TFT LCD displays and their power demands
A 2-inch TFT LCD display typically needs to be refreshed every 20 ms to maintain the image. When bright enough to read, it draws around 30 mA operating and about 3 mA in standby. The power consumption per day will be 259,203.54 mAs, resulting in a total consumption over five years of 473,046,460.50 mAs. That will require 679 batteries. In other words, you’ll need to change the battery every 2.69 days!
E-paper display: power consumption comparison
Compare this with an e-paper display. A typical 2-inch module that integrates the display with an external timing controller requires 2.33 mA for 2.32 seconds to completely refresh the screen. That’s a daily power consumption of 32.43 mAs, or 59,191.32 mAs over five years. This is 8.5% of the nominal capacity of a single coin cell. If you only need a partial update, even less energy is required. E-paper displays consume no energy at all to maintain a static image.
As a conservative estimate, our 2-inch e-paper modules support at least 50,000 updates on just 25% of a CR2032 coin cell’s energy budget. This accounts for the fact that coin cells are warranted for 5 years, exhibit some leakage, and that other module components draw some current. In theory, that’s an operating life of 22 years, based on the operating conditions described. Whichever way you look at it, e-paper is the most viable display technology for ultra-low power IoT applications.
E-paper displays are the most viable display technology for ultra-low power IoT applications, delivering battery life that simply cannot be matched by conventional alternatives.
This blog first appeared on the Power Systems Design website
Blogger: Scott Soong, CEO, Pervasive Displays
The display challenge for IoT designers
You’ve carefully selected your sensor, found the lowest power MCU for your battery-powered IoT application, and optimized your code to minimize energy consumption. You’ve also chosen the lowest power wireless solution. Now you want to figure out how to add a display without trashing the power budget. That’s the challenge faced by many IoT product designers, for example those designing remote meters or smart tags. If they think only in terms of dot matrix displays, it’s a challenge they’ll struggle to overcome.
Let’s assume that you want your display to operate for five years with CR2032 coin cell batteries as the power source. These have a typical stated capacity of 220 mAh. Assuming a real-world operating capacity of 88%, that gives us 193.6 mAh. We’ll base our energy consumption calculations on a requirement to update the display with new information six times each day.
TFT LCD displays and their power demands
A 2-inch TFT LCD display typically needs to be refreshed every 20 ms to maintain the image. When bright enough to read, it draws around 30 mA operating and about 3 mA in standby. The power consumption per day will be 259,203.54 mAs, resulting in a total consumption over five years of 473,046,460.50 mAs. That will require 679 batteries. In other words, you’ll need to change the battery every 2.69 days!
E-paper display: power consumption comparison
Compare this with an e-paper display. A typical 2-inch module that integrates the display with an external timing controller requires 2.33 mA for 2.32 seconds to completely refresh the screen. That’s a daily power consumption of 32.43 mAs, or 59,191.32 mAs over five years. This is 8.5% of the nominal capacity of a single coin cell. If you only need a partial update, even less energy is required. E-paper displays consume no energy at all to maintain a static image.
As a conservative estimate, our 2-inch e-paper modules support at least 50,000 updates on just 25% of a CR2032 coin cell’s energy budget. This accounts for the fact that coin cells are warranted for 5 years, exhibit some leakage, and that other module components draw some current. In theory, that’s an operating life of 22 years, based on the operating conditions described. Whichever way you look at it, e-paper is the most viable display technology for ultra-low power IoT applications.
E-paper displays are the most viable display technology for ultra-low power IoT applications, delivering battery life that simply cannot be matched by conventional alternatives.
This blog first appeared on the Power Systems Design website
Blogger: Scott Soong, CEO, Pervasive Displays
The energy consumption profile of an e-paper display as it updates
The display challenge for IoT designers
You’ve carefully selected your sensor, found the lowest power MCU for your battery-powered IoT application, and optimized your code to minimize energy consumption. You’ve also chosen the lowest power wireless solution. Now you want to figure out how to add a display without trashing the power budget. That’s the challenge faced by many IoT product designers, for example those designing remote meters or smart tags. If they think only in terms of dot matrix displays, it’s a challenge they’ll struggle to overcome.
Let’s assume that you want your display to operate for five years with CR2032 coin cell batteries as the power source. These have a typical stated capacity of 220 mAh. Assuming a real-world operating capacity of 88%, that gives us 193.6 mAh. We’ll base our energy consumption calculations on a requirement to update the display with new information six times each day.
TFT LCD displays and their power demands
A 2-inch TFT LCD display typically needs to be refreshed every 20 ms to maintain the image. When bright enough to read, it draws around 30 mA operating and about 3 mA in standby. The power consumption per day will be 259,203.54 mAs, resulting in a total consumption over five years of 473,046,460.50 mAs. That will require 679 batteries. In other words, you’ll need to change the battery every 2.69 days!
E-paper display: power consumption comparison
Compare this with an e-paper display. A typical 2-inch module that integrates the display with an external timing controller requires 2.33 mA for 2.32 seconds to completely refresh the screen. That’s a daily power consumption of 32.43 mAs, or 59,191.32 mAs over five years. This is 8.5% of the nominal capacity of a single coin cell. If you only need a partial update, even less energy is required. E-paper displays consume no energy at all to maintain a static image.
As a conservative estimate, our 2-inch e-paper modules support at least 50,000 updates on just 25% of a CR2032 coin cell’s energy budget. This accounts for the fact that coin cells are warranted for 5 years, exhibit some leakage, and that other module components draw some current. In theory, that’s an operating life of 22 years, based on the operating conditions described. Whichever way you look at it, e-paper is the most viable display technology for ultra-low power IoT applications.
E-paper displays are the most viable display technology for ultra-low power IoT applications, delivering battery life that simply cannot be matched by conventional alternatives.
This blog first appeared on the Power Systems Design website
Blogger: Scott Soong, CEO, Pervasive Displays