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Relay current draw

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=18712
Printed Date: May 05, 2024 at 7:47 AM


Topic: Relay current draw

Posted By: j84buick
Subject: Relay current draw
Date Posted: September 09, 2003 at 8:35 PM

If I have a single pole double throw relay that will be activated 99% percent of time (even hen car is off) will that any amount of current that I should be concerned about? I know the FAQ says 200 milliamps but I am just not sure what that would translate too over a week of not driving.



Replies:

Posted By: JWorm
Date Posted: September 09, 2003 at 8:56 PM
After a week, I am 99% sure your car will be dead. What are you trying to accomplish with the relay?




Posted By: j84buick
Date Posted: September 09, 2003 at 9:03 PM
I need to detect a circuit when it is broken. What I was planning on doing was a standard relay:

86 = +12 constant
85 = -switched (99% of the time on)
87 = nothing (99% of time on the relay is doing nothing)
30 = -
87a = this will go to a another relay that is waiting to activate a starter kill relay.

This is for an aftermarket shifter with a safety switch. The switch breaks a circuit. The relay will send a - to the starter relay tripping the relay and breaking the starter circuit.

Pretty much all I am trying to do is make this safety switch send a ground when the connection is broken. I could find a 12+ power source only when the key is being turned towards the start position. That might be the easiest thing.




Posted By: j84buick
Date Posted: September 09, 2003 at 9:05 PM
Oh, and dead after 1 week? That doesn't really sound right. That would mean that every car that has an alarm would be dead if not driven after one week with the alarm activated. Because most alarms have at least one relay built in for the starter kill.




Posted By: the12volt
Date Posted: September 09, 2003 at 9:19 PM
j84buick, that would be true if the coil of the relay were energized the entire time the alarm was armed, but the coil of a starter kill relay is only energized when the ignition is on and the alarm is armed or even disarmed depending on the alarm and type of starter interupt (normally open or normally closed). BTW, JWorm is correct. Your battery will be dead within a week if not a couple of days.

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Posted By: j84buick
Date Posted: September 09, 2003 at 9:23 PM
Ok I follow. That makes sense. So all of these people that are making there own starter kills or backup starter kills and using relays are really just draining there batteries eh?

So is there a way to do what I want to do? Wait for a circuit to open and make it send a - to another relay?




Posted By: the12volt
Date Posted: September 09, 2003 at 9:36 PM

That would depend on how they are wiring their starter kill relays.

If your safety switch breaks continuity to ground, you only need one relay to prevent the vehicle from starting.

Connect the terminals of an SPDT relay as follows.
85 to one side of safety switch that opens continuity to ground
86 to ignition
87 to switch side of starter lead
30 to motor side of stater lead

If ground is not present on terminal 85 when you attempt to start the vehicle, it will not start.



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