Wiring from the joystick to the valve is much easier and costs only a fraction of what would be required to route hoses and tubes from the joystick to the hydraulic valve. This allows the freedom to design a more ergonomic operator station without compromising the cost of the equipment. The primary disadvantage as compared to a manual or pilot-operated valve is the higher cost of the electrohydraulic valves.
Electric joystick types
Electric joysticks are manufactured in a wide variety of types, ranging from large hand-operated displacement and force controls to very small finger-operated devices. Each has its own niche application. Joysticks can be further classified into discrete control, which use switch contacts, or proportional control, which use potentiometers (pots), digital encoders, rotary variable differential transformers. Each has its own niche application. Joysticks can be further classified into discrete control, which use switch contacts, or proportional control, which use potentiometers (pots), digital encoders, rotary variable differential transformers (RVDTs), induction coils, or Halleffect devices. Force (nondisplacement) controls primarily use induction coils or strain gauges as output devices. Small finger-operated joysticks are also made in displacement and force types. Displacement joysticks in this category generally use potentiometers and Hall-effect devices for proportional output and microswitches for discrete output.
Switching-type joysticks use high current and voltage mainly on equipment that requires stepped, discrete control of a motor drive. At the other end of the spectrum are finger-operated joysticks that control microswitches. These are often used as simple discrete (bang-bang) controls — one switch closure in each direction — for single-speed directional control.
The most-common use of a joystick is for proportional control of machinery through an electric motor control, electrohydraulic valve, hydraulic pump or computer.
Encoders and RVDTs are highly reliable, non-contacting output devices. Because of their large size and high cost, they are normally used in large controllers that are integrated into equipment that requires highly reliable components, where failure and downtime come at an extraordinarily high cost. Cranes used in metal-producing mills and container-handling terminals are examples of applications using these devices. Strain gauge-type joysticks are generally relegated to use as small force-type joysticks.
This leaves joysticks using pots, induction coil or Hall effect as the most-commonly preferred controllers. Of these three types, the joystick using a potentiometer as a primary output device is predominant.
Pot joysticks using conductive plastic pots have published life spans in excess of 10 million cycles. In applications that don't have severe vibration, this duty cycle results in a very respectable lifetime for the joystick, if it is operated and maintained properly. Because pots are small devices, they can be included as components on both large and small joysticks. This allows flexibility in the design of machine control because the joysticks can be placed almost anywhere.
Electronically, the pot output can be used directly, producing a variable DC voltage, or that signal can be processed further through circuitry to produce a pulse width modulated (PWM) signal, a digital serial stream (RS232, etc.) or other variants of analog and digital signals. Potentiometers also are relatively immune to electrical emissions from outside sources. This makes their operation predictable around high voltage power transmission lines or in any application where the joystick may come in close proximity to a strong electric field.
As the most-widely used type of joystick, pots are found controlling the movements of excavators, agricultural equipment, aerial work platforms, scissor lifts, skid steer loaders, pavers, compactors and a wide variety of other construction equipment.
The disadvantage of using a potentiometer in a joystick is realized only if the application involves very