Modicon Discrete Output Module AS-BDAP-258

 

The AS-BDAP-258 Discrete Output Module is part of the discrete quantity relay output interface module series for the Modicon Compact. Its core attribute is not the logic processing unit, but the electrically isolated output conversion module between the control system and the field execution loop. This module converts the digital control results inside the PLC into switch signals that can directly participate in the on-site loop control through relay contacts. It is suitable for industrial control systems with high requirements for adaptability to load types and clear requirements for isolation safety.

 

 

Brand	Modicon
Model	AS-BDAP-258
Description	Discrete Output Module
Origin	France / USA
Dimension	35*20*10cm
Weight	0.3kg

 

 

1 . Control Instruction Generation Stage

During the normal operation of the PLC, the controller completes the following steps according to the predetermined scanning cycle:

Collect input signals

Execute the user control program

Calculate and update the data in the output mapping area

When a certain discrete output condition in the program is met, the corresponding output bit is set to a valid state inside the controller. This state does not directly act on the field,ld but first remains in the output image area of the PLC.

 

2. System Bus Transmission stage

At the end of this scanning cycle, the controller will uniformly send the updated output status to each I/O module through the Compact series internal system bus.
AS an output module, AS-BDAP-258 only receives output instructions corresponding to its own channel address and does not participate in the data processing of other modules.

 

3. Internal driver Processing Stage of the module

When the AS-BDAP-258 receives the valid output instruction of the corresponding channel:

The internal logic circuits of the module parse the instructions

The drive circuit applies control signals to the relay coil

The relay coil generates a magnetic field, which drives the contact mechanism to operate

This process is accomplished internally by the module and has no direct feedback relationship with the external load status.

 

4. Relay Contact Action Stage

After the relay is driven:

The normally open contact switches from the open state to the closed state

The normally closed contact switches from the closed state to the open state

The change in the contact state constitutes the actual control action of the external circuit, enabling the load circuit to be powered on or off.

 

5. Logic of Action Holding and Release

The relay remains operating under the following conditions:

The PLC program continuously outputs valid instructions

The power supply of the module and the operation status of the system are normal

When the PLC program revokes this output instruction, or the system enters a stop or power-off state:

The module stops supplying energy to the relay coil

The relay contacts reset under the action of the spring force

The output circuit returns to its initial state

 

6. Explanation of the Relationship between Operational Characteristics and Time

Due to the use of relays AS the actuating units, the output actions of AS-BDAP-258 have the following operational characteristics:

The action response time is affected by the mechanical characteristics of the relay.

There is a slight physical delay in output switching

Not suitable for high-speed pulse or high-frequency switching control

This operation mechanism places more emphasis on action reliability, load adaptability and electrical isolation rather than response speed.

 

7. Logic at the Exception and Protection Levels

When there are abnormalities in the external load (such as short circuits, voltage fluctuations) :

The internal control logic of the module will not change the output instructions due to the load status

Relay contacts, as physical isolation points, can reduce the spread of anomalies into the PLC

Single-channel exceptions do not affect the action logic of other channels

 

1 Power off before connection and connection standards
✔ Power-off wiring: Ensure that the wiring is done when the equipment is completely powered off to avoid electric shock or short circuit.
✔ Correct wiring sequence: Connect the output contacts and power supply lines according to the wiring diagram in the original factory manual.
✔ External power isolation: The relay output of this module requires an external power supply, and pay attention to the wiring of the output and the internal logic power supply of the PLC should be isolated.
✔ Terminal inspection: Tighten the terminal screws to ensure a secure and reliable connection, and avoid vibration or loosening causing poor contact.

 

2. Power-on and Testing
Before powering on for the first time, check each connection to ensure it is correct.
After powering on, perform a no-load test first: Do not connect the load at this stage, to verify whether the relay's output logic responds normally.
The n gradually connect the actual load and verify that the output actions are in line with expectations.