Sometimes you may not want to use the entire stroke length of a linear actuator, to restrict the travel distance you will need our external limit switch kit. This tutorial will go over how to connect this up.
How limit switches work
Limit switches are spring loaded buttons that when pressed open the circuit, stopping the motor from spinning any further. These switches have a diode wired across its terminals. Diodes is an electrical component that is equivalent to a one way valve. By wiring a diode across the switch terminals, even when power is cut to the motor, electricity can still flow in the opposite direction. This is important because it allows the actuator to move in the reverse direction after reaching its limit. If the limit switches did not have diodes wired across their terminals, the actuator would be stuck as soon as the limit switch was pressed: unable to move forwards or backwards.
Inbuilt limit switches
All our linear actuators (except the Bullet Mini, Bullet 23 Cal. and Bullet .35) have internal limit switches at the fully extended and retracted positions. These limit switches ensure that when you fully extend (or retract) the actuator it will automatically shut off preventing the motor burning out and/or doing damage to the body of the actuator. However, these limits not adjustable.
If you want to:
- Limit extension
- Limit retraction
- Limit both extension and retraction
then you will need to mount external limit switches.
External limit switches
First you will need our external limit switch kit, a crimping tool or soldering iron, and heat shrink tube/electrical tape for insulation. Firstly mount your actuator in your application and determine where your upper and/or lower limits need to be. Using small screws or bolts attach one (or two) of the limit switches so that the actuator will collide with them when it reaches your maximum/minimum desired position.
Wire the switches to the actuator as shown in the wiring diagrams below. Not that the diodes come pre-installed, wired across the terminals of the switch. Optionally you can also wire in the fuses included with the kit but these are not mandatory.
In multi-actuator and synchronized applications, the External Limit Switches can be installed on the control circuit of the system. This technique works with SYNC boards as well: