What is an Internal Relay What is a Relay?

Internal relays are essentially memory units that cannot directly control external loads, but can only perform various control functions within the PLC, or are directly controlled by external signals.

The internal relay of the CPM1A series PLC and its channel number also include the internal auxiliary relay (AR) The function of the internal auxiliary relay is to control and expand the signal inside the PLC, which is equivalent to the intermediate relay in the contact relay line. CPM1A has a total of 512 internal auxiliary relays, which are numbered 20000 23115 and occupy 200ch 231ch. The internal auxiliary relay does not have the function of holding the state in the state of power failure.

What is a Relay? What does a relay do?

Relays are very common in life, and they are widely used in electronic equipment and power systems. So what is a relay? What does a relay do?

Introduction to Relays:

A relay is an electrical control device. It has an interactive relationship between the control system (also known as the input loop) and the controlled system (also known as the output loop). Usually used in the control circuit of automation, it is actually a kind of "automatic switch" that uses a small current to control the operation of a large current.

Therefore, it plays the role of automatic adjustment, safety protection, and conversion circuit in the circuit.

Its working principle is to use the relationship between the control system and the controlled system that the relay has, when the input reaches the specified value, the relay makes the output circuit of the controlled conduction or disconnection, so as to achieve the role of control. The input quantities here can be divided into two categories: electrical quantities (such as current, voltage, frequency, power, etc.) and non-electrical quantities (such as temperature, pressure, speed, etc.).

Classification of relays:

1. Electromagnetic relay:A relay that produces a predetermined response from the relative motion of mechanical parts under the action of an electric current in an input circuit. It includes DC electromagnetic relays, AC electromagnetic relays, magnetic latching relays, polarization relays, reed relays, energy-saving power relays.

2. Solid state relay:A relay in which the input and output functions are completed by electronic components without mechanical moving parts.

3. Time relay:When the input signal is added or removed, the output part needs to be delayed or limited to a specified time before closing or disconnecting the relay of its controlled line.

4. a temperature relay; A relay that operates when the outside temperature reaches a specified value.

5. Wind speed relay:When the speed of the wind reaches a certain value, the controlled circuit will be switched on or off.

6. Acceleration relay:When the acceleration of the moving object reaches a specified value, the controlled circuit will be switched on or off.

7. Reed relay:This is a relay that uses a reed action that is sealed in a tube and has the dual role of an electric shock reed and an armature magnetic circuit to open, close or convert the line.

8. Other types of relays:Such as photorelays, acoustic relays, thermal relays, etc.

The role of the relay:

The relay has the advantages of fast action, stable work, long service life and small size. It is widely used in power protection, automation, motion, remote control, measurement and communication devices.

As a control element, the relay has the following functions:

1. Expand the scope of control. For example, when the control signal of the multi-contact relay reaches a certain value, it can be changed, interrupted and connected to multiple circuits at the same time according to the different forms of the contact group.

2. Control the big with the small. For example, sensitive relays, intermediate relays, etc., can control very large power circuits with a very small control amount.

3. Comprehensive signal. For example, when a plurality of control signals are input into a multi-winding relay in the specified form, the predetermined control effect is achieved after comparison and synthesis.

4. Automatic, remote control and monitoring. For example, the relay on the automatic device can be combined with other electrical appliances to form a program control circuit, so as to realize automatic operation.