Relays are integral components in any electrical circuit, used to control high power devices with low power signals. They switch on and off the circuit to which they are connected. A relay typically consists of an electromagnet, a spring and a set of contacts. When an electrical signal is applied to the electromagnet, it creates a magnetic field that pulls the contacts together, thereby completing the circuit. In this article, we will discuss the wiring of a 12 volt 40 amp relay, its components, and how you can use it in your electrical circuit.
What is a 12 Volt 40 Amp Relay?
A 12 volt 40 amp relay is an electrical switch that can handle up to 40 amps of current at 12 volts. It operates using an electromagnet that controls the opening and closing of its contacts. It is commonly used in automotive applications, such as to control the high current draws of headlights, fog lights, and other accessories.
The 12 volt 40 amp relay is also used in other high power applications, such as electric winches, aftermarket horns, and other electrical devices that require high current draws.
Components of a 12 Volt 40 Amp Relay
A 12 volt 40 amp relay has the following components:
- Electromagnet – this creates the magnetic field when an electrical signal is applied
- Contacts – these are the switch terminals that open and close with the magnetic field
- Spring – this returns the contacts to their original position when the magnetic field is turned off
- Coil – this is the wire that creates the magnetic field
- Diode – this prevents back EMF or voltage spikes from damaging the relay or other electrical components in the circuit
Wiring a 12 Volt 40 Amp Relay
Wiring a 12 volt 40 amp relay is a straightforward process that requires a few basic tools, such as a wire stripper, crimpers, and pliers. Here are the steps to follow:
Step 1: Identify the Pins
A 12 volt 40 amp relay has 4 pins, usually labeled as follows:
- Pin 85 – this is the ground pin
- Pin 86 – this is the positive pin that activates the relay
- Pin 87 – this is the normally open (NO) contact
- Pin 87a – this is the normally closed (NC) contact
To determine the pins, look for the label or markings on the relay casing.
Step 2: Connect the Ground Wire
Connect the ground wire to pin 85 of the relay. This wire should have a ring terminal that can be secured to a bare metal surface of the vehicle. This will provide a solid ground connection for the relay.
Step 3: Connect the Positive Wire
Connect the positive wire to pin 86 of the relay. This wire should be connected to a switch or other control mechanism that will activate the relay.
Step 4: Connect the Load Wires
Connect the load wires to either pin 87 or pin 87a, depending on whether you want the circuit to be normally open or normally closed. For example, if you want the headlights to turn on when the switch is activated, connect the positive wire of the headlights to pin 87, and the negative wire to ground.
Step 5: Install the Diode
Install a diode across the positive and negative terminals of the coil, with the cathode (marked end) connected to the positive pin. This will protect the relay and other electrical components from back EMF, which can damage the circuit.
Wiring Diagram for a 12 Volt 40 Amp Relay
Here is a wiring diagram for a 12 volt 40 amp relay:
| Pin | Function | Color | Wire Size |
|---|---|---|---|
| 85 | Ground | Black | 16 AWG |
| 86 | Positive | Red | 16 AWG |
| 87 | Normally Open | Yellow | 10 AWG |
| 87a | Normally Closed | Orange | 10 AWG |
| Diode: 1N4007 | |||
FAQ
What is the purpose of a 12 volt 40 amp relay?
A 12 volt 40 amp relay is used to control high power devices with low power signals. It is commonly used in automotive applications to control the high current draws of headlights, fog lights, and other accessories.
How do I wire a 12 volt 40 amp relay?
To wire a 12 volt 40 amp relay, follow these steps: (1) identify the pins, (2) connect the ground wire, (3) connect the positive wire, (4) connect the load wires, and (5) install the diode.
What is the difference between a normally open and normally closed contact on a 12 volt 40 amp relay?
A normally open contact is open or disconnected when the relay is not activated, and closes or connects when the relay is activated. A normally closed contact is closed or connected when the relay is not activated, and opens or disconnects when the relay is activated.
What is a diode and why is it used in a 12 volt 40 amp relay?
A diode is an electronic component that allows current to flow in one direction only. It is used in a 12 volt 40 amp relay to protect the relay and other electrical components in the circuit from back EMF or voltage spikes that can occur when the magnetic field collapses.
Can I use a 12 volt 40 amp relay for other applications besides automotive?
Yes, a 12 volt 40 amp relay can be used in other high power applications, such as electric winches, aftermarket horns, and other electrical devices that require high current draws.
