Mini LCD display power considerations

Recently, Focus LCDs received a call asking us to design a mini LCD display for use on a model rocket. Being the chief engineer for a number of years at Focus LCDs and having quite a bit of experience in all the newest technologies in the field of LCD displays, I was taken aback to learn that model rockets would ever use an LCD display. It has been some years since I have built and launched these mini-missiles and clearly there have been numerous improvements. My experience with them included losing many rockets and when the parachute failed to deploy, there was very little of the rocket left to launch again. The question plagued me, “why would anyone want to install a LCD module on a kid’s toy?”

To my great surprise, model rockets have come a long way, so far in fact that they are no longer toys. They have become a serious hobby. Some of the engines used to launch these rockets can run as high as $55 each. Adults are willing to invest the money in the hobbies of their youth that they weren’t able to as a kid. With this investment they want the best of the best and for their “toys” to have all the bells and whistles imaginable.

Model trains are another example. Certain locomotives now have a remote control built into them so that they can be controlled by a wireless handheld device. That device contains an LCD and in some locomotives it can even contain a small wireless camera.

The following discussion answers the question of LCDs that utilize a mini LCD display while facing the common concerns of low power consumption and more. It tackles some of the considerations concerning color displays, backlight options, and the ultra-low power requirements of a mini LCD display.

Considerations For The Mini LCD Display

“We want a color LCD because they look really good and more people will buy our product.” This is a common sentiment from a variety of clients that request a new mini LCD display design. The challenge with color LCD’s is that they require more power than non-color (aka: monochrome) displays. If your application is battery powered, color is usually not your first and best option. The exception to this rule is if the display will be on for very short periods of time. A perfect example of this is the cell phone. Cell phones use two-color display technologies: TFT (Thin film transistor) and OLED (Organic Light-Emitting Diode). These color modules draw power, but since the display on the cell phone is only on for a few seconds at a time, the drain on the battery is minimal.

Another consideration to take into account is how the battery will be charged. If the customer needs to keep replacing ‘AA’ or ‘AAA’ batteries every few days, this will become expensive and time consuming. On the other hand, if your product plugs into a wall or some charger, then it will make the pain of a short battery life more bearable.

If you still wish to incorporate a color LCD into your design, there is a new low cost color technology that allows the display to be fully customized to your requirements. This advancement is the Field Sequential Color Display (FSC) and it offers a low cost alternative to full color TFT and OLED displays. This new technology implements an RGB (Red Green Blue) backlight to display brilliant bright colors at a fraction of the cost of a TFT. The FSC is the right solution for product designers who want all the flash and thrill of a color screen, but who are looking for a reasonable power consumption and a reasonable price.

Photo above is of a custom color FSC LCD display

Mini LCD Displays With A Backlight

A backlight is a must if your display will be used in an environment with too little lighting or no ambient light. If you must have a backlight, design your product so that the backlight is on as little as possible. Reducing the time the backlight is used saves on overall power consumption. Below is a case study from one of our customers that illustrates just how big a difference turning OFF the backlight makes.

We worked with an engineer who was designing a portable battery powered device that measured air quality. The device ran on two ‘AA’ batteries and the LCD backlight contained four LED backlights that required 15mA (milliamp) per backlight.

The company’s marketing people wanted a mini LCD display with a backlight that stayed on all the time. After much discussion the design engineer explained that if the backlight was always on, the battery would be dead within an hour.

The marketing people then asked for the backlight to be on as long as the customer held down a button. The engineer advised against this option also since many people will keep the button pressed until the battery dies, thus creating the same problem. If the battery dies within the first hour, the customer will assume that the product is defective and send it back. Worse yet, the customer might post negative reviews of the product online. The final solution was that the backlight stayed on for only 10 seconds every time the button was pressed. Even if the button was held down, the backlight would shut off after 10 seconds. This compromise extended the lifetime of the battery from one hour to 30+ hours. The engineer had commented to us in a joking way that he wanted to replace the backlight button with a thumb tack. That certainly would motivate the customer to be even more conservative in the use of the backlight. Fortunately, however, with the power consumption adjusted the thumbtack idea was discarded.

Mini LCD Display Built For Low Power Consumption

Segment mini LCD display screens have several names within the industry; you may also know them as direct-drive LCD screen displays or multiplex LCD glass. This technology has been in use for several years and due to its popularity it won’t fall out of favor anytime soon.

One of the main reasons for the popularity of static/segmented LCD screen display used as a mini LCD display is their low appetite for power. Products that are powered by battery have a low power budget and consider power conservation as the most important quality in the display. In most applications, the display is the one electronic component with the largest power consumption. As a general rule, a static display with no backlight can operate on as little as 2uA (micro-amps) per cm^2 (Per centimeter squared, about the size of a small finger nail).

Watches, thermometers, and portable test equipment are products that require a mini LCD display with low power consumption, and now we know that model rockets and trains are included in that list. Consider a mini LCD display for your device now that issues of color displays, versatility in backlight options, and the ultra-low power requirements are no issue at all.