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Seeking help with 12v dc motor controller on golf buggy

Discussion in 'Troubleshooting and Repair' started by onedog, Nov 11, 2019.

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  1. onedog

    onedog

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    Oct 4, 2016
    Hi all. I'm new at this and considering repair of a motorised walk-behind straight-ahead (i.e. no reverse, no direction control) golf buggy. Manufacturer was Boska (defunct), power is 12v 28Ah deep cycle battery.

    The buggy was assembled in the car park and behaved itself until 100M down the first hole whereupon it took off by itself. Battery disconnect was the only remedy. The buggy did not respond to the pot attached to the handle, which normally controls on-off and speed.

    I have checked the operation of the pot and it is good - O/C in the OFF position, big ohms in slow position rising to low ohms in the fast position.

    I can't find a circuit diagram for the motor controller board. However, inspection reveals blistering of the OKO K3B12 relay (see pdf attached) casing. Within this 5-pin relay, there is 320 ohms across the coil pins (as per spec) but all other pin connections are O/C. There should be connectivity between at least one other pair. If this is the culprit, I haven't been able to find a replacement source.

    Any suggestions on how to proceed?

    Re the graphics, at the top right of Picture A there is a sort of springy collar which fits around but doesn’t touch the motor -ve terminal and clamps lightly on another component. Is the collar just a heat sink? Anyway, I took it off and snapped picture E so you could see the trace beneath it.

    Picture G is my fishing boat.

    Thanks for looking.
    A.jpg B.jpg C.jpg D.jpg E.jpg F.jpg G.jpg
     
    Last edited: Nov 12, 2019
  2. Tha fios agaibh

    Tha fios agaibh

    2,083
    694
    Aug 11, 2014
    Welcome onedog, I didn't see your relay pdf but that would be a big help tracking down a replacement.
    You might have to try a electronic supplier like digikey or mouser and try and compare terminal spacing of a similar 10a 12v relay.

    That collar is likely a ferite coil to sense current on the wire feeding motor and works in conjunction with H1 hall effect sensor.
     
  3. 73's de Edd

    73's de Edd

    2,794
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    Aug 21, 2015
    Sir onedog . . . . . .

    Au contraire ! . . . . .I find only one fault in the original post . . . being its very end pic.
    As for the initial . . . . . . .
    " and behaved itself until 100M down the first hole whereupon it took off by itself "
    I would have absolutely loved to have seen that . . . . considering that you were having to take off after it, like an instant breakaway of an unleashed dog.

    It seems like to me that the relay function would be for the switching on of power or possibly a switch to direct full power to the drive motor, if not wanting to use the higher end of the variable speed control aspect.

    Is the collar just a heat sink?

    Those 3, . . . . D1 dual diode and Q1 Q2 power semiconductors . . . . . specifically Q1 and Q2 MANDATE heat sinking of their collector connected tabs or they will be burnt toast in a couple of minutes of full power.
    I don't even see any white residue of heat sink residue staying on their tabs, unless they are using less thermally conductive Sili-tab-insulators.


    Within this 5-pin relay, there is 320 ohms across the coil pins (as per spec) but all other pin connections are O/C.

    Consult this below . . . and confirm that the actual closed contacts as shown, are being closed, in its unpowered state. I think that a 9V battery would have enough ooooomph to pull in your relay armature to test the other contacts for their closure when coil power is then present.
    In my reading of the boards foil path associated with the relays 3 contacts the non energized power contact that has the movable contact leaf resting upon it, is connected to a non connected foil circle.


    On your relay, the only apparent fault I see is that someone in assembly, let some clear epoxy drip onto its casetop.

    Your cause of failure failure fault to me, seems to be those paralleled power transistors of Q1 and Q2 might have shorted from Collector to Emitter, and that would cause max power motor speed at that instance of occurrence.
    Take an ohmmeter and test from C-E to confirm. Also pass on their identifier numbers as well as their dual power diode companion.


    73's de Edd . . . . .

    It's been a particularly rough day. I got up this morning and put a shirt on and a button fell off.
    I picked up my briefcase, and the handle came off.
    Now, I'm afraid to go to the bathroom.



    .
     
  4. onedog

    onedog

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    Oct 4, 2016
    Sorry about the missing pdf. Here it is. I have annotated the graphic (page 3 RHS) by adding pin numbers.

    I was not familiar with hall effect sensor but I'm learning - thank you.
     

    Attached Files:

    Last edited: Nov 13, 2019
  5. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    Indeed the " Collar" is being a split ferrite toroid which is detecting higher current flow thru the negative motor lead which it surounds .
    The induced magnetic field therein is being proportional to the current flow thru the wire, The magnetic field is further concentrated between its gap which has a Hall effect sensor mounted within the gap.
    How about the Q1 Q2 status ? To be . . . . or not to be shorted, that is the question.
     
  6. onedog

    onedog

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    Oct 4, 2016
    Mr Edd
    1. While I can see that the blob atop the relay is probably epoxy, I include here another snap showing a bubble on the relay case directly above pin 5 (as numbered by me in the pdf above).
    2. You are so right. D1,Q1 and Q2 tabs are thermally connected through some sort of material to a heatsink attached to the controller's casing.
    3. I won't be able to check out Q1 and Q2 until the coming weekend. I'll report back. H.jpg
     
  7. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
  8. onedog

    onedog

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    Oct 4, 2016
    Hola Sir Edd
    I have yet to check the relay as you suggested. I'll try to do it this morning.

    Both Q1 and Q2 show 5 ohms C to E. I can't get further info on D1, Q1 or Q2 without de-soldering and I don't think I've got the skill set for that.
     
  9. Alec_t

    Alec_t

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    Jul 7, 2015
    Job to tell from the pic in post #6, but the transistor to the left of the relay looks as though it might be fried too.
     
  10. onedog

    onedog

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    Oct 4, 2016
    Earlier, I said that the resistance of the coil in the relay was 320Ω as per spec. Big Newbie mistake - the resistance was 320KΩ, i.e. 1000 x spec.

    Alec_t...
    Great spotting on transistor Q3 - see new pic.

    So re the relay, any pointer on where I go to find a replacement with the same pin layout would be appreciated. J.jpg
     
  11. Alec_t

    Alec_t

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    Jul 7, 2015
    If you measured 320k the relay coil has gone open-circuit.
     
  12. onedog

    onedog

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    Oct 4, 2016
    The only Google info I can find on the blown relay points to Anglia in the UK and I have emailed them. Is there any other way to find an alternate suitable relay with the same footprint?
     
  13. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    I posted a link to one that'd work in post 7.
     
    Martaine2005 likes this.
  14. onedog

    onedog

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    Oct 4, 2016
    I saw that but the pin positions are different. The relay I'm trying to replace claims to have an "industry standard footprint" so I thought I'd be able to find the same footprint from a different manufacturer - maybe not so? So how would I fit the suggested relay to my PCB?
     
  15. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    Looks the same to me.
    Screenshot_2019-11-20-06-52-28-1.png Yours

    Screenshot_2019-11-20-06-55-03-1.png My suggestion.
     
  16. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    ALAS, no . . . .the pin out on your specified relay has the coil PCB connection pins being located 180 degrees across from each other.
    On the oKo relay the coil PCB has both of its coil contacts being spaced apart side by side on one side of the relay . . . thus . . . its being a wierd duck from the normal relay.
    He gave a marked up MECHANICAL drawing dimensions and POSITIONING of its coil connections footprint in his post # 4..

    One dog . . . . . solder-er-er-er-er ing " newbie " . . . can you now desolder with out burning up your PCB ? or do you need some practice expertise, to then be able to pull off a multi leaded (5) component and reinstall on another PRACTICE piece of electronics PCB ?
     
    Last edited: Nov 20, 2019
  17. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    Perhaps I'm brain dead this morning but I don't see the difference.
    Heres the Oko original from post #4
    Screenshot_2019-11-20-09-08-50-1.png
    And heres the proposed G5LE replacement
    2019-11-20 09.07.37.png
     
  18. 73's de Edd

    73's de Edd

    2,794
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    Aug 21, 2015
    EXTREME last part of Pee Dee Eff . . . bottom right corner . . . HIS relay has the pins 1 and 2 coil connections being awry from your submitted relay. (5 and 2 on your drawings numbering assignments. )
    upload_2019-11-20_8-50-59.png
     
    Last edited: Nov 20, 2019
    Tha fios agaibh likes this.
  19. Tha fios agaibh

    Tha fios agaibh

    2,083
    694
    Aug 11, 2014
    Thanks, I was looking in wrong section.
     
  20. Tha fios agaibh

    Tha fios agaibh

    2,083
    694
    Aug 11, 2014
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