Character LCDs for security systems

Security systems require some type of user interface. How else would you turn it on or off? Or know which zones are active?

Most Security control panels do not display graphics, just letters and numbers which make Character LCDs an ideal choice to display such information as:

  • Time
  • Date
  • Zone #
  • System status (On/Off/Ready to Arm)
  • Battery backup status

16×2 STN Character LCD with LED backlight in security panel

In the photo above, the panel incorporates a 16×2, STN Character LCD with tactile buttons instead of a touch screen. It is possible to add a touch screen to a character LCD for a small tooling fee, but the display is so small, it would be difficult to offer the end user more than two or three choices.

If a touch panel were installed, Resistive would be the best option. RTP can be activated by any object (finger, glove, pencil eraser, etc.) and handles outside temperature and humidity conditions better than Capacitive touch panels.

Security systems stay in production for several years, so OEMs need components such as LCDs that tend not to go End of Life (EOL). Character displays meet this need. They have been around since Noah’s ark. (well, maybe not that long) and they will be here for many more years.

Key reasons why character displays are so popular include:

Standard sizes and configurations are in stock

Character displays come in the following, standard configurations:

8×1, 8×2,16×1, 16×2 (most popular), 20×1, 20×2, 20×4 and 40×4.

LED backlights are available for all the above sizes.

These configurations have been available for many years and will not go away anytime soon. They are in stock in our Chandler Arizona warehouse.

Easy to program with a built-in controller/driver chip (ST7066 Controller)

Each character on a display is made up of a 5×8 or 7×10 dot matrix. Each one of the dots are individually turned on and off to create the desired letter, number or punctuation marks.

The advantages of a character LCD is the built-in controller/driver chip (C/D) with preinstalled character table, making it quick and easy for the programmer to select/generate the correct letter, number of punctuation mark. There is no need to address and refresh each of the individual dots. This job is performed by the C/D chip such as the ST7066 Controller

Optional LED backlight for nighttime operation.

Displays need to be readable in the dark, especially on security systems. Therefore, most character LCDs contain a built in LED backlight that can be turned on and off independent of the LCD. This saves power if designed into a battery or solar powered product.

The LED backlight can draw as little as 15mA and up to 75ma+ depending on the brightness and number of LEDs. They can be driven by a 3.3V or 5V power supply and are available in a wide choice of LED colors including RGB (Red, Green, Blue).

Long battery life (1ma or 2ma without backlight)

The current draw for a character LCD, without the backlight on, runs between 1mA to 2mA depending on the size of the glass and the operating temperature. The colder the temperature, the more current needed to keep the segments/characters readable.

They can be built to operate at 5V or 3.3V. 3.3 volts is ideal for battery powered applications but performs poorly in low temperatures. At very low temps, the segments will start to ‘fade’ or ghost.

Standard colors include:

Yellow/Green, Blue/white, Red, Yellow, Green, RGB and many others.

Low Cost:

Character LCDs are one of the lowest cost display options. Prices start in the low two dollar range ($2.00).

Need to order a sample? Click here for our online store with same day shipping.