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Keypads & Interfaces

Keypads and interfaces are the bridge between electronics and the outside world. These tools not only provide the user with a set of controls, but also supply feedback and provide direction. Keypads and interfaces are an integral part of many electronic devices, and their significance is immense. ALMAX develops unique, custom-made keypads and interfaces created to meet our customers’ needs. We offer a broad range of options and features, allowing you to find the ideal interactive technology for your application.

Keypads & Options

ALMAX offers a broad spectrum of options when it comes to their interfaces. From switches and sensors to materials and backlighting, the possibilities for customization are practically endless. However, given the complexity of the design and engineering of keypads, it is important to have the support of experienced and trustworthy experts - something which ALMAX has been providing for over two decades. With our help, the process of implementation can be made simpler and the end-user can benefit from a product with superior usability and appeal.

Why ALMAX for Keypads?

The benefits of using our top-tier interfaces is a long list, but in short: 

  • Innumerable Options
  • Cost-Effective
  • Compact & Thin Profile
  • Efficient Input & Output Controls
  • Built-In Graphics & Cosmetics
  • Water Resistance & Sealing
  • Easy Integration
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Keypads & Options

ALMAX provides a wide variety of available options including switches, sensors, materials, graphics, displays, backlighting, circuitry, and interconnects, making our interfaces extremely customizable

 

With such an overwhelming list, it is important to have experienced and trusted interface experts you can rely on, as the design and engineering of a keypad can be the most important part of a products development, making or breaking the usability and visual appeal for the end-user.

 

Fortunately, with over 20 years’ experience in the field, ALMAX is trusted around the world to help simplify this process for any implementation.

 

TransparentFiller

Graphic Overlay

Backlighting + Spacers

Dome Retainer

Circuit Assembly

Control Technologies

Flex Tail Interconnect

Display Window

Embossing & Textures

Smart Keypad Host System

Why ALMAX for Keypads?

The benefits of using our top-tier interfaces is a long list, but in short: 

  • Innumerable Options
  • Cost-Effective
  • Compact & Thin Profile
  • Efficient Input & Output Controls
  • Built-In Graphics & Cosmetics
  • Water Resistance & Sealing
  • Easy Integration
Request Quote

Keypad Control Technologies

Control Technologies are the interactive components of the interface. These technologies include elements such as switches, rotors, and/or sensors. The control technologies chosen for an interface ultimately determine the manner in which the operator will be interacting with their system. The controls chosen for an interface will influence the overall design and structure of the keypad.

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Membrane Switches are typically used for momentary switches and multiplexed keypads. They are constructed directly into the layers of the keypad assembly, keeping the interface thin and versatile. Membrane Switches come in many different kinds and options such as Metal Domes, Polyester Domes, Tactile, Non-Tactile, Force Sensors, SnapMax Switches and more.

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By employing the capacitance of the human hand for detection, capacitive sensors can be activated by contact or by distance. The beauty of capacitive sensing is that they can be used to substitute a wide range of conventional technologies, including buttons/switches, rotors, potentiometers, resistive touchscreens, hall effect sensors, and more.

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A force sensitive resistor (FSR) is a material which changes its resistance when a force or pressure is applied. In other words, FSRs are sensors that allow you to detect physical pressure, squeezing and weight. They are simple to use and low cost. Conductive film is an example of a force resistance material.

The MaxRotor®, is a fully customizable, non-invasive, low-profile encoder allowing a diverse array of keypad design options. As the only rotor that can be mounted directly into a flexible circuit, the MaxRotor® makes design integration easier than ever. A thin, lightweight component with built-in sealing capabilities prevents the introduction of contaminants and allows for extended lifespan.

Surface mount or thru-hole switches are commonly used in various applications where thickness is not a concern, or due to various housing application requirements. These are no different than the alternatives except that they are self contained in miniature housings which are then soldered/mounted directly to the circuit layer. We generally don’t recommend these due to the large size and additional costs associated with them, but in some rare cases they may be the only option.

Hall Effect sensors are becoming more popular as they can be used in many applications such as sensing position, proximity, speed, current, rotation, velocity and directional movements. Also, since these are sealed, non-contact sensors, they are wear-free having a virtually unlimited life along with immunity to vibration, dust and water.

A light sensor is a photoelectric device that converts detected light energy (photons) into electrical energy (electrons). Light sensors are available in many different types and configurations, but the primary 3 are Photoresistors (LDR), Photodiodes, and Phototransistors. The most common use for light sensing interfaces is detecting ambient light, generally used to auto-adjust backlighting intensity, or screen brightness based on the current environment lighting.

Touch screen optical bonding is a valuable process that can enhance the performance, durability, and aesthetics of touch screens. By reducing the reflection and refraction of light, improving image clarity, contrast, and color accuracy, and providing additional protection against scratches, impact, and chemical damage, touchscreen optical bonding can improve the user experience and reduce maintenance costs.

Touch Screens & Optical Bonding Page

Keypad Graphic Overlays

A graphic overlay is the outermost layer of the keypad. It displays the cosmetic portion of the assembly such as color, text display windows, key functions, etc.

 

Overlays act as intermediary between user and machine by depicting functions, with no conductive traces or circuitry.

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Polyester is the most common choice for an overlay material as the flex life when actuating a switch is much greater. In addition, polyester is resistant to chemicals, acids, solvents, and scratches. It is also tougher, more durable, and available with additional hard coatings for increased durability. If you need the strongest most resilient substrate for a graphic overlay, then polyester is the way to go.

Silicone Rubber keypads are used often in consumer and industrial electronic products due to its low cost and reliability. Using the compression molding properties of silicone rubber to which upon depression of the switch the webbing uniformly deforms to produce a tactile response. When pressure is removed from the switch the webbing returns to its neutral position with positive feedback.

Acrylic (or PMMA – Polymethyl Methacrylate) is a rigid and transparent material that is often used as an alternative to using glass as it is often cheaper and slightly more flexible. It can be printed on the front or backside to change its color and add graphics or instructional information. Acrylic is often used as an overlay with cutouts for rubber switches or without cutouts for capacitive sensing applications.

ALMAX manufactures metal overlays that are designed for rugged environments. The metal unit can be sealed against contamination including dust, water, sea water and oils. It also provides resistance against detergents and chemicals. What metal is used will determine what it the keypad will be resistant to.

Tempered glass is glass that is thermally and/or chemically treated which results in increased material strength. The dielectric constant of glass is higher than that of polyester, polycarbonate, and acrylic, thus allowing for higher key sensitivity for capacitive sensing applications. The abrasion resistance of tempered glass is also superior to many other material options.

In-Mold Decoration (IMD) is a process where a graphic overlay is physically fused to injection molded plastic to form one piece. It is a plastic decorating method that ensures the durability of the graphic overlays and allows for multiple design options for the overlays. Molten resin is injected either in front or behind the graphic overlay to form a bond between the two. Unlike pad printing, screen printing, or hot stamping – where inks and overlays are exposed to the user that can deteriorate over time – IMD parts have a layer of plastic that encapsulates the ink, protecting it from users and the outside environment.

Additional Materials are available for use on overlays, and more information can be found by contacting ALMAX directly. Also, various textures can be added onto an overlay to give it the desired feel and look for the end user.

Keypad Backlighting

Backlighting consists of strategically placed light sources within an interfaces construction, making keypads, legends, and displays easier to read. There are various cosmetic and cost advantages and disadvantages to be considered, based on the backlighting method employed. 

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Indicators use LEDs for their source of light, the main difference being that indicators are top fire LEDs, shooting light directly up through overlay. They also don’t require their own layer to be integrated, and can be mounted directly to the circuit layer. Indicators can be used in combination with other lighting options available and provide a simple and effective way to translate processes to the operator.

Light Guide Film is a 0.005-0.020“layer that incorporates microdots pressed into the imaged areas that are to be backlit. Cutouts are made in the film to place side view LEDs at the appropriate location. The light rays from the side view LED travel through the film and are refracted upwards towards the surface of the overlay once it hits the microdots, producing a uniform backlighting effect.

The addressable LED is the latest advance in the quest for a simple, scalable and affordable full-color LED. Red, green and blue LEDs are integrated alongside a built-in driver chip all on a single tiny surface-mount package controlled through a single wire (or two dependant on LED chosen). They can be used individually, chained into longer strings or assembled into still more interesting form-factors.

Electroluminescent backlighting on flat user interfaces with graphic overlays provides uniform illumination when backlit with electroluminescent (E/L) lamps. E/L lamps are custom-manufactured with very thin layers of plastic film with a transparent conductive surface with encapsulated phosphors that illuminate when energized.

A fiber optic lamp consists of two or more layers of woven fiber-optic cloth used to form a light-emitting area. The fibers coming off one end are bundled into a ferrule and coupled to one or more LED light sources. The light from the LED is evenly distributed by the use of very thin plastic fibers. Fiber optic lamps are generally used to achieve more uniform backlighting across a broader area of a keypad. 

Keypad Circuits & Substrates

The Circuit Layers primary function in a keypad is connecting onboard electronic components together in a compact space.

 

Substrates are the carrier for the circuitry to be printed or etched onto, while the circuits provide pathways for electrons to flow between components.

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Flexible circuit technology provides significant additional capabilities beyond other available methods. These include reduced packaging requirements, improved reliability, shock and vibration performance, high-speed signal performance, harsh environment performance, and reduced cost opportunities. They can also be manufactured using a multitude of various substrates and conductive materials.

Rigid circuits simply refers to using standard PCBs (or printed circuit boards), which are typically made from copper-clad cloth or fiber that is infused into a resin material. The cloth/fiber used, along with the resin material, creates a cloth-to-resin ratio to determine its laminate type designation (FR-4, CEM-1, G-10, etc.). FR-4 is easily the most common rigid substrate used today.

Hybrid Circuits are an innovative process which blends the durability of traditional electronic circuits with the extreme malleability of flexible circuits. This combination allows us to create a uniquely resistant solution that is extremely bendable and can adapt to many kinds of shapes and situations. 

Rigid-flex circuits combine the best of both rigid boards and flexible circuits integrated together into one circuit.  The two-in-one circuit is interconnected through plated thru holes. Rigid flex circuits provide higher component density and better quality control. Designs are rigid where extra support is needed and flexible around corners and areas requiring extra space. Note that these are different than Hybrid Circuits.

Smart Keypads

Smart Keypads® implement onboard co-processing units that communicate using standard communication protocols. Smart Keypad’s allow host systems to alleviate high GPIO usage and precious processing consumption.  Customizable from top to bottom, Smart Keypads® reduce your design & development complexity, allowing our customers to reach faster time to market deadlines, reduce costs, and achieve overall simpler integration throughout the product development process.

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Smart Keypads® implement onboard co-processing unit(s) that can either be an ALMAX custom programmed Microcontroller, or utilize off-the-shelf integrated circuits such as GPIO expanders, LED Drivers, Capacitive Drivers and more.

One of the less thought of benefits of Smart Keypads is a reduction in tail or interconnect traces and size. Because the only thing needed to communicate with a smart keypad is serial communications, the number of traces that need to come off of the keypad can be reduced in some cases all the way down to just 3 lines. This can bring about space savings as well as hefty cost reductions and shorter production times.

Smart Keypads® generally utilize standard communication protocols and are chosen based on customer request or through ALMAX recommendations. Typical protocols used for Smart Keypads are RS485, I²C, SPI, MODBUS, 1-Wire, UART, and more.

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