Earlier this month, we published an article on the introduction to touchscreen technology, focusing on capacitive touchscreens. Let’s take a closer look at resistive touchscreens.
How do resistive touchscreens work?
Resistive touchscreens are mechanically activated by the application of pressure. On this basis, two transparent layers of glass or plastic – generally polycarbonate or PET film – are stacked one above the other and coated with a transparent, electrically conductive metal coating called indium tin oxide (ITO). The sheets have a uniform resistance value over their surface. These conductive sheets are separated by thin, compressible “spacer dots” to prohibit contact. The spacer material is limited to polymers that can be manufactured into small, cushioning beads or UV coated from monomers. The dots are usually printed onto the bottom layer at intervals. A DC voltage is applied across the two layers and electrodes are placed on each edge of the screen to collect the position data.
Pressure is essential to the working of the resistive touchscreen. Whereas in a capacitive touchscreen, a finger or stylus approaching the screen alters the capacitance of the touch location, resistive touchscreens utilize finger pressure to make an electrical “short” in a circuit.
When the screen is touched (pressure is applied), the spacer dot is compressed, which enables electrical contact between the two sheets. The layers connect at the point of pressure, thereby forming a voltage divider; the entire bottom layer takes on the same value as the top layer touch-point potential. At this voltage divider, the electrical resistance can be measured and the exact position of the pressure points determined. The position information is collected by the electrodes and transmitted to a small controller with precision down to the millimeter. This data is then relayed to a connected computer that reacts accordingly to the signal. For a resistive touchscreen, no pressure means no connection between the conductive sheets – no signal is produced.
Benefits of a Resistive Touchscreen:
- Responsive to various types of inputs, including pens, heavy gloves, etc
- Can work in rain and resistance to other fluids, i.e.
- Not susceptible to electromagnetic interference due to mechanical activation
- Suitable for handwriting recognition
- Does not support multi-touch (cannot use two fingers)
- Not very sensitive and significant pressure is needed for activation
- Distortion in electric field between layers can cause errors in touch detection
- Flexible membrane is vulnerable to damage from sharp objects
Resistive touches are cheaper and more suitable than capacitive touchscreens in single-touch, heavy duty applications. For instance, food and beverage processing facilities may harbor many foreign particles that would interfere with a capacitive touchscreen, but a resistive touchscreen would not be affected. A resistive touch’s flexible polymer coating shields the underneath glass layer from exposure, making it suitable for food and beverage environments with “no exposed glass” policies and other rugged environments.
Hoffmann + Krippner’s touchscreen solutions are functional as an individual component or can be integrated into keyboards with complete electronics. They can be customized according to customer requirements, from basic prototypes to large-scale production.
Find more information about touchscreens and which solution works best for your application here.
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Ariadna is a junior at Cornell University studying Materials Science and Engineering. She is a staff writer for The Cornell Daily Sun and a member of the Nanoscale Materials for Energy Lab.