Alarm clock speaker trigger

[batman]

I'm looking for a circuit that i could put across the speaker of an alarm clock, and when the speaker is making sound, the circuit turn on a relay. Can someone help me with this?

 

[tansis]

This should do the trick,but.........
It should be noted that this circuit does not "latch". The relay and LED operate momentarily in response to audio peaks.
Never the less it's a good place to start.

**broken link removed**

 

[batman]

thanks, but i was preferring something that would attach to the speaker itself, and not be a microphone to place in front of it. wouldnt that be triggered by ambient noise i the room?

 

[Electric Rain]

Yeah, I've always wanted to do that too. Is it so you can have your own alarm circuit? Just wondering. And yes, it would pick up ambient noise. So, the only way to do this, is to take your alarm clock apart, and try to trace the circuit back from the speaker to the "alarm out", and solder your circuit there. Sorry it's not much in detail. Let me know what you find out and good luck.

 

[Sebi]

You can triggering a flip-flop via 10nF serial condenser from speaker out,if speaker another pin connected to negative. When the signal not enough for flip-flop input, apply a transistor prestage.

 

[sam_h]

You could always use PNP transistor in series with the speaker, then set that to trigger a thyristor, and the thyristor to trigger you relay.

 

[batman]

So basically take my input from one pin of the speaker and amplify the heck out of it?

 

[0x34]

Here's a quick idea off the top O'me head.... Not prototyped, but I'm sure it'll do what you want.

 

[batman]

cool, i'll try it