In a Previous Video: TFT LCD with Integrated Touchscreen Functionality
In a previous video, I showed you how to utilize a TFT LCD with integrated touchscreen functionality. While this is a great way to display data and interact with your projects, it has its limitations.
Measuring Current Consumption
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When measuring the current consumption of the whole project, we get current draws of around 200 milliamps. This might not be a problem if you work with mains voltage, but let's consider a scenario where this project is powered by a battery. For example, an INR18650-25R battery with a nominal voltage of 3.6 volts and a nominal discharge capacity of 2500 milliamp hours.
Energy Consumption
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The LCD requires around 1 watt while displaying its image. This means we could theoretically power it for only up to 9 hours, which is not ideal for portable projects.
EPaper Modules: A Solution
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Fortunately, I recently discovered ePaper modules, which claim to have ultra-low power consumption. I got myself two of them from the company Waveshare and will be exploring how they work and how easy it is to control them with an Arduino development board in this video.
Unboxing and Features
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I ordered a 4.2-inch ePaper display with a resolution of 400x300 pixels and a 7.5-inch one with a resolution of 640x384 pixels. Even before ordering, I noticed that their price points are pretty close to regular TFT LCDs at the same size.
The small ePaper module comes on a PCB featuring a TXS0108 year voltage level shifter and a connector with all the important data and power lines. The bigger ePaper module is just the bare LCD, which needs to be connected to the ePaper heads. These features also include a female header for easy connection to Raspberry Pi.
Powering up without Power
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The small ePaper screen displays an image without being connected to any power or data lines. This is possible due to MED technology, which stands for its ability to consume minimal energy even when not powered.
Getting Started with the Small ePaper Module
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Instead of focusing on connecting the bigger module to Raspberry Pi, I will be exploring how to control and use the small ePaper module in this video.
To get started, you can purchase an Arduino development board and follow along with my experiments.
WEBVTTKind: captionsLanguage: enIn a previous video I showed you how to utilize such a TFT LCD with integrated touchscreen functionalityNow while this is a great way to display data and interact with your projects, it is not perfectif we measure the current consumption of the whole project, we get current draws of around 200 milliampsOf course that is not a problem if you work with mains voltage,But let's imagine we power this project with a battery. Like this INR18650-25Rwhich comes with a nominal voltage of 3.6 volts and a nominal discharge capacity of2500 milliamp hours. So an overall energy of 9 watt hoursThe LCD requires around 1 watts while displaying its imageWhich means we could theoretically power it for only up to 9 hoursWhich is not that great for portable projectsThankfully though I recently discovered so called ePaper modules, which claimed to have an ultra low power consumptionThat is why I got myself two of them from the company Waveshare. And in this videoWe will not only find out how they work, but also how easy it is to control them with an Arduino development boardLet's get started*Intro music plays*This video is sponsored by JLCPCB, about whose PCB pricesyou will be amazed before ordering, and about the quality after orderingOrder ten PCBs today for only 2 dollars, with 24-hour turnaroundFor the purpose of experimenting with ePaper displaysI got myself a 4.2 inch one with a resolution of 400 by 300 anda 7.5 inch one with a resolution of 640 by 384And even before ordering I noticed that their price points is pretty close to regular TFT LCDs at the same sizebut anywaythe small ePaper module already comes on a PCBwhich features a TXS 0108 year voltage level shifterAnd a connector which led through all the important data and power linesThe bigger ePaper module on the other hand is pretty much just the bare LCDWhich we have to connect to the ePaper heads that once again features the voltage level shifterthe same connector as the smaller moduleAnd additionally a female had are to easily connect it to Raspberry PiBut that is not the goal for this video. So instead let's rather focus on the small ePaper screenAs you can see it displays an image without even being connected to any power or data linesThe reason for that is the MED technology, which stands for "microencapsulated electrophoretic display"To better understand what that means, let's take a look at the ePaper screen under the microscopeBy using the biggest magnification factor, we can see that the black and white area consists of small dotsThose dots are actually capsules with an average diameter of 40 micrometers which are filled with a transparentviscous polymerInside those capsules are white and black electrically charged particlesWith white possessing a positive potential and black possessing a negative potentialso by applying an outer electric fieldThose particles align with it and thus build up either white or black color on the front or back sideTo prove this the black and white color on the front side of the ePaper display should be inverted on the backsideWhich as you can see, is correctall those capsules are controlled by an active matrix, in order to display the intended pictureAnd that is basically the working principleSometimes there are variations by for example having only white particlesBeing suspended in a black polymer or having colored particles or color filters to create an RGB ePaper displayWhich you can also easily orderThis technology is basically the reason why the module can display its image for up to weeks or monthswithout requiring any power. And with the basics out of the wayI connected the 4.2 inch module through the included cable to an Arduino UnoAccording to the manufacturers hardware connection guides, which I found in the wiki for the moduleBut, wait a minute! The manufacturer says we should use a 3.3 volt microcontrollerInstead of a 5 volt one like the Arduino UnoNow I tested the module extensively with the Arduino Uno and never got any problems, but just to be on the safe sideI swapped the Uno with an Arduino Pro MiniWhich are powered and programmed through 3.3 volt FTDI breakout boardTo control the display, We have to utilize the three line or four line SPI communication protocolWhich you should be familiar with if you watched my basics video about itThe datasheet of the ePaper module gives us all the information about what data we have to send overbut we can interact with it much easierFor that I downloaded the provided example code from the manufacturerafter adding the included library to the Arduino folderI opened up the demo sketch which I then immediately uploaded to the ArduinoAnd as you can see, the ePaper now displays a small demo screen before switching back to the image we are already familiar withWe can also observe that the display refresh takes around three seconds andFlashes the display several times which according to the manufacturer is normalBut how exactly can we create texts objects or even pictures?Well for the text and object aspects the library comes with a few commands that we can useTo fully understand the functionality though, I would definitely recommendexperimenting with all those commands since it took me around an hour to just create a simple image like thisThe other way to display a picture is by turning it, pixel by pixel,into hexadecimal values. Like it is done here with the butterfly imageThat means that for example a value of 0xC3- which is 11000011 in binary -means that the first two and last two pixels will be white while the rest will be blackSo 8 pixels get represented with one hexadecimal value which on the other hand means that with a resolution of 400 by 300We would need 15,000 hexadecimal valueswhich I will certainly not write by handInstead I got myself an image file I want to display on the ePaperscaled down to resolution of 400 by 300 pixels with GIMPAnd continued by downloading the provided image to LCD softwareAfter opening it, I imported my scaled down imageAdjusted these settings a bit and created a dot C file with it, which has all the required hexadecimal valuesso after replacing the butterfly hexadecimal values with those, anduploading the code, You can see it that displaying pictures with this module is pretty straightforwardYou only have to be careful to not exceed the programming space of the ArduinoLast but not leastI interrupted the power supply lines and added my energy multimeter in seriesin order to find out that the ePaper module draws around 200 microamps while doing nothing,and around 17 micro-watt energy while refreshing the displayOf course we could decrease those values by properly using the sleep mode of the modulebut even like this those values are already far better than the traditional LCD andWe could refresh a new image around half a million timesOr let the display do a job for around 568 days continuouslyWith just one charged up batterySo, all in all, ePapers are great at displaying static pictures,offer a low power consumption, a wider viewing angle than traditional TFT LCDs and are easy to read inindirect and direct sunlightbecause their particles are reflective, which is not the case for traditional LCDsbut then again you cannot see them in the darkAnd with that being said, I hope you learnt a bit about ePapers and how to control them easily with an ArduinoIf so, don't forget to like, share, and subscribeStay creative and I will see you next time!
