Electric Gurus - Relay needed to shut of Amp ????

poormansporsche

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I have a Head unit with built in bluetooth and is rubbish so I have a parrot fitted - which works fine but the head unit has no "mute" wire. The Parrot stops the sound to my speakers when I receive a call but does not stop the sound to my subs as they go direct by the rca leads. So what I want to do is build a relay that can stop the switching power to my amp that is controlled by the mute wire from my parrot ???

My local radio shop bod has said about some people have fitted a "five way" relay to sort this ? any idea what it might be or other thoughts ???


cheers


Brett
 

Druk

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I'm no expert but you need to determine if the mute wire from the parrot is a permanent live when activated or does it just pulse. That would affect which relay to choose or if it was even possible.
 
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poormansporsche

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thanks - its seems to be that its just a "earth" when activated ?
 

markaz

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I would have thought a normal relay that cuts off the "power on" signal wire to the amp should do it
 

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thanks - its seems to be that its just a "earth" when activated ?
That would be equally fine as long as the 'earth' was permanently activated by the Parrot for as long as reqd. A relay uses a feed and earth to work it's operating solenoid so you could use it just a well as a feed to activate said solenoid.
 
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poormansporsche

poormansporsche

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well after 4 hours of searching ive found a diagram of the required relay, £3.50 from Maplins, sorted :)
 
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poormansporsche

poormansporsche

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I take it the "feed" for the relay should be rather low powered with something like a 3/5 amp fuse in it ??
 

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Without seeing any of the diagrams I can't say if this is relevant, but something to be aware of is 'back EMF', a voltage generated whenever there is a change of current through a coil. This voltage is proportional to the rate of change of the current through it, and can be quite high.

If the mute feed from the Parrot changes state quickly the relay coil could generate a high voltage spike which may damage the Parrot, depending on what the mute terminal is connected to internally.

It may be worth checking with Parrot whether the mute output can connect to a relay coil.
 

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Simple to resolve the back emf with a diode (1N4001 should do) across the coil windings.
Big problem I see is with noise as it is on the line in.
Simple enough circuit though.
 

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Something like this. View attachment 59968 As I say, may be noisy. Not a good solution.

That shows a supply activation. Need to know how much current it will source.

If it is an earth activation, use a 12v supply to the coil, but check how much current it can sink.
Diode cathode is always to positive side.
1N4001 can be changed for 4002 4003 or higher.
 
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