IO-Link reference designs for proximity sensing and enhanced distributed control

August 19, 2014 // By Graham Prophet
Integrates the attributes of IO-Link into a proximity sensor and a 16-channel digital-input hub, two subsystem reference designs from Maxim Integrated provide very accurate, low-power optical proximity sensing (MAXREFDES27#) and enhance distributed control with a compact digital-input hub (MAXREFDES36#).

Modern 'smart' manufacturing relies heavily on high-speed automation and superior sensing. With that comes an increased need for versatile and accurate proximity sensing—never an easy task—and more system sensor inputs. Both of these new space-saving subsystems integrate the IO-Link standard for industrial applications. The MAXREFDES27# proximity sensor employs the IO-Link protocol to provide efficient two-way communication between a controller and a remote optical sensor. The MAXREFDES36# digital hub uses the IO-Link protocol to enhance distributed control, enabling 16 digital inputs to reside near binary sensors, thereby reducing expensive and bulky cabling at the PLC side and enabling higher DI density.

The MAXREFDES27# IO-Link subsystem reference design lets operators tune and calibrate an optical proximity sensor with excellent accuracy, up to 14 bit resolution. Integrated DC-DC low-power conversion increases system efficiency. The design is tunable and can be calibrated for different surfaces and light levels.

The board integrates the DC-DC converter, an IO-Link transceiver, the proximity sensor, and a Renesas RL78 microcontroller. It uses 150 mW (typ); the IO-Link provides self-configuration, efficient two-way communication between sensor and control module, and several protection mechanisms. The entire design fits on an 8.2 x 31.5mm PCB.

Industrial control typically has a ‘rat’s nest’ of input wires running from various sensors to the digital-input module of the programmable logic controller (PLC). This conventional setup is difficult to troubleshoot and expensive to maintain. The MAXREFDES36# IO-Link subsystem merges 16 of these digital inputs into its hub and eliminates 15 cables connected to the PLC. It consumes 235 mW of power and is 60% smaller than current solutions. This space-saving digital hub lets manufacturers fit more digital inputs into each system controller. It simplifies operation complexity, reduces maintenance costs, stabilises low-power consumption, and increases uptime.

The design integrates DC-DC power converter, two 8-channel digital-input serialisers, an IO-Link transceiver, and a Renesas RL78 microcontroller on one board. Again, self-configuration, short-circuit and shutdown protection, thermal warnings, and drive capability