As resistive and capacitive touch technologies have become more cost effective with far greater performance, these high-tech HMI designs have become more widespread across all industries from consumer products, to medical, and even military applications. Manufacturers continue to phase out the legacy dome and tactile switches with higher reliability touchscreens that offer far superior flexibility, fewer moving parts, and the ability to downsize and consolidate system components. However, this brings a new and unique set of program concerns such as integration, firmware development, obsolesce/material risk, and most importantly understanding what technology works best for the right application. This webinar will review the technology behind today's touchscreen products and the steps necessary to bring next-generation products to market. For more information on our human-machine interface solutions visit http://www.epectec.com/user-interfaces/.

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From Mechanical HMIs to Touch
Old vs New Technology
08.30.18

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Agenda
 “Old” vs “New” Generation HMI Technologies
 When to use FPC (Polyimide)
 Capacitive Touch & Touchscreens
 Switch from Membrane Switch to Capacitive Touch
 How to Nextgen your SMART HMI Device

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“Old” vs “New” Generation HMI Technologies

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“Old” Generation HMI Technologies
 1980’s Technologies
– Membrane Switches
– PCB Mounted Switches
– Elastomeric Keypads
– Hard Plastic Keycaps
– Flexible Circuits
– EL Backlight
 Technologies are still common today.
 High reliability products when designed right.

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“New” Generation HMI Technologies
 Breakthroughs In Materials
– Hard Coated Overlay Films
– Light Guide Films (LGF)
– Copper On Polyimide/Kapton
– Shielding Designs
– Optical Bonding Adhesives
– Touchscreens, PCAP, Resistive

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“New” Generation HMI Technologies (continued)
 Cost Reductions Of Legacy Technologies
 Embedded Systems
– Microcontrollers
– Firmware
– SMART Devices

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When to use FPC (Polyimide)

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When To Use FPC (Polyimide)
 Ultra High Reliability Devices
– Circuit layout and design is vital
 Fine Trace Widths
– Footprint reduction, tail exit location
 Surface Mount Components
– Small package LEDs, ICs
 Minimal Cost Impact for Small Devices
– ~20 in2 or less
 Excellent for Capacitive Touch
Case Study: 15x reduction in
measured circuit measured
resistance 31 Ω vs 2 Ω

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Capacitive Touch & Touchscreens

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Capacitive Touch Switches
 Sleek, Glossy Interface
 No Mechanical or Moving Parts
– Switches designed of clear conductive ink or copper traces

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Capacitive Touch Switches (continued)
 Do not behave as a normally open switch
– Must be paired with microcontroller
 Uniform backlighting options
 Digital control of switch function and sensitivity
Example of capacitive
touch switch
X
X
X
X
X
Similar to membrane
switches, but with the
domes removed

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Material Properties - Capacitive Touch
 The dielectric constant defines key sensitivity.
 The higher the dielectric constant of the material, known as “k”, the higher the
key sensitivity.
– (ex. the easier it is to trigger the switch)

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Material Properties - Capacitive Touch (continued)
 Overlay thickness and application drive material selection
 Select the right material for the application
– Wipe downs
– Harsh chemicals
 Perform abrasion testing
Hard coated Acrylic and
Tempered Glass are hardest

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Switch from Membrane Switch to Capacitive Touch

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Move from Membrane Switch to Capacitive Touch Switch
 Elimination of normally open dome
switches
 Addition of firmware and
microcontroller
 Inexpensive off the shelf
components
PC GUI Test
Interface
Customer
Controller
Minimal Cost Impact In Switch From Membrane Switch To Capacitive Touch

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Touchscreens
 Resistive Touch
– Two conductive flexible sheets with an air gap
– Poor response to light touch
– 5 wire design is most common
 Projected Capacitive Touch (PCAP)
– Glass overlay with transparent conductive coating
– Change in capacitance correlates to switch closure at X-Y locale
– Some designs have the microcontroller embedded on the flex tail

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Touchscreens (continued)
 Operational Considerations
– COTS vs Custom
– Resolution/Size
– Multitouch
– Gloves
– Moisture

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How to Nextgen your SMART HMI Device

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How to Nextgen your SMART HMI Device
 Understand your existing design
 Review technology examples
 Requirements matrix
– Must have vs Nice to have
 Qualification requirements
 Have a plan for your firmware
* Embedded System Requirements Checklist

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Summary
 Current HMI technologies offer high reliability solutions, with sleek
features that are truly customizable.
 Use today’s technology to guide the user through the experience.
 Multiple cost effective resistive or capacitive touch options exist for
your project.

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Our Products
Custom Battery Packs Flex & Rigid-Flex PCB’s High Reliability SMART HMIs
RF Product Solutions Cable Assemblies Printed Circuit Boards

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Q&A
 Questions?
– Enter any questions you may have
in the Control Panel
– If we don’t have time to get to it, we
will reply via email

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Thank You
Check out our website at www.epectec.com.
For more information email sales@epectec.com.
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