Contactless power and data transmission delivers wear-free connections
23 February 2026 
Conventional connectors and sliprings have limitations in some industrial applications. A contactless data and power transmission technology called NearFi can overcome these, allowing data at up to 100Mbit/s, as well as 50W of power, to be transmitted across a short gap. DigiKey application engineer, Rolf Horn, explains how.
Flexible and highly reliable connections are essential in industrial applications, such as those used in robot tools and rotating devices like precision indexing tables. Those systems experience high movement and rotation and are often exposed to dirt and vibration that can cause conventional connectors or sliprings to fail.
Designers need new options to overcome the limitations of conventional solutions in these and other challenging applications. The new option must be able to support secure duplex Ethernet connections up to 100 Mbps and transfer up to 50W of power for sensors and other components across a gap of 12mm (or 40mm for data only).
Flexible mounting options are necessary to support a wide range of system designs, and a simple, visible LED indicator is required for quick diagnostics.
Operation in harsh industrial settings requires an IP65 environmental rating, and the solution must meet IK06 per EN 62262, indicating that it can withstand external mechanical impacts with an energy of up to 1 Joule. Simple installation or replacement can reduce maintenance costs and downtime.
Robot reliability challenges
Frequent tool changes for robots used in automated assembly processes can present significant challenges for connectors. Those tool changes can require hundreds of mating/unmating cycles every day.
Each cycle exposes the contacts to contaminants and causes wear due to contact friction. If the connectors are not precisely aligned, contacts can get bent.
The result is reduced connector reliability and unpredictable downtime for maintenance. In addition to connectors for tool attachment, some robots use sliprings to transmit data and power in rotating arms and joints.
Slipring limitations
Sliprings can also be found in wind turbines, as well as in food and pharmaceutical processing and packaging lines, and other industrial processes. Like conventional connectors, they can be damaged by exposure to contaminants and can experience excessive mechanical wear.
Sliprings can become hot due to friction and may require attention to thermal management. In some applications, sliprings can be subjected to strong vibrations or sudden impacts that can result in damage, cause unstable contact pressure, or even mechanical failure.
Both conventional connectors and sliprings can create machine design challenges related to size and movement constraints, as well as access requirements for maintenance. This adds to the numerous application challenges, including intermittent connections caused by vibration, dust, dirt, and contact wear, among others.
NearFi
Using “better” connectors may offer an opportunity for incremental improvement in performance or reliability. But what’s really needed is an out-of-the-box approach that eliminates the most vexing connector challenges. Phoenix Contact’s NearFi technology fits that bill.
NearFi is a non-contact technology that supports wear-free and reliable communication and power delivery across an air gap of a few centimetres or through non-metallic materials, such as plastic, glass and wood. When transmitting only data, NearFi can connect across an air gap of 40mm. Power, or combined power and data transmissions, can connect across air gaps of 12mm.
NearFi uses 60GHz wireless technology to transmit data and inductive coupling to deliver power from a base coupler to a remote coupler. Couplers have housings rated IP65 and IK06, along with M12 connections, ensuring wear-free and maintenance-free operation in demanding industrial environments.
The NearFi system gives designers three options:
- Data and power can be transferred simultaneously using a 1234224 base coupler with a 1234225 remote coupler.
- Power can be coupled without data support using a 1234226 base with a 1234229 remote.
- Data can be transmitted without power using a 1234232 base with a 1234234 remote.
Full-duplex Ethernet
With NearFi, data is exchanged simultaneously in both directions without latency. The use of two parallel 60GHz connections on separate frequency bands – one for the uplink and one for the downlink – enables full-duplex real-time data transmissions. This makes it suitable for time-critical industrial protocols, such as Profinet and EtherCat. Because the transmission technology is protocol-independent, it can be used with any standard Ethernet protocol (Figure 1).
Figure 1: NearFi can support protocol-agnostic, full-duplex 100 Mbit/s Ethernet transmissions. (Image: Phoenix Contact)The use of near-field communication (NFC) is a key factor in NearFi performance. Unlike conventional far-field communication, which relies on propagating electromagnetic waves that travel indefinitely through space, the energy in NFC does not radiate out indefinitely. It decays rapidly with distance. NFC is a low-power technology that further mitigates the possibility of electromagnetic interference (EMI).
The use of NFC also ensures reliable coexistence with existing wireless technologies, such as WLAN or Bluetooth. Also, standard industrial interference spectrums don’t impact NearFi transmissions, eliminating the need for frequency planning when deploying NearFi.
The limited range means that multiple NearFi links can be run near each other without interference. The bottom line is that NFC enables reliable, maintenance-free, high-speed data transmissions with substantial immunity to EMI. Finally, an LED ring on the coupler housings displays the connection status and facilitates troubleshooting, thereby speeding up setup and diagnostics.
Bit-oriented transmissions
The use of a synchronous, bit-oriented transmission technology is another key to NearFi’s performance. Bit-oriented technology contrasts with the packet-oriented transmission of other wireless communications.
Packet-oriented implementations generally suffer from significant latency. The data arrives at the transmitter and must be put into packets before transmission. At the receiver end, the packets are unpackaged before the data is output to the system.
In NearFi synchronous transmissions, data is sent directly, bit by bit, as it arrives, with no packing or unpackaging. This produces a continuous datastream and almost eliminates latency. That’s why NearFi is well-suited for time-critical industrial Ethernet protocols, such as time-sensitive networking (TSN), Profinet and EtherCat (Figure 2).
Figure 2: NearFi uses bit-oriented transmissions to mitigate latency challenges associated with traditional packet-based communication. (Image: Phoenix Contact)In addition, because the data is transmitted without buffering or packaging, NearFi is protocol-transparent and can handle any Ethernet protocol without requiring configuration.
NearFi addresses security concerns by limiting communication to a short distance. It can also support high-level security measures, such as encryption, authentication and tokenisation.
Delivering power
The NearFi system uses inductive power transmission operating in a frequency range of 100–148.5kHz – similar to that used in some smartphone wireless chargers. Up to 50W (24V DC at 2A) can be transmitted, and with parallel connections, up to 100W.
Active closed-loop control delivers constant power transmission over the entire working area. The transmission of two electrically isolated voltages (each at 50W) is also supported. Like data connections, power delivery uses a base coupler and remote coupler.
The base coupler receives 24V DC power from a source such as a controller. The integrated communication power/sensor voltage converter, also known as the US converter (where “U” is the notation for voltage in German), converts the 24V DC power into high-frequency power for inductive transmission. The remote coupler receives high-frequency inductive power and converts it back to 24V DC in the UA (actuator voltage) converter for use in I/O, switches, sensors, actuators and other functions (Figure 3).
Figure 3: Power is inductively coupled between a base coupler and a remote coupler. (Image: Phoenix Contact)Fast Startup
The NearFi Fast Startup function enables the quick (<500ms) re-establishment of real-time links. That’s possible because power transmission and data communications begin while the NearFi couplers are still approaching each other.
Fast Startup can reduce cycle times significantly in applications such as robot tool changes. The bidirectional data transfer capability of NearFi also enables the new tool (or other attachment) to identify itself to the system, confirming that it’s the correct item.
Other applications
NearFi couplers can be brought together facing each other, with an offset, or at a tangential angle. They can also be used in applications where the base coupler is stationary while the remote coupler rotates (Figure 4). NearFi couplers are ready to use out-of-the-box, eliminating the need for programming and speeding up application development and deployment.
Figure 4: In this application, the remote coupler on the left is rotating while the base coupler on the right is stationary. (Image: Phoenix Contact)The same features that make NearFi suitable for use in robot tool changes can also support the needs of applications such as automated guided vehicles (AGVs) and material and workpiece carriers.
Rotating antennas, such as those found at airports, can benefit from replacing conventional sliprings with NearFi couplers. Similarly, precision indexing tables are used in industrial applications, as well as in bottle fillers within the food and beverage and pharmaceutical industries.
NearFi technology solves a host of seemingly intractable problems. It wirelessly delivers protocol-agnostic 100Mbit/s Ethernet, plus 50W of power, and is flexible and easy to use. NearFi couplers are designed for use in harsh industrial settings, with IP65 and IK06 ratings, as well as M12 connections.
