Hardly any machine or device can function without traditional controls such as buttons, switches or keyboards. They still form the basis of most Human Machine Interfaces.
The Human Machine Interface is as old as the first machine developed by humans – thus, the history of control elements dates back to antiquity. It all began with purely mechanical levers and handwheels. With the advent of electrification, it became possible for the first time to operate controls remotely from the function or machine. This led to significant advances in operator safety and allowed users to control all functions or multiple machines from a central control station.
Various designs have been – and continue to be – used: with buttons, push-buttons, rocker switches, and toggle switches or levers, operators can trigger two mutually exclusive options – for example, on/off. Rotary knobs and switches, sliders and slide switches can be used to activate a variety of options or control a function with varying values, such as dimming a light.
Advantages of Electromechanical Controls
Although technologies such as touchscreens or smartphones are increasingly used as Human Machine Interfaces, traditional electromechanical controls still have their place. For instance, they are still essential for critical functions (emergency stop), but even. But even non-critical input operations are sometimes represented by mechanical interaction elements. Encoders, for example, enable the precise input and confirmation of values through rotary push controls, and a tactile grid provides the user with the necessary haptic feedback. The increase in industrial production, higher safety requirements and the growing use in home automation and automotive solutions is ensuring solid growth in the push-button market: market analysts from Dataintelo have predicted an annual increase of eight percent from 2022 to 2030 for industrial applications alone.
Flexibility through Bus Systems
Traditionally, individual controls were discretely connected to the corresponding actuator with one-to-one wiring. But as machines became more and more complex, the installation process became very time-consuming. For complex control systems, thick bundles of cables often needed to be connected to the plant. Today, it is possible to use control elements that communicate with actuators via a bus system, which means that all the switches and buttons are connected via just one line. This saves space and weight and significantly reduces the effort required for maintenance and diagnostics. In the industrial sector, for instance, IO-Link is often used, while in the automotive field, the CAN bus is more common. As well as significantly reducing the amount of wiring, these smart control elements also have the advantage that they can be reprogrammed. If a machine is extended, for example, a switch can be reassigned to a new function. The switching elements can also be individually configured – such as the sensitivity of capacitive buttons or the force-travel curve. Integrated microcontrollers also enable smart functions, such as the timely prognosis of maintenance needs through self-diagnosis.
In the past, especially in the field of working machines, it was often said that operators could “feel” the machine better through traditional hydraulic controls. However, today’s electronic systems also provide mechanical feedback to the machine operator with the help of “force-feedback” solutions.
HMIs for Gamers
When computers started to be integrated into machines and systems, keyboards began to triumph as a Human Machine Interface. Various technologies have become established, but mechanical keyboards are currently trending and are making particular headway among computer gamers: they use small switches under each key to send the corresponding signals. As a result, these keyboards are more expensive than membrane keyboards but offer improved performance in terms of response time and tactility, which are essential for professionals and gamers. Another advantage is their longer lifespan; they last more than 50 million keystrokes, while membrane-based keyboards can only endure about 10 million strokes. In addition, mechanical gaming keyboards allow the user to precisely adjust the operation of the keys to their needs.
Keyboards for Industry
Keyboards are also used in the industrial sector. Here, robust construction, ease of operation and reliable function are of primary importance. The input unit must be protected against vibration and shocks, or even designed to be explosion-resistant. It should be protected against water, dust, dirt, oils and chemicals, and be able to withstand temperature fluctuations. In addition to appropriately encapsulated “classic” keyboards, membrane keyboards and silicone rubber keypads are also used.
Input keyboards are often used today as a supplement to touch systems, depending on the application. Tried-and-tested input components, such as membrane keyboards, silicone rubber keypads and push-buttons remain the preferred choice – including in terms of costs – in devices that have a limited number of functions, require good visibility and are in constant use. This is because the financial expenditure for programming a graphical user interface between human and machine is a significant factor. The rule is: not everything that is technically possible is also economically viable.
