Magnetic Cable Connector Guide: Designing the Complete Assembly

• The magnetic cable as a complete assembly
• Guidance, compression and conduction
• Six parts of the cable assembly
• Choosing the contact count
• Length, conductors and end-to-end mapping
• Selecting the opposite termination
• Validation before production
• Inputs for a dedicated cable design

A magnetic cable assembly combines a guided contact head, conductive spring contacts, cable conductors and a defined opposite termination. Select it as a complete power-and-signal interface: contact functions, wire size, length, retention and validation all need to suit the OEM device.

The magnetic cable as a complete assembly

The mating interface typically has a device-side receptacle and a magnetic head on the cable. Select and verify the two as a matching pair.

A typical engagement sequence is:

1. Magnetic attraction assists placement of the mating pair.

2. The spring contacts compress against matching surfaces.

3. The engaged contacts provide the assigned supply, return, data, identification or control paths.

4. Retention maintains the intended mating state under the defined loads.

5. A sufficient separating load releases the joint; verify its magnitude and direction.

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Guided engagement can assist difficult-to-see docking and avoid conventional plug insertion. Controlled release is another possible feature, with the actual capture range, retention and handling validated for the product.

Distinguish a contact component from a finished cable assembly.

A contact component may contain the magnets and electrical contacts. The complete cable also requires specification of:

• Conductors

• Insulation

• Cable strain relief

• Overmolding

• Required length

• Conductor size

• The opposite, source-side termination

For OEM charging or communication, the complete construction determines the interface capability.

Guidance, compression and conduction

Magnets, spring contacts, housing and conductors work together. Electrical continuity requires the appropriate mating position and contact compression.

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Magnetic guidance

Attraction brings the matching interfaces toward the intended position.

Magnet placement and polarity can favour the correct direction; housing keying may add control. Validate possible orientations and partial engagement rather than assuming magnets eliminate every incorrect connection.

Select the appropriate retention, not simply the strongest magnet.

Balance the force against:

• The connector envelope

• Supported device weight

• Cable loads and their direction

• Handling requirements

• Required contact stability

• Intended release behaviour

Spring-contact engagement

In the defined mating position, the contacts compress against their targets.

The internal spring loads the plunger against its pad. Correct working travel can accommodate limited axial tolerance between the cable head and device, with lateral alignment and stops set by the housing.

Specify these contact inputs:

• Permitted working travel

• Installed working height

• Force within the working range

• Contact resistance

• Specified finish

• Contact geometry

Insufficient compression may cause intermittent contact.

Excessive compression can increase stress and wear.

Conductive circuit paths

Assign every contact from the device circuit.

Possible functions include:

• VCC

• GND

• Data

• ID

• Engagement detection

• Control

The circuit continues beyond the contact through the termination, conductor, cable and opposite end. Include every part of that route in electrical and thermal assessment.

The allowable load belongs to the complete cable configuration; a contact’s isolated rating cannot substitute for it.

Six parts of the cable assembly

Review the magnetic cable as an integrated mechanical and electrical assembly.

Mating head and housing

The head supports and positions the magnets and conductive contacts.

Possible forms include:

• Circular

• Oval

• Rectangular

• A dedicated low-profile form

Choose the mating form from the available enclosure and operating clearances rather than appearance alone.

Compliant conductive contacts

Spring contacts form the mating electrical paths.

Material, finish, force and internal construction influence:

• Allowable current

• Contact resistance

• Resistance to the specified corrosion exposure

• Mating-life performance

• Electrical continuity under the intended duty

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For a Magtor assembly, review the configuration’s allowable current, contact and insulation resistance, and temperature conditions alongside its geometry. Electrical and mechanical requirements need to be agreed together.

Magnets

Magnets provide guidance and retain the joint.

Magnetic design inputs include:

• Required magnetic material and grade

• Magnet dimensions

• Number of magnets

• Polarity arrangement

• Mating gap

• Housing and contact geometry

Magnetic polarity can support orientation control when reviewed with the housing, pinout and circuit protection.

Conductor and cable specification

The cable links the mating head to the power source, controller or other specified electronic equipment.

Define these cable inputs:

• Number of conductors

• Wire size / AWG

• Cable length

• Insulation material and requirements

• Required shielding

• Flexibility and flexing duty

• Allowable temperature range

These conductor and jacket details can limit the assembly just as much as the mating contacts.

Strain relief and molded construction

The transition beside the contact head can experience repeated cable bending.

Suitable strain relief can reduce conductor fatigue near the termination. Verify the actual flexing duty rather than treating it as a guarantee against cable failure.

A molded construction may contribute:

• Protection of the mechanical transition

• The intended external appearance

• Sealing where the complete design supports it

• A defined cable exit angle

Opposite-end termination

The other end may use:

• USB-A

• USB-C

• Unterminated conductors

• A wire terminal

• A board-side connector

• A dedicated mating connector

Magtor can review magnetic cable configurations with USB-A, USB-C, bare-wire or dedicated ends. Confirm the actual functions and matching interface for the chosen construction.

Choose the end from the system’s electrical and mechanical architecture.

Choosing the contact count

A contact count does not dictate one universal set of electrical functions.

Identify all independent paths and required returns before selecting the count.

Illustrative allocations are:

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These allocations are examples, not fixed wiring or protocol standards.

Two-contact magnetic cable

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Two contacts may provide a simple supply-only allocation.

One example assigns a positive path and return.

That may suit DC supply or charging where no separate communication path is needed, with the appropriate charging electronics and protection.

Wearables, small chargers and compact rechargeable products are possible uses for that power-only arrangement.

Three-contact magnetic cable

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A third path may provide one additional defined function, such as:

• Engagement detection

• Identification

• A temperature-related signal

• A defined single-channel communication path

• Charging-control signalling

Consider three contacts where the product needs such a function beyond the supply and return. The added path does not inherently increase charging speed.

Four-contact magnetic cable

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One possible four-path allocation is:

VCC / GND / Data+ / Data−

Confirm that example against the actual drawing; it is not a universal four-contact magnetic wiring rule.

A different device might allocate:

VCC / GND / ID / Control

Magtor’s four-contact wiring discussion explains how the assignment follows the application. Define levels, protocol, numbering and mating views before production.

Keep this distinction explicit:

Contact count alone does not establish a communication protocol.

Five- and eight-contact magnetic cables

Additional paths can accommodate combinations of:

• Power

• Ground

• Several defined signals

• Device-identification functions

• Sensor paths

• Charging-control signals

• Implemented communication paths

Supply or return contacts may be paralleled where required. Assess current sharing, contact states, conductors and temperature rise; allowable current does not simply multiply with the contact count.

Choose the number from the circuit map and available envelope together.

Length, conductors and end-to-end mapping

A contact part is only one section of the route. Designing a complete cable requires the length, conductors and both terminations to be assessed together.

Cable length and voltage drop

For otherwise comparable material, cross-section and temperature, increasing conductor length increases resistance.

Evaluate voltage drop using the current and resistance of the path being assessed:

Vdrop = I × R

At low current, the loss may fit within the device’s voltage margin; confirm that margin rather than assuming it is negligible.

At higher current, excessive resistance can cause:

• Reduced voltage at the receiving device

• Slower charging where the resulting supply condition limits it

• Additional cable heating

• Greater power loss

Select length with the required current and permitted drop, as well as the routing and handling needs.

Conductor size

Cross-section influences conductor resistance and permissible load in the actual cable and environment.

A higher-current assembly may need larger conductors than a small wearable charging cable. Confirm the complete installed thermal conditions.

Larger conductors also create mechanical trade-offs, which can include:

• Greater cable outside diameter

• Increased stiffness

• A larger termination head

• Additional cable loading on a small product

Balance resistance and heating against routing, flexing and device support.

End-to-end contact mapping

Trace every function through the complete route:

Device PCB → Receptacle contact → Magnetic spring-contact interface → Cable conductor → Opposite termination

This mapping is particularly important for dedicated cables with different mating forms at the ends.

Avoid matching numbers without checking the wiring:

Do not assume magnetic contact 1 connects to contact 1 of a USB or board connector. Define the actual conductor mapping and the viewing direction at each end.

Approve the complete wiring drawing before prototype termination.

Initial and aged contact resistance

The magnetic interface adds its own resistance and corresponding voltage drop to that of the conductors.

Its resistance may change with:

• Working contact pressure

• Wear of the finish

• Contamination

• Corrosion

• Installed working height

• The specified mating duty

Measure the relevant resistance changes during reliability validation, including the intended wear and environmental conditions, rather than relying only on the first sample.

Selecting the opposite termination

Choose the opposite end for the actual equipment and its electrical functions, not merely a familiar connector appearance.

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USB-A

USB-A can be considered where the intended equipment uses a compatible conventional port, including:

• A compatible charger

• A compatible computer interface

• A suitable power adapter

• Compatible industrial equipment

A compatible USB-A source can serve a basic 5 V charging design. Confirm the source, cable and receiving-device requirements; this does not establish a higher-current or fast-charge capability.

USB-C

USB-C is an option for compatible modern sources and devices. Keep the connector form separate from the functions implemented through it.

A USB-C end does not establish that a magnetic cable supports every USB data mode or USB Power Delivery function.

USB-IF distinguishes the Type-C connector form from implemented data and power capabilities. Confirm the actual conductors, control functions and applicable validation; this interface description is not USB certification.

Specify whether the USB-C implementation requires:

• Basic supply functions

• USB 2.0 data

• A defined higher-current load

• USB Power Delivery

• The required CC functions

• Other explicitly defined protocol functions

The magnetic end must provide the necessary paths and support the assigned electrical functions as part of that complete implementation.

Bare conductors or terminals

Unterminated conductors may suit:

• Prototype work

• Internal equipment connections

• Test fixtures

• A dedicated power supply

• Industrial system integration

A matching terminal can simplify installation into the intended equipment. Confirm the conductor preparation and terminal compatibility for the actual connection.

Dedicated opposite-end connector

An OEM interface may call for:

• A specified JST-type connector

• A board-to-wire interface

• Circular connectors

• A dedicated board connection

• A proprietary mating interface

The cable links two systems with their own functions and constraints. Treat it as an electrical and mechanical interface, rather than only an external accessory.

Validation before production

One successful charging event does not qualify an assembly for production. Validate it against the intended electrical load, duty and exposure.

Set the validation plan from the actual use of the complete cable.

Electrical validation

Relevant measurements may include:

• Contact resistance

• Cable resistance

• Voltage drop

• Performance at the specified current load

• Temperature rise

• Unintended open or short paths

• Insulation resistance

Use the expected operating load and representative configuration where appropriate, alongside the required unpowered checks.

Mating-duty validation

Repeated engagement can affect:

• Spring-contact components

• The contact finish

• Magnetic mating surfaces

• Housing

• The cable strain-relief transition

Cable-flexing validation

Evaluate repeated bending near the connector head under a defined, representative duty.

A contact pair can still conduct while an internal cable conductor is degrading. Check cable fatigue separately from mating-contact performance.

Retention over the required duty

Confirm suitable holding and release behaviour across:

• The specified mechanical cycles

• The temperature exposures

• Permitted assembly-tolerance variation

• Representative cable loads and pull directions

Environmental validation

Depending on the application, assess:

• The specified salt-spray exposure

• Thermal cycling

• Humidity exposure

• Sweat and relevant chemical exposure

• Required vibration duty

• Dust exposure

• Defined ingress conditions

Magnetic attraction does not itself provide a water seal.

Validate the housing, seals, cable entry, mounting interface and complete enclosure for the required water exposure and mating state.

A magnetic contact cable can form part of a sealed design, but its protection comes from the implemented assembly and test conditions. No single general description establishes an IP result for the finished product.

Inputs for a dedicated cable design

Begin with the device functions and constraints before comparing existing cable forms.

For sample or quotation review, define these inputs:

Scroll horizontally to view every column.

For a small OEM device, useful mechanical inputs include:

• A device 2D drawing

• A device 3D model

• The PCBA position

• Enclosure wall thickness

• Available mating-interface space

• Required cable exit direction

These inputs let the supplier review the contact assembly against the complete mechanical envelope and tolerance stack.

When another interface may be preferable

Guided attachment can be convenient, but a magnetic cable is not the suitable choice for every system.

Consider a different mating structure where:

• The connection must stay mechanically locked against a very high pull load.

• Substantial magnetic metal debris can reach the interface.

• Universal third-party cable interchangeability is essential.

• The system requires a specific standardized industrial connector.

• The required high-speed interface cannot be validated with the proposed magnetic construction.

• Unintended magnetic release is unacceptable to the device operation.

Choose from the required operating conditions and failure consequences, then assess the available architectures.

Cable-design summary

A magnetic cable assembly integrates magnets, compliant contacts, conductors, housing, strain relief and the opposite termination. Assess that complete construction as the product’s interface.

Two contacts may provide a simple supply and return. Three-, four-, five- or eight-contact examples can allocate additional detection, communication, identification or control functions where implemented by the device.

Review the complete conductive route:

PCB → Magnetic receptacle → Spring-contact mating pair → Cable conductors → External termination

Specify contact count and functions, load, length, wire size, retention, working height and exposure together. The assembled configuration sets the applicable limits.

Early agreement on those requirements can reduce avoidable redesign and support meaningful prototype validation. Confirm the cable in the representative device and operating conditions before production approval.