Siemens 3TK2834-1BB40 Safety Switch / Relay Module for Machine Safety Circuits

Product Overview

The Siemens 3TK2834-1BB40 is a safety relay module (also referred to as a safety switch) designed for monitoring emergency stop circuits, safety gates, and light curtains in industrial machinery. It complies with safety standards up to Performance Level e (PL e) and SIL 3 when configured appropriately. The module operates on 24 V AC/DC and features two safety outputs (redundant) and auxiliary signaling contacts. It is part of the SIRIUS 3TK28 series of safety relays, known for compact design and easy wiring.

Key Features of 3TK2834-1BB40

The relay module has 4 safety inputs that can be configured for single or dual-channel operation with or without cross-circuit detection. It provides two normally open safety contacts (redundant) and one auxiliary normally closed contact for status monitoring. The unit includes a feedback loop for monitoring external contactors (EDM). It features a removable terminal block for easy replacement and LED indicators for power, channel status, and fault. The module uses a start-up test that requires manual reset (or automatic) depending on wiring.

The 3TK2834-1BB40 is rated for a switching capacity up to 5 A per safety contact at 230 V AC. It has a response time of less than 20 ms. The device is approved for use in safety-related applications per ISO 13849-1 and IEC 61508. It operates in ambient temperatures from -25°C to +60°C and mounts on a 35 mm DIN rail. The power consumption is 3 W typical. The part number 3ZX1012-0TK28-7CA1 may refer to a related accessory or documentation.

Technical Specifications

• Manufacturer: Siemens AG

• Part Numbers: 3TK2834-1BB40, 3ZX1012-0TK28-7CA1

• Series: SIRIUS 3TK28

• Product Type: Safety Relay / Safety Switch

• Supply Voltage: 24 V AC/DC (±10%)

• Power Consumption: 3 W (max)

• Number of Safety Inputs: 4 (dual-channel configurable)

• Safety Outputs: 2 NO (redundant, 5 A @ 230V AC)

• Auxiliary Output: 1 NC (signaling)

• Feedback Input (EDM): Yes

• Safety Level: PL e (EN ISO 13849-1), SIL 3 (IEC 61508)

• Response Time: < 20 ms

• Terminal Type: Removable screw terminals

• Operating Temperature: -25 to +60 °C

• Degree of Protection: IP20

• Mounting: DIN rail (35 mm)

• Certifications: TÜV, CE, cULus

Functional Description

The safety relay monitors the status of emergency stop buttons or guard switches connected to its inputs. When both channels (e.g., dual-channel NC contacts) are closed and the start button is pressed, the relay energizes its two internal safety contacts, allowing power to flow to the machine's contactors. If any safety input opens (e.g., emergency stop pressed), the safety contacts drop out instantly. The feedback loop monitors external contactors to ensure they have actually opened. The auxiliary NC contact provides a signal to a PLC for status.

Applications

The 3TK2834-1BB40 is used in machine tools, packaging machinery, conveyor systems, and robotics to implement emergency stop circuits and guard door interlocking. It is a drop-in replacement for failed safety relays in existing Siemens-controlled equipment.