Motor to raise/lower sun shades?

Discussion in 'General Electronics Chat' started by s_mack, Jun 6, 2014.

  1. s_mack

    Thread Starter Member

    Dec 17, 2011
    187
    5
    Hi. I've never done anything with motors before so I'm a bit out of my element. Yes, I can do the research... but given the importance of this project (or rather, the lack of importance) I figured I might short-cut and ask for some quick help before investing time.

    I bought a couple outdoor sunshades from Costco. They have a manual hand-crank mechanism for raising/lowering them. It sucks. Call me lazy, but we don't bother using the damn things because:


    1. It takes over 90 cranks for full travel
    2. We can't leave the crank rod connected because the wind bangs it against the window so we have to find the crank everytime we need it (or leave it on the floor but that's ugly)
    World changing problems, right? No, admittedly this isn't a big deal. Its just annoying enough that I started wondering if I could attach a motor to the things instead.

    But I don't really know what's involved. I figure I want something in the vicinity of 60rpm. The shade is 8 feet x 8 feet but its not all that heavy (< 10 pounds including the rod). I did some quicky calculations and figure its about 32 ounce-inches of torque that I'd need since the crank mechanism has a 5:1 gear.

    I don't know if that's a particularly "powerful" motor, what kind of controller is needed, etc. Ideally, I'd want a way for it to stop before it goes too far in either direction. And ideally, a momentary switch would be used to control, preferably with one-touch operation (ie. press "down" and walk away while it lowers it all the way down. Or press-hold for more control. Like most car power windows work).

    Worth doing? What do you think?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,565
    2,379
    You should be able to attach a small motor, a simple spring scale on the end of the crank, would give you the break-away torque and motor needed.
    I assume you are going to remove the crank and couple the motor direct?
    Max.
     
  3. enggricha

    Member

    May 17, 2014
    62
    1
    A geared DC motor with a H bridge config for bidirectional Up/ Down movement, with some limit switches at either ends with some simple on off switch to get the whole thing going should be a easy enough for some one who can figure out "32 ounce-inches of torque"
     
  4. s_mack

    Thread Starter Member

    Dec 17, 2011
    187
    5
    Actually, my "plan" was to leave the crank in place because its integrated with the rod support... just eliminate the crank rod and turn the crank with the motor instead of the rod. I figured this would have the advantage of utilizing the crank's gearing, which then (I suspect) puts less load on the motor.
     
  5. s_mack

    Thread Starter Member

    Dec 17, 2011
    187
    5
    Don't give me too much credit on the "figuring". I simply took the weight of the shade and the circumference of the roll.

    I guess I just didn't want to get into a situation where I start researching and building this thing and then find out that this is actually a relatively massive motor and I need a 6 foot long heatsink and I'm causing blackouts in my neighborhood.

    From both your responses, this sounds like a fairly small and simple project (right?) so it should be worth pursuing?
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,565
    2,379
    I would take a break-away torque reading as I mentioned, then look at removing the crank handle, this may leave a shaft that you could attach a small motor to and the gearing still in place?
    Max.
     
  7. s_mack

    Thread Starter Member

    Dec 17, 2011
    187
    5
    That's a good idea about the torque reading and yes, I'll do that. But I hope people with experience with this sort of thing can help me determine what kind of motor I should be looking at with that. Let's say I'm right and it required 32 ounce inches... do I look for a motor rated for 10% over? 50% over? 1000% over? I don't have the experience in this arena to know how far off of ideal these things operate at.

    As far as the crank mechanism... could you clue me in on why you'd remove the crank handle? Perhaps I should take a photo of it, but to me it would seem easiest to leave it all in place and have the motor turn the crank handle. The shaft has a small gear on the end and perpendicular to that is (what I would call) a worm gear, which is turned by the crank handle. Because it is integrated into the bracket, it would be somewhat difficult to to turn the shaft directly. I could remove the plastic handle and turn the worm gear directly but I guess i'm not seeing the benefit. The detriment would be not having the handle in case manual operation is later required.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,565
    2,379
    A small DC motor may be one option, a good source may be an auto wrecker for one, but often they are not compact.
    32 ounce-in seems a tad high effort required on a crank for blinds, especially worm drive?
    If you leave the crank on and attach to that, then you have to come up with a mechanism that re-creates the manual operation.
    How did you intend doing that?
    Max.
     
  9. pilko

    Senior Member

    Dec 8, 2008
    213
    20
    The crank is just the bent piece at the person end of the shaft assembly.
    Use an automotive window motor from Ebay (powerful , around 60rpm and cheap.)
     
  10. s_mack

    Thread Starter Member

    Dec 17, 2011
    187
    5
    And that's why I'll check as you suggested... but I'm still asking whether I should be spec'ing one near whatever torque is determined or if it should be over-spec'd [considerably?]?
    Well, the manual operation is simply turning. Seems to me that motors are pretty good at that ;) I was thinking that all I would have to do is attach a hook to the motor. Put the hook through the crank's loop and Bob, as they say, is my proverbial uncle. Perhaps I'm missing something.
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,565
    2,379
    I missing it also! You would have to show me in a sketch/example what you have in mind?
    Max.
     
  12. inwo

    Well-Known Member

    Nov 7, 2013
    2,435
    315
    Starting to look like a scroll sign project that I once helped automate.

    I the crank a long rod with a hook? Fitting into an eye on the worm?

    [​IMG]

    How about a dedicated battery drill? Semi manual, but faster!
     
  13. s_mack

    Thread Starter Member

    Dec 17, 2011
    187
    5
    Yeah, you got the idea! Exactly what you described.

    I already hooked a drill up to it. And yes, that worked. That doesn't pass the... err... the wife test :) Ultimately, if I'm going to do this, I don't want it [no offence intended to anyone] "red necked". I want a nice switch on the wall, all wires and most of the mechanisms hidden, etc.
     
  14. inwo

    Well-Known Member

    Nov 7, 2013
    2,435
    315
    It will have to be in a box to hide mechanism and wiring.

    [​IMG]

    What is in the box won't show.:D

    I picture a box with a drill inside and a momentary toggle for up or down.

    If wiring isn't an issue, run line power to the box to run drill.

    If it's hard to hide the wiring, mount the brill so the battery pack is accessible.

    It would still fit the redneck definition, but it could be made to look ok.
     
  15. s_mack

    Thread Starter Member

    Dec 17, 2011
    187
    5
    Fair enough :)

    Wiring is no problem at all. Its a covered deck and the ceiling is made of metal soffiting that can be removed fairly easily. There's already pot lights in the ceiling so half that work is done for me.

    If it wouldn't be a severe code violation, I could hide the motor (or drill, I suppose - but a drill is worth more than a motor!) in the ceiling!


    I'll figure it out from here folks. Thanks for the ideas. I'll come back if I start the project and run into any specific questions.
     
Loading...