ABB CS31 distributed debugging

ABB CS31 distributed debugging

In large-scale production lines or distributed factory automation projects, connecting a large number of sensor and actuator signals to the same control cabinet often leads to complex wiring, high costs, and difficult troubleshooting. The ABB Procontic CS31 system adopts a decentralized architecture - the central unit can be installed in the main control cabinet, while the input/output units are distributed nearby and communicate through a simple twisted pair cable (RS485). This design can reduce wiring costs by up to 80% and support flexible expansion to up to 31 remote sites. This article is based on the original technical documentation of the CS31 system, which systematically explains the selection of central units, system bus installation specifications, address settings, bus refresh time calculation, and troubleshooting methods based on LED and diagnostic markers, providing on-site engineers with a practical engineering guide.

Overview and Architecture of CS31 System

1.1 Core advantages of the system

CS31 is an intelligent decentralized automation system, whose core design concept is to distribute the processing power of the controller on site. Compared with traditional centralized systems, CS31 has the following significant advantages:

The wiring cost has been significantly reduced: all remote I/O units are connected to the central unit through an RS485 bus, eliminating the need to individually pull wires for each sensor.

Modular expansion capability: The system can add new remote units at any time while running, and the central unit will automatically recognize them.

Transparent programming: In user programs, remote I/O channels are processed in the same way as centralized I/O, without the need for additional programming effort.

Built in diagnostic function: Each remote unit is equipped with a microprocessor, dedicated to managing input/output and diagnosis, and can quickly locate faults through the TEST button.

1.2 Application Scenarios

CS31 is particularly suitable for the following scenarios: sensors and actuators on distributed process lines (such as multiple workstations in packaging machinery), systems that require flexible expansion of switch values, and scenarios where I/O units are installed outside the control cabinet but the communication distance does not exceed 500 meters. In addition, the system may contain multiple central units, but only one serves as the master and the others as slaves. When bus communication is interrupted or the master station fails, each slave station can still continue to execute its own program to achieve emergency operation.

Central unit selection and characteristics

The CS31 system supports multiple central units, and engineers need to choose based on program capacity, I/O points, and functional requirements.

2.1 07 KR 31/07 KT 31 (2k instruction)

These two entry-level central units have a capacity of 2k instructions (approximately 8k bytes) and are suitable for small decentralized applications. Main features:

12 24V DC digital inputs

8 outputs (KR31 is a 2A relay output, KT31 is a 0.5A transistor output)

1 10kHz high-speed counting input

Built in RS232 serial port (can be set as programming, ASCII, or MODBUS master/slave)

Real time clock, lithium battery life of 10 years

Password protected user program

The working voltage can be selected from 24V DC, 120V AC, or 230V AC

When in use, the ECZ plug-in base should be inserted, and the unit address (0-61) should be set on the base through DIP switches. This model can operate as a CS31 bus master, slave, or independent controller.

2.2 07 KR 91 (7k instruction)

Provide larger program capacity (7k instructions/28k bytes), suitable for moderately complex applications:

20 digital inputs, 12 relay outputs

1 10kHz high-speed counting input

Battery pluggable (07 LE 90)

24V DC or 115/230V AC powered version

The 24V DC version comes with an additional parallel interface that can be connected to communication modules (such as 07 KP 90 RCOM)

The input of this model is divided into three electrically isolated groups, and the output is divided into three common terminal groups, with a maximum of four relay outputs per group. Attention: For versions powered by 24V DC output, when connecting inductive loads (such as DC relay coils), freewheeling diodes must be connected in parallel at both ends of the load.

2.3 07 KT 92/07 KT 93 (7k instruction+30k user data)

This is the most powerful CS31 central unit, suitable for complex applications:

07 KT 92: 12 digital inputs, 8 transistor outputs, 4 12 bit analog inputs (0~10V~20mA/0~5V), 2 12 bit analog outputs (-10~+10V), 1 50kHz high-speed counter

07 KT 93:24 digital inputs, 16 transistor outputs, 1 10kHz high-speed counter

Two RS232 serial ports (COM1 can be programmed or ASCII, COM2 is fixed as MMC)

07 KT 92 R262 and 07 KT 93 R171 versions have built-in ARCnet interface (BNC coaxial, 93 Ω, 2.5Mbit/s)

The user program can be modified online in RAM and saved to Flash EPROM after completion

Engineering selection suggestion: If analog processing is required, choose 07 KT 92; If a large amount of digital I/O is required and there is no demand for analog, choose 07 KT 93; If you need to access the ARCnet network, select the R262/R171 suffix version.

2.4 Other special units

07 GV 93: Three axis positioning module, receiving incremental encoder feedback (± 10V set value), with a maximum speed of 100m/min, supporting 300 positioning datasets/axes.

UCZA/UCZB: Early high-capacity central unit (8k/16k instructions), supporting SCZ bus expansion couplers.

PCZB/CS20:2k instruction compact unit with built-in high-speed counter.

CS31 System Bus (RS485) Installation Specification

The system bus is the core of the CS31 distributed architecture, and incorrect wiring can lead to unstable or complete communication interruption.

3.1 Bus cable specifications

Shielded twisted pair cables must be used, recommended models: ALCATEL MCX-T or DRAKKA dracoda 2903. Specific requirements:

Cross sectional area: 0.22~0.8 mm ² (AWG 24~18)

Stranded density:>10 twists/meter

Characteristic impedance: 100~150 Ω

Distributed capacitance:<150 nF/km

DC resistance: ≤ 100 Ω/km

3.2 Bus topology and terminal resistance

The CS31 bus adopts a master-slave architecture, with only one master station on a bus. The maximum number of stations is 31 slave stations+1 master station, and the maximum length between the two ends of the bus is 500 meters.

120 Ω, 1/4W terminal resistors must be installed at both ends of the bus (connected between BUS1 and BUS2 terminals). The following central units have built-in resistors: UCZA/UCZB, 07 CS 61, 35 CS 91, which must be connected at the end of the bus. For the 07 KR/KT series central unit, if it is located at the bus endpoint, an external 120 Ω resistor needs to be connected between terminals 1 (BUS2) and 2 (BUS1) of the ECZ base.

3.3 Shielding Grounding

The shielding layer should be continuously looped through the SHIELD terminals of all CS31 devices and only grounded directly near the main station. If there are strong noise sources (such as frequency converters, motors, etc.) inside the control cabinet, it is recommended to ground the shielding layer through a 1nF Y-class capacitor to avoid low-frequency ground loop currents.

Important rules:

All CS31 products installed in the same control cabinet must be connected to the same ground.

The grounding wire should be as short as possible (less than 25cm).

Connect cables with a cross-sectional area of at least 16mm ² between different control cabinets.

Noise components (frequency converters, motors) should not share grounding between two cabinets, and their grounding points should be close to the noise source itself.

3.4 Power grounding type

Select the appropriate grounding method based on the on-site power supply system:

IT system: The neutral point is not grounded, and the metal casing is grounded. In noisy environments, each control cabinet should use a shielded isolation transformer (even the 24V DC version requires it).

TT system: neutral point grounding, metal shell grounding. This is a conventional industrial power distribution method.

Address setting and I/O address mapping

4.1 DIP switch on ECZ base

All remote I/O units are installed on the ECZ plug-in base. The DIP switch on the base is used to set the unit address (group number):

Switch number function

Set the address from 2 to 7 (binary weighted: 32/16/8/4/2/1), ON=1

For the configurable I/O unit (ICS 08 L1): ON=all channels are forced to output, OFF=configured by the program

8 channel number offset: OFF=channel 00~07, ON=channel 08~15

Example of address calculation: Set DIP switches 2 (32), 3 (16), and 5 (4) to ON, then address=32+16+4=52.

4.2 I/O Address Structure in Central Unit

In the user program, the address format for remote I/O points is E xx, yy (input) or A xx, yy (output), where:

Xx: Unit address (group number, set by DIP switches 2-7)

YY: Channel number within the unit (00~15, affected by DIP switch 8)

For 07 KR 91/07 KT 92/07 KT 93 as the main station:

It is recommended to use even addresses (8,10,12... 60) for binary units

The simulation unit only allows the use of addresses 0-5

Switch 8 is recommended to be set to OFF (channels 00~07)

Note: If two remote units are set to the same address, the master station will consider them disconnected and report an FK3 type error (error identifier 15) when detecting signal conflicts.

Bus refresh time calculation

The master CPU polls all slave stations at a fixed cycle. The bus refresh time (T rb) depends on the number and type of slave stations. The calculation formula is:

For the 90 series main station (07 KR 91, etc.): T rb=T offset+T communication

For the 30 series main station (07 KR 31, etc.): T rb=T offset+T communication+n × 100 µ s

among which

T offset=2000 µ s (fixed)

N=Number of slave stations

T communication refers to the communication time of various types of slave stations, with typical values as follows:

Unit type communication time

07 KR/KT 31/91/92/93 (slave, default configuration) 750 µ s

ICSI 08 D1 (8 inputs) 323 µ s

ICSO 08 R1 (8 relay outputs) 260 µ s

ICSK 20 F1 (12 inputs/8 relay outputs) 452 µ s

ICSE 08 B5 (8 analog inputs, 12 bits) 1355 µ s

ICSA 04 B5 (4 analog outputs) 700 µ s

Calculation example: A 90 series master station with 1 ICSK 20 F1 (452 µ s)+1 ICSO 08 R1 (260 µ s)+1 ICSI 16 E1 (387 µ s)+1 ICFC 16 L1 (516 µ s)+1 ICSC 08 L1 (387 µ s). The sum of T communication is 2002 µ s, plus a T offset of 2000 µ s, resulting in T rb ≈ 4ms.

Programming and Debugging Tools

6.1 Programming software

907 PC 331: Used for 07 KR/KT 91/92/93 and 07 KR/KT 31, supports instruction lists, function block diagrams, and ladder diagrams, and can run on IBM compatible PCs.

907 PC 29: Used for PCZB and CS20.

TCZ handheld terminal: used for programming, testing, and diagnosis, capable of editing programs online or offline.

6.2 Terminal Mode

Connect VT100 terminal or PC (9600 baud, 8 data bits, no checksum, 1 stop bit) through RS232 serial port (COM1), and then enter<CR>, 1 (select TERMINAL), 2 (select CHAR.MODE), N (maintain baud rate) in order to enter terminal mode. Common commands:

G: Launch user program

A: Suspend user program

WARM: Hot Start

KALT: Cold Start

Z: Display variable status

Y: Force modification of variable values

D: Display program

S: Edit program

SP: Save the program to Flash EPROM

Remote unit diagnosis and troubleshooting

7.1 Use the TEST button for diagnosis

Each remote unit (I/O module) has a TEST button and LED indicator light on the front. Operation Method:

Press the TEST button, and the LED of the currently selected channel will flash (starting from channel 0).

Release the TEST button, and the diagnostic information for this channel will be displayed on LED 0-7 for approximately 3 seconds.

Press the TEST button again to switch to the next channel.

After pressing the last channel, pressing TEST again will perform a light test (all LEDs will light up), and then releasing the DIP switch settings on the ECZ base (LED 0 corresponds to switch 1, and so on).

Press and hold the TEST button for more than 10 seconds to clear all faults stored in the unit.

The meaning of LED display (taking ICS 08 L1 as an example):

LED 0 (Unit error): Internal error within the unit

LED 1 (Bus error): Bus communication error (unit did not receive a call from the master station)

LED 3 (Cut wire): Input or output disconnection (to be detected after configuration)

LED 4 (Overload): Overload

LED 5 (Short circuit): Short circuit

LED 6 (Output): This channel is configured for output

LED 7 (Input): This channel is configured as an input

7.2 Error Flags in the Central Unit

The CS31 central unit classifies errors into four levels (FK1~FK4) and stores them in specific flag bits:

Address for detailed information of error class meaning flag bits

FK1 fatal error (system operation is no longer safe) M 255,11 MW 254.00~07

FK2 serious error (user program may not run properly) M 255,12 MW 254,08~15

FK3 minor error (such as remote unit disconnection) M 255,13 MW 255.00~07

FK4 warning (such as output overload, disconnection) M 255,14 MW 255,08~15

FK3 Common Error Identification (MW 255.00):

15: Remote unit disconnected (at the same time MW 255.01=unit type, MW 255, 02=group number)

16: CS31 bus error (no remote units on the bus)

17: NCB/NCBR bus amplifier error

200: The set cycle time (KD 00,00) is too short, causing CPU overload

FK4 Common Error Identification (MW 255,08):

1: Internal error in remote unit

2: Input/output disconnection

4: Overload

8: Short circuit

Steps to eliminate errors:

Eliminate physical faults (repair broken wires, eliminate overload).

Use the CS31QU function block (in the user program) or MAIL command (terminal mode) to confirm the error.

Set the error flag (M 255,13 or M 255,14) to 0 in the program or perform a cold/hot start.

7.3 Status Word EW 07,15

EW 07, 15 is a comprehensive status word, meaning:

Bit 0:=1 indicates no FK2 type errors

Bit 1:=1 indicates (as a slave) that it has been included in the bus cycle by the master station

Bit 2:=1 indicates that the real-time clock is valid

Bit 3:=1 indicates that the battery is valid (voltage is normal)

Bit 8~15: The maximum number of remote units that have appeared on the bus since the last power on or cold start

Common faults and solutions

8.1 Communication Failure

Phenomenon: The BE (Bus Error) and RE (Remote Unit Error) LEDs on the central unit light up.

Possible reasons and solutions:

Bus disconnection or short circuit: Check the bus cable and measure whether there is a 120 Ω terminal resistance between BUS1 and BUS2.

A remote unit loses power or is damaged: Check the power LED of the unit. If the unit is normal but there is no communication, try unplugging the module again.

Address conflict: If two units are set to the same address, the main station will consider them as disconnected after detecting a signal conflict. Check the DIP switch settings on all ECZ bases.

The initialization time of the simulation unit is too long: The simulation unit takes a long time to initialize after being powered on. If the main station polls during this period, it will report a "no remote unit" error (FK3 code 16). The system constant KW 00,09 can be set to allow the master station to wait for a sufficient number of slave stations to go online before starting the user program.

8.2 Short circuit or overload of output unit

Phenomenon: The red LED K of 07 KT 92/93 lights up, and the corresponding output channel automatically shuts off.

Solution: Check if the output load exceeds the rated value (transistor output 0.5A or 2A, depending on the model). Whether the output automatically recovers after the short circuit is eliminated depends on the setting of the system constant KW 00,08. Default (KW 00,08=0) is automatic recovery; If set to 1, manual confirmation is required through the program or TEST button.

8.3 Program cannot start

Phenomenon: After power on or hot start, the RUN LED does not light up and the FK3 LED lights up.

Possible reasons:

KW 00, 09 is set to n, but the actual number of slave stations connected to the bus is less than n. At this time, the master station will not start the user program.

There is a syntax error in the user program (FK4 error identifier 131). Use the FEHLER command in terminal mode to view the error register, or download the program again through programming software.

The cycle time KD 00.00 is set too short, and the CPU cannot complete all tasks in one cycle (FK3 error 200). Solution: Increase KD 00,00 appropriately (at least 5ms integer multiple), and check the CPU load rate through the AL command (should be below 80%).

8.4 Input signal not detected

Phenomenon: The switch on site has been activated, but the corresponding E address value in the central unit remains unchanged.

Reason:

The input common terminal (ZP1. x) is not properly connected to 24V or 0V. Check the wiring.

The input signal voltage has not reached the threshold (ON threshold of 24V signal ≥ 15V, OFF ≤ 5V).

The position of DIP switch 8 on the ECZ base is incorrect, resulting in channel number offset (for example, when switch 8=ON, the actual physical input corresponds to E xx, 08~15, not E xx, 00~07).

The input delay setting is too long (default 8ms, can be changed through configuration). In rapid response situations, it can be adjusted to a smaller size.

Maintenance and spare parts recommendations

Battery replacement: 07 KR 91/07 KT 92/07 KT 93 uses 07 LE 90 lithium battery module with a lifespan of approximately 5000 hours (25 ° C). When replacing, be sure to keep the central unit powered on, otherwise the data in RAM (including some flags and real-time clock) will be lost. After inserting the new battery, check that the "Battery" red LED should turn off.

Grounding inspection: Check every six months whether the functional grounding terminal (terminal 18) on the ECZ base is reliably connected to the ground of the control cabinet, and the cross-sectional area of the grounding wire is not less than 6mm ². Special attention: The Faston terminal (6.3mm) should be directly connected to the grounding of the switchgear.

Environmental requirements: The operating temperature of CS31 equipment is 0-55 ° C, humidity is ≤ 75% (annual average), and there is no condensation. If installed in an environment with conductive dust or corrosive gases, the equipment must be placed in a cabinet with a higher protection level.

Spare parts inventory recommendation: For critical production lines, it is recommended to stock one central unit of the same model, at least one commonly used I/O remote unit (such as ICSI 16 D1 or ICSO 08 R1), and several ECZ bases.