slowing down speed on garage door opener

Discussion in 'The Projects Forum' started by diy549, May 16, 2009.

  1. diy549

    Thread Starter Member

    May 16, 2009
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    Hello,
    I'm new to the forum and I have a question for you all. I am building a bed that slides up into a wall, the bed slides on guided tracks into a vertical position. I am done with the construction side of it and its working perfectly. Now, I need help with the electrical side of it. To make things simple, I figured I would use a garage door opener because the bed basically works like a garage door. The problem is garage door openers travel about 7 inches per second and thats too fast for comfort. I want it travel about 2-3 inches per second and this where I'm stuck. If you guys could tell me what I need to make this happen it would be great. I'm assuming I cant just throw a speed controller in there. I was thinking I should go with a older model because the are a lot less complicated as far as the electronics.

    Thanks guys and gals
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    What kind of motor controls the garage door, DC or AC?
     
  3. diy549

    Thread Starter Member

    May 16, 2009
    11
    0
    They come in AC and DC, Which ever is easier, It doesn't matter to me.

    thanks
     
  4. Mike2545

    Active Member

    Mar 26, 2009
    116
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    I would like to see video of this...
     
  5. diy549

    Thread Starter Member

    May 16, 2009
    11
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    Don't have a video, but here is the CAD sketch:
    [​IMG]
     
  6. PRS

    Well-Known Member

    Aug 24, 2008
    989
    35
    Man, what a cool bed! LOL and I like it. If you use a DC motor speed control is a matter of reducing the supply voltage. You can do this with a very simple voltage divider, but you'll have to find 2 high wattage resistors. Do you need to reverse the motor to open and shut? Reversing requires a double pole double throw relay rated for the current drawn by the motor.
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,699
    907
    Ah,great fodder for comedy TV in the 1950's.

    First, it seems you need to maintain torque. A universal AC/DC motor can be easily controlled with a triac, but loses torque. Are you sure you want the mechanical belt drive plus screw/chain drive of a garage door opener? Are you using counter springs so the actual power needs may be quite small?

    A DC motor or three phase motor can be controlled and maintains good torque. New controllers cost about $100 to 200 on ebay. If you go the three phase route, you want a controller that inputs 110V single phase and outputs 3 phase. The DC controller will also input AC and give DC output.

    If you plan on building it yourself, then I would suggest the DC motor approach. The controller designs are simpler. If you go commercial, I would lean towards the 3-phase approach, if you can find a small enough 3-phase motor. Total cost would be a consideration too. This recommendation assumes you only need a 2:1 reduction.

    Another option would be to get a gearhead motor. That would give you the best torque of all. A belt drive reduction would also be an option.

    John
     
  8. diy549

    Thread Starter Member

    May 16, 2009
    11
    0
    I figured I would use a garage door opener because it seemed like it would be perfect for my application. The bed is very light, I can push it in with little effort, way less than any garage door with torsion springs. Plus with the door opener, its very easy to set the limit distance and it comes with the wireless controller. I am a big diyer but I've spent so much time on this project I'm not really interested in building my own system IF the door opener will work.
     
  9. DonQ

    Active Member

    May 6, 2009
    320
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    I would go with just changing the gear ratio. Either with gearing the motor down, or maybe even just using a smaller sprocket to drive the chain. Particularly using a smaller sprocket would be so much easier than an electronic control
     
  10. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    My thoughts exactly. Very cheap, very effective.
     
  11. CDRIVE

    Senior Member

    Jul 1, 2008
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    If the motor is a universal (brush) type it can run on AC or DC. With that in mind, if you feed the motor with 1/2 wave rectification you will cut its duty cycle by 50% which should slow it down.
     
  12. diy549

    Thread Starter Member

    May 16, 2009
    11
    0
    After further consideration, I'm going to stop being lazy and build a system more specific to my project. It will come out to about the same price and I can have better control of the speed and power. I found a inexpensive 86" linear shaft and bearing off craigslist. Using the basic design of garge door rail system, I'll use a chain to drive the bearing up and down powered by a 12 or 24volt motor. Throw in a speed controller, power supply and a momentary switch and call it a day. short, sweet and simple...

    what do you think of one these motors. Scroll down.
     
  13. mik3

    Senior Member

    Feb 4, 2008
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    That is a good idea but first calculate the required torque and moving speed before choosing the motor.
     
  14. CDRIVE

    Senior Member

    Jul 1, 2008
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  15. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Why would you want to use a low-voltage DC motor? My recommendation for a DC motor was for one that would use rectified household voltage. Treadmills are a good source for such motors and their controllers.

    I don't have a clear picture of the mechanics of how the bed will be flipped up. Can you post a sketch?

    John
     
  16. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    A salvaged garage door opener appears to have 1/3 hp capacitor start 120 V AC 1750 RPM motor geared down 22:1 with 2 in chain sprocket. Not easy to change gearing.
     
  17. CDRIVE

    Senior Member

    Jul 1, 2008
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    Can you scrounge another 22:1 sprocket assy? Then you can fabricate a 44:1 from the two.
     
  18. mik3

    Senior Member

    Feb 4, 2008
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    Another solution is to use an oil pump and make a hydraulic system. The advantage is that you can easily control the speed of the piston with a flow valve.
     
  19. DonQ

    Active Member

    May 6, 2009
    320
    11
    I think he might have meant that there was a 22:1 gear reduction in the motor, followed by a 2" sprocket driving the linear chain.

    I would still think that a further gear reduction would be easier than rebuilding the whole arrangement with new motor, DC supply, adjustable speed drive, etc.

    Something like using the current 2" sprocket to drive an 8" sprocket with a short loop of chain, and another 2" sprocket coaxial with the 8", now used to drive the original linear chain. This would give an additional 4:1 reduction.
     
  20. PRS

    Well-Known Member

    Aug 24, 2008
    989
    35
    Before putting alot of money into it, stay with your garage door opener with its AC motor. Use a 2:1 transformer to change the input voltage to 60 volts. That will slow it down but reduce the torque. You said the bed opens and closes easily -- easier than the garage door. That means you can sacrifice torque to slow the speed. Experiment with the voltage needed using a variable xformer if you have access to one. But if want to spend a little money to have a really classy system that is almost noiseless, Mik3 has the right idea. Go with hydraulics.
     
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