Other Touch Technologies

The next time you are using a touch screen ATM, simply touch the screen without applying any pressure. You will find that the machine will not accept any input.

Apply pressure on the screen and it will start working. This is resistive touch technology in action.

A resistive touch screen is made of two transparent layers of glass or plastic, each coated with a conducting layer of Indium Tin Oxide (ITO). The conducting sides face one another and are separated by an air gap.

When pressure is applied by the user, the top layer bends and touches the bottom layer. This causes a small amount of current to flow at the point where they connect. The location of the touch event can then be measured by the sensors.

Unlike most other types of touch screens (capacitive, infrared touch screen technology ) these screens have moving parts. Depending on how they are fabricated, these screens can be classified as:

Analog 4 wire resistive

In this variant, if the top sheet has electrodes for the vertical direction (Y), the bottom sheet will have electrodes for the horizontal direction (X). The top and bottom sheets measure each others’ voltages and based on that sensors can determine the location of the touch point.

Analog 5 wire resistive

In this variant, the voltage of the bottom sheet is measured by the top sheet, with electrodes placed at four corners of the bottom sheet. The top sheet does not have any electrodes.

Analog 8 wire resistive

These screens are similar to Analog 4 wire screens. The only difference is an extra set of electrodes, which automatically take care of alignment and recalibration issues that crop up in the 4 wire screens over long term use.

Pros of Resistive Touch Technology

• Inexpensive to make
• Can accept an input from anything, including pens, gloved fingers etc
• Can be easily assembled from the component parts; screens and sensors
• Can work in rain or in the presence of other fluids

The Baanto ShadowSense Advantage

Resistive touch screens have a number of issues which are addressed by ShadowSense touch screens.

ShadowSense vs Infrared Touch

Using LEDs and light sensors placed on the vertical and horizontal axis of a bezel, the Infrared system casts a grid of light across the screen. When an object touches the screen, it interrupts the light beams on the grid causing the light to be blocked from the sensor. This loss of light is used to determine the location of the touch. Since the LEDs and sensors make a grid, the touch results in an X and Y coordinate from the beam break. These coordinates then communicate with the display to react with the software on screen.

• Can be accidentally activated due to high ambient light
• Suffers from lower resolutions creating inaccurate touch points
• Cannot distinguish between user input or foreign objects like mud or insects crawling on the screen
• Response times are slow as the operation is CPU intensive

Infrared touch screens have several issues that can impact their performance. ShadowSense touch screens are similar to infrared touch screens as both use infrared light and both have sensors, but that is where the similarity ends. ShadowSense has significant advantages over conventional infrared touch technology. Curious? – discover the ShadowSense advantage.

ShadowSense vs Surface Acoustic Wave Touch

To truly understand the ShadowSense advantage, it’s important to explore other touch technologies, how they work, and what they can do.

Surface Wave Acoustic (SAW) technology operates by tracking sound waves above the human hearing range, also known as ultrasonic waves, to detect the location of touch points on the screen. This technology is perimeter-based, such as Infrared and Optical touch technology, but use sound instead of light for its calculations.

A SAW touch screen is made up of a glass sheet with three components: transmitting transducers, receiving transducers, and reflectors. The transmitting transducers produce ultrasonic waves that skim over the surface of the screen, get reflected and are captured by the receiving transducers.
When a soft matter like human skin, touches the screen, the surface acoustic waves are absorbed, and the receiving transducers do not register any input. Based on this lack of sound the sensors can calculate the location of the touch event.

• Do not function with a pen or any other hard material
• High multi-touch latency
• Can malfunction when dirt, oil, or droplets stay on the screen
• Perimeter can’t be sealed from the environment and so attracts buildup in bezel

Surface Acoustic Wave has several issues that can impact performance and universal deployment. ShadowSense has significant advantages over SAW touch technology. Curious? – discover the ShadowSense advantage.