To operate a relay, with audio signal

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How do you want it to operate? Will the relay latch on once sound is detected? Or do you want it to chatter on and off in sympathy with the sound?
 
All you need to do is get a small relay that works at the same voltage as the vibrator motor and use that to trigger whatever larger devices from that.

Typical cell phones supply around 3 volts to the motor so just look for a relay that works at that voltage.

The other option would be to run the speakers input wires through a bridge rectifier and convert the sound signal to DC and use that to power the small 3 volt relay.

Does triggering the relay have to work multiple times or just once?
 
alec_t said:
How do you want it to operate? Will the relay latch on once sound is detected? Or do you want it to chatter on and off in sympathy with the sound?
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Yes, I want to latch it once sound is detected.




I need it to latch it once the signal is detached. how to do that?
 
Depending on exactly what you want I would signal condition the audio, run the conditioned audio into a comparator and use a ref voltage as a trip level, use the output of the comparator to latch a D flip flop that can be reset once latched. All depends on what you have exactly to work with and how much diversity you want in the final circuit. If you want to set a trip level for example, use the comparator, if not leave it out. Whatever you want.

Ron
 
It's possible to use the audio from the speaker to operate the relay, but it would be simpler and cheaper (no amplifier needed) to use the vibrator motor activation as the relay operating control, as suggested above. Would you be happy with that?
 
alec_t said:
It's possible to use the audio from the speaker to operate the relay, but it would be simpler and cheaper (no amplifier needed) to use the vibrator motor activation as the relay operating control, as suggested above. Would you be happy with that?
Click to expand...


thank u sir, I also can use vibrator motor activation. actually i want to make a call to a cellphone & it will activate a relay. which will disconnect a main power supply: say 220v, 0.5 amp & i also need to the circuit remain unconnected when I disconnect the call.
 
I foresee problems. Any junk or mistaken call, not just one you make deliberately, will operate the vibrator motor. And to use the speaker signal instead of the motor signal would need someone at the receiving end to answer your call before the speaker could become active, thus making the relay etc superfluous.
 


I just need it for a project so i dont bother for junk call. but is circuit which will hold the relay. or similar, I want to the circuit remain unconnected when I disconnect the call.
 
I just need it for a project so i don't bother for junk call. but is circuit which will hold the relay. or similar, I want to the circuit remain unconnected when I disconnect the call.
Click to expand...

Use a DPDT relay. One set of contacts closes connecting of the external load and the second set closes and provides power from the battery to the coil after the fist power signal has stopped.

Add a normal closed pushbutton on the battery power supply line from the second set of contacts and you have a simple reset system as well.
 
thank U very much sir.

very nice forum, U all helped me even on my foolish question thanks a lot you all.
 
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