How can I build an door alarm that sends a signal wirelessly to buzzer maybe 30m away when the door is opened?

I need to hear the front door open from quite a way away and I can't really run wires all the way. The signal would need to travel wirelessly from the front door of my business to the buzzer at the other end of the premises.I can't seem to buy a pre-made version nor a kit for this anywhere! Would there be a way I could use a kit with a reed switch ie magnetic sensor on the door but somehow wire it to a transmitter instead of a buzzer? Then I'd need a receiver connected to a buzzer I suppose.  I've no idea really where to start.

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Wolf Seril7 years ago
I would try wiring the magnetic sensor to a wireless doorbell (the button part), and have the bell part to where you need it. It should be pretty simple but I can't be sure without seeing your parts.
Lydboots (author)  Wolf Seril7 years ago
Hi Wolf Seril
I think that sounds like what I'd want to do ... somehow!
Here in the UK Friedland sell remote doorbells for about 20 quid.
Short of that, I can suggest some suitable bits and pieces. Where are you in the world ?

Lydboots (author)  steveastrouk7 years ago
Hi Steve
I'm in Sydney Australia. I haven't found one here that does what I want. Not a doorbell (that someone presses) but a door alarm that goes off automatically when the door opens.
This is what you want:
I'm surprisd there aren't such things in Oz !

Lydboots (author)  steveastrouk7 years ago
Me too! When I asked at Jaycar (a sort of Electronics DIY store) they said "people ask for something like that all the time but we don't have one"!

It looks like you had the village idiot in the shop.

Lydboots (author)  steveastrouk7 years ago
It's no good Steve! thanks for the link BUT
I obviously haven't explained myself - I don't want a door bell!
I want an alarm that sounds when the door is opened (a warning to me that someone has entered) & I want that bell/alarm to be quite a distance away from the door so that it doesn't deafen the customer but if I'm out the back I can hear it.
Does that make sense now?
Its the same thing: Mount a button OVER the top of the door: As it opens, the door presses the button, as it closes it presses the button.

Lydboots (author)  steveastrouk7 years ago
Now that's a cool idea. Most doorbell buttons aren't raised & the buttons have to be pressed in but maybe I can find one that, mounted on the door frame can survive the edge of the door scraping across it frequently
Use a microswitch
Lydboots (author)  steveastrouk7 years ago
OK - but can you explain how I'd do that please?
Hi Lydia,

This is an even better idea

Put the magnet in the top of the door, and put a little bracket to space the switch off the door frame by 10 cm or so. The switch is activated as the door opens and as it closes, but not when its open or closed, if you see what I mean.

Lydboots (author)  steveastrouk7 years ago
I think this takes me back to my original question!
"a reed switch ie magnetic sensor on the door but somehow wire it to a transmitter instead of a buzzer?"

So do you think if I bought a wireless doorbell & a magnetic sensor I can somehow connect them?!
Yes, the magnetic sensor replaces the button.
I agree. Radio Shack sells one in the US that I use in my office.
evasdaddy6 years ago
Here is what you are looking for. Available at Radio Shack.