SPDT relays have three contacts on one side and two contacts on the other. The three contacts on the left, called coil contacts, are separated from the common contact by insulated contacts called NC or normally closed (NO). The other two contacts are called open and closed contacts, respectively. In the next section, we'll discuss what these terms mean, how they work, and what type of relays we should use in our circuits.

SPDT relay
A SPDT relay is a common type of electrical switch that has two electrical contacts in a series configuration. One of the contacts is connected to the battery. The other contact is connected to a different circuit. A single pole double way relay has a coil connected to the battery and a switch S1 in series. This allows current to flow through the fans on Custom T73 PCB relay supplier both ends. When the switch is energized, the T terminal connected to contact 1 opens the shunt.

SPDT relays are also commonly referred to as SPST-NC or Four Pole Double Throw. They all have two terminals, one connected to a form A contact and one connected to the other. In contrast, SPST-NO relays have only one Form A contact and two terminals. This means there is no difference between them other than the name. The SPDT relay has only one single pole contact, but both of its contacts are normally open and normally closed.

Normally Open, Timed Close (NOTC) Contacts
A normally open, timed close (NO-TC) contact is a switch with two terminals and a form A contact. Current flows through the coil, moving the armature and changing the contact state. To use a NOTC relay, you must have an actuator to turn it on or off. Normally open relays do not have any time delay settings, so they cannot be used to delay the starting of the motor.

NOTC relays are used to control large amounts of electrical power. NOTC contacts indicate that the coil is energized for a period of time. When the coil is de-energized, the power to the load is cut off. The contacts will then open again and power will return to the load. This process is called quitting.

SPDT relay with two terminals
A SPDT relay with two terminals is an electronic device with two electrical contacts in parallel positions. As can be seen from the figure, no DC voltage is passed through the single coil of the SPDT relay. The relay is controlled by connecting the T terminal to the first contact. This will open shunt 2 and cause current to flow through fan 1.

There are different types of SPDT relays. Usually, they have a common terminal connected to the coil. This makes it ambiguous which pole is open or closed. However, the terms "SPNO" and "SPNC" help resolve ambiguity. Depending on the configuration, there may be two open circuits or two closed circuits in the SPDT. When you use SPDT relays, make sure to select the correct type to match your application.

Single ended single pole single throw relay
A single-pole single-throw (SPST) relay is a switch that operates by opening and closing an electrical circuit. A switch in series with the relay contact terminals connects the circuit to the battery. When switch S1 is closed, the contacts open and the LED lights up. When the switch is open, the contacts will close and the LED will illuminate. This is a common method of opening or closing a circuit.

SPST relays with one terminal have 5 pins and two contacts. The center pin on the left has a common contact and the other two are coil contacts. Contacts are marked NC or NO, or both. The coil connections are electrically isolated from the common contact and are not physically connected to other contacts. This makes the relay ideal for applications where one circuit has a low voltage and another has a high voltage.