Audio Power to Activate a sensitive Relay

service

You are looking for a tone decoder...

You will need to know the frequency of the received tone in order to build a decoder. Although the LM567 IC is quite old and, more than likely, out of production, they will be available for quite a long time. Look at the data sheets and we'll see.

Building on Lord Garth's suggestion, here's a practical starting point from which you can adapt:

One point about 567s is that I've found they are often difficult to trim for an exact match of frequency. You need to use a pot, and things can subsequently drift around. The datasheet is fairly cryptic, as I recall, giving the values required in a couple of crude graphs, which are labeled badly.

-------- Regards, Robert Monsen

"Your Highness, I have no need of this hypothesis." - Pierre Laplace (1749-1827), to Napoleon, on why his works on celestial mechanics make no mention of God.

I've recently seen a bandpass filter -> signal using opamps on Bill Bowden's site:

It looks to be a bandpass filter into a level detector, and from there into a solid state relay. This one flipflops (first whistle on, second whistle off) so you may need to mess with it for your application.

Also, You'll have to fiddle with the filter values to get it to recognize your tone, unless you are lucky. The computation for the resistor values required is shown.

Thanks a lot for your help guys , I will take your tips into consideration. I will use the 567 as I have several and my tone is very close to 2 khz.

Cheers...Gerry

service

the

that