baby alarm

[Meklaud]

I'm interested in making a baby alarm;when baby cries mother should somehow be alarmed.Baby sleeps on the 1st floor while mum is in the kitchen.I'm interested in solution of transmitting a signal from the baby's room to mother.Should it be blue tooth gadget or something better?

 

[gerty]

You didn't fill in your location so I don't know if it'll be available to you, but Radio Shack makes an intercom that you just plug into a power outlet and it works off the house wiring. No need to run any wiring, both units must be powered from the same transformer that powers the house.

 

[zachtheterrible]

How about a good ol' baby monitor??

But if u insist on building ur own, i recommend this circuit cuz its real simple and works great. It'll transmit 100 feet or so with a piece o junk clok radio (1/4 a mile with a nice radio). I would also recommend hooking up a wall transformer to the circuit so u don't have to worry about battery. Anything from 3-12v will work (obviously if you give it 3 volts, it won't transmit as far). Hope this helps. Hollar if u need help with the inductor :lol:

 

[stevez]

Zach-how stable is this FM transmitter? I think you said that you've built one or more. The few that I've built stay on the same frequency about long enough to demo that the thing works. I never did bother with improvements because I had little use for it anyway. There are a couple of moderate cost kits (Ramsey as I recall) that are more stable because of crystal timebase and PLL. Would be nice to know of simple design that is stable but maybe 'simple' means you live with lots of drift.

 

[zachtheterrible]

yeah, ive built a couple. the problem that i had w/ frequency drift was MY BATTERY WAS ALMOST DEAD :twisted: . i felt so stupid. But ive not had any drift with them any more. I turned it on in my room upstairs with some Metallica on, and then listened to it downstairs for an hour or two on a stereo. So drift is non-existent (unless you put your hand too close to it)