Touch Sensors, Exactly How You Want Them

 

Lens Choices

Sensor Patterns & Sizes

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Matrix Style Sensor - double diamond pattern, good for gestures

Discrete Style Sensor - specific touch points

  • cost effective
  • better handles harsh user environments
  • helps prevent false touches
  • requires less development time

Slider Style Sensor - cost effective with ability to touch at any point on the X axis

Size of Sensor - The off-the-shelf sensors come in standard sizes (4.3", 5.0", 7.0", 10.4", etc.), however, most industrial and commercial applications are not designed around that size or shape display and have different requirements. Custom sensors allow for any shape and size required.

Acrylic - available in standard thicknesses, including 0.06" (1.5 mm) and 0.118" (3.0 mm), acrrylic is a durable polymer material. Xymox uses only hard coated scratch resistant acrylic for best performance.

Chemically Strengthened Glass - including popular trade names such as Gorilla Glass®, this material provides an excellent touch surface and looks great.

Polycarbonate - a key advantage of polycarbonate is impact resistance, but the trade-off is a softer surface that can be scratched more easily. While scratch resistant coatings are very helpful, the overall surface is not as hard as acrylic or glass.

 

Controller Choices

Tail Location & Design

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The tail connects the electrodes of the sensor to the inputs of the controller. Off-the-shelf sensors use a bonded tail and the length and location are fixed, often requiring the electronics to be reconfigured. A custom sensor can place the tail in most any location on the sensor and can be the exact length that best meets the requirements. Moving the tail on the sensor is often much easier than moving electrically noisy components or adding specialized shielding to those components.

The length and location of the tail can make a significant difference in the cost of the overall part, both through material costs and physical dimensions pertaining to the manufacturing configuration. By strategically positioning the tail in the optimal location, more parts can be printed per sheet, thus optimizing the cost, and integration with the circuitry can happen in the best manner.

There are 2 main ways to create the tail:

Integrated Tail - printing conductive traces on the same polyester sheet that the sensor is made from. Think of it like an extension of the sensor itself. Integrated tails provide the most reliable connection to the sensor. Kodak HCF film with PEDOT allows for an extremely tight bend radius for final assembly - meaning the finished assembly is very durable.

Bonded Tail - made from a different flex circuit and bonded to the sensor. This is the standard configuration for ITO sensors. You typically see the orange colored polyimide tail connected to the transparent sensor using conductive bonding materials to make the electrical connections. One advantage of this style is the ability to include the controller for the sensor on the tail itself (called chipon-flex or COF.) The disadvantage is generally high cost. ITO sensors require this type of tail since ITO is not flexible and would crack.

Integrated tails remove the potential reliability concern associated with bonded tails.

The controller is the brains of the operation. The sensor detects changes in capacitance, and the controller chip is required to interpret those changes.

The standard option sensor most likely with come with a controller on a flex circuit bonded to the sensor. Ask yourself if this is the best controller for the application? Are the settings in the controller optimal for the application? Unfortunately, these settings are not configurable when using the standard sensor option. Most likely they are tuned for consumer applications – not designed for gloves, wet applications, etc.

It is most economical to have the controller be part of the main control board. Placing the controller directly on the tail is only economical when space on the main board is limited. Space is typically not a concern with our customers.