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How to turn your Zytronic touch sensor into a touch screen monitor

09 October 2018

Touch screen monitors are one of the best options for human machine interfaces (HMI), the user and complex equipment in medical, retail, and industrial work environments. But how do you create a touch screen monitor, using a Zytronic touch sensor? Here we will go through the steps needed to create a “Zytronic” touch screen monitor.

Choosing your monitor

There are countless monitor suppliers, offering a wide range of options, the monitor choice will depend greatly on the end application. Important points to consider are: Where will the touch screen be used? If the monitor will be used in an outdoor environment, you may want to consider a monitor with enhanced or high brightness which will be easier to view in direct sunlight. Additionally, it may be advisable to consider a monitor with an improved cooling system if the location will be subject to high ambient temperatures. If the touch monitor is to be used in an interactive digital signage application, e.g. for use in retail or museums and running high resolution content, then perhaps a UHD (aka 4K) monitor would be best. If you’re planning to use the screen in an industrial application, typically, a tough, hard-wearing monitor will be required, to withstand the more strenuous rigors of use in locations such factories, mines and petrochemical plants. Fortunately, thanks to Zytronic’s advanced touch controller technology, our projected capacitive touch sensors are compatible with almost all industrial, commercial and consumer monitors, and are relatively, unaffected by electronic noise, so your choice of display won’t be restricted.

Designing your own Zytronic touch sensor

Now that you have chosen your monitor, you’re ready to design your own Zytronic touch sensor. To do this you’ll need to know several things

  • What is the active/viewable area of the display?
  • What impact resistance is required (influencing the thickness of the touch sensor)?
  • Does the touchscreen need any printed borders or logos applied?
  • Are there any special glass treatments or filters needed for the application?

When you have all this information you can use our “design your own touchscreen” tool on the Zytronic website or contact your local Zytronic sales representative to discuss the requirements.

We’ll then use the basic information provided to create a detailed technical drawing of your new touch sensor for you to review and approve.

Attaching your touch sensor to the monitor

Once you’ve agreed upon the touch sensor design and your prototype order is in place, you’ll then need to consider how you wish  to attach it to your monitor. The2 most popular methods are either VHB (very high bond) tape, or optical bonding. VHB tape, is an extremely strong double-sided adhesive tape that is used to “stick” the perimeter of the touch sensor to the monitor frame, it is a relatively inexpensive method of bonding, and depending on the tape chosen, can resist dirt, and moisture, while maintaining the required air gap for touch sensor functionality and allowing air flow to be directed over the surface of the display for cooling. We would normally recommend at least a 3mm air gap, and for larger screens or displays expected to operate in hot environments, 6mm+. For information about using VHB tape to attach a touch sensor to a monitor, see our integration tips at: https://zytronic.co.uk/insights/article/focus-on-integration/ Optical bonding is a method in which the entire rear surface of the touch sensor is attached to the viewable area of the display. This is achieved by flooding the air gap in between them with an optically clear adhesive such as, Silicone, Epoxy or Polyurethane, and then curing the material to give a durable, optically clear bond. This method provides benefits such as reduced light refraction (parallax), improved light transmission from the display and prevents the screen “fogging up” in humid conditions. However, on the downside, optical bonding can be expensive, is typically a permanent solution with no way of changing the display or touch sensor, should one become damaged, and thermal management of the display can become more of an issue in outdoor applications, as sunlight energy is directly transmitted to the display. Furthermore, this method of attachment reduces the electrical isolation between the display and touch overlay, and therefore electromagnetic interference of the projected capacitive touch sensor may become an issue, especially on larger screens. Therefore, extensive testing should be carried out before the final assembly design is fixed.

Testing the assembly

Once the initial touchscreen monitor design has been prepared, it’s advisable to test a prototype system before moving to production. Our ‘smart’ software tool (Zyconfig™) is free to download from our website and provides an easy-to-use step by step guide taking the user through a series of simple set-up stages. Zyconfig is compatible with most common operating systems, including Windows, Linux and Android. Firstly, the software automatically scans the touchscreen and controller to check integrity and stability of the system on several factors, such as system ‘noise’ (electromagnetic interference or EMI) levels, controller and sensor operation. These checked criteria are shown as a ’pass’, ‘warning’ or ‘fail’, depending on their condition. The next step involves a basic set up routine where the user touches defined points displayed on the screen. This optimises the touchscreen controller sensitivity settings, detecting ambient EMI and adjusting the ‘noise’ filters to suit, and determining appropriate responsiveness to an applied touch without the need for the user to manually set any complex parameters. Finally, a simple touch calibration follows to ensure the controller coordinates are mapped corrected to the display image on the screen. After this set up routine has been completed satisfactorily, you will be able to bond your touch sensor to the monitor with confidence.

Attaching the touch controller

The controller should be positioned so that the touch sensors flat, flexible tails (FCB) can comfortably reach the ZIF connectors on the controller and should ideally be mounted at least 5mm above any metalwork. It is recommended to mount the controller to the rear or the monitor using double-sided adhesive gasket, or metal stand-off points. The controller should then be electrically ‘grounded’ to the metal chassis of the monitor, using low impedance cables. The flexible tails may need to be gently bent into place -  please refer to our user Manuals and Instructional Videos, and remember that they can be folded but not creased, and they should not be pulled tightly (stressing the joint between tail and touch sensor). Once you’ve connected everything, we recommend running the Zyconfig tool again, to double check all the parameters and then the set-up is complete. This should have taken less than a few of minutes to carry out. Now you’re ready to go with your new Zytronic touch screen monitor.    

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