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Inline Key Switch or Tamper Resistant control for mains devices?!

shabaz

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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  • 0 in reply to beacon_dave

    I'll see if I have a plate. In any case, it's a pleasure working with sheet plastic, I have not had the chance to build much recently so I don't mind doing that.

    Incidentally, a super-cheap way of creating the plate (with zero tools!) could be to heat up a load of the Polydoh stuff and mash it around the plug (probably a good idea to wrap some paper around the prongs to thicken them, and Vaseline it too! Maybe better to use a sacrificial mains plug in case the hardened Polydoh doesn't eject : )

  • 0 in reply to shabaz

    If any of the plug pins are slightly out of line with each other, then the grip will be significant with a moulded approach. Depends on how much shrinkage Polydoh has. Might be able to wiggle it a bit before it fully hardens to give it just a little freedom around the pins and to allow for the BS pin spacing tolerance.

    In the past I've used 2-part resin body/wood filler paste for creating parts for prototypes. It's about the only free-form material I've ever had success/enjoyed working with. Not too messy/runny, sets quickly, can be cut/sanded and smells great.   

    I have however seen some very nice small-scale work done with fine-grade concrete mixes which I could be tempted to give a go. It can take on a whole new look if you use the right aggregates and sand/polish it up after and apply sealing lacquers. I think combined with flexible filament in a 3D printer to create release moulds, then it could be interesting.

    A non-moulded 13A plug will often have a bit of movement in its pins so may release easier than a moulded one.

    Dipping the pins in melted wax before moulding might also work. Depends on the working temperature of the Polydoh vs the melting point of the wax though Slight smile

    One advantage of Lego is that you can always claim that you are 'just playing with Lego' Slight smile

    It will be interesting to see what you can come up with.

  • 0 in reply to shabaz
    shabaz said:
    I'll see if I have a plate.

    Cheapest source for that type of plates, is a set of plastic kitchen cutting boards. Either in  a 1£ shop, or at a flea market, you'll find enough material for years.