Create Signal from Latched Ground Output to Momentary Ground Pulse

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=145738
Printed Date: May 10, 2025 at 6:50 AM

Topic: Create Signal from Latched Ground Output to Momentary Ground Pulse

Posted By: miketheman
Subject: Create Signal from Latched Ground Output to Momentary Ground Pulse
Date Posted: November 01, 2019 at 9:04 AM

I have a vehicle GPS tracker that when commanded will put out a latched ground output meant to control a relay such as a remote fuel cut off if the vehicle gets stolen. I also have a remote starter installed in the vehicle that has a single ground activation wire, and rather than paying a monthly fee for a second device I want to use the ground output from the GPS tracker to pulse the activation wire on the remote starter. I know how to create a pulse to latched relay circuit but not sure how to do it the other way around.

Thanks in advance.

Replies:

Posted By: the12volt
Date Posted: November 01, 2019 at 9:08 AM

Look at the constant to momentary output diagrams here: https://www.the12volt.com/relays/relaydiagrams.asp

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Posted By: the12volt
Date Posted: November 01, 2019 at 9:10 AM

https://www.the12volt.com/relays/relaydiagram43.html

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Posted By: miketheman
Date Posted: November 02, 2019 at 8:34 PM

This looks good but won't it is cause a drain on the battery when the vehicle is off?

Posted By: eguru
Date Posted: November 05, 2019 at 7:01 AM

miketheman wrote:

I have a vehicle GPS tracker that when commanded will put out a latched ground output meant to control a relay such as a remote fuel cut off if the vehicle gets stolen. I also have a remote starter installed in the vehicle that has a single ground activation wire, and rather than paying a monthly fee for a second device I want to use the ground output from the GPS tracker to pulse the activation wire on the remote starter. I know how to create a pulse to latched relay circuit but not sure how to do it the other way around.

Thanks in advance.

Just capacitively couple the input with a 470uF capacitor (positive to the input). Add a 1K pullup resistor from the input to +12V. No relay required.