/off mode.

    Thanks. MK
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Can you draw up a schematic of what you have described so far, and include some more details?

    Like, which battery terminal does the control box wire go to, where does the other side of the reed switch connect to?

    Any idea of the trolling motor current draw?
     
  3. italo

    New Member

    Nov 20, 2005
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    A motor usually draw considerable amount of current therefore if the original reed was use to open-close then the problem is a stuck reed. to replace it is no a big deal. find some reed switches anywhere except this time add an interface power transistor or FET to do the power work. it should last for a long time. Here you can get help to build such a device but like the sarge say need the operational current and the inrush if possible. then we can help. Or take a chace and build it for 26 amps and hope for the best.
     
  4. mattkinz

    Thread Starter Member

    Mar 1, 2009
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    How can I tell the amp draw? Nothing is printed on the motor, nothing on the control box. I have a volt meter and what is written on the battery.

    BTW, I appreciate the help. MK
     
  5. gerty

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    Aug 30, 2007
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  6. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    The gauge of the wire into the factory box and to the trolling motor should give you a hint for current rating.

    If it is 14Gauge or so, use a 20 Amp reed switch. If it is larger diameter wire, use a bigger switch (typically double the needed size). This keeps the heat down so the contacts do not weld together when turning the motor off and on.
     
  7. Externet

    AAC Fanatic!

    Nov 29, 2005
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    Larger reed switches that can handle high currents exist; hard to find and can be costly, and not fully reliable.
    A small reed switch can control a relay. That could be the missing 'control box'
     
  8. thatoneguy

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    Feb 19, 2009
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    You are correct. I read it as "reed switch IN a control box" somehow.
     
  9. mattkinz

    Thread Starter Member

    Mar 1, 2009
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    The wires from battery seem about 12 gauge, they are crimped with a 10/12 crimp.

    battery wires go to control box and then wires out to motor seem to be 12 gauge as well.

    The set into control box is ga 12 and out to motor is ga 12.

    The on/off switching is done with cylindrical reed switch with a tiny(by comparison) double wire with one casing. each inner wire is very fine and both wires metal taken together may be smaller than 22 gauge.

    I think there is circuitry in the box that allows the switching of the major current via the reed switch. The original switch may have been a weak point and was covered with a fragile plastic dome prone to breakage when bouncing around a dive boat.

    I hope this info can help. I have the broken switch and it no longer responds to magnet to give any continuity. If the switch welded itself, it would be permanent on. It is permanently non functional.

    The switch, however seems to not handle much current at all.

    thanks for suggestions folks. MK
     
  10. mattkinz

    Thread Starter Member

    Mar 1, 2009
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    Here is attached picture of the unit in operation. The diver hangs on the handle area and the remote reed switch is under right thumb .
     
  11. thatoneguy

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    Feb 19, 2009
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    I'm trying to reconstruct this entire simple system, so bear with me if you have the time (both to read this huge post, and do the tests:eek:).

    Generic "Toggle Switch", or "Red Button", mechanical switches cannot operate underwater unprotected, as the contents would be flooded with saltwater (from image above, I'm guessing seawater, which is conductive). So that shoots down your first quick fix, although a switch would be a good test on dry land /shop area to make sure everything else works.

    With a functional submersible: Does control box make an audible "Click", or vibration that can be felt on outside of control box thumb control is depressed? Does the motor have only two speeds, off and full power? If so, the bulk of this post may be skipped (See Last paragraph)!

    Do you have a DMM/Digital Multimeter with resistance and diode voltage check/measure? ***

    [total time, 5 minutes]: Could you measure and post the results, both on resistance check and diode check modes, exchange leads red for black for each test as well, and note any significantly different readings between red/black probe swapping on the following list. I am assuming the "control box" is metal, or has a metal part that is "Ground", when "case" is mentioned, I am referring to "ground": positive/negative ground test are first four, NO BATTERY PRESENT!

    • Resistance & Diode check Batt+ WIRE to Reed Switch in
    • Resistance & Diode check Batt- WIRE to Reed Switch in
    • Resistance & Diode check Batt+ to Control Box
    • Resistance & Diode check Batt- to Control Box
    • Resistance & Diode check - Motor to Reed In
    The tests above are simply "Black Boxing" to confirm quiet relay or solid state "guts". Resistances should nearly be the same no matter the lead polarity. Diode Check, sometimes to often not.

    *** If you have a DMM with auto-protection beyond a input fuse for current measuring. I suggest a used Fluke 12-B or higher end 87, or similar to get started. Try to stay clear of $5-$10 DMMs, but if that's all you have, you can get by. If you find this hobby fun and interesting, a Quality DMM will save you much time and confusion from bad measurements!

    Unless the audible/tactile click test mentioned first conclusively show the control box is a relay, I'd like to get all information to create a diagram, which you can refer to in the future, if you buy another with no controls at all, so you can create something that will fix it. Pressure / waterproofing is the hardest part. What depth is max for these units?

    --ETA: 12ga Wire with Crimp on Ends indicates 10-20A continual, 40A for short periods such as motor start, assuming < 10ft run. This is on the safe side to match manufacturer practices and your stated battery size.
     
    Last edited: Mar 3, 2009
  12. mattkinz

    Thread Starter Member

    Mar 1, 2009
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    The motor is pure on/off and full power for on, then off.

    The box does make a clicking sound to turn on the motor. There are connectors with gold plating and o-ring seals for the different wires. The one for the reed switch had 2 contacts. By shorting with piece of metal across the 2 contacts, the box did click and the motor turned on.

    I have an analog voltmeter? is there a way to measure current flow to determine how small a reed will work?

    It seems there is a relay inside the plastic sealed box and the reed switch must only function to allow the relay to connect.

    The switch seems to be encased in a threaded cylindrical plastic piece with nylon nuts and o-ring seals where the dome goes through a hole in the plastic handle of the unit. I have information on toggle switches for U/W usage but the reed allows instant off when your hand releases the handle. You certainly do not want your U/W scooter to motor itself to the abyss.

    I have found sources for cylindrical threaded reed switches but not the domed part, or the nuts/ o-ring setup Though should be fairly easy to jury rig a waterproof and pressure proof setup to go to 110 ft. which is rated depth.

    For that matter, A regular reed switch could be mounted inside the plastic handle and sealed with urethane based sealant and a neodymium magnet should do the switch operation right through a few mm of plastic and a plumbing fitting could be screwed and sealed through the existing hole. MK
     
  13. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    If the highest range is under 500mA, you may be blowing the fuse, so have a spare.

    In Voltage Mode, put the red lead on the battery, then touch both sections of the plug, one at a time, that would go into the reed switch. Whichever one Does NOT show a reading would be Positive.

    Then switch to current mode (mA/A) at the highest range available on your meter. Put the red lead on the Positive part of the plug (the one that showed no difference from battery voltage), and black lead on the other part of the plug.

    One of two things will happen:
    A) Relay will click, and you will see the current drawn on your meter (if needle tries to bury itself to the left, switch Red and Black. some analog meters have Red/Black reversed when in current mode.
    B) Relay will make a "ClClk" sound, and you will have no reading on your meter, and need to install a new fuse.

    Most 12V Bosch type relays (most common) have a 75 or 150 Ω coil resistance, so the measured current should be under 300mA by a good amount. If it is more than that, something is odd.

    That's how you measure current, and will know the switch ordered will work. Another option is to simply measure the resistance between the two "rings" on the reed plug, WITH BATTERY DISCONNECTED if it is over 75 ohms, you should be fine. (I = V / R) 184mA = 13.8 V / 75Ω

    If it is Under that current, or over that resistance, depending on the measurement you took, here is an example of a magnetic reed replacement that would work:
    [URL="http://www.mouser.com/Search/...roductDetail.aspx?qs=KFo7JewZbUFhEiG0Dv2Zgg== Looking through their, and many o...the plug. Keep us updated on how it works!
     
  14. mattkinz

    Thread Starter Member

    Mar 1, 2009
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    I did try to test as per instructions. I figured out positive and negative lead on the wires to the reed switch.

    On my voltmeter, there is section for DC Volts, this was placed on 10,

    Then I changed to amperes, this part of the meter had" DC A" The range was 500 micro amps, 5m (milliamps?) and 0.25. I used highest setting or 0.25 , and the needle maxed out on the meter. No click heard. repeated a couuple of times and no different findings.

    Now what? Thanks for helping me out. MK
     
  15. thatoneguy

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    Feb 19, 2009
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    Did the fuse blow?

    .25 would be 250mA or 1/4 amp. If the relay didn't click at all, AND the fuse is good, I'm confused.

    The meter in current mode essentially acts like a piece of wire, so the relay should have triggered, or the fuse should have blown, or my explanation wasn't sufficient for operation on meter.

    Check the fuse to be sure, but the needle shouldn't move at all if no current is flowing (such as when the fuse is blown).

    The One Other thing I can think of is that the relay is for 12/13.8 VDC, and the voltage was too low to engage it. With the additional shunt resistance of the meter in the line, something didn't have enough power to engage the relay. Some meters have a large resistance, which creates a voltage drop (that's what is measured on the meter), but shouldn't be so big as to stop a relay from working.

    ETA: Did the needle hit the right edge when measuring the voltage? Is the battery fully charged?

    Quick video, using a digital meter, but also pertinent to what we are trying to find. http://www.youtube.com/watch?v=iJmxe175hl8

    In current mode, the two meter leads were in the same places you normally put the ends of a wire to turn on the relay?
     
    Last edited: Mar 4, 2009
  16. mattkinz

    Thread Starter Member

    Mar 1, 2009
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    Battery seems pretty much fully charged. The needle went to the max of the meter. Maybe the internal resistance of the meter limited the amt. of current flow enough to prevent relay from working. MK
     
  17. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    When using an analog meter, you should always start on a range higher than any expected voltage or current to be measured to prevent damage when the needle hits the stop peg really hard (20V+ range for measuring a 12V Battery, for example)

    Were you able to disconnect the battery and check the resistance between the two wires at the reed switch plug?
     
  18. mattkinz

    Thread Starter Member

    Mar 1, 2009
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    I repeated test , and shorting the switch contacts starts the motor with attendant click. With the meter at highest setting, the needle maxed out .


    The unit allows unscrewing the contacts for all wires to and from the box. Thus I have access to the wires from battery, wires to the motor and the wires to the switch. How do I use meter to check resistance to the reed switch part of the circuit?
     
  19. thatoneguy

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    Feb 19, 2009
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    To get the resistance of the relay coil (what I've been after, but went a slow way about it...)

    We want to test on a dead circuit. Not dead as in broken, but as in "No Power". So if the battery is the only power source, disconnect it/remove from the watercraft/scuba scooter. Now, unless a charger is plugged in somewhere on it, there should be no voltages anywhere on the unit.

    At this point, Switch your meter to Ohm Mode/Resistance Mode (1k or 2k), and put the leads across the reed switch jack, just as if they were the chunk of wire you were using to start the motor. You should get a reading. If the needle barely moves, try a lower range, but don't go to below about 500 Ohms.

    You should get an accurate reading (+/- 10 ohms). That is the number we need to determine the current ability of the switch you need to get for replacement. Otherwise, if it's too small or the exact size, it could easily arc closed and it would drive itself away.
     
  20. mattkinz

    Thread Starter Member

    Mar 1, 2009
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    When I have my analog unit set on RX1K . There is no response whatsoever to testing of the 2 leads to and from the reed switch.

    Testing the pos lead from battery (without any power) to the pos lead of the reed switch portion of the circuit, the meter needle reading went to 0.3Ω. neg to neg went off the scale past zero. If I understand it, the resistance measured on the rX1K is in thousands of ohms, then I think the resistance of the pos lead of the reed switch portion of the circuit may be 0.3 Ω X 1000, or 300 ohms.

    No one has ever taught me anything about electrical meters and I may be totally wrong. All I have ever had the need to use this function for before is just as a continuity checker.

    One caveat is that the "zero" with meter is to left side and ∞ on Ω scale. When continuity is checked with no resistance, the resistance does not list as 0 , but the needle goes off the scale to the right.

    I'm assuming the reading of 0.3Ω shows the resistance between battery wire and the reed switch. If I have understood correctly, this portion of the circuit may be 300 ohms. Now what do I do? MK
     
    Last edited: Mar 6, 2009
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