Balluff BNS819-B03-R12-61-12-10 | Mechanical Multiple Position Switch — 3-Position Roller, Snap Contact, 6A/250VAC, 12mm Spacing, Aluminum Housing

Part Number: BNS819-B03-R12-61-12-10 Balluff Order Code: BNS0298 Manufacturer: Balluff GmbH Type: Mechanical multiple position limit switch Style: 61 Version: Snap contact Number of Switch Positions: 3 (roller plunger actuators) Plunger Style: Roller Spacing (T): 12 mm between switch positions Continuous Current: 6 A per switch position Rated Operating Voltage: 250 VAC per switch position Approach Speed: 60 m/min max Housing Material: Aluminium, anodised Dimensions: 79 × 48 × 63 mm Installation: Vertical Approach Direction: Longitudinal, parallel to attachment surface Operating Principle: 1–3 switch position: Mechanical (snap contact) Condition: New / Surplus

Overview

The Balluff BNS819-B03-R12-61-12-10 (order code BNS0298) is a three-position mechanical cam switch — a compact aluminium housing containing three independently actuated roller plunger switches at 12mm spacing, each with snap contact action.

The product category is sometimes labelled "multiple position limit switch" or "row position switch," but its physical function is specific: a linear or rotary actuating cam or dog passes along the sensor's length, pressing each of the three rollers in sequence as the machine element travels through its stroke.

Each roller actuates its own independent snap-contact switch at a defined position in that travel, providing three discrete position signals from one sensor body.

This design pattern serves a consistent application need in machine tool and automation engineering: confirming that a multi-position axis or clamping mechanism has reached one of several discrete positions, each of which requires a separate electrical confirmation signal.

Examples include a three-position tool turret where each station requires independent confirmation; a clamping cylinder that must confirm retracted, intermediate, and fully extended positions independently; and index tables where three angular positions each need separate position feedback signals for the machine's safety interlock logic.

The snap contact mechanism produces a crisp, low-bounce switching action as the roller is depressed by the passing actuator.

Snap contacts switch at a defined force threshold and provide a clean ON/OFF transition rather than the gradual resistance change of spring contacts — this characteristic makes them appropriate for machine control circuits where contact bounce or slow transitions could cause false signals in fast PLC scan cycles.

Key Specifications

Three Independent Positions — One Housing

The BNS819 series design combines three switch positions in a single housing rather than three separate limit switches mounted individually along the travel path.

This integration has direct maintenance and installation advantages.

In a single housing, the three roller positions are factory-set at 12mm spacing (the T dimension), which removes the field calibration task of positioning three individual switches at the correct spacings along a bracket.

When the housing is mounted and the actuating cam or dog is designed to the 12mm pitch, all three positions are automatically at the correct longitudinal positions.

In retrofit and maintenance scenarios, replacing a failed three-position switch assembly is a single part swap with one mounting operation and one cable reconnection — rather than three independent operations for three individually mounted switches.

For machine downtime calculations, this represents meaningful time savings when the switch is in an inconvenient location requiring significant disassembly to access.

Snap Contact Mechanism — Clean Switching at Defined Force

The snap contact (also described as "snap-action") mechanism stores mechanical energy in a spring that releases abruptly at a defined trigger point — the actuating force crosses a threshold, the spring snaps from one stable state to the other, and the contacts change state rapidly and cleanly.

The contact transition time is on the order of microseconds, which is fast enough to prevent the arc heating and bounce that slow, gradual contact motion would produce.

For machine tool control circuits where the position switch feeds a PLC input and the PLC scan reads the input state within 10ms, snap-contact switches provide the clean transition needed for reliable state reading.

A slow-acting switch's extended transition period can cause a PLC scan to read the intermediate state as either true or false unpredictably — snap contacts eliminate this ambiguity by transitioning faster than any reasonable PLC scan interval.

6A / 250VAC Rating — Direct Load Switching Capability

The 6A/250VAC rating of each switch position covers the current capacity to directly switch a significant range of industrial loads: relay coils, solenoid valve coils, indicator lamps, and PLC input modules all operate well within this rating.

For motor starting or other high-inrush loads, verify the inrush current against Balluff's contact endurance data — high-inrush loads reduce contact service life, and an intermediate relay is recommended when motor contactors or other high-inrush devices are connected directly to the contacts.

At 12V DC or 24V DC circuit voltages — common in PLC-based machine control systems — the switch's 250VAC/6A contact rating provides substantial margin over the actual load requirements. Standard 24V DC PLC input channels draw 5–15mA; the 6A rating provides a factor exceeding 400:1 over this load, ensuring contact wear at PLC input load currents is negligible throughout the switch's mechanical service life.

FAQ

Q1: What actuator configuration is required to engage all three roller positions?

The BNS819-B03-R12-61-12-10 has three roller plunger positions at 12mm centre spacing in a longitudinal arrangement, with the rollers accessible along the approach surface. The machine must provide an actuating cam or dog mounted on the moving element, with a profile length sufficient to press each of the three rollers as it travels through the switch body's span.

The cam width should be designed to fully depress the roller at each position and clear it before the next roller — the 12mm spacing defines the cam pitch requirement.

For approach parallel to the housing's long axis, the cam travels across all three positions in sequence.

Q2: What is the contact configuration (NO, NC, or both) of each switch position?

The snap contact version of the BNS819 series provides the standard contact configuration defined by Balluff for this series — typically a change-over (CO) contact providing both NO and NC outputs from each position, allowing the installer to use either contact logic at the control panel terminal.

Refer to Balluff's BNS0298 wiring diagram and terminal assignment documentation for the specific contact arrangement at each of the three switch positions and the terminal numbering for the housing's electrical connection.

Q3: Can the BNS819-B03-R12-61-12-10 be used with a rotary cam as well as a linear dog?

Balluff designs the BNS819 multiple position switch for longitudinal approach — the actuating element approaches parallel to the housing's attachment surface, travelling across the switch positions in sequence.

Rotary cam applications are possible if the cam's geometry presents each roller in turn at the correct approach angle and speed.

The maximum approach speed of 60 m/min (1 m/s) applies to the tangential speed of the cam at the roller contact point in rotary applications. Verify the cam profile geometry matches the roller plunger stroke and contact geometry before applying the switch to a rotary actuator.

Q4: Is the aluminium housing grounded, and does it need to be earthed separately?

The anodised aluminium housing of the BNS819 series is the structural enclosure for the switch mechanism.

In installations where the housing may accumulate static charge or is used in circuits where the housing could be at a potential (such as ungrounded machine frames), connecting the housing to protective earth via the mounting hardware is recommended practice per IEC 60204-1 for machine safety. 

Balluff's installation instructions for the BNS819 series provide the specific earthing guidance for the BNS0298 configuration.

Q5: How is the BNS819-B03-R12-61-12-10 connected electrically — what termination is provided?

The BNS0298 uses internal terminal connections within the housing — the "116" designation in the Balluff BNS series coding refers to a terminal compartment connection style, allowing field wiring to screw terminals inside the housing rather than a pre-wired cable or external connector.

The installer routes the control wiring through the housing entry point and connects to the numbered terminal positions corresponding to each switch position's contacts.

This termination method is common for fixed machine installations where the switch is permanently mounted and field replacement involves re-terminating at the housing terminal strip.