Position feedback: Get accurate position feedback from your electric I/O™ actuator

The actuator must be initialised on a regular basis to ensure accurate position feedback. This is typically achieved by a physical endstop switch in both directions, but the accuracy can be reduced over time due to mechanical wear of the switches.

The I/O actuator, however, uses a new initialisation principle called ‘zero point’. With zero point, the position is initialised every time the piston passes a zone from 35-70 mm on the stroke without having to run the actuator to the physical endstops.

By substituting the electromechanical switches with a Hall-based system, the I/O actuator is better geared for operation in challenging industrial environments.

Information about the actuator position can be output as either an analogue or digital signal. Both options are offered to ensure compatibility with various PLCs and preferences.

If you compare the two signal types, there are various pros and cons to consider. As an example, the analogue signal is more prone to noise compared to a digital signal – but under the right conditions, it can also be highly accurate.

The digital signal can be used for more than just the piston position, as it can also be used for endstop signals, constant signal during operation and many other features.

Analogue signals are a common type of feedback signal for PLCs and other control systems in industrial applications. One of the most frequently used is a 0-10 V signal where this voltage range represents the physical stroke length of the actuator.

Keep in mind that this type of analogue feedback is susceptible to noise and voltage drops over long cable lengths, which in turn could lead to inaccurate position feedback. Another common analogue signal is current – often 4-20 mA – which is less susceptible to noise and of course also voltage drops.

For both current and voltage, the feedback range can be scaled specifically to your needs, which can make it easier to integrate into your controls.

The actuator offers several digital position output options which can be configured exactly to your requirements. To offer full flexibility, the yellow and green wires can be used for the following outputs:

Digital position feedback as either single Hall or dual Hall. Single Hall does not take direction into account, and this logic must be programmed in the PLC. Dual Hall has two channels – A and B. Both have their own dedicated wire which makes it possible to determine the direction in which the actuator is running.

As either a supplement to the analogue position feedback or a stand-alone feature, you can choose endstop signals that give a signal when the actuator is fully retracted or extended. The same signal will also be applied if virtual limits are set in either direction – indicating that the actuator has reached its new endstop.

It is also possible to receive digital signals from the actuator while running – something that can, for instance, be used to turn on an LED to indicate that something is moving in the application.

In some cases, it might be beneficial to know when the actuator reaches a predefined endstop zone. This feature makes it possible to define a zone where the actuator can send a digital signal when it is inside that zone or at a current limit in that zone. In this way, you are no longer forced to design your application so that the physical endstop must be reached before receiving a PLC (Programmable Logic Controller) signal.

For most of these digital signals, you can choose between an active high or active low signal for easier integration in the application.

If you are looking for a way to power LED or a hand control, you can also choose a constantly high signal. The actuator will supply up to 100 mA to low-power devices directly.