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Touch dimmer slaves - how do they work?

Discussion in 'General Electronics Discussion' started by GrahamH68, Jan 15, 2014.

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  1. GrahamH68

    GrahamH68

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    Jun 5, 2012
    Can anyone help me to understand how touch-sensitive slave switches communicate with the master dimmer?

    Here's a link to the type of device I'm talking about: http://www.screwfix.com/p/varilight-1-gang-multi-way-400w-touch-dimming-slave-dimmer/93636

    I've done quite a lot of googling but not turned up anything of relevance - perhaps I'm just looking in the wrong places! So any pointers to clear datasheets or resources explaining how they work would be much appreciated.

    Failing that, the next best thing would be some instruction on how I might go about reverse-engineering these things - I have some basic electrical and electronic skills, i.e. I know how not to get electrocuted, and have some basic test equipment in the form of multimeter and basic oscilloscope.

    I'm sure they're probably dead simple, but their secrets completely elude me!

    Thanks for all help and comments offered.
     
    Last edited: Jan 17, 2014
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Obviously there is a communication between the units via the "S" connection.

    I couldn't locate which IC is being used. You will have to open the dimmer and inspect the PCB to find out.
     
  3. Arouse1973

    Arouse1973 Adam

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    They might use the stage lighting standard D54 or have developed their own.
     
  4. GrahamH68

    GrahamH68

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    Jun 5, 2012
    Thanks for your reply Harald. I had figured out that the comms happens along the "S" line, but it is the nature of the signalling that I'm interested in figuring out as I'd like to provide a version of my own Master unit for use with the Slaves.

    I can crack these open - would it help to know the major components in use on both Master and Slave?
     
  5. GrahamH68

    GrahamH68

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    Jun 5, 2012
    Thanks Arouse, I'll definitely look in to that standard and see if it might match up although I suspect it's probably something much simpler such as the slave effectively just transmitting its "touched" or "not touched" status to the master.
     
  6. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    I guess you're probably right. The interface should be rather simple. For exaample no addressing of individual slaves is required.

    If you know the part numbers, you may be lucky and find information about the parts and the protocol.
    If, however, these dimmers use some kind of microcontroller, chances are that the code is proprietary and you will not be able to find it on the internet.
     
  7. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    I think Graham is suggesting that there may not be a protocol. Although the Master device presumably does have a microcontroller, the slaves just need to provide a single true/false indication - either the touch pad is being touched or it isn't. So it could just be an open collector bus or the like, perhaps implemented with optocouplers.

    Actually, that WOULD be a protocol, to be pedantic :)
     
    GrahamH68 likes this.
  8. GrahamH68

    GrahamH68

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    Jun 5, 2012
    I finally have some time to look at this again! Does anyone have any new ideas? I can pull these apart and try to identify components if that helps, but if someone knows straight off how they work that would be fantastic.
     
  9. davenn

    davenn Moderator

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    without specific design info from the manufacturer .... anything would just be a guess, unfortunately
     
  10. GrahamH68

    GrahamH68

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    Jun 5, 2012
    Thanks Dave, I hear what you're saying but sometimes guesses can help to show a way, although I am still hoping that there may be someone out there who has already figured these out.
     
  11. GrahamH68

    GrahamH68

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    Jun 5, 2012
    How time flies when you're too busy at work to play! So here I am again, 4 years on and I wonder if anyone can help me with some insight to how these switches work?
     
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