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An amateur requests help with motors

Discussion in 'General Electronics Discussion' started by Gurkudrengur, Jul 2, 2018.

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  1. Gurkudrengur

    Gurkudrengur

    3
    0
    Jul 2, 2018
    Hi !

    I‘m a student in carpentry and I‘m designing a piece of furniture, a very big expandable desk. Like, go big or go home kind of project. It has been dubbed „Deskimus Prime“. I would very much appreciate a little help considering the electronics needed to make it move. I want it simple, nothing digital or computer controlled, just motors and endstop switches. If you can help, it will be greatly appreciated!

    The desk:
    I have only drawn simple sketches of the desk, since I need to determine the dimension of the motors and components before I make a proper technical drawing.

    20180702_141524.jpg 20180702_141506.jpg

    On the first image is the desk setup closed and locked. On the other, it is fully open. When it is closed it is about 2m wide, 1.3m deep and 2m high. When open, about 3m wide, 2.3m deep, and 2.8 high. Not final dimensions, but somewhere close.

    It will be made of solid Elm wood, so it will be a bit on the heavy side. When it is full of stuff it will be even heavier. So I‘m thinking each motor should be able to move/lift min of 100kg. Except the one for the lid, it can be smaller, like 20kg capacity, and the one for the backside should be bigger, maybe 200kg. Since it will be this heavy, the motors can‘t move to fast. I‘m thinking 1 – 2m / minute, but since I haven‘t completed the design it is hard to say exactly.


    The transformation

    A simple top-view drawing of it closed (left) and open (the other left)


    35d63d925508725c398145b431bca50a.jpg


    · Button is pressed

    · Lid rolls back. Stop.

    · Units 3 and 4 move out together. Stop.

    · Units 2 and 5 move to the sides simultaniously. Stop.

    · Units 2 and 5 are lifted up. Stop.

    · Unit 1 is lifted up. Stop.

    · Units 3 and 4 move to each side. Full stop.


    For this I‘m gonna need 9 motors. As previously said, the one for the lid can be small, the one for the backside (unit 1) around 200kg lifting capacity, and the other 7 with a lifting/moving capacity between 100-150kg.

    Also, I live in Sweden, outlets here are 230V.

    If you have read through everything, thank you ! I hope you can leave some pointers in the comments, whether it‘s help with the project, or someway I can improve my post. I will update as I make progress.

    Thank you !
     
  2. Minder

    Minder

    3,076
    657
    Apr 24, 2015
    I would think small DC motors with high ratio gear boxes, this also give a measure of safety with isolated DC via suitable 230v to 12vdc transformers together with a suitable bridge rectifier.
    You will need to set up some kind of relay sequencer, or use a Smart Relay where the logic is programmable.
    For that number of I/O though you might need an expansion I/O module.
    How have you ascertained it will require that much to move?
    200Kg's!!
    M.
     
  3. kellys_eye

    kellys_eye

    4,275
    1,147
    Jun 25, 2010
    On the KISS principle I'd tell you to look at the motors used in recliner chairs. The key to movement is, as mentioned, the gear ratios used and you'll be surprised how small a motor can be in order to lift 100kg or more. I have a load of old Maxxon geared motors (some with 60:1 and 500:1 reduction boxes) and they'll lift 100kg no problem! They're only 65mm x 40mm (motor) and run from 18V (nominally, they'll work down to 6V).

    As for the movement itself, you can experiment using cardboard and/or plywood to make the sliders and pivots required to achieve the movement and also look at linear rails (like those that support filing cabinet drawers) for smooth horizontal movement.

    Controlling it all can be done with simple limit switches and a cam-driven motorised switch (crude) or a simple digital controller. The actual controller part is the easiest bit! Get the motors, slides and armatures sorted and the control of them can be sorted in a matter of hours.
     
  4. Gurkudrengur

    Gurkudrengur

    3
    0
    Jul 2, 2018
    Thanks for the replies!

    I have been researching your suggestions and a Smart Relay and the Maxon motors sound great!

    I had decided to not go for anything digital, but I did check out a Smart Relay from Phoenix Contact and I am intrigued. I have a basic knowledge of logic gates and the software and programming looks very simple in an introduction video of Phoenix's website. So I might go for that option.
    About the weight, it is a very big desk and it will be filled with all sorts of stuff, some of it rather heavy. I'd rather want to have more power than I require than too little ;)


    I have a question about the cam switch. Does it work with limit switches? I mean, when one limit switch gets triggered, the cam switch changes to the next state, or is it a continuously rotate? I can only find manual ones, or timers. But like I said, I'm an amateur :p
    About the sliders, what you said is exactly what I was planning, and I can get all that sorted by myself.
     
  5. Gurkudrengur

    Gurkudrengur

    3
    0
    Jul 2, 2018
    Update

    So I have been playing around with Phoenix Contact's Logic+ Software, trying to program a simple smart relay. Made little progress there but I think I'm going to need so many inputs in that, that it's gonna be rather expensive.
    So I think I won't use that.

    I'm not finding a cam-driven motorized switch that is suitable, but then again, I'm don't know much...
    I don't know where to go from here.
    Any pointers?
     
  6. kellys_eye

    kellys_eye

    4,275
    1,147
    Jun 25, 2010
    Start by drafting a 'sequence list' - a column of motors and switches and rows with each 'step' of the movement process.

    You may not need any controller as such - each switch could direct power to the next part of the movement as the sequence progresses but you MUST have a known sequence to follow. If you can post such a sequence we may be able to draft a wiring diagram to assist.
     
  7. Minder

    Minder

    3,076
    657
    Apr 24, 2015
    You can also program a sequencer in the Smart Relay.
    You also get a bunch of timers etc, if needed.
    M.
     
  8. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    All of which seem far more complicated than an Arduino, which could also detect faults and shut it down if it was not operating correctly.

    Why the aversion to digital or programming?

    Bob
     
  9. Minder

    Minder

    3,076
    657
    Apr 24, 2015
    Although the Smart Relay is digital (boolean logic) programming.;)
    M.
     
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