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Replacing a momentarily rocker switch with relay switches

Discussion in 'General Electronics Discussion' started by Jamal, Aug 3, 2018.

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  1. Jamal

    Jamal

    5
    1
    May 8, 2018
    cct1.jpg Hi

    A pendent remote connected to an electrical hoist. There is one momentarily rocker switch on the pendent; while pressing the rocker switch on the left or right, motor rotates up and down direction accordingly.

    I like to replace the rocker switch with two relay switches, one to connect the up and one connect info down circuit.

    Please help me to confit what type relay I should use and how it should be wired. Attached is wiring diagram for the pendent and the rocker switch.


    Thank you
    [mod note: fixed image]
     
    Last edited by a moderator: Aug 4, 2018
  2. Tha fios agaibh

    Tha fios agaibh

    2,088
    699
    Aug 11, 2014
    First, i'd be very cautious about altering hoist controls especially if personnel are involved.
    It could present a hazardous situation.

    You didn't say what the voltage or current is but you should ideally use a reversing contactor. They are mechanically interlocked to prevent inadvertently enabling both up at down at the same time and are designed for heavy motor currents.

    Basically wires 12 and 9 would be on one contact for "up" and also on the same relay (contactor) will be 11 and 10 on another contact.
    similarly, the wiring on the other sides of switch would go to your "down" contactor.

    Another safe wiring practice is to electrically interlock the energizing coil of one contactor direction with a normal closed contact of the opposite direction contactor.
     
    davenn likes this.
  3. Jamal

    Jamal

    5
    1
    May 8, 2018


    Thanks John
    To control the hoist I had ordered a control box made for my use back home.

    The control box comes with two set of wired soft touch keys and one wireless switch that can control the motor from two different locations. On the control box, there are two input terminals to power it up and 8 output terminals as follow:

    2 terminals to power the electric motor

    2 terminals to control rotation of the motor

    2 terminals to connect up and down limit switches

    1 terminal for emergency stop

    What I realized was that unlike the motor back home electrical motor I got has only 3 input wires (2 capacitors connected in parallel are connected in series to one of the wires); despite trying all sorts of configuration to replicate 4 wire connect, I had no success, I only hear humming noise from the motor when I press up or down buttons, motor doesnt turn at all!

    So I got an idea, tested left and right output terminals with the neutral terminal, I observed that 110v voltage present when up or down buttons press.

    Now if I connect those terminals to two relays that are connected to pendent’s up an down circuits this configuration meets my needs.

    The control box already has the limiting switches terminals.

    So when I press up or down keys respective control rotation terminal will have voltage that could turn on the relay.

    If I understood your direction, based on the output I get from the control box I would need two 4 pin relays (2 pin to charge the coil and the other pair to connect up or down circuit)
    Question: if only pins 9&12 and 10&11 are to be connect to control up and down circuit why wire 9 is common between up and Dow circuit?
    Thanks
    Sorry for long email
     
  4. Tha fios agaibh

    Tha fios agaibh

    2,088
    699
    Aug 11, 2014
    I agree it's not usually drawn like that, but it works like this;

    The motor uses u1 as run winding (up) and z2 as a start winding (cap in series), then when going down they swap polarity of the caps which causes a 90°phase shift to change motor direction.

    So when going up, power is directly on u1 (up) winding and the opposite winding has the cap installed. When going down, u1 now has the cap attached which will phase shift the direction. By changing power from one side to the other of the cap (note how line power goes to either left or right side of cap depending on bottom contacts) that causes one winding to delay and encourage it to spin the other way.

    Does that answer your question?

    Might want to post some pictures. It would help clarify exactly what you have.
     
  5. Tha fios agaibh

    Tha fios agaibh

    2,088
    699
    Aug 11, 2014
    Here's a crude sketch. Contacts with a line through them are normally closed. 20180803_184447-1.jpg
    Edit: I forgot to add stop button.
     
  6. Jamal

    Jamal

    5
    1
    May 8, 2018
    Thank you sir!
    Attached are the pictures of the control unit and schematic for electrical motor. If I could connect my 3 wires motor to this unit directly (not using the pendent wires) somehow, I trust it would be much easier for me. Would have any idea how I could accomplish that? is it possible at all since the motor is 3 wire and unit output requires 4 wires? thank you IMG_0189[2].JPG IMG_0188[1].JPG IMG_0172[1].JPG IMG_0178[1].JPG
     
  7. Tha fios agaibh

    Tha fios agaibh

    2,088
    699
    Aug 11, 2014
    I have no idea whats in that control box. Probably not feasible because it looks like a foreign voltage (230v ?) controls, while the hoist circuit suggests it's a North American voltage (120v).

    You can't guess at circuitry, know and understand what your hooking up.

    As I said, it's important to first find out what voltage and full load current your motor draws so you can calculate the correct fuse or circuit breaker.

    The limit (overtravel) switches and stop button should be added to the controls ahead of the contactor coil.

    Again I've no idea what current it draws but you probably need a contactor that looks something like this. Screenshot_2018-08-03-22-41-42-1.png
     
  8. Jamal

    Jamal

    5
    1
    May 8, 2018
    Thanks for all your help Dave. I am not sure if details below make any changes to your previous comment.
    There are two connectors (just like what you showed in your post) and a wireless receiver in the box, control box is set up for 110v, my motor is 110V, 7.1Amp, 3/4 HP. There is a transformer that convert 110V to 12DC to power up the wireless receiver. Here is the inside of the yellow box,

    IMG_0179[1].JPG IMG_0180[1].JPG IMG_0182[1].JPG
     
  9. Tha fios agaibh

    Tha fios agaibh

    2,088
    699
    Aug 11, 2014
    My name is John. You might have seen where dave clicked on the "like" button on one of my posts?
    Anyway, It looks like your in business with what you have! Instead of deciphering the existing wiring I suggest just removing the wiring and starting from scratch.

    Now. Looking at the sketch I posted, reinstall the red jumper wires to match what you see.
    You only need to use two main contacts out of the three on each contactor. The normaly closed contact is the narrower one on the right (unlike how I drew it on the left).
    In fact, don't worry about the nc contacts right now. We'll just do the motor leads for now.
    I recommend you use a wire size of 14awg or larger for the motor conductors but 16awg will do if that's what the red wires are.
     
  10. Tha fios agaibh

    Tha fios agaibh

    2,088
    699
    Aug 11, 2014
    For now, just remove the 3 red wires on top and bottom of each contactor. These are the main contacts. Leave the normal closed contact wiring and the rest. It may be ok the way it is.
     
  11. Jamal

    Jamal

    5
    1
    May 8, 2018
    Thanks John, I was writing an email to a colleague of mine (Dave) on a business related issue, I didn’t realize called you his name... sorry!
    Thank you for your suggestions, I am going to give it a try in next few days, I let you how it goes.
    I appreciate the support/attention I got on my problem.

    Cheers!
     
    Tha fios agaibh likes this.
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