MITSUBISHI MELSEC A series PLC（MELSEC-A）

Scope of application and core positioning

Applicable Models

CPU：A1S(S1)、A1SC24‑R2、A2S(S1)、A1SH、A2SHCPU(S1)、A2ASCPU(S1/S30/S60)

Base, power supply I/O、 Full range of AnS modules for communication, positioning, etc

positioning

Authoritative manual for hardware installation, wiring, safety, maintenance, and fault codes

Targeting professional electrical personnel, emphasizing personal safety and equipment reliability

Safety precautions (highest priority)

Danger level (DANGER)

An external safety circuit must be established (emergency stop, limit, forward and reverse interlock)

The installation wiring must be completely powered off, and touching the terminals with electricity is strictly prohibited

The battery is not rechargeable/disassembled/heated/short circuited, only A6BAT is used

Output fault may remain on/off, critical outputs require external monitoring

Attention level (CAUTION)

Distance between signal line and power line * * ≥ 100mm * *, anti noise interference

Terminal screw torque 59~88N · cm, anti loosening/short circuit

No modification, opening, or parallel connection of power modules allowed

Module core specifications

1. Power module (key parameters)

Model input voltage output fuse/protection

A1S61P 100/200VAC 5VDC 5A overcurrent/overvoltage

A1S62P 100/200VAC 5V 3A+24V 0.6A overcurrent/overvoltage

A1S63P 24VDC 5V 5.5A overcurrent/overvoltage

A1S61PN 100~240VAC 5VDC 5A CE certification

2. Input module

Type: AC input, DC input, high-speed DC input

Points: 16/32/64 points, grouped and isolated in common ground

Response: High speed 0.1ms, normal 10-30ms

Voltage resistance: 500~1500VAC isolation

3. Output module

Type represents model, current response

Relay A1SY10 2A/point 10ms

Controllable silicon A1SY22 0.6A/point 1ms

Transistor A1SY40 0.1~2A/point 0.5~2ms

4. Hybrid I/O modules

A1SH42:32 input+32 output, DC transistor high-speed type

A1SX48Y18: 8 inputs+8 outputs, relay output

Installation specifications

Environmental Requirements

Temperature: 0~55 ℃, humidity: 10~90% RH

Altitude: ≤ 2000m, pollution level 2

Mechanical Installation

Vertical installation, with a distance of ≥ 30mm between the top and bottom to ensure heat dissipation

DIN rail: TH35-7.5, screw spacing ≤ 200mm

The module buckle is in place, and the torque of the fixing screw is 78~118N · cm

EMC and LVD compliance

Control cabinet metal grounding, cabinet door low impedance connection

Large area grounding of shielding layer, non single spot welding wire

Add a noise filter to the power inlet and separate the input and output wiring

Wiring specifications

Grounding requirements

LG/FG must be grounded with wire diameter ≥ 2mm ² and length ≤ 30cm

Separation of strong and weak electricity, single end grounding of shielded cables

Power on sequence (mandatory)

Power on the PLC host

Power on external load power supply

Turn on the start switch

Prevent momentary erroneous output.

I/O wiring

AC input/output: withstand voltage 1500~2830VAC

DC input/output: 500VAC isolated

Public end grouping, prohibit cross group mixing

Fault safety design (must be implemented)

External safety circuit

Emergency stop, hardware limit, forward and reverse interlock

Output overload external fuse protection

CPU exception handling

Watchdog timeout, CPU failure: all outputs turned off

Communication failure: Remote I/O output turned off or maintained

Maintenance and upkeep

routine inspection

Module fixation, terminal fastening, and LED status are normal

Environment free of dust and corrosive gases

Regular inspection (6-12 months)

Voltage measurement, grounding resistance, insulation status

Battery replacement (low voltage alarm M9006/M9007)

Battery Specifications

Model: A6BAT, saving program and power down data

Error Code and Handling (Core)

Common high priority errors

10: Instruction error → Program instruction illegal

11: Parameter error → Parameter damage or configuration exception

20: RAM error → Memory hardware failure

22: WDT error → scan timeout, dead loop

31: I/O verification error → module missing/model mismatch

32: Output blown → Load short circuit or fuse broken

70: Battery error → low voltage or not connected

Key questions and answers

Question 1: Why is it necessary to build an external safety circuit for Mitsubishi A-series PLC? What specific tasks need to be done?

answer

Due to CPU failure, output breakdown, and communication abnormalities, PLC may mistakenly output or fail to shut down, which can cause personal injury and equipment damage.

Must be built:

Emergency stop circuit, upper and lower limits of travel, forward and reverse interlock

Key output external monitoring and circuit breaker protection

Power on sequence and power interlock circuit

Question 2: What are the three mandatory rules that must be followed for EMC anti-interference in the installation and wiring of A-series PLCs?

answer

The distance between the signal line and the power line is ≥ 100mm, and parallel bundling is prohibited

Shielded cable with large-area metal grounding, without using single thin wire welding

The power inlet is equipped with a noise filter, and the cables on both sides of the input and output are completely separated

Question 3: What is the reason for the WDT error (code 22) reported by the A-series PLC? How to quickly investigate?

answer

Reason: The program scanning time exceeds the watchdog limit time, which is commonly caused by program dead loops, excessive computation, and transient power outage interference.

Troubleshooting steps:

Check if the program has a dead loop/FOR NEXT mismatch

Split the process using CJ instructions to shorten scanning time

Check for power fluctuations and confirm if the D9005 monitoring voltage is normal