Touchscreens are everywhere these days. Tablets, phones, ticket machines, cash dispensers – they’ve all benefited. But, applying touchscreen technology to large screens is rather more difficult. Here’s why, and how Sharp solved the problem with their flagship 80” BIG PAD Pro interactive whiteboard solution.
How Ordinary Touch Screens Work
The easiest way to make a capacitive touch screen is to coat one side of the screen with a transparent conductive layer, such as indium tin oxide. A small voltage is applied to the four corners of the screen and this creates a uniform electric field. When a human finger touches the other side of the glass the device’s controller can determine the location of the touch from the change in the capacitance as measured from the change in voltage in the four corners of the panel.
The limitations of standard capacitive touch screens
Standard touch screens are fine for small screens and simple applications, which only need one touch at a time. Multi-touch is not possible with conventional capacitive touch technology and there can be problems with false touch activations, due to unexpected signals from environmental electrical changes. The usual touch technology for a large format display is based on infrared (IR) which can have touch latency issues.
Understanding P-CAP Touch
With Projected Capacitive Touch (also known as PCT or PCAP), conductive wires are layered in rows and columns on two parallel sheets of glass; essentially a grid pattern of fine wires is created and voltage is then applied sequentially to the rows and columns. Wherever the screen is touched by a finger the controller identifies the change in capacitance in the grid of wires. PCT screens can recognise multiple touch points. However, ‘noise’ and unintended touch inputs can still be a problem.
80" PN-80TC3 - Breaking New Ground
The PN-80TC3 professional-class interactive whiteboard enhances the Projected Capacitive Touch technology with an advanced controller and faster sampling techniques. The controller employs a unique algorithm which through increased sampling speeds of 220Hz and stronger signal creation reduces the amount of noise right down to 1/8 of that which would otherwise be expected. Touch accuracy is improved, unintended and false inputs are almost completely eliminated, and latency (time lag) is virtually eliminated.
The user experience
BIG PAD’s touchscreen can recognise up to ten simultaneous touches with pinpoint accuracy and as many as four people can use it at the same time. The Sharp Pen software also utilises unique technology, which allows pen pressure to influence the visible result. The speed and accuracy of the touch input using this approach results in a natural and fluid writing experience, which along with pressure sensitivity feels almost identical to writing on an old-style whiteboard with marker pens.