ABB Pluto Safety PLC Maintenance and Troubleshooting

Complete guide for on-site maintenance and troubleshooting of ABB Pluto safety PLC

In the field of industrial safety control, ABB Jokab Safety's Pluto series safety PLCs have become the core of many mechanical equipment safety systems due to their unique dynamic signal technology, modular design, and safety levels up to PL e/SIL 3. From the standalone S20/S46 to the A20/B16/B20/B46 models that support Pluto bus networks, Pluto greatly reduces wiring workload with its flexible I/O configuration and serial sensor capability. However, as equipment ages or systems upgrade, engineers often face challenges such as on-site fault diagnosis, unit replacement, and configuration migration. This article is based on official technical data and systematically elaborates on the hardware characteristics, dynamic/static signal wiring points, Pluto Manager programming skills, typical fault code interpretation, and complete replacement process of Pluto series controllers, helping maintenance personnel quickly recover and optimize safety systems.

Overview and Selection Points of Pluto Series Models

Pluto safety PLCs are divided into two categories: standalone communication type and Pluto bus type. The former is suitable for independent small security systems, while the latter can network up to 32 Pluto units to achieve distributed security control.

1.1 No bus model

Model I/O Total Safe Input IQ (Input/Non Safe Output) Analog Input Safe Relay Output Safe Transistor Output

S20 20 8 8 1 (I5, 0-27V) 2 (Q0,Q1) 2 (Q2,Q3)

S46 46 24 16 3 (I5, 0-27V) 4 (Q0,Q1,Q4,Q5) 2 (Q2,Q3)

1.2 Model with bus

Model I/O Total Safety Input IQ Analog Input Safety Relay Output Safety Transistor Output Current Monitoring

A20 20 8 1 2 2 2 channels (IQ16, IQ17)

B16 16 8 1 0 0 0 None

B20 20 8 1 2 2 None

B46 46 24 16 3 4 2 None

Key selection tips:

When networking or multi Pluto collaborative control is required, a bus model must be selected (the model suffix is not specially marked, but it needs to be confirmed that Pluto bus is supported).

If only current monitoring is required (such as silent lights), A20 is the only model that provides current monitoring (IQ16, IQ17, range 0-1.0 A ± 10%).

B16 has no secure output and only provides input and IQ, suitable for pure input monitoring scenarios.

All models of IQ terminals can be individually configured as safe inputs or non safe outputs (such as indicator lights, status signals), and can even be used as both inputs and outputs (such as reset buttons with lights), significantly saving I/O points.

Core Technology: Dynamic Signal and Series Sensor

Pluto's most distinctive technology is Dynamic Signal. Unlike traditional static 24V signals, dynamic signals are a square wave (alternating high and low, about 200 times/second) generated by Pluto and transmitted step by step through safety sensors. After passing through a properly functioning sensor, the signal is reversed once. When the signal returns to Pluto, the controller determines whether the line is short circuited, open circuited, or crossed by comparing the waveforms sent and received.

2.1 Dynamic Signal Types

Pluto can generate three independent dynamic pulses: A pulse, B pulse, and C pulse. Short circuits can be detected between different types of pulses. Each input terminal can be configured in Pluto Manager to receive the desired signal type (A/B/C and whether it is inverted).

Advantage:

A single channel can achieve PL e/Category 4 (traditional static signals require dual channels).

Up to 10 Eden non-contact sensors, SPOT light curtains, or Tina adapters can be connected in series to the same input terminal while maintaining the highest level of safety.

Greatly saves I/O points, for example, only 1 input is needed for 10 safety gates.

2.2 Static signals and OSSD

Static signal (+24V): suitable for traditional mechanical switches. To achieve Category 4, two inputs (dual channel) must be used.

OSSD signal: from devices with built-in fault monitoring such as light curtains. Pluto can receive OSSD output, but it should be noted that two OSSD signals cannot be connected to the IQ terminal at the same time, and should be connected to a dedicated I input.

2.3 Three state characteristics of IQ terminals

The IQ terminal is a major innovation of Pluto. Each IQ terminal can be independently configured in Pluto Manager as follows:

Secure input (dynamic or static)

Non safety output (+24V PNP, maximum 800 mA)

Simultaneous input and output: A typical application is a reset button (input) with an indicator light (output), occupying only one terminal.

Note: When IQ is used as a safe input, its characteristics are exactly the same as I input, and it supports dynamic signal concatenation.

Practical Hardware Installation and Wiring

3.1 Mechanical Installation

All Pluto units are installed on 35 mm DIN rails (compliant with IEC 60715).

Maintain a minimum gap of 5mm between units to ensure heat dissipation.

The terminal block can be plugged and unplugged, and the unit can be replaced without disconnecting the wires.

Environmental temperature: -10 ° C to+50 ° C for operation, -25 ° C to+55 ° C for storage and transportation.

3.2 Power Supply and Grounding

Working voltage: 24 V DC ± 15% (approximately 20.4-27.6 V).

Recommended external fuses: S20/A20/B16/B20 use 6A; S46/B46 use 10A.

Electrical insulation category: Class II (compliant with IEC 61010-1).

The current consumption of all safe inputs I and IQ is 5.1 mA (at 24V), with a maximum withstand overvoltage of 27V continuously.

3.3 Example of Dynamic Signal Series Connection

Connect single channel dynamic Eden sensors (multiple in series):

Pluto's T0 or T1 terminals output dynamic signals (A pulses).

The input of the first Eden is connected to a dynamic signal, and the output is connected to the input of the next Eden in series.

The output of the last Eden returns to Pluto's I input terminal.

Configure the input as the corresponding dynamic signal type (such as A pulse) in Pluto Manager.

Connect Tina adapter (for emergency stop button, safety switch):

Tina adapter can convert mechanical contacts into dynamic signals. Also supports up to 10 serial connections.

Connect the dual channel static switch:

Use two I inputs and connect 24V signals to two contacts respectively. Configure as dual channel equivalent in the program.

3.4 Bus Terminal and IDFIX

Pluto bus: using CAN bus, with a speed of 100-1000 kbit/s and a maximum line length of 600 m (150 m at 400 kbit/s). Both ends of the bus need to be connected to terminal resistors R-120 (order number 2TLA020070R2200).

IDFIX: Used to assign a unique address to each Pluto. There are four versions: R (read-only address), RW (programmable address), DATA (including AS-i security code), and PROG (used for single Pluto program storage/recovery). IDFIX is connected between the ID terminal and 0V.

Pluto Manager Programming and Configuration

Pluto Manager is a free software that can be downloaded from ABB's official website and supports ladder programming and T Ü V certified functional blocks.

4.1 Three step project approach

I/O configuration: Define the signal type (static/dynamic A/B/C, inverted or not) and IQ direction (input/output/bidirectional) for each I and IQ terminal.

Variable naming: Assign symbol names to input (I), output (Q), hold memory (M), global bus memory (GM), and register (R).

Ladder diagram programming: Build safety logic using functional blocks such as TC1RTI dual channel monitoring, dual manual control, mute, timer, etc.

4.2 Examples of Key Function Blocks

TC1RTI (Block 3): Dual channel safety input with test input, reset input, and reset indication. When the function block is ready and waiting for reset, the IndReset output flashes; TCfault is activated when there is a dual channel fault.

Two manual controls (Block 16): used for NO/NC contact pairing, requiring simultaneous action of the left and right four inputs within 0.5 seconds, and correct standby state (right_de0=0, right_nC=1, left_de0=0, left_nC=1).

Silent light monitoring: Block 20/21 is used for silent lights (Q16/Q17), while Block 22/23 supports power settings (watts).

Safety encoder: used for single or multi turn absolute encoders to generate safe position and velocity values, with dual encoder differential monitoring (MaxDiff ≤ 2%).

4.3 Program Download and Bus Distribution

Connect any Pluto unit through a programming cable (RS232 or USB).

After compiling the project in Pluto Manager, select 'Download'. The program will automatically distribute to all other Pluto units in the network through the Pluto bus, and each unit will extract the corresponding logic based on its configuration.

The IDFIX ROG can also be used to copy programs in a single Pluto system: connect the IDFIX ROG to the ID terminal, and the program will be automatically written after power on.

Fault diagnosis: LED and system registers

5.1 Hardware Status LED

The Pluto unit front panel provides multiple LEDs for quick status determination:

Meaning of LED color

Power green power supply is normal

Run green program

Error Red System Error (such as watchdog, bus failure)

Bus yellow (flashing) Pluto bus communication activity

I/O red/green specific I/O point status (defined after configuration)

5.2 System registers and user errors

Pluto has a 7-segment display (located on the front panel of models A20/B20, etc.) that can display error codes. The user program can display custom error codes (200-299) by writing to system register 11 (SR11).

Common error code meanings:

Alarm 01: Emergency stop button triggered

Alarm 02: Door open

Alarm 03: Machine hatch open

These codes can be written into SR11 and displayed on a 7-segment screen. System register 11 will prioritize displaying Pluto's own errors (such as bus faults) before displaying user-defined errors.

5.3 Troubleshooting of Bus Communication Malfunctions

Check if the terminal resistor is installed (only at both ends of the bus).

Check if the bus cable is a dedicated CAN bus cable (yellow, 2 × 0.50 mm ², model 2TLA020070R3000).

Using a gateway (GATE-D2/C2) as a bridge can filter unnecessary bus data and extend communication distance.

When there is an error, the bus response time will increase by 10-40 ms.

5.4 Handling of Safety Output Malfunctions

The transistor output (Q2, Q3) is -24 VDC (negative output), mainly used to control contactors and valves. This unique potential helps detect short circuits to ground or with other potentials.

Relay output contact capacity: AC-1/AC-15 250 V/1.5 A, DC-13 24 V/1.5 A.

If the output load exceeds the rated value, the internal protection will turn off the output and the Error LED will light up.

Equipment replacement and configuration migration

When Pluto units need to be replaced due to hardware failures or upgrades, they cannot be simply plugged in or unplugged, and consistency in program, address, and bus configuration must be considered.

6.1 Replace with the same model (without bus or bus model)

Record original configuration: Connect online through Pluto Manager and upload project files (. plp or. pl7). If communication is not possible, backup files need to be used.

Set up a new unit:

Install the new Pluto IDFIX (if any) to its original location.

If using IDFIX ROG, the program can be directly copied to the new unit.

Download program: Connect the new Pluto through a programming cable to download the project.

Verify I/O: manually trigger each safety input, observe the corresponding output action, and use Pluto Manager's online monitoring function to check the status.

6.2 Upgrade to different models (e.g. S20 → B20)

Due to possible variations in the number and types of I/O, it is important to note that:

I/O mapping adjustment: The IQ10-IQ17 of the original S20 may need to be remapped to the corresponding terminals of the new model.

Dynamic signal configuration: Retain the original signal type settings.

Bus address: If the original system uses a bus, the node address of the new Pluto must be consistent with IDFIX or software settings.

Program compatibility: Pluto Manager automatically checks if the feature block supports new hardware. It is recommended to compile and correct errors in offline mode first.

6.3 Using IDFIX ROG for Program Backup and Recovery

IDFIX ROG is a program storage device specifically designed for single Pluto systems. The steps are as follows:

Backup: Connect the IDFIX ROG to Pluto's ID terminal and 0V, and the program will automatically write to the IDFIX ROG after power on.

Recovery: Connect IDFIX ROG to the new Pluto, and the program will automatically write to the new unit after power on.

This method does not require a computer and is very suitable for quick on-site replacement.

6.4 Replacing Gateway (GATE Series)

The Pluto gateway (GATE-P2/D2/C2/E2) is used for communication with PROFIBUS, DeviceNet, CANopen, Ethernet, and other devices. Attention should be paid when replacing:

DIP switch settings: Node address, baud rate, etc. must be consistent with the original gateway.

Firmware version: Some gateways (such as GATE-E2) support web server configuration, and the IP address needs to be reset.

Bus filtering settings: If the original gateway has enabled bus bridging and filtering functions, it needs to be reconfigured on the new gateway.

Gateway integration and bus bridging

7.1 Overview of Gateway Models

Characteristics of Model Protocol

GATE-P2 PROFIBUS DP-V0 automatic detection baud rate (≤ 12 Mbit/s), address DIP switch (0-99)

GATE-D2 DeviceNet supports ODVA 2.0 and can serve as a CAN bridge to filter bus data

GATE-C2 CANopen complies with CiA DS-301 and can serve as a CAN bridge

GATE-E2 EtherNet/IP, PROFINET, Modbus TCP built-in web server, 10/100 Mbit/s

7.2 Data exchange capability

From Pluto to the higher-level PLC: Access Pluto's I/O and global variables (GM). Each gateway has a maximum of 64 Boolean values and 8 16 bit registers.

From the higher-level PLC to Pluto: Non safety control data can be written, and it also supports 64 Boolean values and 8 registers.

ABB provides functional blocks for mainstream PLCs (Siemens, Rockwell, etc.) to simplify integration.

7.3 Bus Bridge Function (GATE-D2/C2)

When the Pluto bus distance exceeds 600 meters or segmented isolation is required, the gateway can be configured as a bridge:

Two gateways are connected back-to-back (from one bus segment to another).

The built-in filter can prevent unwanted data from crossing bridges, reduce bus load, and allow for longer distances.

Security encoder application

Pluto combined with RSA 698 absolute encoder can achieve safe position and speed monitoring, suitable for robots, gantry frames, eccentric presses, etc.

Safe Encoder function block: reads an encoder and outputs position and velocity values. Node address and range need to be configured.

Safe Encoder Multiturn: Read two encoders, calculate the average, and monitor the difference (MaxDiff ≤ 2%). Output position and speed.

Encoder Cam function block: activates output Q based on position value, and can set minimum/maximum limits (supports crossing zero points).

Wiring: The encoder is directly connected to the Pluto bus, with a maximum of 16 encoders. Each encoder has a unique node address (set through DIP switches or software).

Common Problems and Maintenance Suggestions

Possible causes and solutions for the phenomenon

After Pluto is powered on, the Error LED stays on. The program is lost or there is a hardware failure. Download the program again; Check the power supply voltage; Replace unit

7-segment display of "E" or digital flashing bus communication error check for repeated terminal resistance, cable connection, and node address

Dynamic input always remains 0. Sensor serial sequence error, signal type mismatch. Confirm if sensor output is normal; Check the signal type settings (A/B/C and inversion) in Pluto Manager

The safety output cannot be set to ON. The reset condition is not met, and the dual channel difference timeout check reset button is pressed; Monitor TCfault or EDM feedback signals

Gateway without communication DIP switch setting error, inconsistent baud rate, check node address and baud rate; Check the grounding of the cable shielding layer

When the IQ terminal is used as an output, the indicator light does not light up. IQ is not configured as an output or load short circuit check Pluto Manager setting; Measure output voltage

Regular maintenance:

Check the response time of all safety inputs and outputs every six months to ensure compliance with safety distance calculations.

Use Pluto Manager's "monitoring" function to record changes in I/O status and proactively detect signal jitter.

For applications that use silent lights, regularly test the light disconnection detection function (through current monitoring or function block fault output).