Table of Contents
What are the terminals of a relay?
A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.
How are the terminals of a current relay marked?
Terminals L, S, and M are typical identifier terminals for current relays. L is for Line, S is for Start winding, and M is for Main winding. This should help technicians wire a current relay to a compressor’s motor. Remember, when a start capacitor is being used, terminals 2 and 3 may come into play.
Does polarity matter on a relay?
Yes, polarity in a DC relay will determine the magnetic field direction – but remember the solenoid / magnet is acting on a lump of iron. Not usually a magnet. So in general polarity is irrelevant.
What do the numbers mean on the bottom of a relay?
Numbers of a Relay Note that each pin is numbered. 85 and 86 are the coil pins while 30, 87, and 87a are the switch pins. 87 and 87a are the two contacts to which 30 will connect. If the coil is not activated, 30 will always be connected to 87a. Think of this as the relay in the Normally Closed (OFF) position.
What is common terminal?
The common terminal is one of three electrically active terminals on a 3-way switch (not including the ground terminal that is located on the metal frame of the mounting ears). The common terminal is the “bridge” between the power supply and the load (typically a light fixture).
What terminals connect to the contacts on a potential relay?
Potential Relay Connections Potential relays have 5 terminals: 1, 2, 4, 5, and 6. Only 3 terminals are used: 1, 2, and 5. Terminals 2 to 5 are the coil terminals. Terminals 1 to 2 are the normally closed contact terminals. Terminal 1 is always connected to the start capacitor.
Which two pins are connected when the relay coil is energized?
RELAY ENERGIZED (ON) Current flowing through the control circuit coil (pins 1 and 3) creates a small magnetic field which causes the switch to close, pins 2 and 4. The switch, which is part of the load circuit, is used to control an electrical circuit that may connect to it.
How are relays labeled?
Although most relays are labeled at the bottom, you can always find the 30 pin set perpendicular to pins 87 and 87a for easy identification to the power source. Realizing that 85 and 86 are the coil pins, these pins will be transferring the current through the coil.
How do you read a relay?
Relays are switches that open and close circuits electromechanically or electronically. Relays control one electrical circuit by opening and closing contacts in another circuit. As relay diagrams show, when a relay contact is normally open (NO), there is an open contact when the relay is not energized.
Which is ground on a relay?
The relay must be on the ground side of the load when the voltages above the coil are hot. The case should be grounded. The relay can be on either side of the load for hot switch voltages that are lower than the coil.
Does positive and negative matter on a relay?
Polarity does not matter.
Does it matter which way you put in a relay?
The orientation of the relays shouldn’t really matter. On the bottom of the relay you will see the numbers 85, 86, 87 & 30 marked. 85 & 86 are the terminals connected to the relay coil (the relay control circuit) and 87 & 30 are the terminals connected to the switch contacts (the relay load circuit).
What happens if relay is backwards?
Often seen as a quick fix, using the wrong relay for the application can cause inadvertent voltage spikes. Many relays, if installed for the wrong application, could and will cause a short (Internal Relay Circuit) and most likely cause functionality issues or even damage to the vehicle computer systems.
What does a relay number mean?
We call that a relay or shadow number and its purpose is to route calls through Dialpad to display your Dialpad caller ID over your mobile phone. Here are just a few benefits to using relay numbers: Calls made from your forwarding device use your Dialpad caller ID rather than your device’s personal number.
What do the numbers on automotive relays mean?
3, Automotive Relay terminals: such as 30 for the movable end, 87 for the normally open end, 87a for the normally closed end, 85, 86 for the coil end, also useful for 1 to 5, 1, 2 for the coil end, 3 for movable End, 4 represents the normally closed end, and 5 represents the normally open end.
What does 87 mean on relay?
High current Terminal Which Circuit? Definition 87 High current (load) Output to device, normally open, pulled closed when coil is energized 87a High current (load) Output to other device, normally closed, pulled open when coil is energized.
What is common terminal in PLC?
The common terminal is the terminal that serves as the common return path for all I/O points in the bank. Sink/source I/O circuits combine sinking and sourcing capabilities. This means that the I/O circuitry in the PLC will allow current to flow in either direction, as shown below.
What is the function of common terminal in a switch?
A one way light switch has two terminals which is a common marked as COM or C. The common is for the live wire that supplies the input voltage to the switch. The other terminal is marked as L1 and is the output to the light fixture.
