Electric Linear Actuators with Feedback Sensors
It is always essential to be informed about the basics and factors leading up to choosing a product before committing to the specific model for your needs. Firgelli is a vertically integrated, electric linear actuator and control system manufacturer with the ability to customize products to meet your specifications.
When an electric linear actuator is equipped with feedback sensors, the actuator can actively communicate its stroke position to the control system (sometimes referred to as positioning). These output sensors also allow for the control box to precisely control the actuator’s stroke at all times. While this is not required on all linear actuators, positional sensors are required on those with more complex functionality. For example, if an actuator needs to move synchronously with another, feedback sensors are necessary for monitoring and ensuring both linear actuators remain in sync, regardless of differences in load. Additionally, feedback sensors are crucial for memory positioning and other special features that require knowing here the actuator’s stroke position is at all times. This can include, but is not limited to, motor speed, conditional movement, and other features.
The four main feedback/positioning sensors that Firgelli uses within our linear actuators are:
Hall Effect Sensors
Optical Encoder Sensors
Encoder optical sensors are Firgelli’s most recommended type of positional sensors for electric actuators because they are small enough to fit in compact spaces, providing higher resolution and digital output for positioning and synchronization
Hall Effect sensors are activated by a magnetic field, which is comprised of two important characteristics: flux density and polarity. The output signal from a Hall Effect sensor is the function of the magnetic field density around the device. When the magnetic field density around the sensor exceeds a certain pre-determined threshold, the sensor detects it and generates an output voltage call the Hall Voltage.
Optical Sensors are also very popular and we now sell these in our Premium Actuator range. They offer very high precision, compact and highly reliable. The way an optical sensor works is that it has a small disc plate that rotates and in the disc there are a series of holes. The optical sensor simply counts the number of holes as the disc rotates. The disc is located in the gear box and is geared down so that it requires a lot of rotations for just a small amount of travel which in turn is what gives you greater resolution.
Optical sensors are commonly used due to their cost - efficiency. These sensors also maintain their quality over time and generally have ultra-long lifespans. This positioning sensor is available on all Firgelli Premium electric actuator models.
Potentiometers, also known as POT sensors, are generally the most commonly used output sensor in the industrial marketplace. They have a wiper contact linked to a mechanical shaft that can either be rotational or linear in their movement. This causes the resistance value between the wiper and the two end connections to change giving an electrical signal output that has a proportional relationship between the actual wiper position on the resistive track and its resistance value. In other words, resistance determines position. As the linear actuator lead screw turns, the resistance value between the wiper and the two end connections will change, and each resistance value will correspond with the position of the linear actuator’s stroke.
One advantage of the POT sensor versus a Hall sensor is that when the power is off, the POT will keep the information of the position, while a Hall sensor or optical sensor will lose the positional information and need to be reset. Firgelli sells Potentiometer Linear Actuators also in our FA-35, FA-150, FA-200, FA-240 series.
However, potentiometers are slightly less accurate in their readings in comparison to the Hall Effect sensor due to the initial installation process however, this is not detrimental to the overall position reading. Reed sensors are magnetic feedback sensors. There is an electrical switch which is operated by an applied magnetic field, and the sensor as a whole contains a pair of contacts on ferrous metal reeds in a hermetically sealed glass envelope. The contacts may be normally open, closing when a magnetic field is present, or vice versa. The switch may be actuated by a coil, making the reed switch return to its original position. With force from each rotation of the lead screw and position of the linear actuator stroke length, the reed switch will open or close.