Difference between resistive and capacitive touch panel

Capacitive Touch Screen

Projected capacitive touch screen contains X and Y electrodes with insulation layer between them. The transparent electrodes are normally made into diamond pattern with ITO and with metal bridge.

Human body is conductive because it contains water. Projected capacitive technology makes use of conductivity of human body. When a bare finger touches the sensor with the pattern of X and Y electrodes, a capacitance coupling happens between the human finger and the electrodes which makes change of the electrostatic capacitance between the X and Y electrodes. The touchscreen controller detects the electrostatic field change and the location.

Resistive Touch Screen

A resistive touch screen is made of a glass substrate as the bottom layer and a film substrate (normally, clear poly-carbonate or PET) as the top layer, each coated with a transparent conductive layer (ITO: Indium Tin Oxide), separated by spacer dots to make a small air gap. The two conducting layers of material (ITO) face each other. When a user touches the part of the screen with finger or a stylus, the conductive ITO thin layers contacted. It changes the resistance. The RTP controller detects the change and calculate the touch position. The point of contact is detected by this change in voltage.

Which Is Better Capacitive or Resistive Touchscreen?

  Resistive Touch Screen Capacitive Touch Screen
Manufacturing Process Simple More complicated
Cost Lower Higher: Depending on size, number of touches
Touch Screen Control Type Requires pressure on the touchscreen. Can sense proximity of finger.
Power Consumption Lower Higher
touch with thick gloves Always good more expensive, need special touch controller
Touch Points Single Touch Only Single, two, gesture or Multi-Touch 
Touch Sensitivity Low High (Adjustable)
Touch Resolution High Relatively low
Touch Material Any type Fingers. Can be designed to use other materials like glove, stylus, pencil etc.
False Touch Rejection False touches can result when two fingers touch the screen at same time. Good Performance
Immunity to EMI Good Need to special design for EMI
Image Clarity Less transparent and smoky looking Very high transparent especially with optical bonding and surface treatment
Sliders or Rotary Knobs Possible, but not easy to use Very good
Cover Glass None Flexible with different shapes, colors, holes etc.
Overlay Can be done No
Curve Surface Difficult Available
Size Small to medium Small to very big size
Immunity to Objects/Contaminants on Screen Good Need to special design to avoid false touch
Resistant to Chemical Cleaners No Good
Durability Good Excellent
Impact Ball Drop Test Surface film protected Need special design for smash
Scratch Resistance As high as 3H As high as 9H
UV Degradation Protection Less protection Very good

What Are Resistive Touch Screens Used For?

Resistive touch screens still reign in cost-sensitive applications. They also prevail in point-of-sale terminals, industrial, automotive, and medical applications.

What Are Capacitive Touch Screens Used For?

Projected Capacitive Touch Panel (PCAP) was actually invented 10 years earlier than the first resistive touchscreen. But it was no popular until Apple first used it in iPhone in 2007. After that, PCAP dominates the touch market, such as mobile phones, IT, automotive, home appliances, industrial, IoT, military, aviation, ATMs, kiosks, Android cell phones etc.

If you have any questions about Orient Display capacitive touch panels. Please feel free to contact: Sales Inquiries, Customer Service or Technical Support.

How does a Graphic LCD work?

An Introduction to Graphic LCD Displays

Graphic LCD Displays normally refer to monochrome graphics LCD displays or dot matrix LCD displays. Although color TFT (Thin Film Transistor) and OLED (Organic Light Emitting Diodes) displays to meet all the definitions of graphic LCD displays and can also be categorized as graphic LCD displays, monochrome graphics LCD displays have been in the market much earlier than color TFT displays and they become the legacy type of display. That is the reason that Graphic LCD displays only refer to monochrome, not the full color.

What are Graphic LCD Displays?

Compared with Character LCD Displays which can only display digits or alphanumeric, graphic LCD displays can display digits, alphanumeric, and graphics. They played very important roles in the early stages of LCD display history.

Graphic LCD displays are identified by the number of pixels in vertical and horizontal directions. For example, 128 x 64 dot matrix graphic display has 128 dots/pixels along the X axis, or horizontal, and 64 dots/pixels along the Y-axis or Vertical. Each of these dots sometimes referred to as a pixel, can be turned ON and OFF independently of each other. The customer makes use of software to tell each dot when to turn ON and OFF. The early engineering work has to light/map pixel by pixel, which is very tedious work. Thanks to the LCD controller advancement, Some Orient Display graphic LCD products have many images in the memory already which greatly helps engineers to reduce the workload and make the products much faster to the market. Please check with our engineers for details.

Orient Display provides dot matrix formats of 122×32, 128×64, 128×128, 160×32, 160×64, 160×160, 192×48, 192×64,202×32, 240×64, 240×160, 240×128, 282×128, 320×240 etc.

Graphic LCD Interface

There are some popular graphic LCD interfaces, such as 8 bit or 16 bit 6800 and/or 8080 MCU interface, 3 or 4 wire SPI interface, I2C interface etc.

Fluid Options of a Graphic LCD Display

There are many options for graphic LCD displays, all of them derived from STN (Super-Twisted Nematic Display). TN (Twisted Nematic Display) or HTN (High-performance TN) displays are rarely used in graphic LCD displays because of their poor contrast and narrow viewing angles.

  • Positive displays can include: yellow-green STN, gray STN, positive FSTN;
  • Negative displays can include: blue STN, negative FSTN, FFSTN, ASTN;

Backlight Options of a Graphic LCD Display

LCD itself can’t emit light. In order to be observed under the dim light, the backlight has to be used. Back to 10 years ago, Backlight can be LED (Light Emitting Diode), CCFL (Cold Cathode Fluorescent Lamps) or EL (Electroluminescent) backlight. Thanks to the development of LED technology, especially the breakthrough of the blue and white LED technologies, LED backlight dominates the market. LED backlight can be made either bottom lit and side lit with various colors For more information, please refer to Orient Display Jazz Graphic LCD Display and Backlights.

Graphic LCD Display Controller and Drivers

The LCD controller is a small microprocessor that converts the customer’s software code (aka firmware) to information that the LCD can understand. LCD Drivers control the complex AC voltage requirements for the LCDs and they need a LCD controller to keep refreshing the individual pixel information to their drive circuitry. These ICs will typically be integrated into the LCD Modules either by COG (Chip on Glass) or COB (Chip on Board) technologies.

Sitronix is the world’s biggest graphic LCD controller manufacturers. The headache for most engineers is that LCD controllers can EOL (End of Life) a lot. Please make sure to discuss with Orient Display engineers for the most updated information to keep 5-10 years supply life.

How to use a graphic LCD Display?

An Introduction to Graphic LCD Displays

Graphic LCDs (liquid crystal displays) have a special position in the display industry. With the fast development of gadgets and digital devices, manufacturers need the latest technologies and techniques to provide high-quality products and services.

Graphic LCD Displays normally refer to monochrome graphics LCD displays or dot matrix LCD displays. Although color TFT (Thin Film Transistor) and OLED (Organic Light Emitting Diodes) displays to meet all the definitions of graphic LCD displays and can also be categorized as graphic LCD displays, monochrome graphics LCD displays have been in the market much earlier than color TFT displays and they become the legacy type of display. That is the reason that Graphic LCD displays only refer to monochrome, not the full color.

Graphic LCD Interface

There are some popular graphic LCD interfaces, such as 8 bit or 16 bit 6800 and/or 8080 MCU interface, 3 or 4 wire SPI interface, I2C interface etc.

Applications

LCD modules are used in various devices and applications. They make it possible for mobile phones, laptops, and televisions to produce clear images. They can also be seen in watches, calculators, and digital readers to help users read text easily. Moreover, the automotive industry is utilizing this technology as well. Car manufacturers integrate them into interior designs to provide a display of various information and allow access to services such as GPS navigation.

Benefits

Low cost, easy to manufacture, low power consumption are the main benefits for monochrome graphic displays.

Graphic LCD tutorial

In this tutorial, the working and pinout of 128×64 graphical LCD AMG12864AR-B-Y6WFDY-AT-NV-Y (2.9″ 128×64 Graphic LCD Module) will be described. It has 128 columns and 64 rows, 128×64 has 128×64=8192 dots.

Graphical LCD controller

Graphical LCD is controlled by two S6B0108 controllers. A single S6B0108 controller is capable of controlling 4096 dots. So, for controlling a graphical LCD we need two S6B0108 controllers.

Further graphical LCD half’s division

Each half is further divided into 8 pages of equal sizes. Each page size is 8 rows and 64 columns. Each page contains 8*64=512 dots.

Page distribution in Pixels

Each page contains 64 pixels (64 columns and 8 rows). output on these pixels. Each pixel lights up when it is 0 and becomes off when it is 1. Each pixel contains 8 dots.

Graphical Lcd (128×64) Pinout

Please refer to Page 8 of the AMC12864A specification.

Graphical LCD pins are the same as other character LCDs. Only two new pins are introduced with the graphical LCD. These are CS1 and CS2. CS1 is chip select 1 it selects the first half or first S6B0108 controller of LCD. CS2 is chip select 2 it selects the second half or second S6B0108 controller of LCD. Both CS1 and CS2 are active low. By active-low I mean for selecting a first or second half, make its associated pin (CS1, CS2) low 0. All the other pins E (enable) R/W (read/write) RS or D/I (register select) works in the same way as for normal LCDs.

Like other LCDs we also first have to initialize graphical LCD.

How to use Graphic LCD Displays with Raspberry Pi?

How to connect Graphic LCD to Raspberry PI?

The article shows how to hook up a 128×64 graphics LCD display to a Raspberry Pi.

LCD used is a 128×64 with LCD controller of ST7565. It can be powered directly from the Raspberry Pi 3.3V rail. It requires 5 GPIO pins for data.

The schematic is, CS (Chip Select), RST(Reset) and A0 (Register Select) can be connected to any 3 GPIO pins. In this example, 8,24 and 25 are default values. Different values can be specified as parameters when instantiating the ST7565 Python class. SCLK (Serial Clock) on the GLCD goes to GPIO 11 which is the Pi’s serial clock. SID (Serial Input Data) on the GLCD goes to GPIO 10 on the Pi which is MOSI. GPIO 10 and 11 must be used for SID and SCLK. Vdd is connected to a 3.3V pin on the PI and the grounds are also connected.

The LCD has a RGB backlight. The LED pins can go to GPIO’s 16,20 and 21. To control the color from the Pi, specifying RGB pins when instantiate the ST7565 class. The resistors must be placed in series to limit the current to prevent LED breakdown. The LED brightness can be changed by using different values of resistors. It will be best to adjust the current to be around 20mA, of course, different values will result in a different mix of colors. It is very difficult to mix a pure white color. Please calculate the resistor value carefully, at 40mA, the LED brightness will decrease sharply with time, with the current of close to 60mA, the LED might be breakdown and be permanently damaged.

How to program a Graphic LCD?

The display is 128 pixels horizontal by 64 pixels vertical. The LCD can be broken into 8 horizontal pages. They are numbered from 3 to 0 and 7 to 4 up to down. Each page includes 128 columns and 8 rows of pixels. To address the pixels, specifying the page and column number, and send a byte to fill 8 vertical pixels at once.

The display has SPI (Serial Peripheral Interface) to connect to Pi. SPI requires 3 lines MOSI, MISO and Clock. The Pi is the master and the GLCD is the slave. In this example, Only writing to GLCD and not ready, so the connection to MOSI and Clock lines are needed. MOSI is the output from the Pi to the GLCD and the Clock synchronizes the timing.

  1. Enable SPI on Raspberry Pi first
  2. From the raspi-config menu, select Advanced Options, then SPI. Then select Yes for “ Would like the SPI interface to be enabled”. Hit OK, Reboot. Select Yes for “ the SPI kernel module to be loaded by default”. Reboot the Pi after enabling SPI. Then test SPI using IsmodIt should return SPI_bcm2708 or spi_bcm2835 depending on the Pi version. The python SPI library requires python2.7 dev which can be installed with apt-get install:
  3. The Python SPI library is called py-spidev. It can be installed using git:GLCD Python library for the Pi can be downloaded from the GitHub site.
  4. The main ST7565 library (st7565.py) handles drawing, text & bitmaps, and a font module (xglcd_font.py) to load X-GLCD fonts. Here are the basic drawing commands which to create points, lines, rectangles, circles, ellipses, and regular polygons:For more details, please refer to the reference below or contact our engineers.