low voltage lcd displays free sample

This graphic LCD module acts as a shield for Arduino Uno-style microcontrollers. The pins on the carrier board match up to the Arduino Uno"s ports, so the module simply presses on and is fully and correctly connected. Plus, this carrier board is able to be connected to either a 3.3v logic level or a 5v logic level device. (Read our blog post if you have questions about logic level.)

This is a thin, extremely low-power 128x64 graphic LCD display module. It has no backlight, so consumes no power illuminating the display. However, if you wanted to backlight the module, the rear polarizer is transflective, so you could add your own lighting solution there. This display is perfectly suited for hand-held or any application requiring low power consumption or a very thin display. A row of icons is shown automatically top of the display without having to be rendered. This display has an integrated controller and the tail is designed to mate with standard 18-conductor 0.5mm pitch ZIF connectors (typical would be Omron XF2L18351A/ DigiKey P/N OR754CT-ND).

Ultra-low-power displays consume very little energy, and the two primary technologies used for these types of displays are bistable and low refresh rate displays. They are used when there is a need for a battery-powered device, want maximum life between charges, and the content being displayed does not change very frequently.

The common uses for ultra-low-power displays are e-readers and electronic price tags. Some of the other applications we have seen are secondary displays for handheld devices and battery-powered products like locks, remote-mounted homes, and industrial products.

Probably the most well know bi-stable low-power display is e-paper technology historically used on e-readers. This technology is available in both monochrome and color.

E-paper is a reflective technology and, with good ambient light, has an excellent contrast ratio. One of the characteristics of e-paper is that the background is white, whereas many reflective display technologies like LCD have a gray or greenish background. One disadvantage is that E-paper requires front lighting if used in low-light conditions.

Displaying static images on an e-paper display uses very little energy (uW). However, it can require more power (mW) to update the screen than other technologies like LCD in the same size and resolution.

The first step of building a low-power TFT is to move to a reflective or transflective display and eliminate the power consumption of the backlight when the display can use ambient light.

Choosing a Transflective display is a good trade-off since it comes with a backlight that, when turned, the display becomes reflective. However, there is some trade-off in that the reflectance of a transflective display is lower than a pure reflective display. We use an advanced LCD driver chip to reduce the power further to drive the display at different refresh rates.

We use an advanced LCD driver chip to reduce the power further, which allows the display to be driven at different refresh rates. The drivers have two modes; a standard TFT mode that enables the display to operate like a standard TFT being able to do video rate, 60Hz, updates, and a low-power mode where the display refreshes at a rate of 1Hz. This mode is excellent for holding static images and using very little energy. Figure 2.0 depicts the driving methodology. Using these drivers, you can reduce the power of the digital portion of the display by 60%.

Table 2.0 shows a comparison study that we did for a thermostat application to compare different low-power technologies. In this study, the display is active for 15 minutes, and then it shows static images for the remainder of the day.

Conclusion: Depending on your application, either low-power TFT or e-paper may be suitable. If power is critical for your application and requires maintaining an image on display for long periods, consider these great technologies.

US Micro Products has designed displays with both technologies for special low-power applications and can do the same for your product. So let us help you with your display requirements; we have expertise that spans multiple markets and technologies.

Many projects benefit from a small display as a user interface. For very low power applications this is usually a no-go as the display needs too much energy. I have used e-paper displays from Kent: while these e-paper displays do not need any power to keep the image, changing the display content is not for free, plus is very slow (around 1 second needed to update the display). So I was looking for something low power and fast for a long time, until Christian (thanks!) pointed me to a display from Sharp: both very low power and fast:

And even better: Adafruit has a breakout board for that display available (https://www.adafruit.com/product/1393) :-). The display on the board is the Sharp LS013B4DN04 with 96×96 monochrome pixel resolution. The display is a cross between a e-paper and normal LCD. The ‘background’ color is a nice silver color. What looks cool with this display is that the pixels show up like little mirror:

On the Adafruit breakout board, EXTMODE is pulled LOW: the clocking has to be provided by software. With software a special ‘VCOM’ command is sent to the display:

Each line of the display can be updated with a command: sending line number, then the number of bytes (12 for the 96 bits) followed by a trailing 16 zero byte:

That Sharp Memory Display is a really cool one. The Adafruit breakout board has its price ($39.95). It took me a while to get the protocol right, but now I have very low power display and driver in my inventory :-). There is an example project on GitHub, and the SharpMemDisplaycomponent is available on GitHub and will be part of the next McuOnEclipse component release. If you are interested in the sources only, they are available on the McuOnEclipseLibrary project.

AOur production quality follow ISO9000 standard system, stable design team,22 years experience of QC team and strictly quality control system guarantee the production quality. accept third part inspection,we have mechanical checking,display checking,high&low temperature storage&operating test during high humidity condition,EMC test(optional) for every design .

The use of liquid crystal displays (LCDs) in user interface assemblies is widespread across nearly all industries, locations, and operating environments. Over the last 20 years, the cost of LCD displays has significantly dropped, allowing for this technology to be incorporated into many of the everyday devices we rely on.

The odds are high you are reading this blog post on a laptop or tablet, and it’s likely the actual screen uses LCD technology to render the image onto a low-profile pane of glass. Reach into your pocket. Yes, that smartphone likely uses LCD technology for the screen. As you enter your car, does your dashboard come alive with a complex user interface? What about the menu at your favorite local drive-thru restaurant? These are some everyday examples of the widespread use of LCD technology.

But did you know that the U.S. military is using LCD displays to improve the ability of our warfighters to interact with their equipment? In hospitals around the world, lifesaving medical devices are monitored and controlled by an LCD touchscreen interface. Maritime GPS and navigation systems provide real-time location, heading, and speed information to captains while on the high seas. It’s clear that people’s lives depend on these devices operating in a range of environments.

As the use of LCDs continues to expand, and larger screen sizes become even less expensive, one inherent flaw of LCDs remains: LCD pixels behave poorly at low temperatures. For some applications, LCD displays will not operate whatsoever at low temperatures. This is important because for mil-aero applications, outdoor consumer products, automobiles, or anywhere the temperature is below freezing, the LCD crystal’s performance will begin to deteriorate. If the LCD display exhibits poor color viewing, sluggish resolution, or even worse, permanently damaged pixels, this will limit the ability to use LCD technologies in frigid environments. To address this, there are several design measures that can be explored to minimize the impact of low temperatures on LCDs.

Most LCD displays utilize pixels known as TFT (Thin-Film-Transistor) Color Liquid Crystals, which are the backbone to the billions of LCD screens in use today. Since the individual pixels utilize a fluid-like crystal material as the ambient temperature is reduced, this fluid will become more viscous compromising performance. For many LCD displays, temperatures below 0°C represent the point where performance degrades.

Have you tried to use your smartphone while skiing or ice fishing? What about those of you living in the northern latitudes - have you accidently left your phone in your car overnight where the temperatures drop well below freezing? You may have noticed a sluggish screen response, poor contrast with certain colors, or even worse permanent damage to your screen. While this is normal, it’s certainly a nuisance. As a design engineer, the goal is to select an LCD technology that offers the best performance at the desired temperature range. If your LCD display is required to operate at temperatures below freezing, review the manufacturer’s data sheets for both the operating and storage temperature ranges. Listed below are two different off-the-shelf LCD displays, each with different temperature ratings. It should be noted that there are limited options for off-the-shelf displays with resilience to extreme low temperatures.

For many military applications, in order to comply with the various mil standards a product must be rated for -30°C operational temperature and -51°C storage temperature. The question remains: how can you operate an LCD display at -30°C if the product is only rated for -20°C operating temperature? The answer is to use a heat source to raise the display temperature to an acceptable range. If there is an adjacent motor or another device that generates heat, this alone may be enough to warm the display. If not, a dedicated low-profile heater is an excellent option to consider.

Made of an etched layer of steel and enveloped in an electrically insulating material, a flat flexible polyimide heater is an excellent option where space and power are limited. These devices behave as resistive heaters and can operate off a wide range of voltages all the way up to 120V. These heaters can also function with both AC and DC power sources. Their heat output is typically characterized by watts per unit area and must be sized to the product specifications. These heaters can also be affixed with a pressure sensitive adhesive on the rear, allowing them to be “glued” to any surface. The flying leads off the heater can be further customized to support any type of custom interconnect. A full-service manufacturing partner like Epec can help develop a custom solution for any LCD application that requires a custom low-profile heater.

With no thermal mass to dissipate the heat, polyimide heaters can reach temperatures in excess of 100°C in less than a few minutes of operation. Incorporating a heater by itself is not enough to manage the low temperature effects on an LCD display. What if the heater is improperly sized and damages the LCD display? What happens if the heater remains on too long and damages other components in your system? Just like the thermostat in your home, it’s important to incorporate a real-temp temperature sensing feedback loop to control the on/off function of the heater.

The first step is to select temperature sensors that can be affixed to the display while being small enough to fit within a restricted envelope. Thermistors, thermocouples, or RTDs are all options to consider since they represent relatively low-cost and high-reliability ways to measure the display’s surface temperature. These types of sensors also provide an electrical output that can be calibrated for the desired temperature range.

The next step is to determine the number of temperature sensors and their approximate location on the display. It’s recommended that a minimum of two temperature sensors be used to control the heater. By using multiple sensors, this provides the circuit redundancy and allows for a weighted average of the temperature measurement to mitigate non-uniform heating. Depending on the temperature sensors location, and the thermal mass of the materials involved, the control loop can be optimized to properly control the on/off function of the heater.

Another important consideration when selecting a temperature sensor is how to mount the individual sensors onto the display. Most LCD displays are designed with a sheet metal backer that serves as an ideal surface to mount the temperature sensors. There are several types of thermally conductive epoxies that provide a robust and cost-effective way to affix the delicate items onto the display. Since there are several types of epoxies to choose from, it’s important to use a compound with the appropriate working life and cure time.

For example, if you are kitting 20 LCD displays and the working life of the thermal epoxy is 8 minutes, you may find yourself struggling to complete the project before the epoxy begins to harden.

Before building any type of prototype LCD heater assembly, it’s important to carefully study the heat transfer of the system. Heat will be generated by the flexible polyimide heater and then will transfer to the LCD display and other parts of the system. Although heat will radiate, convect, and be conducted away from the heater, the primary type of heat transfer will be through conduction. This is important because if your heater is touching a large heat sink (ex. aluminum chassis), this will impact the ability of the heater to warm your LCD display as heat will be drawn toward the heat sink.

Insulating materials, air gaps, or other means can be incorporated in the design to manage the way heat travels throughout your system on the way toward an eventual “steady state” condition. During development, prototypes can be built with numerous temperature sensors to map the heat transfer, allowing for the optimal placement of temperature sensors, an adequately sized heater, and a properly controlled feedback loop.

Before freezing the design (no pun intended) on any project that requires an LCD display to operate at low temperatures, it’s critical to perform low temperature first. This type of testing usually involves a thermal chamber, a way to operate the system, and a means to measure the temperature vs time. Most thermal chambers provide an access port or other means to snake wires into the chamber without compromising performance. This way, power can be supplied to the heater and display, while data can be captured from the temperature sensors.

The first objective of the low-temperature testing is to determine the actual effects of cold exposure on the LCD display itself. Does the LCD display function at cold? Are certain colors more impacted by the cold than others? How sluggish is the screen? Does the LCD display performance improve once the system is returned to ambient conditions? These are all significant and appropriate questions and nearly impossible to answer without actual testing.

As LCD displays continue to be a critical part of our society, their use will become even more widespread. Costs will continue to decrease with larger and larger screens being launched into production every year. This means there will be more applications that require their operation in extreme environments, including the low-temperature regions of the world. By incorporating design measures to mitigate the effects of cold on LCD displays, they can be used virtually anywhere. But this doesn’t come easy. Engineers must understand the design limitations and ways to address the overarching design challenges.

A full-service manufacturing partner like Epec offers a high-value solution to be able to design, develop, and manufacture systems that push the limits of off-the-shelf hardware like LCD displays. This fact helps lower the effective program cost and decreases the time to market for any high-risk development project.

In a competitive market where fast designing is needed, how far will liquid crystal displays (LCDs) be an option for design engineers? Let’s find out.

Ten years ago, my senior told me that the LCD is going to die, but it has paved its way into our everyday life, starting from our phones to our vehicles. Segment LCDs were simple in design where an input channel was given directly to display digits. Even if videos could not be displayed, these LCDs were used on old auto meters and were pre-designed. Though a little complicated in design, thin film transistor liquid crystal displays (TFT LCDs) are becoming quite popular in smartphones and vehicles nowadays.

Liquid crystal can guide the light. For a TN LCD when the transistor of the TFT circuit is turned off and the LC changes the orientation of light rotation. After light passes through both the polarizers, we see the LCD completely white. However, when the circuit is turned on, the polarizer blocks the light, resulting in a black image. Hence liquid crystal is the core of the design that can direct the light as per its rotation.

Fig. 3 shows the comparison for the same photo on two different displays when the liquid crystal is rotated in the IPS and TN modes. The performance varies as the angle changes. We notice that IPS has a better performance.

It is a display panel that uses liquid crystal to control the amount of light that comes from the backlight. The TFT acts like a switch that controls the liquid crystal. Each segment of liquid crystal is like a shutter that either blocks or allows light to pass through. Fig. 4 shows a TFT LCD where the top is an open cell and the bottom is the backlight.

The open cell has a nickel crystal sandwiched between the colour filter glass and the TFT array glass on which the transistor is built. The backlight structure contains a lot of optical sheets like diffuser, prisms, light guide, and reflectors. Backlight is of two types, namely, direct light that refers to the LEDs which are directly laid below the LCD. This method is used for big-size LCDs like TV or signage. For small- and medium-size LCDs, like phones or laptops, the side light is used where the LEDs are to the side of the LCDs.

Memory LCD is the integration of one-bit memory into each LCD pixel. This makes sure that data transmission from outside the module is not needed when the displayed image does not change. The advantages that they offer are:

Low energy and power consumption. Two main reasons exist for the same. First the reflective displays do not need a backlight. Second, the memory needed integrated with the pixel does not need to be refreshed when showing a statistical image. For instance, in a 6.9cm (2.7-inch) screen, the power consumed is only 50µW when there is no image updating, whereas when an image data updates the power consumed is 175µW. The important thing to note here is that, unlike conventional LCDs where power is consumed at milliwatt (mW) level, TFT LCDs consume power at a microwatt (µW) level, confirming the long life of the battery.

Since the location of the sensors in IoT must be remote and needs a longer battery life, memory LCDs are widely recommended. Fig. 5 shows applications where memory LCDs can be majorly used, which are available from 2.5cm (1 inch) to 11.2cm (4.4 inch), in both black-and-white and colour. They can also be used in smart watches.

Second is low power consumption. As we know the LCD runs at 60Hz in one frame. When the IGZO is turned on we only need a part of the frame and not the whole, resulting in a lot of power being saved.

Third, we achieve a LCD bezel. For instance, in a-Si TFT, the gate driver (COG) is at one side of the LCD, which cannot minimise the LCD side border. But for IGZO, monolithic gate drivers are used to build on both sides of the LCD, thus achieving a narrow frame.

Then there is the touch display. The touch and LCD signals are bound to interfere with each other, causing a problem. This is avoided in IGZO panels, as the touch detection can be activated when the IGZO TFT is in a rest mode. When the LCD is off, the touch is turned on and vice versa.

The beauty of reflective LCD panels is their suitability for outdoor displays. Transmissive displays use a light source as the backlight, which, unfortunately, because of the ambient light, dulls the display. However, in reflective displays, the ambient light is utilised instead of a backlight. The features in a reflective IGZO are:

With no backlight being needed, we notice from the figures that around 95% of the power consumed is reduced. Similarly, the amount of heat generated is also reduced, leading to the fact that the number of fans needed to cool down the LCD drastically decreases. This makes the reflective LCDs much more reliable.

The remarkable fact is that, even an 80cm (31.5-inch) LCD can be run on a mobile battery (2500mAh) with a video being played for 24 hours without charging. Solar panels provide the freedom to move the system to different places. The solar panels along with the mobile batteries can help in signages located at bus stops, avoiding a lot of trouble. Not only bus stops, but this can also be implemented at petrol stations, vending machines, etc. There are various panel sizes available as samples and for mass production.

Regarding interfaces, there exist RGB and LVDS interfaces in the market, for many years. The RGB interface (for low-resolution panels) is mainly used for cars and motorcycles. The LVDS interface (for high resolution) is commonly used for industrial usage. Smartphones are using MIPI interface (low power consumption). EDP (power saving) is widely being used for laptop and monitor panels.

With such advantages that LCDs offer, design engineers have a tough job in choosing the right one. David suggests that it is best to match a design with different systems and interfaces before making the final selection. LCDs surely have the potential of being chosen as the best option for any application.

LCD displays don’t emit light by themselves. They need a light source, and LED backlights are now dominating the market. In this article, Orient Display’s Bill Cheung provides a complete overview of LED backlight technology, discussing different types, driver technologies, color deviation, brightness options and more.

LCD (liquid crystal display) has long been the dominant technology in the display world. Certainly, there are some emerging competing display technologies—such as OLED (Organic Light Emitting Diode) [1] and micro-LED—that have the potential to threaten LCD’s position in the market. But both are currently only used for niche and high-end markets.

An LCD display can’t emit light by itself. In order to have an LCD display [2] used in a dim environment, a backlight has to be used as the light source. There are a few different technologies that are able to produce backlight ranging from EL (electroluminescent), CCFL (cold cathode fluorescent lamps) and LED (light emitting diode). However, a breakthrough in blue LED technology by Shuji Nakamura [3] led to LED backlights dominating the market.

LED backlights have low power consumption and produce much less heat than other backlight technologies, which extends the durability and performance of the other display components. Furthermore, this reduces the risk of fire and explosion. LED backlights are also driven with DC (direct current) and low voltage (can be as low as 1.5V), which are good for battery drive and emit no interference to the circuitry. With the development of LED technology, the LED chips become small. So, it is possible to produce very thin backlight (0.5mm thick or thinner).

LED backlight can be classified as bottom (array) lit and side (edge) lit backlights, and each have their plusses and minuses. The advantages of the bottom lit (array) backlight are that it is uniform and bright. Its disadvantage is high current draw, thickness, heat dissipation and cost. Meanwhile, the advantages of the side lit backlight are its thinness, flexibility in design, low current and lower cost. The main disadvantage of the side lit backlight is its non-uniformity—hot spots can be seen from most of the side lit backlight from certain angle. Figure 4 compares the bottom lit and side (edge) lit backlight LCD types.

Now let’s look at LED backlight structures. An LED backlight can be simplified into layers starting with a LED chip, light guide, diffusor and reflector (Figure 5). This is the lowest cost structure. Except for some very low current efficiency LCD displays—such as utility meters, battery-powered clock, watch, GPS and so on—most LCD displays need backlights to be visible in the dim lighting. Most often the backlight is actually at the back of the LCD. In rare cases, this light can be done as front light. The traditional LCD structure with LED backlight shown in Figure 6.

Direct current driving: This is the simple and low-cost way to drive a LED backlight, however, be mindful of the current limit otherwise the LED life can deteriorate quickly. The solution is simply to add a current limiting resistor in the circuit. Current limitation resistors value calculation formula: R = (V0– Vf)/If.Also be mindful of reverse drive, otherwise, the LED chip can break down easily.

LED driver with constant voltage: Using a constant voltage LED driver makes sense when using an LED or array that has been specified to take a certain voltage. This is helpful because constant voltage is a much more familiar technology for design and installation engineers. Moreover, the cost of these systems can be lower, especially in larger scale applications.

There are a variety of ways to connect a backlight and LCD module electrically. It can be done with wires that are soldered on the LCD or LCD module. It can be connected using pins, which can be soldered onto the LCD or LCD module. A third way is to use a FPC (flexible printed circuit), which can be soldered or plugged in a ZIF (zero insertion force) connector. And finally, there is the connector method. With this method you use connectors which can be plugged into mating connectors.

In actual LED backlight production, most customers will accept the LED color for two big categories: white with yellowish (warm) and white with bluish (cold). Of course, the LED brightness will also need to be defined. For general application, most customers will accept a brightness tolerance of 70 percent.

It is extremely hard to estimate the LED backlight lifetime or MTBF (mean time between failures) because there are so many variable factors. However, the most important is the temperature on the LED chip. The factors that can affect the LED chip temperature include: surrounding temperature, humidity, driving current, voltage, backlight design (how many LED chips to be used, how close to each other, heatsink design), backlight manufacturing process (type and thickness of adhesive), quality of the LED chip and so forth.

To test the LED life is also very time consuming, requiring at least 1,000 hours. That’s the reason why no LED manufacturers can guarantee LED backlight life and most backlight manufacturers also are reluctant to provide lifespan data. As for LCD manufacturers, they need to discuss it with the customer to understand the applications and provide suggestions. It is normal that the LCD datasheet lists the typical life time and avoids providing a minimum lifetime. From Figure 10, we can see that over room temperature, the current needs to decrease as the temperature increases. At over 85°C, the LED is not usable.

Now let’s use the theoretical calculation approach. As we previously mentioned, LED life is affected by a lot of factors: surrounding temperature, humidity, driving current, voltage, backlight design (how many LED chips to be used, how close to each other, heatsink designed), backlight manufacturing process (type and thickness of adhesive), quality of the LED chip and so on. LED chip manufacturers are not willing to give absolute values of LED chip lifetimes, but there is a theoretical calculation that we can use.

For the LCD module side, using better aperture opening ratio, anti-reflection coating on surface, optical bonding. This results in higher cost. Actually, this measure is not to increase LED backlight brightness directly but to increase to the visibility to users.

Bill Cheung is an engineering lead and marketing manager at Orient Display, an LCD and display technology provider with over two decades of industry experience in delivering cutting edge display solutions. You can browse Orient Display"s knowledge base [7] to learn more about LCDs.