wireless signal to activate beeping noise?

WIll you have line of sight between transmitted and receiver? If so, consider using infra-red or ultra-violet LEDs / Transistors for the signaling. You could even use an old TV remote controller as the transmitter.

As for a loud noise from a something the size of a watch battery - that might be pushing things a little too far! Since sound is effectively the movement of air, you either have to have a large sounding area, or long travel of the sounding area to produce a loud noise.

Can you post some dimensions of how big (small) the receiver needs to be?

WIll you have line of sight between transmitted and receiver? If so, consider using infra-red or ultra-violet LEDs / Transistors for the signaling. You could even use an old TV remote controller as the transmitter.

As for a loud noise from a something the size of a watch battery - that might be pushing things a little too far! Since sound is effectively the movement of air, you either have to have a large sounding area, or long travel of the sounding area to produce a loud noise.

Can you post some dimensions of how big (small) the receiver needs to be?

Kenny, thanks for your response.

There will be no line of sight between the sender and receiver. In fact, one of the major needs for this is that it can be accomplished without seeing the receiver at all.

When I imagine the size of the receiver, I am thinking of something about the size of a standard watch battery, or a quarter. Or let's say something smaller than the head of an average house key.

As for making the sound, that's a good point you bring up. I hadn't considered that. I had a small device that could make a sound up to

110 db, but then again that device was still quite a lot bigger than my imagined receiver. How loud a sound do you think I could make with a device the size of a watch battery?

R gould

A beeper the size of a watch battery....geezz I expect no louder than your average beeping digital watch....

For all I know, a firecracker exploding (size of a watch battery) is still not loud enough.

D from BC

For how long? I have a piezo alarm that produces about 100-110 dB from two watch batteries. But not for long (maybe 10-15 minutes). Its bigger than what you describe, but most of this is due to the size of the piezo transducer.

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Paul Hovnanian	paul@hovnanian.com
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Procrastinators: The leaders for tomorrow.

Do you mean that it will only be useable for 15 minutes before it is dead?

Also, I wouldn't actually need it to be 100 db... half of that would suffice, I think (I'd have to test that.)

gould

Put a cicada inside it.

How you activate it is your problem. :^)

Tim

-- Deep Fryer: A very philosophical monk. Website @

Is an antenna size considered? Ken

Human hearing is logarithmic. Half the power is 97dB. Half the decibel level, 50dB is around the level of the fan in my computer at 1meter and the sound level in my garden with a few cars doing 30mph a couple of hundred meters away. 50dB at 1m will only be noticed by people close by if it goes off in a big room with people moving around or talking.

Ken's question about antenna size is an important consideration, would a 6inch diameter loop be possible? I assume you are in the USA, do you care about FCC rules? Nobody will notice a few ocasionally strong transmissions.

Battery size is going to be an issue.

One idea is to use a 4watt CB radio transmitter to get a strong signal. A small loop antenna, tuned to resonance at 27MHz with a capacitor would pick up enough signal to turn on a transistor that completes a circuit to allow current from a couple of watch batterys to flow through a buzzer. Almost zero power use when inactive. A loop antenna is polarised so you might want to use to two perpendicular to each other.

If you want to use a low power transmitter you will have to use a sophisticated receiver. Given the constraints you will have to buy an off the shelf module.

Bob

Bob

use the 'planet' as a form for the antennae loop, that will get you the maximum diameter for effective signal pickup

tune it to some off beat freq nobody uses,

create a transmitter to just emanate some same freq signal to force the tuned circuit into resonance

you dont need too much distance i hope

use the tuned osscillations to somehow trigger a closure (field effect xistor switch?) of battery power to a piezo buzzer

the buzzer could be made the same diameteras the sphere to also maximize the decibel output

Check here:

I've got this one:

I use it to get two Arduino boards talking to each other. They're good up to 150m which is a fair distance and the one I've got operates on

434MHz.

Producing noise, yes. The batteries can power the alarm in a passive state for many months.

--
Paul Hovnanian	paul@hovnanian.com
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Procrastinators: The leaders for tomorrow.