In a previous video I showed you how to utilize such a TFT LCD with integrated touchscreen functionality Now while this is a great way to display data and interact with your projects, it is not perfect if we measure the current consumption of the whole project, we get current draws of around 200 milliamps Of 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 INR18650-25R which comes with a nominal voltage of 3.6 volts and a nominal discharge capacity of 2500 milliamp hours. So an overall energy of 9 watt hours The LCD requires around 1 watts while displaying its image Which means we could theoretically power it for only up to 9 hours Which is not that great for portable projects Thankfully though I recently discovered so called ePaper modules, which claimed to have an ultra low power consumption That is why I got myself two of them from the company Waveshare. And in this video We will not only find out how they work, but also how easy it is to control them with an Arduino development board Let’s get started *Intro music plays* This video is sponsored by JLCPCB, about whose PCB prices you will be amazed before ordering, and about the quality after ordering Order ten PCBs today for only 2 dollars, with 24-hour turnaround For the purpose of experimenting with ePaper displays I got myself a 4.2 inch one with a resolution of 400 by 300 and a 7.5 inch one with a resolution of 640 by 384 And even before ordering I noticed that their price points is pretty close to regular TFT LCDs at the same size but anyway the small ePaper module already comes on a PCB which features a TXS 0108 year voltage level shifter And a connector which led through all the important data and power lines The bigger ePaper module on the other hand is pretty much just the bare LCD Which we have to connect to the ePaper heads that once again features the voltage level shifter the same connector as the smaller module And additionally a female had are to easily connect it to Raspberry Pi But that is not the goal for this video. So instead let’s rather focus on the small ePaper screen As you can see it displays an image without even being connected to any power or data lines The 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 microscope By using the biggest magnification factor, we can see that the black and white area consists of small dots Those dots are actually capsules with an average diameter of 40 micrometers which are filled with a transparent viscous polymer Inside those capsules are white and black electrically charged particles With white possessing a positive potential and black possessing a negative potential so by applying an outer electric field Those particles align with it and thus build up either white or black color on the front or back side To prove this the black and white color on the front side of the ePaper display should be inverted on the backside Which as you can see, is correct all those capsules are controlled by an active matrix, in order to display the intended picture And that is basically the working principle Sometimes there are variations by for example having only white particles Being suspended in a black polymer or having colored particles or color filters to create an RGB ePaper display Which you can also easily order This technology is basically the reason why the module can display its image for up to weeks or months without requiring any power. And with the basics out of the way I connected the 4.2 inch module through the included cable to an Arduino Uno According to the manufacturers hardware connection guides, which I found in the wiki for the module But, wait a minute! The manufacturer says we should use a 3.3 volt microcontroller Instead of a 5 volt one like the Arduino Uno Now I tested the module extensively with the Arduino Uno and never got any problems, but just to be on the safe side I swapped the Uno with an Arduino Pro Mini Which are powered and programmed through 3.3 volt FTDI breakout board To control the display, We have to utilize the three line or four line SPI communication protocol Which you should be familiar with if you watched my basics video about it The datasheet of the ePaper module gives us all the information about what data we have to send over but we can interact with it much easier For that I downloaded the provided example code from the manufacturer after adding the included library to the Arduino folder I opened up the demo sketch which I then immediately uploaded to the Arduino And as you can see, the ePaper now displays a small demo screen before switching back to the image we are already familiar with We can also observe that the display refresh takes around three seconds and Flashes the display several times which according to the manufacturer is normal But 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 use To fully understand the functionality though, I would definitely recommend experimenting with all those commands since it took me around an hour to just create a simple image like this The other way to display a picture is by turning it, pixel by pixel, into hexadecimal values. Like it is done here with the butterfly image That 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 black So 8 pixels get represented with one hexadecimal value which on the other hand means that with a resolution of 400 by 300 We would need 15,000 hexadecimal values which I will certainly not write by hand Instead I got myself an image file I want to display on the ePaper scaled down to resolution of 400 by 300 pixels with GIMP And continued by downloading the provided image to LCD software After opening it, I imported my scaled down image Adjusted these settings a bit and created a dot C file with it, which has all the required hexadecimal values so after replacing the butterfly hexadecimal values with those, and uploading the code, You can see it that displaying pictures with this module is pretty straightforward You only have to be careful to not exceed the programming space of the Arduino Last but not least I interrupted the power supply lines and added my energy multimeter in series in order to find out that the ePaper module draws around 200 microamps while doing nothing, and around 17 micro-watt energy while refreshing the display Of course we could decrease those values by properly using the sleep mode of the module but even like this those values are already far better than the traditional LCD and We could refresh a new image around half a million times Or let the display do a job for around 568 days continuously With just one charged up battery So, 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 in indirect and direct sunlight because their particles are reflective, which is not the case for traditional LCDs but then again you cannot see them in the dark And with that being said, I hope you learnt a bit about ePapers and how to control them easily with an Arduino If so, don’t forget to like, share, and subscribe Stay creative and I will see you next time!