i ran 3 amplifiers off a 30A bosch relay and just used the remote trigger wire from the head unit to switch the relay on. ran that setup for about 1.5 years and never had a problem, still using the head unit now on a much smaller setup (one amplifier) and have removed the relay and just use the remote trigger from the head unit straight to the amplifier. still works fine.
a Pioneer head unit like yours isn't easy to kill, i don't think you'll really need the diode, but if you want it then go ahead.
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Car headunit wiring query.. Calling all electrical guru's!
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I see, thanks for the info, I have never considered this. I have run a relay off the amps remote lead previously a few times with no issues, maybe those particular decks were not effected.
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As the magnetic field around the coil collapses when the relay turns off it induces a current in the coil, resulting in a negative spike (generally in the vicinity of -400V) back into whatever is driving the relay, depending on what the headunit uses to switch the remote output this sort of back EMF may quickly kill it, by placing a reverse biased diode across the coil provides an alternative path for the spike, thus preventing it from damaging the drive electronics.Originally posted by artman View PostIf all you are wanting to to do with your head unit remote turn on wire is trigger the relay, wire this wire to one side of the relay coil, the other side of the coil to earth. The relay coil doesn't have a polarity
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Going off your wiring description, the pins on the relay are irrelevant for the diode orientation (assuming you have the two correct pins for the coil) the cathode of the diode should connect to whereever the blue wire from your head unit connects and the anode should connect to the black wiring.Originally posted by Thirteen13 View PostGoing off how i have described the numbers ? The blue/white amp wire i assume supplies the power that connects to pin 85, meaning that i need to solder the cathode onto pin 85 and the anode onto pin 86, as pin 86 has the ground on it.?
im a bit lost myself LOL
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i want to prevent the back EMF when the coil switchs off so put in a quenching diodeOriginally posted by artman View PostWhy do you need a diode to power the relay?
If all you are wanting to to do with your head unit remote turn on wire is trigger the relay, wire this wire to one side of the relay coil, the other side of the coil to earth. The relay coil doesn't have a polarity
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Why do you need a diode to power the relay?
If all you are wanting to to do with your head unit remote turn on wire is trigger the relay, wire this wire to one side of the relay coil, the other side of the coil to earth. The relay coil doesn't have a polarity
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Going off how i have described the numbers ? The blue/white amp wire i assume supplies the power that connects to pin 85, meaning that i need to solder the cathode onto pin 85 and the anode onto pin 86, as pin 86 has the ground on it.?Originally posted by jbrewster View PostDiode needs to be reverse biased, i.e. cathode pointing to the positive terminal, assuming that your pinout is correct (I don't remember these things by pin number I look at the diagram on the side of the relay
) you have your diode correctly oriented.
im a bit lost myself LOL
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Diode needs to be reverse biased, i.e. cathode pointing to the positive terminal, assuming that your pinout is correct (I don't remember these things by pin number I look at the diagram on the side of the relayOriginally posted by Thirteen13 View PostWith the Diode set between 86(anode) and 85 (cathode) ?
) you have your diode correctly oriented.
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Sorry, misunderstood. The article I linked explains the usual relay terminals, 85/86 are the coil, often the relay schematic is shown on the relay too.
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I know how to wire up the amp..... Im not asking about that.....
Im asking the sequence to attach the spades to the relay and how to lay the quenching diode.
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The remote wire out of the head unit goes to the remote input on the amp, this does not draw much current, no relays required, its basically a signal for the amp to turn on. Then you wire the +ve terminal of the amp direct to the car battery with suitable capable wiring gauge (and fuse as close to battery terminal as possible) and do the same for earth to the amp with decent cable to sound chassis point near amp (no fuse required).
A nice article explaining relays: Browser Warning
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Well ive been doing some further research. Basically most amps need about 20ma to power up. The Amp wire puts out 300ma. So using the relay should take around 100ma and still leave me plenty for an amp.
what i need to know now is
just needed some extra advice on this. I want to rig up the Quenching diode to this rig also.
Would the wiring be:
Black: 86 + 87
Blue: 85
Green: 30
With the Diode set between 86(anode) and 85 (cathode) ?
Using the relay method has been proven time over and over to work. So its just a matter of wiring it up
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Right, I suspected there might be something like that, it is entirely possible that the time it takes for the relay to energise won't be sufficient for it to detect the change (though most headunits will delay a bit before turning on the amp to prevent thumps and such), best bet is probably a delay relay, actually engages X time after it gets powered, best way to find out is to try it though.
It is possible to use a transistor of some description for this, though a MOSFET would be a better option, the trick would be making it sufficiently robust, and whether or not it'd have sufficient delay between being powered and switching the handbrake line for it to be recognised (though there are fairly simple fixes for that).
I'd suggest you "suck it and see" if a standard automotive relay prevents your amp from powering up you can get more sensitive relays from places like Jaycar, you want a 12V coil "reed" relay, though you'll need to be able to solder to use one. They take less current to energise leaving more signal for your amp remote input.
There is another option using only automotive relays but you'd need 3 of them...
Mind if I was designing the thing I'd make it ignore any handbrake signal which conicided with the amp remote line going active specifically to "fix" that scenario (though a delay relay will fix that too).
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Re-reading the manual it suggests the green wire needs to be connected to the power supply side of the handbrakes.
Just some further reading into needing a relay, it seems with newer HU's to get around just simply earthing out the green wire, the handbrake safety needs to have no power going to it before it starts up, once the car is running, when it receives the power signal/earth signal (as in from putting the handbrake on) then it says ok DVD ON. Because the Blue/White amp wire only sends power after the deck is started up, thats why this method running off a relay would immitate NO power on start up, AMP Wire gets power, engages relay then adds power to green wire.
This would suggest that either a manual switch or a relay be used to close and open the earth signal.
What about using a transistor ?
Would drawing some of the power from the amp wire into the relay cause problems to power up the amp ?
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There are a few features on the deck like using the keypad to make bluetooth calling which gets locked out when the handbrakes isnt on, hence why i want ot bypass that, cause making a call on the deck is as hard as changing a song!Originally posted by ausfitter View PostMate you dont need a relay for any of that. Earth out your handbrake wire in the harness and you wont have an issue with the video as previously stated, but as also stated by yourself aswell, it is illegal. As for the remote wire (amp wire), just run it straight to the amp... No need for relays or anything weird like that. Car audio is a piece of cake mate, just dont try and make it complicated
Ive rigged up amps and speakers and subs and stuff so i know its easy, but ive never encounted this bypass before. I did read that the new decks are more complex in there design and people have simply earthed out the handbrake wire and it still doesnt work..
Apprently it needs a pulse of signal to activate, hence like the handbrake, when you pull it on that creates the "pulse" as its engaged. However if you took the handbrake off i assume then it would prevent the screen from working. with that theory then if it has a perminent earth then it should work, therefore the pulse thing is BS!
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