{"id":6271,"date":"2019-08-12T17:00:19","date_gmt":"2019-08-12T21:00:19","guid":{"rendered":"https:\/\/dronebotworkshop.com\/?p=6271"},"modified":"2023-04-12T11:20:06","modified_gmt":"2023-04-12T15:20:06","slug":"touchscreen-arduino","status":"publish","type":"post","link":"https:\/\/dronebotworkshop.com\/touchscreen-arduino\/","title":{"rendered":"Touchscreen Display with Arduino"},"content":{"rendered":"\n

\"Download \"Parts<\/a> \"View<\/a> \"Download<\/p>\n

Introduction<\/span><\/h2>\n

Touchscreen displays are everywhere! Phones, tablets, self-serve kiosks, bank machines and thousands of other devices we interact with make use of touchscreen displays to provide an intuitive user interface.<\/span><\/p>\n

<\/div>\n

Today we will learn how touchscreens work, and how to use a common inexpensive resistive touchscreen shield for the Arduino.\u00a0 Future videos and articles will cover capacitive touchscreens, as well as a touchscreen HAT for the Raspberry Pi.<\/span><\/p>\n

Before we discuss how these devices work, let’s first look at their history.<\/span><\/p>\n

\"Touchscreen<\/p>\n

History of the Touchscreen<\/span><\/h2>\n

Although touchscreens seem to be everywhere these days we tend to forget that just a few decades ago these devices were just science fiction for most of us. For many people, the touchscreen concept was introduced 30 years ago in the television series <\/span>Star Trek: The Next Generation<\/span><\/a>.<\/span><\/p>\n

Eric A Johnson, a researcher at the Royal Radar Establishment in Malvern UK is credited for describing and then prototyping the first practical touchscreen. HIs device was a capacitive touchscreen, and it\u2019s first commercial use was on air traffic control screens. However, the touchscreens used then were not transparent, instead, they were mounted on the frame of the CRT display.<\/span><\/p>\n

In 1972, a group at the University of Illinois filed for a patent on an optical touchscreen. This device used a 16×16 array of LEDs and phototransistors, mounted on a frame around a CRT display. Placing your finger, or another solid object, on the screen would break two of the light beams, this was used to determine the position and respond accordingly.\u00a0<\/span><\/p>\n

The first transparent touchscreen was developed at <\/span>CERN<\/span><\/a> in 1973. CERN is also home to the Large Hadron Collider, and this is where Tim Berners-Lee invented the World Wide Web.<\/span><\/p>\n

The first resistive touchscreen was developed by American inventor George Samuel Hurst in 1975, although the first practical version was not produced until 1982.<\/span><\/p>\n

In 1982 the <\/span>University of Toronto’s<\/span><\/a> Input Research Group developed the first multi-touch touchscreen, a screen that could interpret more than one touch at the same time.\u00a0 The original device used a video camera behind a frosted piece of glass. Three years later the same group developed a multi-touch tablet that used a capacitive touchscreen instead.<\/span><\/p>\n

The first commercial product to use a touchscreen was a point-of-sale terminal developed by Atari and displayed at the 1986 COMDEX expo in Las Vegas. The next year Casio launched the <\/span>Casio PB-1000 pocket computer<\/span><\/a> with a touchscreen consisting of a simple 4\u00d74 matrix.<\/span><\/p>\n

LG created the world\u2019s first capacitive touchscreen phone, the <\/span>LG Prada<\/span><\/a> used a capacitive touchscreen and was released in early 2007. A few weeks later Apple released its first iPhone.<\/span><\/p>\n

How Touchscreens Work<\/span><\/h2>\n

Although there have been many technologies used to create touchscreens the two most prevalent are Resistive and Capacitive touchscreens.<\/span><\/p>\n

Most early touchscreen devices were resistive, as this technology is generally less expensive than capacitive screens. However, nowadays capacitive screens are more common, being used in the majority of smartphones and tablets.<\/span><\/p>\n

Each technology has its advantages and disadvantages, which I will describe below.<\/span><\/p>\n

Resistive Touchscreens<\/span><\/h3>\n

Although they were invented after capacitive touchscreens, resistive touchscreens are probably the most common type used by hobbyists. The reason for that is the price and performance, resistive touchscreens are cheaper than capacitive ones and they are generally more accurate.<\/span><\/p>\n

\"Resistive<\/p>\n

A resistive touchscreen consists of two thin layers of material, separated by a tiny gap.\u00a0 Spacers are used to maintain the gap and keep the two sheets apart.<\/span><\/p>\n

Both sheets have a conductive side, and they are arranged so that the conductive sides face one another.\u00a0 The top sheet is both flexible and transparent. The bottom one is also transparent, however, it is usually solid.<\/span><\/p>\n

In operation, the resistance between the two sheets is measured at different points. Pressing down upon the tip sheet will change that resistance, and by comparing the measurement points it can be determined where the screen was pressed.\u00a0 Essentially, it creates a pair of voltage dividers.<\/span><\/p>\n

\"Resistive<\/p>\n

Resistive touchscreens come in a number of different configurations:<\/span><\/p>\n

4-Wire Analog<\/span><\/h4>\n

In a 4-Wire Analog touchscreen, there are two electrodes or \u201cbusbars\u201d on each of the conductive layers.\u00a0 On one layer these electrodes are mounted on the two X-axis sides, the other layer has them on the two y-axes.\u00a0<\/span><\/p>\n

Each layer has wires connected to the busbars. The top ones are the X+<\/em> and X-<\/em> connections, the bottom ones are labeled Y+<\/em> and Y-<\/em>.<\/span><\/p>\n

This is the most inexpensive method of designing a resistive touchscreen. The touchscreen display that we will be working with today uses this arrangement.<\/span><\/p>\n

5-Wire Analog<\/span><\/h4>\n

In a 5-Wire Analog touchscreen, there are four wires, one connected to a circular electrode on each corner of the bottom layer. A fifth wire is connected to a \u201csensing wire\u201d, which is embedded in the top layer.<\/span><\/p>\n

Touching any point on the screen causes current to flow to each of the bottom electrodes, measuring all four electrode currents determines the position that the screen was touched.<\/span><\/p>\n

With fewer components and a simpler design, the 5-Wire Analog touchscreen is considered to be a bit more durable than other designs.<\/span><\/p>\n

8-Wire Analog<\/span><\/h4>\n

This 8-Wire Analog touchscreen uses an arrangement of electrodes identical to the 4-Wire variety. The difference is that there are two wires connected to each electrode, one to each end.<\/span><\/p>\n

While this is the most expensive arrangement it is considered to be more reliable.<\/span><\/p>\n

Resistive Touchscreens – Advantages & Disadvantages<\/span><\/h4>\n