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DaLite 12v screen trigger needs 83mA.. Marantz AV 12v trigger supplys 44mA.. HELP?

Discussion in 'Projectors, Screens & Video Processors' started by cavaleri, Mar 16, 2005.

  1. cavaleri

    cavaleri
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    I'm having a problem with triggering my DaLite Tensioned Contour Electrol, which has a built-in 12v triggering relay to drop the screen. My projector (sanyo plz-v3) does not have a 12v trigger, but my Marantz SR9300 does. I'm running into the same problem that others have mentioned here, where the AV trigger does not supply enough amperage to trip the relay in the screen, which needs a minimum of 83mA. The marantz only puts out 44mA. When you connect everything together, and try to trip the screen, the voltage drops to nearly zero.

    does anybody have a solution for this? I'm willing to try to build something if necessary, but I would prefer a one-stop shopping solution... Is there a device that can take a low amperage 12v, and send out a 12v signal at higher amperage? (is this a transformer?)

    many thanks for any help on this!
     
  2. MikeK

    MikeK
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    You could do this with a 12V mains adapter and a 12V miniature relay, for about a tenner or so. Use a high sensitivity relay, such as

    http://cpc.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=SW01445&N=401

    A suitable mains adapter (adjustable too :) ) - there are loads of these available though (but I'd use a regulated one if it were me).

    http://cpc.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=PW00966&N=401

    I'm sure you could get these from Maplin too.

    This is all assuming that the screen drops whenever 12V is present on it's control input, and closes again when 12V is removed - I don't have an electric screen you see.

    Wire the relay's coil across the 12V trigger output, and it's "normally open" contacts in series with the screen's control input and mains adapter.
    When you switch the amp on, the 12V trigger voltage will energize the relay's coil, and close it's contacts, which will then connect the 12V output of the mains adapter directly to the screen's control input.
    Likewise, when you switch the amp off, the 12V trigger voltage will be gone, the coil will de-energize, causing the contacts to open, and the mains adapter's 12V to be removed from the screen's control input, which should then close.
    You'll aslo need to connect a protection diode across the coil of the relay, just in case!
    You may also need a little box to house the relay (so the job doesn't look scruffy :) ). CPC have a selection for under a quid - something like

    http://cpc.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=EN55739&N=401


    PS - don't forget, if the screen and trigger voltages etc don't work as described in the itallicy bit, then forget all this. Post back with how it does work and I'll try and figure another cheap way!
     
  3. cavaleri

    cavaleri
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    Hey Mike,

    wow, that was a fast reply.

    I think I should have double checked the origin of this forum, as I now see that this is a dedicated UK forum. .. I happen to reside in the USA, and am working with 110v power in my home, do you happen to know if they make similar devices as you describe that can operate on 110?

    very many thanks for all of the help here!

    best,
    robert
     
  4. MikeK

    MikeK
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    Actually Robert I just discovered there is another thread just below this one called "Remote screen operation" which covers pretty much the same subject (in fact it reminded me that I'd forgotten the protection diode across the relay coil in the above post)

    The "adapter" as we call them on this side of the pond is simply a plug in DC PSU - like you use with a laptop, phone etc. In the US it will simply be 110V input/12V output instead of our 240/12 - and I suspect probably even cheaper over there than they are here, a few dollars I suspect! Everything else would be the same - but do have a read of the other thread for other people's thoughts on the subject.

    The relay I suggested above should draw about 17mA through it's coil (which is 700ohms), so would be within the spec of your amp which you said could drive 44mA.
     
  5. MikeK

    MikeK
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    BTW - I don't think it's dedicated to the UK as such, just that we tend to assume that a member is from the UK unless we know otherwise.
    The last time I checked, overseas members were just as welcome as UK ones.

    Obviously, our electrical system and regulations are different to the US, and a lot of consumer AV gear is different (although a fair bit is the same unit with a different model name, and some is in fact identical), but other than that, there's really little difference IMO (except our sense of humour is a tad drier than yours :) :) :) - generally speaking of course !!)
     

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