Digitalization in Hydraulics – Power Amplifiers with IO-Link

Just in time for the Hydraulix Congress – “DIGITALIZATION IN HYDRAULICS – Knowing What Really Matters!” – W.E.St. Elektronik published an article in O+P magazine about the use of IO-Link technology in power amplifiers. You can find the full article in the download section!

Plug-in amplifiers for proportional valves are a simple and cost-effective solution for controlling single-solenoid valves. Typically, the setpoint is provided via an analog signal (0…10 V or 4…20 mA). Parameterization is done directly on the plug or via various interfaces (e.g., USB). These amplifiers have been widely used for over 30 years. Now, products with IO-Link interfaces are available.

IO-Link is a globally standardized point-to-point communication protocol (IEC 61131-9) for sensors and actuators. The IO-Link community aims to develop and promote the technology, which is widely accepted across manufacturers. While many sensors are already available, actuator development is progressing more slowly. Yet, IO-Link is ideal for controlling proportional valves, offering:

• Digital, interference-resistant communication
• Simple wiring
• Parameterization directly via the PLC (no special software required)
• Automatic parameter transfer during device replacement
• Diagnostic and feedback capabilities
• Galvanic isolation between IO-Link and power electronics

In the age of Industry 4.0, the shift to digital interfaces is inevitable. IO-Link, as a point-to-point connection, can easily replace analog interfaces.

Experience Pays Off - PAM-190-P-IO

The IO-Link interface is as easy to use as an analog one, making its integration into a plug-in amplifier for proportional valves a logical step - despite some technical challenges.
Space in the plug housing is limited, and low self-heating and galvanic isolation between power and IO-Link supply are required. Since this is not a high-priced product, smart design is key. Based on our experience with the analog PAM-190-P, we knew how to approach the design. Galvanic isolation for analog current measurement is complex and costly.
Our solution? We used two 32-bit high-performance processors, requiring isolation only for digital signals. One processor handles IO-Link communication, the other manages current control and signal conditioning (ramps, min-max, etc.).
While this may seem excessive in terms of computing power, the simplified circuit design results in fewer components, higher reliability (MTTFd), and lower cost.

Implementation and Parameterization

The modular approach allows the communication electronics to be easily and affordably integrated into various electronic assemblies. The setup is similar to the standard PAM-190-P, but analog signals are replaced with digital ones. No shielding is needed, reducing costs. Pre-assembled cables and M12 connectors save time. This connector is used to control pressure valves, throttle valves and also directional control valves (then with two connectors).

The amplifier is tailored for hydraulic applications and includes current control, ramp functions, and min-max settings. The output stage is identical to our standard amplifiers. IO-Link devices are parameterized using standard tools provided by PLC manufacturers, often integrated into their development environments. This eliminates the need to learn separate software like WPC-300.

Mit dem IO-Link Konzept kann jetzt ein Tool sowohl für die verschiedenen Sensoren als auch für unseren Steckerverstärker verwendet werden. Was man nicht mehr hat, sind die analogen Signale, die mit einem Multimeter gemessen werden können. Es sind natürlich die typischen Störungen auf den analogen Signalen auch nicht mehr relevant. Mit Blick auf I4.0, die Digitalisierung und eine deutlich erweiterte Diagnostik ist dies aber auch der Weg in die Zukunft.

Impact on Hydraulics

In addition to a wide range of IO-Link sensors, proportional valves can now also be controlled via IO-Link. For hydraulic systems, this means a unified interface that can even be used to set pressure. Thanks to our modular concept, further developments - from pressure control to positioning systems - are possible. IO-Link is a key building block for the future of modern, digital hydraulic systems.