DC Linear Actuator
It is the unit that converts the rotation of a DC motor into linear push or pull motion through a lead screw and gearbox. It is driven with two power cables, changes direction when the polarity changes, and draws current by seating against a mechanical stop at the end of stroke. It is the load with which the ST42, KS250 and PT500 modules are frequently used.
In typical 12 V and 24 V actuators the stroke varies between 50 mm and 1000 mm and the push force from a few hundred newtons to a few kilonewtons. As the force increases the speed drops; the catalogue always gives the two together.
Three points matter when using it with a driver:
- End of stroke: If the actuator does not have its own internal limit switch, the motor stalls at the end of stroke. Current-sensing stop uses this rise to cut the motion and makes external limit wiring unnecessary.
- Threshold setting: The threshold must stay above the real running current but below the stall current. On the PT500 this is set independently for the two directions with the A1 and A2 trimmers.
- Start-up surge: On a loaded start the current rises to several times the rated value; the ramp time softens this surge.
On models with internal limit switches, current measurement can be misleading because of the diodes at the motor end; in that case it is safer to use the existing limits.
The context in which this term is used: DC Motor Driver Selection Guide