Memory stick plugs the IO-Link gap

01 March 2011

It is still early days for the IO-Link smart sensor communication technology, and IO-Link masters, that allow the full functionality of the technology to be utilised, are not yet widely available.

A ‘memory plug’ from ifm has been introduced to allow plant operators to bridge the gap and manage sensor data simply and quickly. It is about the same size as a USB memory stick and contains non-volatile memory for saving data. However, it is designed specially to work in conjunction with IO-Link interface factory sensors.

The plug has two Ecolink M12 connectors at either end: one connects directly to the sensor, and the other connects with the I/O block device, which is often an AS-interface block. The memory plug is actually attached to the I/O block and is connected with a cable to the sensor. This keeps it at a safe distance from the sensor.

The purpose of the plug is to capture the sensor configuration data and save it. If a new, empty memory plug is attached to a sensor it automatically stores the data of the sensor, including the type of sensor that it is. This happens at power-on.

In the IO-Link scheme, it is the IO-Link master that is supposed to do this, so in the absence of the master, the memory plug steps in and performs this critical function. It’s a quick fix for a hole in the rapidly expanding IO-Link market, but one that might stay around for a long time, particularly for limited installations that don’t want to bother with IO-Link masters.

Once the configuration data are absorbed, the memory plug doesn’t do anything. Following this initial rush of data, there is no further communication between the sensor and the memory plug; nothing happens during normal operation. It just sits there on the I/O line and passes all signals straight through from the sensor to the I/O block. The I/O block subsequently transfers the signals to the higher-level controller without delay. In the example shown in the photo this transfer is done over the AS-i bus.

However, there are two situations where the memory plug will wake up. If an operator changes the configuration data in the sensor, the memory plug takes note of this and updates itself with the new data. Thus, the plant operator can always be sure that the memory plug is storing the latest configuration data.

A second situation arises if and when anything happens to the sensor. The machine operator simply needs to plug in a new sensor and the memory plug automatically downloads the configuration data to initiate its activity.

The memory plug can also be used to transfer data to multiple sensors. After reading and storing data from a connected IO-Link sensor, if the machine operator then connects a sensor of the same type, the data record stored on the memory plug will be copied onto the new sensor. This configuration data will replace the default factory settings on the new sensor. The operator can transfer the data to as many sensors as he likes.

At SPS/IPC/Drives CEE saw the modules connected to various flow, pressure, and temperature sensors as well as the typical binary sensors and AS-interface modules.

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