Does AntiSwitch really eliminate the need for external limit switches?
Yes, in applications where the mechanical end point is clear, AntiSwitch eliminates the need for limit switches and limit wiring. But two conditions are essential: the mechanics must withstand the stall force for the duration of detection, and there must be a measurable difference between the normal operating current and the stall current.
AntiSwitch works from the current rise at the moment of stalling against the mechanical stop. Therefore the system must be able to carry the stall force during the short time until the threshold is detected and the output cut. If thin sheet metal, a plastic gear or a weak joint can deform under that force, current-based end stopping is not sufficient on its own.
The second condition is current discrimination: as the load gets heavier, the normal operating current approaches the stall current. If the two are very close, the threshold will either trigger early or never trigger. The threshold must be calibrated above the real operating current and below the stall current.
Situations where you should still prefer an external limit switch:
- If the stopping point is not a mechanical stop but a free position.
- If an independent limit verified by a contact is required for safety reasons.
- If the load varies with the season or temperature and the current profile shifts.
The presence of an independent limit for each direction on the PT500 (A1/A2) makes it possible to set correctly when the current profile of the up and down directions differs. On the KS250, AntiSwitch is built in and works with the same logic.
Full topic: DC Motor Driver Selection Guide