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Membrane Keypads

Membrane keypads and membrane switches offer designers of electronic equipment a flexible, customizable user interface which is compact, versatile, reliable and assembly friendly.

Membrane Features

Electronic Imaging offer membrane keypads/switches that can incorporate the following:

  • Stainless Steel Tactile Inserts,  giving a positive “click” when keys are pressed.
  • Dome embossed buttons (no inserts) – providing a softer tactile response.
  • Embossing of logo’s and keys with a rim emboss or pellow emboss.
  • LCD Windows can have a high gloss for clarity applied to otherwise “matt” finished overlays.
  • Embedded LED’s in white, red, green, orange, blue.
  • Transparent tinted LED windows in the colour of your choice.
  • “Dead front” Windows which are invisible until back lit. (like seatbelt signs in most cars)
  • ZIF or Female Clinch Connectors for tail termination. ( tail pitch of 2.4′ or 1mm).

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Construction

Constructed of layers of polyester (PET) film combined with spacers and adhesive, electrically conductive inks are printed onto the film to form a circuit. Total thickness is typically 1-2mm. Depending on the application and environment, graphic overlay materials can be specified to resist harsh environments such as high moisture, high UV and chemicals. Tactile Feedback of switches can be built into the keypads by insertion of stainless steel tactile discs or embossing of the overlays. Electronic Imaging can supply either Female Clinch or ZIF connectors (see specifications here)

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Lighting Options

Electroluminescent Lighting (EL)

EL lighting can be incorporated into membrane keypads, and is achieved through a printing process, thus giving great flexibility in customizing the design to your specific application.

A layer of phosphorescent material is printed between two conductive electrodes. When an AC current is applied to the electrodes the phosphor emits light.

 

This technology has a definite life cycle – in a typical application, this would be a half life of about 3000 hours. EL panels are driven by an AC source, commonly 120AV at 400Hz. An inverter derives this from DC supply of 5-24VDC. The higher the frequency, the higher the light output. The lifetime is also inversely correlated to the frequency – increased light intensity reduces lifetime. Often the Integration of a light sensor or timer within the circuit to switch the panel on and off extends the effective life of the EL panel.

Electroluminescent Lighting Panels are sensitive to humidity, moisture, and UV light, all of which are taken into account at the design stage.

Lumitex Woven Fibre Backlighting

Lumitex is a patented woven fibre optic sheet commonly used for applications such as LCD backlighting, Membrane switches, machine vision applications.

A computer controlled loom produces a sheet of precisely laid optical fibres, which is then laminated into layers to form the backlighting panel.

The thin panel is heat and EMI free and provides superior brightness, longer life, and significant design flexibility when compared with other backlighting methods. Power requirements can be as low as 10-20mA at 2 VDC and no inverter.

The light source is LED, or gas filled bulb, or halogen, and can be simply changed.

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The above image shows the fibre optics bundled into a round ferrule where a light source is then attached.

Applications

Electronic Equipment requiring a user interface such as:

  • Eftpos Terminals
  • Hand held instruments/test equipment
  • Electric Fence Controllers
  • Petrol Station Pump Keypads
  • Weighting & Measuring Equipment

Above: Fibre optics bundled into a round ferrule where a light source is then attached.

Quality Tests

In addition to standard quality checks through the production process, Electronic Imaging performs testing for:

  • Button Actuation force (when specified)
  • Switch Actuation life (mechanical finger)
  • Loop Resistance (all work)
  • Continuity / High Resistance test (every switch)

Understanding your needs

We can assist with advice at the design stage of a product development. Contact us here.

Information that is helpful in providing an accurate quote will include the following:

  • Company Contact Details
  • Quantity Required?
  • Dimensions of membrane?
  • Tail Length?

Operating Voltage

  • Operating Voltage (V)?
  • Operating Current (mA)?
  • Max Loop Resistance (ohms)?
  • EMI Shielding required?
  • ESD Shielding required?

Contact Configuration

  • Matrix?
  • Common bus?
  • Combination?

Tactile Switching

  • Stainless Steel Inserts?
  • Inserts & Emboss?
  • Emboss Only?

Termination

  • None?
  • Clampon Female?
  • ZIF?

 

Usage

Estimate of daily key actuation

  • Low (0-15 actuations per day)
  • Med (30 + actuations per day)
  • High (100 + actuations per day

Environment

  • Outdoors?
  • Humidic Sealing?
  • Chemical or toxic exposure?

Overlay

  • Number of colours?
  • Material Finish (Gloss or Matt)?
  • LED Display or Windows?
  • Transparent Tints or Dead fronts?

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