Relay Output Programmable Logic Controllers (PLC)
Last Updated: January 16, 2025 Reviewed by: Jon Lowy, consulting engineer
Description
Relay Output Programmable Logic Controllers (PLCs) are devices used in industrial control systems to manage and automate processes. They are designed to receive inputs, process them according to a programmed logic, and then produce outputs. The relay outputs in these PLCs are typically used to control devices that require higher voltages and currents, as they provide electrical isolation between the PLC and the controlled devices.
Working Principle
Relay Output PLCs operate by using relays to switch power loads. The PLC's central processing unit (CPU) executes a stored logic control program, which determines when certain events should occur based on inputs received from sensors. The relays in the PLC are driven by the output signals from the CPU, which energize the relay coils to open or close contacts, thereby controlling the connected devices. This setup allows for flexible control of various processes, making relay output PLCs useful for applications that require switching of high-power devices.
Applications
Relay Output PLCs are commonly used in applications where high-power devices need to be controlled. For example, they can be used in manufacturing plants to control motors, pumps, and other heavy machinery. They are also suitable for applications that require switching of high-voltage lighting systems or heating elements in industrial settings.
Advantages over other Programmable Logic Controllers (PLC)
Relay Output PLCs offer the advantage of handling higher voltages and currents compared to solid-state output PLCs. This makes them ideal for applications involving high-power devices. Additionally, the isolation provided by the relay contacts enhances safety by preventing electrical interference between the PLC and the controlled devices.
Limitations
One limitation of Relay Output PLCs is their slower switching speed compared to solid-state outputs. This can be a drawback in applications requiring rapid switching. Additionally, the mechanical nature of relays means they are subject to wear and tear, which can lead to maintenance issues over time.
Considerations
When considering Relay Output PLCs, it is important to evaluate the initial costs, which can be higher due to the need for robust relays capable of handling high power. Operating expenses may also be higher due to the potential need for more frequent maintenance and replacement of worn-out relays. However, their durability and ability to handle high-power applications can offset these costs in the right scenarios. Accuracy in control is generally reliable, but the mechanical nature of relays should be considered in applications requiring precise timing.
from RS Components, Ltd.
Mini-PLC STG-580 MOD [See More]
- Output: Relay Output; Frequency or Pulse; Digital, PWM, Solid State
- Outputs: 6
- Inputs: 5
- Input: DC Input; Analog Input; Analogue, DC Digital
from Heilind Electronics, Inc.
PLC,CD12,8I/4O 8A RLY,24VDC, LCD DSPLY,MILLENIUM 3 [See More]
- Output: DC Output; Relay Output
- Outputs: 4
- Inputs: 8
from DigiKey
OPTA RS485 [See More]
- Output: Relay Output
- Outputs: 4
- Inputs: 8
- Input: Analog Input; Digital
from Allen-Bradley / Rockwell Automation
Controller, 8 110-120V AC Inputs, 4 configurable analog input with thermistor voltage reference out, 7 Relay Output, 1 Analog Output, Embedded Ethernet Port and RS-232/485 non-isolated Serial port, Embedded RTC, MicroSD Card support, 2 Plug-In slots, with RTB terminals [See More]
- Output: Relay Output
from ifm efector inc.
For simple control functions in vehicles and mobile machines. With many multifunctional configurable input and output channels. High-performance CAN interfaces for various communication tasks. For use in driver's cabin and control cabinet. Freely programmable to IEC 61131-3 with CODESYS 2.3. From... [See More]
- Output: Relay Output; Analog Output
- Input: Analog Input; Frequency or Pulse; Resistance
- Maximum Channels: 14
- Network Options: CANbus
from RS Components, Ltd.
Mini-PLC STG-680 MOD [See More]
- Output: Relay Output; Frequency or Pulse; Digital, PWM, Solid State
- Outputs: 10
- Inputs: 10
- Input: DC Input; Analog Input; Analogue, DC Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 24VDC [See More]
- Output: Relay Output
- Outputs: 4
- Inputs: 6
- Input: Digital
from Allen-Bradley / Rockwell Automation
Micro850 Controller, 14-120V AC Input, 10-Relay Output Controller [See More]
- Output: Relay Output
from RS Components, Ltd.
Mini-PLC STG-700 STEP [See More]
- Output: Relay Output; Digital, Power Stepper Motor, Solid State
- Outputs: 6
- Inputs: 4
- Input: DC Input; Analog Input; Analogue, DC Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 24VDC [See More]
- Output: Relay Output
- Outputs: 6
- Inputs: 8
- Input: Digital
from Allen-Bradley / Rockwell Automation
Micro850 Controller, 14-24V DC/V AC Input, 10-Relay Output Controller [See More]
- Output: Relay Output
from RS Components, Ltd.
FX3S CPU 24VDC 16/14 I/O [See More]
- Output: Relay Output; Relay
- Outputs: 14
- Inputs: 16
- Input: Sink, Source
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 24VDC [See More]
- Output: Relay Output
- Outputs: 6
- Inputs: 8
- Input: Digital
from Allen-Bradley / Rockwell Automation
Micro850 Controller, 28-120V AC Input, 20-Relay Output Controller [See More]
- Output: Relay Output
from RS Components, Ltd.
FX3S CPU 24VDC 6/4 I/O [See More]
- Output: Relay Output; Relay
- Outputs: 4
- Inputs: 6
- Input: Sink, Source
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 24VDC [See More]
- Output: Relay Output
- Outputs: 4
- Inputs: 6
- Input: Digital
from Allen-Bradley / Rockwell Automation
Micro850 Controller, 28-24V DC/V AC Input, 20-Relay Output Controller [See More]
- Output: Relay Output
from RS Components, Ltd.
FX3S CPU 24VDC 8/6 I/O [See More]
- Output: Relay Output; Relay
- Outputs: 6
- Inputs: 8
- Input: Sink, Source
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 24VDC [See More]
- Output: Relay Output
- Outputs: 6
- Inputs: 8
- Input: Digital
from Allen-Bradley / Rockwell Automation
1763 MicroLogix 1100 System, MicroLogix 1100, 120/240V ac power, (10) 120V ac digital inputs, (2) 10V analog inputs, (6) relay outputs [See More]
- Output: Relay Output
- Input: AC Input
- Maximum Channels: 10
- Computer Interface Options: Ethernet Port and Isolated RS-232/RS-485 combo port
from RS Components, Ltd.
FX3S CPU 24VDC 12/8 I/O [See More]
- Output: Relay Output; Relay
- Outputs: 8
- Inputs: 12
- Input: Sink, Source
from DigiKey
Programmable Logic Controller (PLC) Panel Mount 24VDC [See More]
- Output: Relay Output; Frequency or Pulse; Transistor Output; PWM
- Outputs: 6
- Inputs: 8
- Input: Digital
from Allen-Bradley / Rockwell Automation
1762 MicroLogix 1200 System, MicroLogix 1200, 120/240V ac power, (14) 120V ac digital inputs, (10) relay outputs [See More]
- Output: Relay Output
- Input: AC Input
- Maximum Channels: 14
- Computer Interface Options: RS-232C Port
from RS Components, Ltd.
FX3S CPU 100-240VAC 16/14+2 I/O [See More]
- Output: Relay Output; Relay
- Outputs: 14
- Inputs: 16
- Input: Sink, Source
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 12VDC [See More]
- Output: Relay Output
- Outputs: 6
- Inputs: 8
- Input: Digital
from Allen-Bradley / Rockwell Automation
1762 MicroLogix 1200 System, MicroLogix 1200, 120/240V ac power, (24) 120V ac digital inputs, (16) relay outputs [See More]
- Output: Relay Output
- Input: AC Input
- Maximum Channels: 24
- Computer Interface Options: RS-232C Port
from RS Components, Ltd.
em4 local nano-PLC, B26-ET, 24 VDC [See More]
- Output: Relay Output; Frequency or Pulse; PWM, Relay
- Outputs: 8
- Inputs: 12
- Input: Analog Input; Analogue, Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 24VDC [See More]
- Output: Relay Output
- Outputs: 4
- Inputs: 6
- Input: Digital
from Allen-Bradley / Rockwell Automation
MicroLogix 1400, 20 digital 120V ac inputs, 12 Relay outputs, 110/240V ac power [See More]
- Output: Relay Output
- Input: AC Input
- Maximum Channels: 20
- Computer Interface Options: Ethernet Port, Isolated RS232/485 and Non-Isloated RS232C Serial Ports.
from RS Components, Ltd.
em4 B26-ET Starter Kit, glossy black [See More]
- Output: Relay Output; Frequency or Pulse; PWM, Relay
- Outputs: 8
- Inputs: 12
- Input: Analog Input; Analogue, Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 100 ~ 240VAC [See More]
- Output: Relay Output
- Outputs: 6
- Inputs: 8
- Input: Digital
from RS Components, Ltd.
Logic Controller STG-560 CAN [See More]
- Output: Relay Output; Frequency or Pulse; Digital, PWM, Solid State
- Outputs: 5
- Inputs: 5
- Input: Analog Input; Analogue, Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 24VDC [See More]
- Output: Relay Output
- Outputs: 6
- Inputs: 8
- Input: Digital
from RS Components, Ltd.
Logic Controller STG-660 CAN [See More]
- Output: Relay Output; Frequency or Pulse; Digital, PWM, Solid State
- Outputs: 9
- Inputs: 10
- Input: Analog Input; Analogue, Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 100 ~ 240VAC [See More]
- Output: Relay Output
- Outputs: 14
- Inputs: 16
- Input: Digital
from RS Components, Ltd.
Easy control Relay outputs. [See More]
- Output: Relay Output; Relay
- Outputs: 6
- Inputs: 12
- Input: Analog Input; Analogue, Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 24VDC [See More]
- Output: Relay Output
- Outputs: 14
- Inputs: 16
- Input: Digital
from RS Components, Ltd.
Logic Controller STG-800 [See More]
- Output: Relay Output; Frequency or Pulse; Digital, PWM, Solid State
- Outputs: 9
- Inputs: 5
- Input: Analog Input; Analogue, Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 100 ~ 240VAC [See More]
- Output: Relay Output
- Outputs: 28
- Inputs: 32
- Input: Digital
from RS Components, Ltd.
Logic Controller STG-810 [See More]
- Output: Relay Output; Frequency or Pulse; Digital, PWM, Solid State
- Outputs: 9
- Inputs: 5
- Input: Analog Input; Analogue, Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 24VDC [See More]
- Output: Relay Output
- Outputs: 28
- Inputs: 32
- Input: Digital
from RS Components, Ltd.
Logic Controller STG-820 [See More]
- Output: Relay Output; Analog Output; Analogue, Digital, Solid State
- Outputs: 9
- Inputs: 3
- Input: Analog Input; Analogue
from DigiKey
Programmable Logic Controller (PLC) Chassis Mount, DIN Rail 24VDC [See More]
- Output: Relay Output; Transistor Output; PWM
- Outputs: 10
- Inputs: 16
- Input: Analog Input; Digital
from RS Components, Ltd.
Logic Controller STG-850 [See More]
- Output: Relay Output; Frequency or Pulse; PWM, Solid State
- Outputs: 9
- Inputs: 10
- Input: Analog Input; Analogue, Digital
from DigiKey
Programmable Logic Controller (PLC) Chassis Mount, DIN Rail 24VDC [See More]
- Output: Relay Output; Transistor Output; PWM
- Outputs: 10
- Inputs: 16
- Input: Analog Input; Digital
from RS Components, Ltd.
PLC, 16 Dig Inputs, 8 Rly Outputs, RS485 [See More]
- Output: Relay Output; Relay
- Outputs: 8
- Inputs: 16
- Input: Digital
from DigiKey
Programmable Logic Controller (PLC) Chassis Mount, DIN Rail 24VDC [See More]
- Output: Relay Output; Transistor Output; PWM
- Outputs: 10
- Inputs: 16
- Input: Analog Input; Digital
from RS Components, Ltd.
PLC, 16 Dig Inputs, 8 Rly Outputs, RS485 [See More]
- Output: Relay Output; Relay
- Outputs: 8
- Inputs: 16
- Input: Digital
from DigiKey
Programmable Logic Controller (PLC) Chassis Mount, DIN Rail 24VDC [See More]
- Output: Relay Output; Transistor Output; PWM
- Outputs: 10
- Inputs: 16
- Input: Analog Input; Digital
from RS Components, Ltd.
PLC, 16 Dig Inputs, 8 Rly Outputs, RS485 [See More]
- Output: Relay Output; Relay
- Outputs: 8
- Inputs: 16
- Input: Digital
from DigiKey
Programmable Logic Controller (PLC) Chassis Mount, DIN Rail 24VDC [See More]
- Output: Relay Output; Transistor Output; PWM
- Outputs: 10
- Inputs: 16
- Input: Analog Input; Digital
from RS Components, Ltd.
PLC. Starter Kit, MilleniumEVO, Ethernet [See More]
- Output: Relay Output; Relay
- Outputs: 8
- Inputs: 16
- Input: Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 24VDC [See More]
- Output: Relay Output
- Outputs: 16
- Inputs: 24
- Input: Digital
from RS Components, Ltd.
Logic Module EASY-E4-UC-12RC1 [See More]
- Output: Relay Output; Relay
- Outputs: 4
- Inputs: 8
- Input: Analog Input; Analogue, Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 100 ~ 240VAC [See More]
- Output: Relay Output
- Outputs: 16
- Inputs: 24
- Input: Digital
from RS Components, Ltd.
Logic Module EASY-E4-UC-12RCX1 [See More]
- Output: Relay Output; Relay
- Outputs: 4
- Inputs: 8
- Input: Analog Input; Analogue, Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 24VDC [See More]
- Output: Relay Output
- Outputs: 16
- Inputs: 24
- Input: Digital
from RS Components, Ltd.
Logic Module EASY-E4-UC-16RE1 [See More]
- Output: Relay Output; Relay
- Outputs: 8
- Inputs: 8
- Input: Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 24VDC [See More]
- Output: Relay Output
- Outputs: 8
- Inputs: 8
- Input: Digital
from RS Components, Ltd.
MilleniumEVO KIT, Smart Relay with embed [See More]
- Output: Relay Output; Relay
- Outputs: 8
- Inputs: 12
- Input: Analog Input; Analogue, Digital
from DigiKey
Programmable Logic Controller (PLC) DIN Rail 24VDC [See More]
- Output: Relay Output; Transistor Output
- Outputs: 16
- Inputs: 24
- Input: Analog Input; Digital
from Iwaki America and Walchem, IWAKI America Inc
Walchem ’s WIND WebMaster ® sets a new standard for Industrial Water Treatment Controllers. The WIND WebMaster ® has a flexible multi-input/output platform, a wide range of analytical sensor measurement capabilities, and an extensive assortment of integrated communications and data... [See More]
- Output: Relay Output; Analog Output (optional feature)
- Inputs: 15
- Total Points: 23
- Outputs: 8
from STW Technic
Designed for harsh environments, freely programmable [See More]
- Output: DC Output; Relay Output; Analog Output; PWM
- Inputs: 24
- Total Points: 36
- Outputs: 12
from Mitsubishi Electric Automation, Inc.
The FX3G is an introductory compact PLC and is the newest addition to the FX3 series, designed for simple yet performance-critical applications. Incorporating innovative FX3 series technology the customer is presented with a suite of benefits. Features: • 3rd Generation Compact PLC. •... [See More]
- Output: Relay Output; Transistor Output
- Inputs: 36
- Total Points: 60
- Outputs: 24
from Mitsubishi Electric Automation, Inc.
The FX3U is the original dual system-bus, high-speed, fully expandable compact PLC designed to seamlessly control communication, networking, analog, and positioning systems. With a maximum of 384 controllable local and networked I/O via CC-Link/AS-i, the FX3U uses its power and flexibility to... [See More]
- Output: Relay Output; Transistor Output
- Inputs: 64
- Total Points: 128
- Outputs: 64
from Mitsubishi Electric Automation, Inc.
The FX3UC is the new ultra-compact high speed, fully expandable PLC. Based on 24V DC power and using connector-type transistor I/O, the FX3UC is designed for space conscious and modular applications. Created inline with the FX3U series, the FX3UC incorporates such attributes as built-in high speed... [See More]
- Output: Relay Output; Transistor Output
- Inputs: 48
- Total Points: 96
- Outputs: 48
from Mitsubishi Electric Automation, Inc.
The FX1N is an introductory micro PLC meant for simple yet performance-critical applications. With internal positioning capabilities, comprehensive expansion options, and a battery-less maintenance-free design, the FX1N provides a competitive answer for controlling systems with up to 128 I/O. [See More]
- Output: Relay Output; Transistor Output
- Inputs: 36
- Total Points: 60
- Outputs: 24
from Mitsubishi Electric Automation, Inc.
The FX3S is the fit-and-forget PLC solution for space and cost conscious applications requiring up to 30 I/O. This minimum-expandability, battery-less maintenance free controller is perfect for handling straightforward processes and can be hidden away in locations without regular maintenance... [See More]
- Output: Relay Output; Transistor Output
- Expandable: Expandable
- Total Points: 30
- Input: DC Input
from Mitsubishi Electric Automation, Inc.
The FX1S is the fit-and-forget PLC solution for space and cost conscious applications requiring up to 30 I/O. This minimum-expandability, battery-less maintenance free controller is perfect for handling straightforward processes and can be hidden away in locations without regular maintenance... [See More]
- Output: Relay Output; Transistor Output
- Inputs: 16
- Total Points: 30
- Outputs: 14
from Mitsubishi Electric Automation, Inc.
The L Series is Mitsubishi's newest controller line, donning an innovative and easy-to-expand rack-free design. The single-CPU architecture includes built-in Ethernet and Mini-USB interfaces, a SD/SDHC memory card slot for program storage and data logging, and 24 I/O for positioning and high-speed... [See More]
- Output: Relay Output; Transistor Output
- Inputs: 10
- Total Points: 18
- Outputs: 8
from Mitsubishi Electric Automation, Inc.
The Alpha2 is a controller designed to address simple control applications at the lower end of the industrial and commercial control markets. With simple analog processing integrated, a straightforward programming style and a built-in display, the Alpha 2 is a highly affordable control solution. [See More]
- Output: Relay Output
- Inputs: 15
- Total Points: 24
- Outputs: 8