There are many LCD display types to choose from. Some are new cutting edge technology and other are older legacy types of displays. Although even some of the legacy type of LCD displays make use of cutting edge technology. The goal of this article is to provide the reader with a brief overview of the uses, advantages and disadvantages of each type of display.
Segment LCD’s, also called static or direct drive are an older technology but are still in heavy use today. These displays are reliable and have been in use for many years. They show no signs of going away anytime soon.
The goal of this display is simplicity. Their only job is to display letters, numbers and icons. There is no 3-D effect or range of brilliant colors and most do not contain a touch screen or any other type of human interface. They normally are not equipped wit a controller/driver chip.
In fact, you could reduce the static/direct drive LCD down to the simple formula of one pin equals one segment. If you need a display that contains a 7 segment number, you need 7 pins. The exception to this is if you increase the number of backplanes and convert this to a multiplex display.
The formula for a multiplex display is a little more complicated. One pin equals 2 or 4 segments. The advantage of multiplexing is that you reduce the number of pins which, in turn, reduces the cost of the display and the amount of time required to mount the display to a PCB.
One disadvantage of multiplex display over direct drive displays is that the refresh rate is slower and this may allow the segments that are ON to ‘fade’ or not look as sharp. Some times this is referred to as ‘ghosting’. This is not a very common occurrence as the technology has improved since the days of pagers and low cost calculators.
When a customer cannot decided what LCD display type to use we have a general rule: If the total number of segments is 20 or less, we advise a static (direct drive) display since a display with 20 pins is low cost to build and to install on the PCB.
Once the number of segments exceed 20, we recommend multiplex. A display with more than 120 segments becomes cost prohibitive.
If your design exceeds 120 segments we would recommend converting your design to a graphics type of LCD display that makes use of the controller driver chip. The controller driver chip allow the number of connections for multiple segments to be reduced to 14 or 16 pins. This LCD technology is covered later in the article.
While monochrome displays are simple and can come across as somewhat boring, there are some key advantages to consider when choosing which of the LCD display types to go with.
Low Power LCD Displays
One key advantage of the monochrome LCD display is that they are not power hungry. They operate with very little current draw. This becomes an ideal choice when the only power you have is a battery. These displays are built to operate at 3.0V, 3.3V (in some case they can operate as low as 1.7V) and 5V. The current draw for a display with no backlight can run as low as 6uA per cm^2. (Note: The lower the operating temperature of the LCD, the greater the power required).
If all you need to display is what time it is, the current temperature, or the number of gallons, and your customer does not wish to pay for vibrant, flashy power-hungry color, then this display will work perfectly for you.
Customizable LCD Displays
The majority of the static or multiplex displays we offer have been customized to meet the customer’s requirements. This is a great advantage to consider when choosing one of the LCD display types you will use in your product.
A customized static or multiplex display allows you to have the display built to the dimensions you require. You can select the following options:
The tooling or NRE (non-recurring engineering cost) of this type of display is much lower than newer technologies and the MOQ (minimum order quantities) are also lower than other types of displays.
If your goal is to display basic information, with a low tooling cost and you need to operate on a low power budget than the best type of LCD Display is a static or multiplex LCD.