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Help repairing power lift

Discussion in 'Troubleshooting and Repair' started by dmccoyks, Sep 26, 2017.

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  1. dmccoyks

    dmccoyks

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    Sep 26, 2017
    I am disabled and have a power lift for my wheelchair. Recently The two momentary push buttons broke off that move it up and down. I am hoping that I can replace the current switches with an aftermarket switch and just solder it to the board or jumper it from the wires. Please see attached pictures. Thank you for any help. I really appreciate it.

    Yellow - 3 prong switch locations
    Red top right - 12V DC input
    Red top left - 12V DC power to the motor
     

    Attached Files:

  2. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    Only problem is figuring what wire goes where. If you have the broken part of the switch it might lend some clues. Or, if the black bases of the switches have numbers on them, that'd help too.

    Plan B is to guess at it.

    I'm guessing the common pin of the switch is the center pin. The two outside pins are normally open and normally closed.
    I believe the normally closed of one switch must be closed in order for the other direction switch to work. This is a safety interlock feature.
     
  3. dmccoyks

    dmccoyks

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    Sep 26, 2017
    Thank you so much for your quick replay. I will put a multimeter to it tom and see if I can give you some more information. Do you know what type of switch i need? Is it considered an SPDT On On Or?

    Also I don't believe it has any interlock safety feature because when it broke the UP button was pushed in and it continued going up until I turned it off?
     
    Last edited: Sep 26, 2017
  4. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    Momentary Spdt like this one but I'm not certain of orientation of pins. Some have common pin on one side as opposed to the center.
     

    Attached Files:

  5. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    Looks like they are only using the normally open portion of the switch in the circuit.
    In other words, any switch that will close the top two pins circled in yellow (last picture) should work provided it has an adequate current rating.
     
  6. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    Sir dmccoyks . . . .

    Need for you to tell me if I am being right on that units manner of operation.
    Your original switches . . . . . that are now gutted of both their shafts and internal switching contacts by extreme blunt force trauma. . . . .INITIALLY worked like this.
    You turned on the end POWER switch and then hit the appropriate PUSHBUTTON ACTION switch such it that made initial contact long enough for the motor unit that ran that linear actuator arm (YELLOW) will be moving on its own.
    (There are limit switches and a cam that are inside of its motor end plate . . .that then keeps the motor still running, after you let up on the initial temporary switch press, that you intiated the start up action with.)
    The linear drive arm internal limit switches will STOP the system automatically at either extreme limits of its movement.
    That NEC POWER RELAY takes care of the motors POWER aspects, so the pushbutton switches will actually only carry the meager power necessary to power the coil units of that POWER relay . . . which identification and the specs I give you as:

    http://pdf.datasheetcatalog.com/datasheet/nec/EP1F-B3L2TT.pdf

    Each pushbutton switch is a SINGLE POLE DOUBLE THROW . . .SPDT . . . momentary contact unit and you want to check the possible 180 degree rotation possibility / ambiguity such that its installed contacts that are normally OPEN are being connected across the designated two RED or BLUE positions. My marked YELLOW No Connection . . .contacts are not even being used.
    That way, when you press a switch, either the RED or BLUE contacts go into a shorted condition, as long as you have the button pushed down, then it pops up and disconnects as you release pressure on it, of course the motor is auto running by itself by then..
    I believe that this is being your unit and its linear activator drive that does the lifting.

    Photo Referencing of boards two sides:

    [​IMG]

    Photo Referencing of installed SYSTEM:

    [​IMG]

    73's de Edd

    .
     
    Last edited: Sep 26, 2017
  7. dmccoyks

    dmccoyks

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    Sep 26, 2017
    Thanks for all the help. Here are some more pictures and hopefully helpful information. When I connect the green lines the lift moves up and down accordingly. I can't get me mind around how the switches work.

    Board
    A - Input
    A1 - 12v
    A2- Gnd

    B - D.C. Motor output
    B1 - 12v
    B2 - Gnd

    C - UP Button switch - top to bottom of switch
    C1 - 12v
    C2 - Gnd
    C3 - Post

    D - Down Button switch - top to bottom of switch
    D1 - 12v
    D2 - Gnd
    D3 - Post

    E - Power On/Off Switch
    E1 - 12v
    E2 - Gnd


    Switch sizes - 1/2 x 1/4 x 1
     

    Attached Files:

  8. dmccoyks

    dmccoyks

    23
    0
    Sep 26, 2017
    This is how it works and yes that is the correct Armstrong lift in the picture.

    1. I turn the unit on with the Toggle Power Switch on the end (Ref E)
    2. Press and hold either power Up or Down (Ref C and D) and release when it is in correct position. There doesn't seem to be any limits or safety functions because it continues to run as long as the buttons are held in


    "Each pushbutton switch is a SINGLE POLE DOUBLE THROW . . .SPDT . . . momentary contact unit and you want to check the possible 180 degree rotation possibility / ambiguity such that its installed contacts that are normally OPEN are being connected across the designated two RED or BLUE positions. My marked YELLOW No Connection . . .contacts are not even being used.
    That way, when you press a switch, either the RED or BLUE contacts go into a shorted condition, as long as you have the button pushed down, then it pops up and disconnects as you release pressure on it, of course the motor is auto running by itself by then..
    I believe that this is being your unit and its linear activator drive that does the lifting."

    Please see my last post with my picture referencing the Green Lines connected to make the switch move up and Down. I don't believe I won't to short RED or BLUE since C1 D1 are 12v and C2, D2 are Gnd?

    Please let me know what other information I can provide that is helpful. Thanks so much for everyone's help
     
  9. dmccoyks

    dmccoyks

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    Sep 26, 2017
     
  10. dmccoyks

    dmccoyks

    23
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    Sep 26, 2017
     

    Attached Files:

  11. Tha fios agaibh

    Tha fios agaibh

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    720
    Aug 11, 2014
    It works by changing polarity to the motor with an H-bridge circuit. It's not a short. Positive feeds relay and Negative is switched through the switch.

    If you scared you could use a 1 amp glass automotive fuse to short it out.
     
    Last edited: Sep 26, 2017
  12. dmccoyks

    dmccoyks

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    Sep 26, 2017
    Ok thanks. Can you recommend a switch that might work then. The pin spacing is approximately 1/8" and the switch is Approx 1/2 x 1/4 x 1. I can drill the holes or modify as needed once I find an appropriate switch. The hole size is 1/4 x 1/4"
     
    Last edited: Sep 26, 2017
  13. Tha fios agaibh

    Tha fios agaibh

    2,128
    720
    Aug 11, 2014
    Screenshot_2017-09-26-16-49-10.png
     
  14. Tha fios agaibh

    Tha fios agaibh

    2,128
    720
    Aug 11, 2014
    I believe it's the same but read the specs
     
  15. Tha fios agaibh

    Tha fios agaibh

    2,128
    720
    Aug 11, 2014
    Read the specs to see if it meets your needs.

    Was there a problem with the Oem switch I posted?
    It's certainly more robust.
     
  16. dmccoyks

    dmccoyks

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    Sep 26, 2017
    Does the amperage make much difference?
     
  17. dmccoyks

    dmccoyks

    23
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    Sep 26, 2017
    The size is a little bigger which isn't an issue but the distance between the pins is only .154". It shows the common on this switch as position 2 is that correct configuration?
     
  18. dmccoyks

    dmccoyks

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    0
    Sep 26, 2017
    After looking more at the switch you recommended, I think it will work. Thanks so much!
     
  19. Tha fios agaibh

    Tha fios agaibh

    2,128
    720
    Aug 11, 2014
    I got the number EB2011 from the picture you posted so I assume it's what you want.

    Good luck.
     
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