A Normally Open (NO) contact is a type of switch or relay contact that remains open (doesn't conduct electricity) in its un-energized state. This means when the switch isn't actively flipped or the PLC isn't sending a signal, the NO contact acts like a break in the circuit, preventing current flow.

Here's a breakdown of how an NO contact works:

• Un-energized State: This is the natural state of the NO contact. Imagine a light switch on a wall that's turned off. In this scenario, the NO contact is open, similar to a gap in a wire. Because of the open circuit, current cannot flow.
• Energized State: When the switch is activated (flipped on) or the PLC sends a signal, the NO contact changes state. It closes, creating a connection like a completed circuit. This allows current to flow through the circuit.

Analogy: Think of a light with a wall switch.

• Normally Open (NO): When the switch is off (normal state), the NO contact is open, and the light is off (no current).
• Energized by Flipping the Switch: Turning the switch on energizes the NO contact, which closes the circuit and allows current to flow, turning on the light.

Applications of NO Contacts:

• Turning on devices: NO contacts are commonly used in circuits to control power to lights, appliances, or other equipment. Flipping a switch (or PLC signal) activates the NO contact, completing the circuit, and turning on the device.
• Logic in PLC Programming: By combining NO contacts with other elements in a PLC program, you can design complex control systems. For example, an NO contact could be used to trigger a specific action only when a certain condition is met.

Understanding NO contacts is essential for various applications in electrical circuits and PLC programming. They offer a way to control current flow based on switch activation, allowing for creating desired functionalities.