Detect audio signal

C

Captain Haddock

Senior Member
Is there anyway picaxe could detect an audio signal with a view to switching over a relay or similar when detected and switching back when signal goes?
I'm trying to find a way to connect a music source and a vhf radio to a bluetooth transmitter so when a signal comes over the vhf the music cuts out and the radio only comes through.
Bluetooth devices with this capability don't seem to exist.
It's probably way beyond my abilities but worth asking the tech geniuses before abandoning the thought.
 
Hi Captain,
Do the signals have a similar dc level or amplitude levels?
If they have different levels, then you could rectify them to trigger your picaxe via adc.
Good luck...........
 
Put a 330 ohm resistor in series with an LED, then put them across the speaker output. If the LED shines when sound should be heard, then you know the level is enough to drive the LED in an opto-isolator. ( You may need to try a lower value resistor, but 330 is a safe starting value. )

Once you prove this, it is easy to interface the opto-isolator to a Picaxe.
( Using an opto-isolator also isolates the radio circuits from the Picaxe, always a good idea. )
 
cpedw said:
Don't most marine VHF sets have a LED that lights when receiving? Mine does. That must be a signal that could be used to switch a FET or relay.
Click to expand...
No it's just says "busy " on the lcd screen, I don't want to mess with the internals in any way as it's a critical safety thing.
I'm out cruising not just earwigging.
 
30 years ago we used a circuit board about 2cm x 2cm to provide a relay output from a speaker input. Some security alarm panels had a horn speaker output but no 12V output to switch strobes or 12v sirens. This board solved our issue but may no longer be available.
May be worth checking electronic security companies or a google search for speaker to relay modules on Ebay. (China make modules for every thing.)
 
Just had a moment to Google for modules. Only found modules for speaker protection relays. What I had in mind was a simple circuit, a relay and few other components. I'll search my shed stuff on the weekend as I'm sure a module is there somewhere. If I find it I'll draw the circuit for all.
 
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