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The Pros And Cons Of Using A Segmented LCD

The Pros And Cons Of Using A Segmented LCD

Oct 8th 2021


The use of segmented LCDs is incredibly common. Everywhere you look, you are likely to come across a segmented LCD. Whether it is the fuel gauges on gas pumps, digital wristwatches, calculators, or the timer on your microwave, there is a high likelihood of you coming across a segment LCD.

Segment LCDs are one of the oldest display technologies. Their benefits and utility in a variety of markets are endless due to their high accessibility, energy efficiency, ease of production, and most importantly, affordability. In turn, this makes segment LCDs very prevalent in a wide range of products and applications.

Segment LCDs, AKA static LCDs or glass LCDs, have fixed graphics and are made up of two pieces of ITO (indium tin oxide) glass with a twisted nematic fluid sandwiched in between. A majority of segment LCDs are designed fully custom according to your requirements. Each segment—which is any line, dot, or symbol that can be turned on and off independently—will turn “on” when power is applied to its associated pin.

Like all technologies, segmented LCDs have their advantages and limitations. Below, this article will cover some of the benefits of using segmented LCDs.

Price and Customizability

The simplistic makeup of a segment LCD results in significantly lower prices than newer, more complex technologies such as OLEDs or TFTs. In fact, they are often called “glass only displays” because a majority of them are glass with small metal leads attached to two edges of the display.

Some factors that affect piece price are overall size, quantity, and additional componentry, while the base tooling fee for a custom segment LCD will only be increased by additional componentry. Segment LCDs most often have a price range from as low as $0.20 Dollars for low cost, high quantity designs up to 20 or more dollars for designs requiring value added services or low quantities. The primary factors in price vary according to the size of the glass, quantity of LCDs, and other variables.

Still, even with additional componentry, the price of segment LCDs can be significantly less than many other display technologies and are more customizable to boot. For example, segment LCDs can be designed to your exact specifications and have the ability to remain within budget, while simply customizing TFT glass to a specific, non-standardized size will have a tooling fee of several hundred thousand dollars. When customizing other display technologies, it is usually recommend to start out with an off the shelf size and design the rest of the product around the display. With segment LCDs, there are, within reason, no limitations for customization.

A wide variety of additional components can be added to your design. Some common examples are backlights, ribbon connectors or LCD driver chips to reduce pin count or control the biasing of multiplexed LCD designs (to learn more about multiplexing segment LCDs, read our application note here). Therefore, it is important to take this into account if you are concerned with price. If you are uncertain as to whether your segment LCD design will require additional components, contact Focus LCDs’ design experts for guidance.

Reliability

The simple and effective design of segment LCDs mean that there is a low probability of failure in the field. For example, without a controller, segment LCDs are less at risk of ESD issues.

When failure does occur, it is much easier to determine the root cause in comparison to complex display technologies because there are very few components to segment LCDs. Thus, less potential causes of failure to investigate. Additionally, since segment LCDs have been in use for decades, common points of failure are well known and usually have straightforward fixes. This is why they are often favored for use in unfavorable environments. Survival gadgets such as radios, compasses, and thermometers often integrate segmented LCDs.

Power Consumption

The power intake of segment displays is substantially less than other display technologies. This ultimately makes them one of the best displays for devices powered by minimal power sources like low ampere batteries or stored solar energy.

There are a few different reasons why segment LCDs usually consume less power.

    Optional Backlight:

Positive mode segment LCDs can be readable without a backlight in well-lit environments due to their polarizer. A reflective polarizer reflects one hundred percent of ambient light and produces an easy to read, sharp image, similar to a mirror. Transflective polarizers reflect a large percentage of ambient light and allows a backlight to be added for nighttime operation. Without a backlight, the display draws significantly less power, making them feasible for handheld and battery powered products. Most segments can operate on less than 1mA without a backlight.

If the LCD is negative mode or used in dark environments, it is recommended that a backlight is used with the display. If you require a backlight and power consumption is a concern, you can use PWM (post width modulation) to dim the backlight in brighter settings, or simply turn it off when it is not in needed.

    Multiplexing:

    When a display is multiplexed, the LCD segments are only on a fraction of the time that they are being used. For example, if a display uses 4:1 multiplexing, this means that each segment is only being powered 25% of the time that it is used. The segment is powered on and off rapidly making the segment appear to be always on. This saves power while still keeping the visual effect of the LCD normal.

Segment displays usually require a voltage of 3.3V or 5V. If you are producing a handheld or battery powered product, it is useful to note that Focus LCDs has developed segment LCD designs that have been rated to run on a coin cell battery for 10 years or more. Of course, the battery lifetime of the product is depending on many more factors than the LCD and is a concern that will be addressed on the application end.

Efficiency and Lifetime

Most segment LCDs are highly efficient. Considering the amount of energy they utilize. Very little energy dissipates within their system. For this reason, many engineers will resort to the age-old technology of segmented LCDs to this day. There are no display technologies more practical and effective than these highly efficient LCDs.

Another reason why they are considered very practical is their avoidance of EOL (end of life) notices. Since many segment LCDs do not require a driver (the most common cause of EOL for LCDs), you will not need to adjust the design after it has already been implemented. This is beneficial to your product’s lifetime as replacement LCDs of other technologies are not always 100% equivalent and will sometimes require accommodations to your product’s firmware to properly function.

Final Words

In conclusion, segment LCDs are a treasured display technology that will be in use for many years to come. Their customizability, availability, low power consumption, sunlight readability, and affordability make segment LCDs a viable display solution for a variety of industries and products. 

Contact Focus LCDs today to see if a custom segment LCD is a good fit for your project. Focus LCDs = LCDs made simple ®