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wiring diode in relay for negative pulse

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Member - Posts: 2
Member spacespace
Joined: January 25, 2015
Location: Virginia, United States
Posted: January 25, 2015 at 6:15 PM / IP Logged  
Wiring relays for audi central lock pump. The alarm is Pyle pwd701. Only using for lock unlock. The pump in the audi 1997 has negative contacts. The alarm has negative contacts, using relay to protect the alarm. I know the diode goes on the coil side. Does one have it cross the relay wires and which side has white strip. I want to put the diode between the alarm and negitive pulse and the 85 terminal on relay, but am thinking from what I have found she arch here should be between 85 and 86. If trying to protect the negative pulse alarm how should this be wired thanks again. If between 85 and 86 protecting negative terminal where is diode going. I will post in other form but and way to hold remote of the Pyle 701 to have it keep the contact for the power window open - close
i am an idiot 
Platinum - Posts: 13,491
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: January 25, 2015 at 6:48 PM / IP Logged  
Chances are the alarm brain already has a diode across the output wire.
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: January 25, 2015 at 6:49 PM / IP Logged  
What are you trying to protect the alarm from?
You should simply be able to connect the GND door switches to the alarm's door switch GND inputs. There is no need for protection.
If you are talking about isolation as in separating multiple +12V supplies from each other OR preventing GND-switched oututs from effecting each other, then diodes in series with each source/switch with their line ends in the direction of current flow (ie towards the most -ve or GND) and commoned at whichever end applies (typically the line end).
Spike protection is a separate issue. For typical <500mA relay coils 1N4004 or 1N4007 diodes are placed across the coil (85 & 86) with diode-line (cathode) towards the most +ve (conventionally 86).
But since gnd inputs should need no protection, there is no need to add relays and protection from their coils.
Member - Posts: 2
Member spacespace
Joined: January 25, 2015
Location: Virginia, United States
Posted: January 25, 2015 at 9:27 PM / IP Logged  
Thank you. I hooked the first alarm up with no relays but the unlock and lock won't work. I have set it to double pulse and longer time for lock. After extensive testing the a remote alarm was not suppling negative pulse ? defective from factor or something went wrong. I am going to install relays to have less load on new keyless system I have just order. From what you have said I guess I don't need diodes and I will just wire in relays correct? Thanks again for all your help.
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: January 26, 2015 at 1:58 AM / IP Logged  
No, I'm saying that relays should not be necessary, after all they are not providing any protection. (If so, what?) However that was based on relays between door switches and alarms etc.
If relays are used, then spike protection diodes may be necessary.
Independent of the above, diodes may be required to isolate other circuits (eg, one ground-switched circuit from another when using the same ground switch, or separate hot (+12V) supplies.
If your alarm or whatever cannot supply the required current, then sure, use relays. EG, as I understand your case, relay 86 to +12V (IGN etc) and 85 to the grounding/-ve alarm or whatever output with 30 & 87 between the -ve (GND) pulse lock mechanism and GND.
howie ll 
Pot Metal - Posts: 16,466
Pot Metal spacespace
Joined: January 09, 2007
Location: United Kingdom
Posted: January 26, 2015 at 2:55 AM / IP Logged  
Never needed relays on that vehicle.
Lock/unlock wires, plug in driver kick panel, loom coming from driver's door.
First test that you have working negative lock/unlock alarm wires.
Then test the suspect Audi wires to make sure they are the correct lock/unlock wires.
Diode your alarm lock/unlock outputs, inline diodes might be needed on the alarm wires (flip-flop output), 1N4004, bands towards Pyle.
The correct way to use quenching diodes on a relay is across the coil, 85 and 86.
ISO convention places the POS side at 86 and the NEG at 85.
Diode across the two, band to the POS (86).

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