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DIY Electric Screen (HELP)

Discussion in 'Home Cinema Building DIY' started by Xandia, Jan 25, 2005.

  1. Xandia

    Xandia
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    Hi im new to the Home Cinema Game after only having a Projector for about 1 month i am looking at some screen options and i have decided i would like to build a DIY Electric screen mainly due to cost

    I am needing some help in the area of wiring the screen up
    i am using a roller blind which is connected to a Car Window Motor *FREE from a Rover 520 1989 model* i have bought a PSU for it from maplins

    http://www.maplin.co.uk/Module.aspx?ModuleNo=42702&TabID=1&source=15&WorldID=&doy=25m1

    as u can see the motor is 12v 5amp

    all i want to be able to do is control the screen up and down with a IR remote Control like one of these maybe?

    http://www.quasarelectronics.com/3142.htm

    how to stop the thing when it reaches a certain point ? i thought maybe on including 2 magnetic contact reed switches as motor Limiters

    i suppose i would also need to include a 12v Relay to switch the polarity of the motor and to stop it???

    If anyone has any experience in the field of motors / relays , any input or other ideas or maybe a schematic *pushing my luck i think* :)

    Thanks.......
     
  2. MikeRJ

    MikeRJ
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    The reed switches and magnet approach is not a bad one, but I think you may have problems trying to detect when the screen is fully down. If you were intending to put a small magnet on the back of the screen, it will trigger the relay for every rotation of the tube that the screen is wound up on.

    One possibility is to have a cam which is geared down from the tube and operates two microswitches (i.e. one at full up, one at full down). If you used two SPDT switches this would make the wiring very simple, you could simply wire up the two switches in the classic polarity changing configuration, and combine it with a DPDT relay which is remote controlled. If you want a schematic for this let me know.

    Personaly, if I was doing this, I'd use a rotary encoder on the end of the tube and a small PIC micro to decode the position. The beauty of this is that you could program the screen to stop at different positions for different aspect ratios.
     
  3. blairis

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    Hi,

    This thread is rather old now, but hopefully this is still of use.

    Have been looking a building both an electric screen and projector lift myself.
    Have come across these controllers from a company in Australia who ship worldwide.
    They make and sell a Blind controller - the travel is set using a trimpot to adjust the time that the motor is supplied with power. It's rated at 5amps and is compatible with a number of RF revievers they make.
    I think the cost is around $58 AUS.

    Have a look - might be of use (they also make garage door controllers both with and without limit switch inputs that I'm hoping will do the trick for my projector lift).

    http://www.elsema.com.au/bli2.htm

    Cheers,
    Blair
     
  4. jhaworth

    jhaworth
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    Hi

    Again, a late reply, hope it helps. The cheapest way would be to use a shaft encoder, and develop a 2 or 3 bit gray code which would indicate position. Could also use a syncro resolver, bit more expensive though. If you are going to build the motor controller, I would use an H bridge configuration.

    Cheers

    john
     
  5. Babylon

    Babylon
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    Has any one else got one of them jobs were you regularly throw stuff away and think to your self that some one some were would kill for that thing you just dumped ,well in my job I am always throwing away These, they are the motor drives from supermarket fridges that I take out of stores, but they are use in all sorts of Awnings and Shutters, you adjust the up and down stop position with the two white screws in the picture,Found This as well.
     

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