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Constant to Momentary 12V Output Relay Wiring Diagram - Capacitor & Resistor

Wiring diagram of a relay circuit converting constant to momentary 12v output using a capacitor and fixed resistor.

AI caption · Photo 1608 of 1799

This document is a small electrical schematic titled "Constant to Momentary 12v(+) Output," sourced from the12volt.com (visible watermark). It shows how to wire a standard 5-pin automotive relay (terminals 30, 85, 86, 87, and 87a) together with a 1K uf capacitor and a 10K fixed resistor to convert a constant switched 12-volt positive signal into a brief momentary 12-volt positive output pulse. In the diagram, a switched 12v(+) source feeds relay terminal 86, and a fused 12v(+) source feeds terminal 87. A 1K uf capacitor and a 10K fixed resistor are wired in parallel to ground on the terminal 85 side of the relay coil. The momentary 12v(+) output is taken from relay terminal 30. Wire runs are shown in different colors (magenta for the switched input, red for the fused input, green for the capacitor/resistor branch, and dark blue/violet for the momentary output). The diagram is generic and not tied to any specific vehicle make, model, or year; it is a common technique used in 12-volt automotive accessory installations (e.g., triggering devices that require only a momentary pulse from a constant signal). No part numbers, fuse ratings, or vehicle-specific data appear in the document.

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Frequently asked questions

What does this diagram show?
It shows how to wire a relay with a capacitor and resistor to convert a constant switched 12v(+) signal into a momentary 12v(+) output.
What relay terminals are used in this circuit?
The diagram shows a relay with terminals 30, 85, 86, 87, and 87a. Switched 12v(+) goes to 86, fused 12v(+) goes to 87, and the momentary 12v(+) output comes from terminal 30.
What component values are required?
A 1K uf capacitor and a 10K fixed resistor, both connected to ground on the terminal 85 side of the relay.
Where does the momentary output come from?
The momentary 12v(+) output is taken from relay terminal 30.
What power inputs does the circuit need?
Two 12v(+) sources: a switched 12v(+) input to terminal 86 and a fused 12v(+) input to terminal 87.

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