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safely avoiding relays

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=96915
Printed Date: March 28, 2024 at 10:03 AM


Topic: safely avoiding relays

Posted By: 99boty
Subject: safely avoiding relays
Date Posted: September 05, 2007 at 9:57 PM

When sending a low current output [e.g. 200mA (-)] from an alarm brain to a factory wire, a relay is normally used. But in the case where the factory wire is drawing less current than the output is supplying I have read that it is safe to connect the output directly to the factory wire. In general, is the alarm output current always the threshold not to be exceeded by the factory wires? My situation right now is  connecting a 120mA factory disarm output directly to the factory disarm wire that only pulls 9 mA, and by doing so will the factory wire still only have 9mA going through it or the full 120mA? Sorry if this last part is too much into theory, but I'm just curious. Much Thanks.




Replies:

Posted By: mikvot
Date Posted: September 05, 2007 at 10:13 PM
Year, make, model, what system? You should be fine, but list this info to be sure.

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Posted By: KarTuneMan
Date Posted: September 05, 2007 at 11:10 PM
Using a relay to trigger a relay. I don't think it's needed....

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Posted By: JWorm
Date Posted: September 06, 2007 at 12:17 AM
99boty wrote:

My situation right now is  connecting a 120mA factory disarm output directly to the factory disarm wire that only pulls 9 mA, and by doing so will the factory wire still only have 9mA going through it or the full 120mA? Sorry if this last part is too much into theory, but I'm just curious. Much Thanks.




The factory wire will still only pull 9mA through it. No relay needed in this application.




Posted By: eurobink
Date Posted: September 07, 2007 at 1:06 AM

KarTuneMan..

I just read that topic with the (7x blah blah blah) Injectors.. blah blah blah...... pistons this, compression that... i believe it was about finding a tach wire...

hehe.. almost died seeing your comment. .Perfect!

Couldn't leave reply.. OMG.. i have to print that one.





Posted By: Chris Luongo
Date Posted: September 08, 2007 at 9:53 AM
Like JWorm said, the wire in the car will only pull what it wants, regardless of the potential of the source.

It's analagous to you wanting to buy a Coke, and opening your wallet. It doesn't matter if you have $5 or $500 in your wallet, you're still only going to pull out $1 for the Coke.

Or, looking at it the other way, if you were instead to use a relay, you're actually making more current available, not less-------you're making the full current of the car battery available, instead of just the 120mA output of the alarm.

Or, looked at another way, using the relay is like opening up your $10,000 savings account to buy the Coke instead of opening your wallet---still, only $1 will be spent.




Posted By: methinfinity
Date Posted: September 08, 2007 at 10:49 AM
nice analogy

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