Constant Negative
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=144291
Printed Date: May 12, 2025 at 7:48 AM
Topic: Constant Negative
Posted By: 12vlost
Subject: Constant Negative
Date Posted: April 06, 2018 at 4:33 PM
Hi all.
Need to wire a relay to give a constant negative when a negative is removed?
TIA
Replies:
Posted By: wirewise
Date Posted: April 06, 2018 at 6:52 PM
Wire the terminals of an SPDT relay as follows:
85 to 12V+
86 to your switched ground
87a to ground
30 is your constant ground output when your switched ground is turned off/removed
87 not used
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~wirewise~
Verify all wiring with your meter before making any connections!
Posted By: 12vlost
Date Posted: April 06, 2018 at 6:53 PM
Got it sorted thanks, voltage across the coil, pin 30 ground when ground is removed from the coil pin 87a becomes constant ground.Need to convert a NC pir to NO this works great after lots of googling some crazy schematics hope it helps someone
Posted By: 12vlost
Date Posted: April 06, 2018 at 6:54 PM
Thanks wirewise just saw your post after I replied to myself, much appreciated
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