Omron C1000H/C2000H PLC Practical Guide

Omron C1000H/C2000H PLC Practical Guide

Product positioning and core features

Omron C1000H and C2000H are rack mounted PLCs designed for large-scale control systems in the 1980s and 1990s, widely used in fields such as factory automation, process control, and infrastructure. The C1000H supports a maximum of 1024 I/O points (expandable to 2048 points when using remote I/O), while the C2000H is based on 2048 point I/O. The most unique feature of C2000H is the Duplex dual machine redundancy system, which allows two CPUs to be installed on the same rack, one as the active master and the other as a hot standby. When the main CPU fails, it automatically switches, greatly improving system availability.

This article is based on the installation guide manual for C1000H/C2000H. From an engineering perspective, it systematically explains hardware component identification, power selection and current budgeting, rack installation and expansion, I/O wiring specifications, Duplex system configuration, as well as daily maintenance and troubleshooting.

Detailed explanation of system components

2.1 Rack type and slot configuration

C1000H and C2000H adopt a modular rack structure, with different backboards used for different systems.

C1000H CPU rack: Provides multiple models including 3, 5, 6, 8, and 9 I/O slots. The rightmost slot is typically used for power units, while some of the rightmost slots on the backplane (depending on the model) are dedicated to link units (PC Link, Host Link, SYSMAC NET Link, etc.). Common backboards: 3G2A5-BC081 (8 I/O slots+3 link slots), C500-BC091 (9 I/O slots+6 link slots), etc.

C2000H Simplex (single CPU) system: The CPU rack only has 6 I/O slots (model 3G2C5-BC061), which is two fewer than C1000H, but can still connect up to 7 expansion I/O racks.

C2000H Duplex system: There are no I/O units installed on the CPU rack (3G2C5-BC001), but two CPU units and one Duplex unit are installed. All I/O units are installed on an additional I/O rack (3G2C5-BI082), which is connected to the CPU rack via two dedicated cables.

Expansion I/O Rack: Used for expanding I/O points, models include 3G2A5-BI081 (8 slots), 3G2A5-BI051 (5 slots), and the C2000H dedicated 3G2C5-BI083 (with online replacement function).

2.2 CPU Unit

The CPU models for C1000H and C2000H are C1000H-CPU01-EV1 and C2000H-CPU01-EV1, respectively. The CPU itself does not come with power and memory, and requires separate configuration of power and memory packs. The front panel of the CPU provides:

Peripheral connector: can be directly inserted into a programmer (such as 3G2A5-PRO13-E), can be installed directly without cables

Memory pack slot (right side)

Run/stop switch and status indicator light

2.3 Power Supply Unit

The power unit is installed on the far right side of the rack (or in a dedicated slot). The output capacity of different models varies greatly, and the current available for I/O units in different systems is also different. This is the most critical data in engineering selection.

Power supply model Input voltage 5V Output capacity Available I/O current (C1000H) Available I/O current (C2000H Simplex) 24V output

3G2A5-PS221-E AC 100-120/200-240V optional 7A 4A 3A 0.8A

3G2A5-PS223-E AC Same as 12A 9A 8A None

3G2A5-PS211-E 24V DC 7A 4A 3A None

C500-PS213-E 24V DC 9A 6A 5A None

The same model can have different I/O currents under different system architectures, as the Duplex system requires additional consumption of backplane bus current. For example, PS221-E can use 4A in C1000H, but only 3A in C2000H Simplex.

I/O rack power supply (for expansion racks or C2000H Duplex I/O racks):

3G2A5-PS222-E (AC): 7A output, 6.5A available, with 24V 0.8A output

3G2A5-PS212-E (24V DC): 7A output, 6.5A available, no 24V output

Important: When calculating the total 5V consumption of each rack, you cannot just look at the nominal output capacity of the power supply, you must use the "available I/O current" value. CPU, I/O control unit, I/O interface unit, etc. also consume current and need to be included together.

2.4 I/O Control Unit and I/O Interface Unit

I/O Control Unit (3G2A5-II101): Installed in the leftmost I/O slot of the CPU rack, used to connect to the expansion I/O rack. Even in the C2000H Duplex system, it is installed on the I/O rack instead of the CPU rack.

I/O interface unit (3G2A5-II002): One must be installed in the leftmost slot of each expansion I/O rack for communication with the previous level.

2.5 Duplex Unit (C2000H Duplex only)

The Duplex unit (model not separately provided in the manual, but as a system component) is installed between two CPUs and provides the following functions:

System switch: Set the system to DPL (dual machine) or SPL (single machine)

Active CPU selection switch: Select the right CPU or left CPU as the active CPU

CPU ON/OFF switch: Each CPU has an independent switch and must be placed in the ON position to operate in dual machine mode

Status indicator light: indicates active/standby status, errors, etc

When dual machines are working, the active CPU executes programs and controls I/O, while the standby CPU only executes programs but does not output. When a fatal error occurs in the active CPU, the standby CPU automatically takes over. The faulty CPU can be replaced without shutting down (provided that the system has correctly configured the I/O Remove Unit).

2.6 I/O Remove Unit

C2000H unique features. Installed on racks that require online replacement of I/O units, it allows standard I/O units to be unplugged or inserted while the CPU is running (cannot be used for special I/O units). When using, the I/O unit of the rack needs to be "released" from the CPU control through a programmer, and then the terminal block and unit need to be physically disassembled. When replacing online, the output signal may generate short-term pulses, and attention should be paid to the influence of external devices.

2.7 Memory Pack

C1000H/C2000H uses a plug-in memory pack, which is inserted on the right side of the CPU. There are two types:

RAM package: readable and writable, data is held by the battery. Write protection switch (OFF=writable, ON=protective). Multiple models: 8K/16K/24K/32K characters.

ROM package: Using EPROM chips (27128, 27256, 27512150ns access time), data is permanently saved.

Special requirements for Duplex system: Two CPUs must be installed with memory packs of exactly the same specifications (with consistent capacity and write protection switch settings), otherwise a verification error will occur and the system cannot run. When using a RAM package to write a new program, the program on the active CPU will automatically write to the standby CPU (overwriting the original data).

Installation environment and mechanical specifications

3.1 Environmental conditions

Parameter requirements

Operating at an ambient temperature of 0-55 ℃ and storing at -20~65 ℃

Humidity 35%~85% RH, no condensation

Altitude ≤ 2000m

Pollution without corrosive gases and conductive dust

Vibration (mechanical durability) 10-25Hz, double amplitude 2mm, each axis lasting 2 hours

Vibration (electrical durability) 16.7Hz, double amplitude 1mm, 10 minutes on each of the three axes

Impact 98m/s ², 3 times in each direction

3.2 Installation direction and spacing

All racks must be installed vertically (text can be read normally). The CPU rack is located at the top, and the expansion rack is arranged in sequence below it.

The spacing between racks is 70-120mm for C1000H and C2000H Simplex systems, and 50-100mm is recommended for Duplex systems due to the large number of cables.

The total length of the extension cable shall not exceed 12m, and the maximum length of a single cable shall be 2m.

Install directly onto the control cabinet backboard, or use 35mm DIN rails (but rail installation has weak anti vibration ability, and it is recommended to fix it directly with screws in strong vibration environments).

3.3 Heat dissipation

Natural convection cooling does not require a forced fan, but if the temperature inside the control cabinet may exceed 55 ℃, a cooling fan must be installed.

Avoid installing PLC above heating equipment such as high-power transformers.

Ensure that the I/O cable layout does not block the heat dissipation holes.

3.4 Anti noise wiring

The distance between the I/O signal line and the high-voltage power line (>400V 10A or>220V 20A) must be ≥ 300mm; if they must be in the same cable tray, a metal partition with intermediate grounding should be used.

Use AWG14 (2mm ²) twisted pair shielded wire as the signal line.

The power line and signal line are laid separately in different cable trays/conduits.

The control cabinet should be reliably grounded (<100 Ω), and PLC grounding should not be shared with power equipment.

Power selection and current consumption calculation

This is the most error prone step in the installation of rack mounted PLCs. The 'available I/O current' of each rack power supply must be greater than the sum of 5V current consumption of all units on the same rack (including I/O units, special I/O units, link units, etc.).

4.1 Common I/O Unit 5V Current Consumption (excerpt)

Input unit:

3G2A5-ID112 (5-12V DC 16 points): 10mA

3G2A5-ID213 (12-24V DC 16 points): 20mA

3G2A5-ID215 (12-24V DC 32 point slow speed): 160mA

3G2A5-ID218 (12-24V DC 32 point fast): 260mA

3G2A5-ID212 (24V DC 64 point dynamic): 300mA

3G2A5-ID219 (24V DC 64 point static): 340mA

3G2A5-IA121 (100-120V AC 16 point): 180mA

3G2A5-IA222 (200-240V AC 16 point): 180mA

Output unit:

3G2A5-OC221 (relay 16 points): 100mA

3G2A5-OC223 (independent public 16 point): 100mA

3G2A5-OC224 (32 point relay): 200mA

3G2A5-OD411 (transistor 1A 16 points): 160mA

3G2A5-OD412 (transistor 0.3A 32 point): 230mA

3G2A5-OD212 (transistor 0.3A 32 point PNP): 230mA

3G2A5-OD213 (transistor 0.1A 64 point static): 460mA (+5mA/ON point)

3G2A5-OA121 (bidirectional thyristor 1A 16 points): 300mA

3G2A5-OA222 (bidirectional thyristor 1A 250V 16 point): 300mA

Special Unit:

3G2A5-CT001/012 high-speed counter: 330/550mA

3G2A5-PID01-E PID：1400mA

3G2A5-NC103-E Position Control 1 Axis: 1400mA

C500-ASC04 ASCII unit: 500mA

C500-LK009-V1 PC Link：900mA

C500-SNT31-V4 SYSMAC NET Link：1400mA

Link and Remote Unit:

3G2A5-LK010-(P)E I/O Link：600mA

C500-LK103(-P)/LK203 Host Link：1000mA

3G2A5-RM001- (P) EV1 optical remote master station: 700mA

4.2 Example of Current Calculation

A C1000H CPU rack uses PS221-E power supply (with available I/O current of 4A). Installation on the rack: CPU unit (approximately 1A), I/O control unit (approximately 0.3A), one ID218 (0.26A), one OD411 (0.16A), one OA222 (0.3A), one high-voltage meter CT012 (0.55A), and one Host Link (1.0A). Total ≈ 1+0.3+0.26+0.16+0.3+0.55+1=3.57A, less than 4A, feasible. But if another PID unit (1.4A) is added, it will exceed the limit.

Note: The PS222-E power supply for the expansion rack can provide 6.5A, which is more abundant than the power supply for the CPU rack.

I/O wiring specifications

5.1 Terminals and crimping terminals

Use ring clamp terminals and do not directly connect bare wires.

Terminal screw torque: 0.8 N · m.

The terminal block is detachable: simply loosen the upper and lower fixing screws to pull it out without disconnecting the wires.

5.2 DC Input Wiring

Pay attention to polarity. For DC input units, the COM termination method determines the Sink or Source input.

Two wire sensors (photoelectric switches, proximity switches) have leakage current. If the leakage current is greater than 1.3mA, a discharge resistor should be connected in parallel at the input end. Calculation formula:

Maximum resistance value R [k Ω]=7.2/(2.4 × I2 leak (mA) -3)

Minimum power W=2.3/R

5.3 Output wiring protection

Relay output:

Capacity: 2A at 250V AC or 2A at 24V DC (resistive load)

Inductive load (contactor, solenoid valve) lifespan: 100000 operations (AC 240V cos φ=0.4)

Surge absorbers (AC: RC absorbers) must be connected in parallel; DC: freewheeling diode)

Suggest adding 5-10A fuses every 4 output points

Transistor output:

Voltage: 12~48V DC, current specifications vary by model

Leakage current ≤ 0.1mA, residual voltage 1.4~1.5V

When driving TTL circuits, a pull-up resistor needs to be added

When driving surge loads such as incandescent lamps, the surge current can reach 10 times the rated current, and a current limiting circuit needs to be added

Bidirectional thyristor output:

Leakage current of 3~6mA may cause low current loads to not be completely turned off, and parallel discharge resistors are required

Built in non replaceable fuse (5A 250V)

5.4 Special precautions for AC input

The ON response time of the AC input unit is about 35ms, and the OFF response time is about 55ms, which is not suitable for high-speed counting or interruption.

If a reed switch is used as the input contact, its rated current must be ≥ 1A, otherwise surge may cause welding.

Key operating points of Duplex dual machine system

6.1 Initial Settings

Install identical memory packages (with the same capacity and write protection switch) in two CPUs.

Turn the system switch on the Duplex unit to the DPL position.

Turn the active CPU selection switch to RIGHT or LEFT.

Set the ON/OFF switches of both CPUs to the ON position.

After power on, the active CPU starts running and the standby CPU enters a hot standby state.

6.2 Fault Switching

If a fatal error occurs in the active CPU, the system automatically switches to Simplex mode, and the standby CPU becomes the active CPU and takes over control. At this point, the switch status on the Duplex unit no longer reflects the actual active CPU.

If the standby CPU fails, the system will automatically downgrade to Simplex mode, and the active CPU will continue to run.

The faulty CPU can be replaced during system operation (without power outage), but the program needs to be resynchronized after replacement.

6.3 Temporary switch to Simplex mode

When only one CPU is needed for program debugging or writing, the Duplex system can be switched to Simplex mode. Operating procedures:

Place the system in Program mode through the programmer.

Set the ON/OFF switch of the unused CPU to OFF.

The system will run on a single CPU.

Maintenance and troubleshooting

7.1 Regular inspection items

Project standard cycle

Power supply voltage AC: 85-132/170-264V; DC: 20.4-28.8V for six months

Environmental temperature 0-55 ℃ for half a year

Terminal screw torque 0.8 N · m for half a year

Expansion cable lock buckle tightened without looseness for six months

The battery voltage ALARM light does not light up every month

7.2 Fuse replacement

Power fuse (located on the circular knob on the side of the power unit):

Use a Phillips screwdriver to rotate counterclockwise by about 50 ° and remove the fuse holder.

Replacement specification: PS221/222/223 uses 3A 250V (6.35 × 32mm); PS211/212 uses 4A 125V; PS213 uses 6.3A 250V.

Rotate clockwise.

Output unit fuses (such as OD411, OA121, etc.):

After power failure, remove the output unit, open the casing, find the fuse (usually a 5 × 20mm glass tube) on the circuit board, replace it, and assemble it.

7.3 Battery Replacement

The CPU and some memory packs use lithium batteries (3G2A9-BAT08) with a lifespan of approximately 4 years (25 ℃). When the programmer displays "BATT LOW", it must be replaced within one week.

Steps (to be completed within 5 minutes):

Power off (if power has already been cut off, power on for at least 1 minute before turning off).

Open the battery compartment cover (on the right or below the CPU front panel).

Unplug the old battery connector and immediately insert the new battery.

Cover the compartment lid.

After powering on again, if there are still error messages, press the programmer CLR → FUN → MONTR to clear them.

7.4 Common Fault Diagnosis

Possible causes and solutions for the phenomenon

The POWER light is not on and there is no input power supply; Internal fuse breakage measurement power terminal voltage; Replace the fuse

RUN light not on, program error; No END instruction; The mode switch is in the Program check program; Switch to RUN mode

ALARM light constantly on, CPU hardware failure; I/O bus error check expansion cable connection; Replace the CPU

BATT LOW light on, battery voltage low, replace battery within one week

All I/O in the expansion rack is not working, and the I/O control unit or I/O interface unit is not installed; Loosening inspection of connecting cables II101 and II002; Re plug and unplug the connecting cable and lock it securely

Duplex system cannot start. Two CPU memory packets are inconsistent; Duplex unit switch setting error check for memory capacity and write protection switch; Confirm that the system switch is DPL and both CPUs are ON/OFF

The configuration of the "I/O VERITY ERROR" I/O unit during programming does not match the actual situation; Check if the current consumption exceeds the limit when the power capacity is insufficient; Check the I/O unit model and slot position