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hand brake alarm

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=127600
Printed Date: May 05, 2025 at 5:40 PM


Topic: hand brake alarm

Posted By: cairnsgse
Subject: hand brake alarm
Date Posted: June 10, 2011 at 7:00 AM

To all those that replied to my last question thanks . Now my next one is a handbrake alarm .Must sound alarm when handbrake is not applied and drivers door is opened .Must  activate irrespective of ign switch .Both hand brake and door switch use earth to activate lights  .Can buy a redark but over $200



Replies:

Posted By: KPierson
Date Posted: June 10, 2011 at 11:58 PM
2 standard automotive relays:

Relay 1:
Pin 85 - ground from door pin
Pin 86 - constant power
Pin 87 - constant power
Pin 30 - (+) output to Relay 2 Pins 86 and 87A

Relay 2:
Pin 85 - ground from parking brake
Pin 86 - from pin 30 of Relay 1
Pin 30 - (+) output to buzzer of choice
Pin 87A- from pin 30 of Relay 1

How it works - when the door is open Relay 1 is energized sending power to the coil and common contact of Relay 2. If the parking brake is set when the door is open Relay 2 will energize breaking the connection between 30 and 87A. If the parking brake is NOT set the relay will not energize and instead power will be passed from the common terminal to the NC 87A terminal powering the buzzer.

The buzzer will ONLY buzz when the door is open - once the door is shut all relays will deenergize so they will not kill the battery.


Whenever the door is

-------------
Kevin Pierson



Posted By: cairnsgse
Date Posted: June 12, 2011 at 5:17 AM

Exellent and so simple .I really appreciate this ,I owe you a beer

cheers Grant


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