When a small machine, conveyor, or building-services circuit outgrows a handful of relays but does not justify a full PLC panel, engineers usually reach for a micro logic relay (also called a smart relay or compact logic module). Two established families dominate this space: ABB's CL range, represented by the CL-LSR.C12DC2 (order number 1SVR440711R0300), and Siemens LOGO!, represented by the 12/24RCE (order number 6ED1052-1MD08-0BA2). This guide compares how each family is built, what it can do, and which one fits a given application so you can specify with confidence.
What Is a Micro Logic Relay?
A micro logic relay replaces an array of individual timing, counting, and interposing relays with one programmable DIN-rail device. You draw the circuit as simple contact-and-coil rungs on the front panel or in PC software, and the module carries out logic, on/off-delay timing, pulse generation, counters, and time-switch functions. The result is fewer components, simpler wiring, and an easier-to-modify machine sequence than hardwired relay logic.
The ABB CL Range at a Glance
The ABB CL range is built around compact logic relays intended for small and medium control tasks in buildings, lighting, air conditioning, and small standalone machines. The CL-LSR is the entry model: eight digital inputs, four relay outputs, a front display and keypad, and room for 128 rungs, each rung allowing three normally open or normally closed contacts in series plus one coil. Two of its inputs (I7, I8) can be used as analog inputs. Programming is done directly on the device with the display and keys, or from a PC using the CL-SOFT software. Higher CL display-system variants add a full graphic backlit display, up to 256 rungs, and CL-NET networking when an application grows.
The Siemens LOGO! Range at a Glance
Siemens LOGO! is the long-standing competitor to the CL range. The current 12/24RCE pairs a six-line LCD with cursor keys and offers eight digital inputs (four usable as 0–10 V analog inputs) and four relay outputs, with memory for 400 function blocks. Unlike the standalone CL-LSR, the base LOGO! module already includes an Ethernet port, an integrated web server, data logging, and a microSD card slot. The system is modularly expandable, so a project can grow to many more inputs and outputs through expansion modules.
Head-to-Head Comparison
| Feature | ABB CL-LSR.C12DC2 (1SVR440711R0300) | Siemens LOGO! 12/24RCE (6ED1052-1MD08-0BA2) |
|---|---|---|
| Device type | Compact logic relay with display and keypad | Compact logic module with display |
| Supply voltage | 24 V DC (20.4–28.8 V DC) | 12/24 V DC |
| Digital inputs | 8; I7/I8 usable as analog inputs | 8; 4 usable as 0–10 V analog inputs |
| Onboard outputs | 4 relay outputs | 4 relay outputs |
| Program capacity | 128 rungs (3 contacts + 1 coil each) | 400 function blocks |
| Front display | LCD with status indication and keypad | Six-line LCD with cursor keys |
| Programming software | CL-SOFT (CL-LAS.PS002) or on-device keys | LOGO! Soft Comfort or on-device keys |
| Onboard Ethernet | Not on the standalone CL-LSR; CL-NET on higher display-system variants | Yes, with integrated web server and data log |
| Expansion | Output expansion module (CL-LER.2O) and larger CL-LMR/CL-LER master units | Modular expansion modules across the LOGO! system |
| Mounting | DIN rail | DIN rail |
Programming and Usability
Both devices let you build a circuit without a separate programming device: you can wire power, walk through the contact/coil editor on the front panel, and run the machine. The CL-LSR adds a power-flow display that shows the circuit diagram live, which helps commissioning crews trace logic on the bench. For larger programs, CL-SOFT provides setup, storage, simulation, and documentation on a PC. LOGO! owners get the same drag-and-drop workflow in LOGO! Soft Comfort, and the built-in Ethernet and web server make it easier to expose the machine to a network, view data, or serve user-defined pages without an extra gateway.
Typical Use Cases
- Choose the ABB CL family when the project is a standalone sequencing, timing, or counting job in buildings, HVAC, lighting, or small machines, and when the panel benefits from a simple on-device editor and DIN-rail relay output switching.
- Choose Siemens LOGO! when the base module itself needs Ethernet, a web server, or data logging, or when the program comfortably exceeds a few dozen rungs and more function blocks are useful from day one.
- Common ground: both handle pumps, fans, conveyors, doors, and small packaging machines, and both avoid the cost of a full PLC for modest I/O counts.
For broader controller choices, browse our ABB range and the Siemens range, or review the wider PLC collection.
Lifecycle and Spare Parts
Both the ABB CL range and the Siemens LOGO! platform have been in service for many years, so installed bases are large and replacement units are frequently required. When a controller from a mature generation needs to be replaced, matching the exact order number avoids surprises in I/O count, supply voltage, and output type. Our Discontinued Products range and sourcing team can help locate these compact logic modules; send us the part number and we will confirm current availability and compatible alternatives.
Frequently Asked Questions
Is a micro logic relay the same as a PLC?
No. A micro logic relay is a compact, DIN-rail device that replaces small relay and timer circuits with on-panel or PC-programmed logic. A PLC is a more powerful modular system intended for larger, networked, or high-I/O control tasks.
Can the ABB CL-LSR.C12DC2 connect to Ethernet?
The standalone CL-LSR.C12DC2 is programmed from its front display or CL-SOFT and does not include an onboard Ethernet port. Higher CL display-system variants support CL-NET networking for applications that need it.
How many inputs and outputs does the LOGO! 12/24RCE have?
The base module provides eight digital inputs (four of them usable as analog) and four relay outputs. Additional I/O is added through LOGO! expansion modules.
Which one should I buy for a simple pump or conveyor sequence?
For a straightforward standalone timing or interlock task, either family will work. Choose the one whose software, supply voltage, and networking features match your panel, and verify the exact order number before ordering a replacement.
SHLY-PLC is an independent distributor of industrial automation parts. All brand names, model numbers, and trademarks are the property of their respective holders and are used only for identification and compatibility reference.