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Help? AE700 trigger won't switch relay

Discussion in 'Projectors, Screens & Video Processors' started by Dunkwho, Jan 23, 2005.

  1. Dunkwho

    Dunkwho
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    I'm all setup with a relay, power, trigger line etc to lower my screen when my 700 comes on, have tested with a 9V battery in place of the relay but the PJ won't switch the relay.

    Has anyone got the 700's trigger switching something - what bits (specifics please) did you use? I've just grabbed a 12V relay I found in a draw, maybe it needs too much power to energise the coil. Measuring the voltage accross the trigger output it comes up from 0 to about 10.8V, when I complete the circuit to the relay the trigger just dies back to 0.2 :(

    Duncan
     
  2. explicitlyrics

    explicitlyrics
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    to have a voltage as low as that, there must be a very small current flowing through it and hence it would be impossible to switch the relay. It is more likely that you will need a 9V relay or something similar, in order to have a large enough current, this will then energise the coil, switching the relay.
     
  3. summat

    summat
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    Forget lower voltage coils; from what you described (output dropping from 10.8V to 0.2V under load this is a fairly high impedance output and will need buffering to switch the relay.

    Can't find any details on Panny's website for the AE700, but just downloaded their manual for the AE500 - crap information in it -

    "TRIGGER out: Single-line, M3 jack
    When the power is turned on (during
    projection) : 12 V
    When the power is turned off : 0 V"

    Nothing about output load capability.

    I have to assume that this is a signal driven by some logic element, and it has a high output impedance. If this is the case then:-

    1) You're gonna need some form of switching circuit - a darlington pair tranny will do the job.
    2) Even if the PJ could switch a relay, you really, really should protect the PJ from back EMF from the coil.

    The problem, now, is that you'll need a separate PSU for the switching circuit. Nothing special, but another plug socket taken up.

    Let me know if you need any details about how to go about wiring up a buffer amp (switching circuit) for this.

    Mike.
     
  4. explicitlyrics

    explicitlyrics
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    Ok, my mistake.

    After a quick search I found this thread. Seems to have a fair bit on info about using a relay with a trigger. http://www.avforums.com/forums/showthread.php?p=1170773

    As for the AE700 trigger not working, I cant give any more information. I still think a 9V relay has a better chance of working (if you have one lying around might aswell try it). But as summat says, you really should protect the trigger circuit of the projector as in the above thread.

    Good Luck.
     
  5. summat

    summat
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    Ok, 1 question I should have asked...

    This "12V relay I found in a draw[er]", erm, where did this come from?, anything from a car or telephone switching system (erm, where most of my childhood relays came from) are going to draw serious current. Maybe try a new low power relay from Maplins, or somewhere.

    I guess you've got a multi-meter, to have measured the voltage across the coil; could I ask you to measure the coil resistance and post here, it may be useful in diagnosing your problems.

    (re: 9v relay, maybe some scope in this, but I'd like to see the 12v relay's coil resistance 1st).

    Regards
     
  6. Dunkwho

    Dunkwho
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    Thanks all. I kinda thought this low drive might be the case but was spured on by the lack of trigger drive figures in the manual (no figures = useable ... WRONG :) ) and the various mentions of "can be used to control a screen" in the product flyer - hey ho :) I'll go down the transistor & external power pack route, pretty simple to knock up but wanted to see if someone had been any more lucky with a specific relay unit (low current required).

    Thanks for your suggestions ! :)

    Duncan
    Ps - the coil is 10ohms, for what is worth :) !
     
  7. summat

    summat
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  8. MikeRJ

    MikeRJ
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    Either it's not a 12v relay, or you are measuring something wrong. A 12v relay will typical have a coil DC resistance of 150-400 ohms, depending on the contact rating. If it really is 10 Ohms it must be a very heavy duty relay, i.e. 100Amp+ contacts.

    If the projector output can source a few mA @ 5v a simple solution that would avoid any external power would be a solid state relay such as this one from Farnell.
     
  9. explicitlyrics

    explicitlyrics
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    gosh 1.2A is indeed a shocking current! I think Mike may have the answer (heavy duty relay). What sort of size is this relay? (dimensions wise)
     
  10. Dunkwho

    Dunkwho
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    OK OK ... _maybe_ I was using the wrong type of relay. hey - it was in a draw marked "Relay - mains" ... i know _now_ that I wanted one out of the "Relay - 12VDC" draw instead :) he he.

    I've fitted a perfectly working solution last night - its the first time I've been able to stand in my lounge and watch the screen lower\raise into the ceiling void since it was plonked in there, I've been upstairs pushing the button for the last few weeks ! I've used a collection of components from our lab 12VDC relay, DC PSEU, transistor here, one there, blah de blah (under supervision, or can't you tell?) and its switching fine ... happily I managed to avoid any damage to my projector during my experiments.

    Thanks for all you help\support .. shame I didn't come up with a neat, self powered solution but time is running out, new carpet goes down this week and I've a padfull of jobs to complete before then.

    Duncan
     

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