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Home / PLC / Domestic Economic SMART PLC: SR40, SR20, SR30, ST40, ST30, ST20 PLC Controllers

Attributes

Brand -
Category Electronics & Electrical / PLC
Origin -
Model Series SR40, SR20, SR30, ST40, ST30, ST20
Compatibility Siemens S7-200 SMART Architecture
Input Voltage AC 85-264V or DC 24V (Model Dependent)
Digital Inputs 12 to 24 points depending on model
Digital Outputs Relay or Transistor (Source/Sink)
Communication Ports Integrated RS485 and Ethernet (PROFINET)
Programming Software Compatible with STEP 7-Micro/WIN SMART
Mounting Type Standard DIN Rail 35mm
Operating Temperature -10°C to +55°C
Warranty Period 12 Months Manufacturer Warranty

6 reviews

A

Anonymous

Mar 29, 2026

Rating: 5/5

Fast shipping and good packaging

Ordered ten SR20 units for a client project. They arrived well-packaged and programmed easily. The terminal blocks are sturdy and easy to wire.

A

Anonymous

Mar 25, 2026

Rating: 5/5

Reliable and robust

Been running the SR30 in a dusty workshop environment for six months without a single glitch. The relay outputs handle our solenoid valves effortlessly.

A

Anonymous

Mar 25, 2026

Rating: 4/5

Solid performance for the price

These controllers offer about 80% of the premium brand features at half the cost. For non-critical applications, this is the smartest economic choice available.

A

Anonymous

Mar 25, 2026

Rating: 4/5

Great value for small automation projects

The ST20 model works perfectly for our packaging machine. Setup was quick using the standard software. Only giving 4 stars because the manual could be more detailed in English.

A

Anonymous

Mar 12, 2026

Rating: 5/5

Excellent communication features

The built-in Ethernet port on the ST40 makes HMI integration incredibly fast. We connected it to our SCADA system in under an hour. Highly recommended for modernizing plants.

A

Anonymous

Mar 11, 2026

Rating: 5/5

Perfect replacement for legacy systems

We used these SR40 units to upgrade an old production line. The compatibility with existing Siemens code was seamless, and the price point made it feasible to replace all controllers at once.

5 FAQ

Q: Is there a battery required to retain the program?

A: No, these SMART PLCs utilize non-volatile memory (EEPROM) to retain your program and data permanently without the need for a backup battery.

Q: Can I use the original Siemens STEP 7-Micro/WIN SMART software to program these?

A: Yes, these PLCs are fully compatible with the standard STEP 7-Micro/WIN SMART programming environment, allowing you to use existing projects with minimal changes.

Q: Does the SR40 model support analog expansion modules?

A: Yes, the SR40 supports various analog expansion modules for temperature, voltage, and current signals, expanding its I/O capabilities significantly.

Q: Can I connect multiple PLCs via RS485 for Modbus communication?

A: Absolutely. The integrated RS485 port supports Modbus RTU protocol, allowing you to network multiple units as masters or slaves easily.

Q: What is the difference between the SR and ST series?

A: The 'SR' series features Relay outputs suitable for switching AC or DC loads, while the 'ST' series uses Transistor outputs designed for high-speed DC switching and pulse generation.

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