Saturday, 28 June 2025

Pin configuration of a 5 pin relay

 A 5-pin relay is an electromechanical switch that controls a high-current circuit using a low-current signal. It's widely used in automotive and industrial applications.


🔌 Pin Configuration of a 5-Pin Relay:


Here's a standard layout (SPDT: Single Pole Double Throw):


Pin No. Terminal Name Function


85 Coil (-) Connects to ground/negative (coil side)

86 Coil (+) Connects to positive (triggers relay)

30 Common (COM) Main input power (from battery or power source)

87 Normally Open (NO) Connected to 30 only when relay is energized

87a Normally Closed (NC) Connected to 30 when relay is de-energized




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⚙️ Working Principle:


1. When no current flows through the coil (pin 85 & 86):


Pin 30 is connected to Pin 87a.


The load connected to pin 87a is powered.




2. When coil is energized (by applying current to 85 & 86):


Internal switch flips.


Pin 30 connects to Pin 87 instead.


The load on pin 87 is now powered.


87a is disconnected.






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📊 Diagram (Text View):


Coil

       ┌────┐

85 ───▶│    │◀─── 86

       └────┘

          │

         COM (30)

        /    \

     87a     87

(NC)     (NO)



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🛠️ Use Cases:


Automotive lights/fans


Fuel pump control


Switching between two devices


Power window or horn circuit


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