OMRON B7AP-M1 B7APMI Power Coupler, Moving Unit B7AP-M1 B7APM1

Omron B7AP-M1 | Moving Inductive Power Coupler — B7A Series, Wireless Signal & Power Transmission, 12 VDC, 38mA, IP67, 8mm Working Gap, Turntables & Robotic Hands

Overview

The Omron B7AP-M1 is the moving-side half of Omron's B7AP inductive power coupler pair. It mounts on the rotating or moving part of a machine — a turntable, a robotic wrist joint, a pallet that cycles through a conveyor system — and faces its stationary counterpart, the B7AP-S1, across an 8mm working gap.

Between these two cylindrical units, both switch signals and DC power cross the gap without physical contact, through electromagnetic induction, eliminating the slip rings and rotating electrical connectors that rotating machines would otherwise require.

The concept this system addresses is one of the genuinely difficult problems in industrial machine design: how to deliver electrical power and control signals to a part of the machine that rotates or translates continuously relative to the rest of the system.

Slip rings solve it mechanically but require maintenance — brushes wear, contacts oxidise, and the rotating interface becomes a reliability concern proportional to the speed and duty cycle it sees.

Wireless inductive coupling replaces the mechanical contact with an electromagnetic air gap, and the B7AP pair does this while staying within IP67 — a protection rating that tolerates direct water jets and temporary immersion, relevant in wet machining environments.

The B7AP-M1 is the moving unit specifically.

It receives power from the B7AP-S1 (which is connected to the 24V facility supply) via the inductive coupling, and uses that received power to energise the B7A Input Unit mounted on the moving side of the machine.

The B7A Input Unit reads signals from proximity sensors, mechanical switches, or other two-wire sensing devices mounted on the moving assembly, and transmits those signal states back through the inductive coupling to the B7A Output Unit on the stationary side, where they become digital inputs to the PLC or controller.

Key Specifications

How the System Works — Power and Signal Flow

The B7AP system operates through a dedicated electromagnetic coupling architecture that carries both power and signals across the air gap simultaneously, or signals alone if an independent power supply is provided on the moving side.

Power flow: The B7AP-S1 (stationary) generates the electromagnetic field from its 24V DC supply, transmitting power inductively across the 8mm gap to the B7AP-M1 (moving). The B7AP-M1 receives this power and supplies it at 12V DC to the connected B7A Input Unit and any two-wire sensing devices.

This means the sensors and input unit on the rotating side run without batteries and without any wired power connection from the stationary frame.

Signal flow: The B7A Input Unit on the moving side reads the states of connected sensing devices (ON/OFF signals only — the B7A system does not carry analog values).

It encodes these states and transmits them back through the inductive coupling to the B7A Output Unit on the stationary side, using a time-division multiplex scheme.

The B7A Output Unit presents the decoded signals as PLC-compatible logic outputs.

Transmission capacity: When the B7AP transmits both power and signals simultaneously, up to 10 input points can be active at once (limited by the 38mA power budget: 3.8mA × 10 points).

When an independent power supply is provided for the moving side, up to 16 input points can be transmitted.

8mm Working Gap — Installation Precision

The 8mm ±1.5mm working gap specification is the critical installation parameter. The two coupler faces must be separated by between 6.5mm and 9.5mm to maintain reliable transmission. Below 6.5mm, physical contact risk increases as the machine's movement tolerances are exercised; above 9.5mm, signal and power transmission quality degrades and may fail entirely.

Omron's B7AP-S1 includes a setup gauge — a physical tool supplied with the stationary unit to verify correct gap during installation.

The B7AP-M1 includes an operation indicator LED that illuminates when it is within the usable transmission range of the B7AP-S1, providing a real-time visual confirmation during machine setup and after any maintenance that involves moving either unit's mounting position.

Angular misalignment must also be controlled: the two coupler faces should be parallel within 2°. Exceeding this angular tolerance causes progressive signal degradation.

The M30 × 1.5 mounting thread with clamping nut provides secure positioning once the correct gap and alignment are set; the nut tightening torque is 39 N·m maximum.

Non-Metallic Object Pass-Through

The B7AP-M1 and B7AP-S1 transmit signals and power through non-metallic objects (plastic, glass, wood) interposed between the coupler faces.

This characteristic enables system designs where a physical barrier — a protective cover, an inspection window, a structural wall — must separate the stationary and moving sides while still allowing the signal path.

The gap between couplers (including the non-metallic material) must still remain within the 8mm working distance; the non-metallic material is effectively invisible to the electromagnetic field.

Metallic objects in the gap will disrupt or block transmission — the B7AP is not compatible with metal barriers between the coupler faces.

Similarly, parallel B7AP pairs must be spaced at least 60mm apart to prevent mutual interference between adjacent systems.

Applications

The B7AP system addresses the wiring challenges of several specific machine architectures:

Turntables and indexing tables: Pallet or workpiece turntables that rotate to present parts to multiple stations are the canonical B7AP application.

The moving side carries proximity sensors that detect part presence or pallet orientation; these signals must reach the controller without tangling wires.

Robotic wrists and end-effectors: Robotic arms that rotate their wrist joints beyond 360° cannot use cable routes that would wrap and break.

The B7AP inductive interface eliminates the winding cable problem, carrying gripper sensor signals and power across the rotating wrist joint.

Pallet conveyor systems: Pallets that carry their own sensors (part detection, reference pin presence) through a conveyor loop can use B7AP couplers at defined read/write positions along the conveyor, where the stationary unit aligns with the pallet's moving unit for data exchange without physical docking connectors.

FAQ

Q1: Can the B7AP-M1's 2m pre-wired cable be extended to reach the B7A Input Unit if the mounting distance requires it?

No. The B7AP-M1 specification explicitly prohibits extension cables on the moving unit's cable.

The 2m cable must be used as supplied.

If the B7A Input Unit cannot be positioned within 2m of the B7AP-M1 mounting location on the moving assembly, the mechanical layout must be revised so the input unit mounts closer to the coupler. 

The B7AP-S1 (stationary unit), by contrast, can use an extension cable of at least 0.75mm² conductor cross-section to reach its B7A Output Unit at distances up to 100m cable length.

Q2: The transmission delay is 19.2ms standard / 31ms maximum. Is this acceptable for PLC I/O where fast response is needed?

The 19.2ms standard delay represents the additional latency that the B7AP's time-division multiplex transmission adds to the signal path, on top of the PLC's scan cycle and standard I/O response times.

For most proximity sensor-based detection tasks — part presence, pallet orientation, workpiece identification — this delay is well within acceptable limits, as the mechanical events being sensed occur over timescales of hundreds of milliseconds or longer.

For applications requiring faster signal response (e.g., emergency stop detection, high-speed position sensing for motion control), the B7AP system's delay must be evaluated against the application's timing requirements, and faster alternatives such as direct wired connections may be needed.

Q3: What happens to the outputs on the B7A Output Unit if the B7AP-M1 moves out of range during machine operation?

When the B7AP-M1 moves outside the transmission range — either too far from the B7AP-S1 or misaligned beyond tolerance — the B7A Output Unit detects a transmission error. The error handling behaviour depends on the B7A Output Unit model selected: in LOAD-OFF models, all outputs turn OFF when a transmission error is detected, preventing unexpected load energisation.

In models with selectable error processing, the user configures the error response during commissioning. 

The error output signal on the B7A Output Unit also activates, which can be wired to the PLC as a diagnostic input.

Q4: The minimum coupler interfacing time is listed as 0.3 seconds. What does this mean operationally?

This is the minimum time the B7AP-M1 must remain within the transmission range of the B7AP-S1 for a complete and valid signal exchange to occur. If the moving side passes through the stationary unit's field faster than 0.3 seconds — as might happen on a high-speed indexing table where the pallet sweeps past rather than stopping — the system may not complete a full read cycle.

Machine designs that use the B7AP for reading moving sensors must ensure the coupler alignment time at each read position is at least 0.3 seconds, typically achieved by pausing the motion at each read station.

Q5: Is the B7AP-M1 compatible with three-wire (NPN or PNP) sensors, or only two-wire sensors?

The B7A Input Unit connected to the B7AP-M1 supports two-wire sensor connections only (two-wire proximity sensors, magnetic reed switches, mechanical limit switches). Three-wire NPN or PNP sensors cannot be connected to the standard B7A Input Unit on the B7AP-M1 side.

Three-wire sensor compatibility is available only if both the B7A Input Unit and B7A Output Unit are connected with independent power supplies — a configuration that differs from the standard B7AP power-supplied arrangement.

For applications requiring three-wire sensor inputs on the moving side, the independent power supply configuration must be planned and documented during the system design phase.