Concentric LACT4-12V-20 Linear Actuator: 4" Stroke, 12V, 0.5"/s

This 12 V linear actuator can be used in a variety of heavy-duty applications. The motor has 20:1 reduction gearbox that gives the actuator a dynamic load rating of 110 lbs (50 kg) and a maximum speed of 0.5 in/s (1.3 cm/s) , and it is rated to withstand up to 500 lbs when not moving.

AUD$ 288.95

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Supplier Link: [Pololu MPN:2304]


Concentric linear actuator without feedback, opened to show gears


The LD Series of linear actuators by Concentric International (formerly Iowa Export-Import) are 12V DC gearmotors that use a worm drive to move a shaft back and forth along its length. The worm drive ensures that the shaft will hold its position even when unpowered. Two limits switches safely stop the motor at either end of its range, while integrated diodes allow it to reverse direction after reaching a limit point if the supplied voltage is reversed. The actuators are mostly metal, and the entire case is sealed to protect against dust and water (rated IP63).

Connecting the bracket to one end of a Concentric LD linear actuator

The Concentric LD series linear actuators are available in a variety of lengths and with optional potentiometers that are linked to the shaft position, for use in feedback systems. Several lengths are also available in two gear ratios: 5:1 and 20:1. The 5:1 versions have lower load ratings—34 lbs dynamic, 450 lbs static—but allow for higher speeds, up to 1.7 in/s. The 20:1 versions are slower—up to 0.5 in/s—but are rated for dynamic loads up to 110 lbs and static loads up to 500 lbs.

20:1 20:1 w/feedback 5:1 5:1 w/feedback
2″ LACT2-12V-20 LACT2P-12V-20
4″ LACT4-12V-20 LACT4P-12V-20 LACT4-12V-5 LACT4P-12V-5
6″ LACT6-12V-20 LACT6P-12V-20
8″ LACT8-12V-20 LACT8P-12V-20
10″ LACT10-12V-20 LACT10P-12V-20
12″ LACT12-12V-20 LACT12P-12V-20 LACT12-12V-5 LACT12P-12V-5

Mounting brackets are available for attaching the actuators to a structure; two are required for each actuator.

Concentric linear actuator with feedback, 4" Stroke (LACT4P), shaft fully extended

Using the actuator

To test-drive the actuator, simply connect a power source of up to 12 V to the motor leads. Reversing the applied voltage will reverse the direction of motion. A motor controller or motor driver is required for electronic speed and direction control. We recommend our Jrk Motor Controllers for use with the feedback actuators and the Pololu Simple Motor Controller 18v7 for controlling the actuators without feedback, though many of our other motor controllers and motor drivers are capable of powering this actuator.

These actuators have a stall current of 10 A at 12 V, but they will, on average, draw far less than this when used within their load ratings. They draw around 500 mA with no load and can exceed 3 A at their maximum rated dynamic load, so we have found they generally work well with our lower-power jrk 21v3 motor controller with feedback (see the bottom of this page for more information using this controller for closed-loop linear actuator position control). Note, however, that the actuators can briefly draw close to their full stall current when abruptly started or on a sudden change of direction. Such current spikes can be dampened if you take steps to limit the acceleration of the actuator (many of our motor controllers offer optional acceleration limiting).

Dimensional drawings

Diagrams of the linear actuators are shown below. The versions that include potentiometers have a larger gearbox, so their overall size and weight is larger. For more detailed information, including the retracted and extended lengths of each version, see the appropriate datasheet (click the Resources tab above).

Dimensional drawing for the Concentric LD linear actuators with feedback.

Dimensional drawing for the Concentric LD linear actuators without feedback.

Actuator leads

Each actuator has a 3-foot-long cable. On actuators with feedback, this cable is terminated with special female connectors as shown in the left picture below, one for the three potentiometer leads and another for the two power leads. These connectors match male versions on the extension cable for LD linear actuators. Actuator versions without feedback have two unterminated, stripped power leads as shown in the right picture below. Linear actuators without feedback do not have cables that are compatible with the linear actuator extension cable.

Connectors for Concentric LD linear actuators with feedback

Unterminated wire ends for Concentric linear actuators without feedback

Using a jrk motor controller with a linear actuator with feedback

The feedback feature included with our jrk motor controllers make them a great solution for precisely controlling our linear actuators with feedback. Our settings file for the jrk configuration utility makes setup easy, eliminating the need to calibrate the feedback and tune the PID constants. To get started, follow the steps below:

Connecting a linear actuator with feedback to a jrk 21v3 motor controller

  1. If you have not already, read through the Jrk USB Motor Controllers User’s Guide and download its drivers and configuration software.
  2. Connect your jrk to a PC with a USB cable and launch the configuration utility. The red LED should be on, and the green LED should be flickering quickly.
  3. Download the jrk 21v3 settings file for use with LACTxP (1k txt). The settings in this file work with any length actuator that has a feedback potentiometer (model LACTxP), and they were tested on the jrk 21v3, which is powerful enough to drive these actuators in typical applications. These settings should also mostly work for the higher-power jrk 12v12, though a few of them (e.g. current calibration) might need to be adjusted.
  4. In the configuration utility, choose File → Open settings file (Ctrl + O), and navigate to the location of the settings file you downloaded in step 3.
  5. Click on the PID tab of the configuration utility and verify that the proportional and derivative coefficients are not zero. If they are zero, the settings file was probably not loaded properly and you should try performing the previous step again.
  6. Click “Apply settings to device”.
  7. With your power supply off, connect your linear actuator to your jrk using the connections shown in the picture to the right. The picture shows a jrk 21v3, but the connections will be the same if you use a jrk 12v12.
  8. Turn on Power.
  9. On the Error tab, choose “Clear Errors”. The “No power” and “Feedback disconnect” errors will clear. The red LED will turn off, and the yellow LED will blink slowly.
  10. On the Input tab choose “Set Target” to move your actuator to the target position.

While this setting file gives precise control over most of an actuator’s range, you might find decreased performance very near the extremes due to the limit switches. If your project requires better control near the actuator’s limits, you might need to recalibrate the feedback settings for your particular actuator.



Stroke: 4 in
Weight: 36 oz

General specifications

Gear ratio: 20:1
Free-run current @ 12V: 500 mA
Stall current @ 12V: 10 A
Linear speed @ 12V: 0.5 in/s
Linear force @ 12V: 110 lb1
Maximum duty cycle: 25%2
Feedback potentiometer included?: N


This is a dynamic load rating. The actuator is rated to withstand 500 lbs when not moving.
One minute of continuous operation in four minutes.


File downloads

Datasheet for Concentric LD3 series linear actuators (1MB pdf)
This is a more complete datasheet for Concentric’s L3D series of linear actuators; our LACTx actuators are a subset of this series.
Dimension diagram for LACTx linear actuators (170k pdf)
Dimension diagram for LACTxP linear actuators (191k pdf)
Load specifications for 12V linear actuators (408k pdf)
LD series product sheet from Concentric International (246k pdf)
jrk 21v3 settings for linear actuators (1k txt)
Use a jrk 21v3 to precisely control our Concentric LD series linear actuators with feedback. Instructions for using this file can be found on the linear actuator product pages.


What are the differences between the generic linear actuators and Concentric linear actuators?

The Concentric actuators are very similar to our generic actuators, but they differ in a few ways:

  • The Concentric actuators use different gearboxes to offer different combinations of speed and force while the generic ones use the same gearboxes but different threading pitch on the drive rod.
  • The feedback on the Concentric actuators with feedback pots is better than on the generics in the sense that nearly the full range of the feedback pot is used. On the generic actuators, typically only a subset of the feedback pot range is used (e.g. 10% for the 4" version). This is probably the main way in which the Concentric actuators are better.
  • Concentric actuators have a recommended maximum duty cycle of 25%; the generic actuators have a recommended maximum duty cycle of 15%.
  • Concentric actuators have a static load rating significantly higher than their dynamic load ratings; the generic actuators just have dynamic load ratings, and we do not recommend exceeding those.
  • A generic actuator is less expensive than the comparable Concentric actuator.

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