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Ask an Expert Forum Inline Key Switch or Tamper Resistant control for mains devices?!
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Inline Key Switch or Tamper Resistant control for mains devices?!

shabaz
shabaz over 2 years ago

Hi,

For one reason or another (elderly relative), I'm looking for a way to prevent operation of a mains appliance (about 6A at 230V AC) unless, say, a key of some sort is inserted, to prevent them from using the appliance themselves. It doesn't need to be a high-security solution, it could simply be a plastic key for instance, that could be pushed in and rotated, to enable the appliance.

I don't wish to cut holes in the appliance, and really do want to do this inline with the mains wire. 

Is there any existing product that could do this? If not, is there any suggestion that I could fit into a small plastic enclosure myself? I don't have access to a 3D printer, so it ideally needs to be a solution that I could make using conventional tools (electric drill, saw, etc). 

One way I can think of, is to find some sort of enclosure where a rocker switch could be fitted recessed, and then have a small padlock such that it prevents the switch from operating. But it probably requires a custom box : ( Another way could be to have a Bluetooth controlled relay. I could design this, but I'd rather find an off-the-shelf solution. 

I'm sure I can't be the only one wanting to do such a thing, but I'm having no luck googling for this. 

Anyone come across anything that could help?

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Top Replies

  • shabaz
    shabaz over 2 years ago +6
    It arrived today, I'd say it is a 7/10 product.. it will certainly fit many plugs, but the build quality looks very average. The hinge looks fragile, although perhaps that's deceptive. I don't know. …
  • charlieo21
    charlieo21 over 2 years ago in reply to anniel747 +5 suggested
    Definitely the simplest and cheapest option, we have those in the lab, it works perfect to avoid someone use an equipment without authorization. Another option are those smart plugs that you can control…
  • beacon_dave
    beacon_dave over 2 years ago +5 suggested
    A long shackle padlock combined with a Lego Brick sized block with a hole in it (placed between the pins) could probably fit over a 13A plug top preventing it from being plugged into a socket. I don…
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  • anniel747
    anniel747 over 2 years ago
    This reply was deleted.
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  • charlieo21
    0 charlieo21 over 2 years ago in reply to anniel747

    Definitely the simplest and cheapest option, we have those in the lab, it works perfect to avoid someone use an equipment without authorization.

    Another option are those smart plugs that you can control with any smart home assistant. 

    https://www.amazon.com/WiFi-Smart-Plug-Outlets-Function/dp/B07Q1L6311/ref=asc_df_B07Q1L6311?tag=bingshoppinga-20&linkCode=df0&hvadid=80058242473102&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4583657824634358&th=1

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  • charlieo21
    0 charlieo21 over 2 years ago in reply to anniel747

    Definitely the simplest and cheapest option, we have those in the lab, it works perfect to avoid someone use an equipment without authorization.

    Another option are those smart plugs that you can control with any smart home assistant. 

    https://www.amazon.com/WiFi-Smart-Plug-Outlets-Function/dp/B07Q1L6311/ref=asc_df_B07Q1L6311?tag=bingshoppinga-20&linkCode=df0&hvadid=80058242473102&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4583657824634358&th=1

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  • shabaz
    0 shabaz over 2 years ago in reply to charlieo21

    Nice-looking unit! There will for sure be UK versions similar to this. I'm definitely fine with glueing a mains plug permanently to such a product. It's an excellent solution.

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  • anniel747
    0 anniel747 over 2 years ago in reply to shabaz

    Careful about those amp ratings.

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  • cstanton
    0 cstanton over 2 years ago in reply to charlieo21

    I have the tapo smart sockets, and a problem that regularly happens with them is that the relays become stuck closed, which means that it ends up "always on" regardless of remotely turning it off. This apparently happens to a few different types.

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  • Gough Lui
    0 Gough Lui over 2 years ago in reply to cstanton

    To be fair, many cheap plugs are likely to have the issue depending on the load because of:
    - Cheap relays with questionable contact plating
    - High-inrush current loads (e.g. switching power supplies with capacitors discharged and no soft-start NTC, possibly rapidly cycled)
    - No snubber network across the relay contacts in these lower-cost designs

    It's just a fact of life when it comes to relays that they still need to be used correctly ...

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  • anniel747
    0 anniel747 over 2 years ago in reply to cstanton

    Common problem with overrated relays.

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  • shabaz
    0 shabaz over 2 years ago in reply to cstanton

    Maybe I've been unlucky always, but I've never had a good experience with TP-Link stuff : (

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