Dimmer switch through a relay

Discussion in 'Electronics & Electrics' started by kjparker, Jan 31, 2019.

  1. kjparker

    kjparker Member

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    I am looking at smart plug like this one sold at bunnings https://www.brilliantsmart.com.au/ on one of my downlights at home.

    From a safety perspective, I dont see an issue, as the transformers are all wired to a plug top, and I would simply unplug it, and put this device in the middle.

    My concern is based around how these kinds of devices would behave with the dimmer switch inline? theoretically, the relay should be fine, I'm just wondering how the controller (esp8266) would behave.

    Thought?
     
  2. Technics

    Technics Member

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    Without knowing the inner workings of the smart wifi plug or the type of dimmer used (leading or trailing edge) it's pretty hard to be specific. If it's a leading edge dimmer then the smart plug will not be the resistive load that the dimmer is designed to work with and this can cause the TRIAC in the dimmer to oscillate. This may prevent the smart plug from operating at all.

    A trailing edge dimmer might work as long as the brightness is not set too low. Even then, it may still have problems if the design of the power supply in the smart plug draws little or no current when close to the zero voltage crossing in the AC cycle. It is quite likely that the smart plug behaves that way with a bulk capacitor for the power supply supplying the current during this part of the cycle.

    That's the theory anyway. In practice you won't know for sure unless you try it. Even if it does work there's a fair chance the smart plug will stop working when the light are dimmed down low. The smart plug will not have been designed to work with the output of a dimmer. Dimmable LED bulbs face similar issues with dimmers but they have bleeder and/or damper circuits built in to deal with it.
     
    Last edited: Feb 1, 2019
  3. ArmoureD

    ArmoureD Member

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    Id say the smart plug might use a capacitive power supply to run, and feeding it a modified sine wave (dimmed) would probably render it inoperative.

    Have you looked at smart bulbs instead? You'll have to get the dimmer removed prior though.
     
  4. Technics

    Technics Member

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    I thought that originally as well but took a quick look at the product. The USB plug on the side all but rules out a dropper based on capacitive reactance.
     
    Last edited: Feb 1, 2019
    ArmoureD likes this.
  5. pantner

    pantner Member

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    Is this in your roof space? If so, I definitely see a safety issue.
    Things like that won't be rated to sit inside your roof space and I would wager if it failed and caused a fire you would be up 'you know what creek'.
     

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