mount the sensor by aligning the magnet to the coin…
To make life easier use a hot melt glue, easier still if you have a cordless glue gun. This makes for very easy Removal of the sensor for battery change etc…
Interesting idea. Most coins from most countries are not magnetic. In the US, there’s only been one magnetic coin, that was during World War II when they ran out of copper.
It looks like the UK took some of its copper based coins and started using steel for the base in 1992, then did the same with some of its silver based coins in 2012.
We should also note that many open/close sensors might be affected by a magnet if the case is not specifically designed for it. So I’m not sure this would be my first choice, but you could certainly try it and see if it works. it’s unlikely to be an issue for PIR motion sensors, though, so that’s good news.
I’ve done this with motion sensors and temperature sensors. I have not tried contact sensors. Given that the back of the aeotec motion sensor already has a magnet I’m sure it’s fine.
I use Sugru, which is moldable silicon glue which starts out soft and pliable and dries to a firm rubber consistency. Really clever stuff. Also easily removable without damage to the surface underneath by scraping it off. And excellent temperature and moisture range. You can fix a mug handle with it and then run the mug through the dishwasher, no problem. It comes in lots of colours, although at our house we mostly use black, white, and silver-grey.
holds up to 2 kg / 4.4 lb on glass, ceramics, wood, metal, plaster, most plastics and fabrics. Also works on most brick and stucco.
I use it to affix SwitchBot to devices like blenders and aircon controls. And to mount sensors and even tablets. I also use it successfully in the car, where most other removable products melt away in the summer.
And I use it in the bathroom to hang some small shelves on the shower tile. And to make bobbin hooks that won’t hurt if you fall on them.
And it’s nonconducting, so you can use it to repair cracked cables. If you want to get really fancy, you can even manually press it into a 3D printing mold.
And if you want a removable option that doesn’t use magnets, they recommend legos! Sugru one Lego to the wall/desk/dashboard/wherever and another to the detachable object. One guy even did this on his cast so he could use his phone one handed! Brilliant!
Like I said, I love this stuff. . I’ve been using it for about 5 years now.
The only thing is it comes in a box with multiple small packets. Once you open a packet you have to use the small blob inside within 30 minutes, since it begins solidifying as soon as it’s exposed to air. So you do need to plan ahead.