FeatherQuill - 34+ Hours of Distraction-Free Writing
Introduction: FeatherQuill - 34+ Hours of Distraction-Free Writing
I write for a living, and spend most of my work day sitting in front of my desktop computer while churning out articles. I built FeatherQuill because I wanted a a satisfying typing experience even when I'm out and about. This is a dedicated, distraction-free word processor in the style of a laptop. It's most important features are an extremely long battery life (34+ hours of typing), a mechanical keyboard, and a quick boot-up time
FeatherQuill is built around a Raspberry Pi Zero W, which was chosen for its low power consumption. That is running DietPi in order to keep the OS as lightweight as possible. When turned on, it will automatically load a simple terminal-based word processor called WordGrinder. The time it takes to go from power on to typing is about 20-25 seconds.
The battery pack is made of eight 18650 lithium-ion batteries, each of which has a capacity of 3100mAh. The total capacity is enough to last 34+ hours while typing. A dedicated hardware switch lets you turn off the LCD for a "standby" mode. 267
In standby the Raspberry Pi will continue to run as normal and the battery pack can last more than 83 hours.
Supplies
* Raspberry Pi Zero W
* 18650 Battery Cells (x8)
* LiPo Charging Board
* 5" Touchscreen LCD
* 60% Mechanical Keyboard
* Small Magnets
* Micro USB Adapter
* Nickel Strips
* USB C Extension
* 3mm Heat Set Inserts
* M3 Screws
* 608 Skateboard Bearings
* Switches
* Short USB Cables and HDMI Cable
Additional Supplies You May Need:
* Clamps
* Gorilla Glue
* 3D Printer Filament
* Solder Flux
* Wire
Tools:
* 3D Printer (I used a BIBO)
* Soldering Iron (This is mine)
* Hot Glue Gun (Like this)
* Screw drivers
* Allen/hex keys
* Files
* Dremel (Not required, but helps to trim/clean up as necessary)
Step 1: Power Consumption and Battery Life
For this project, battery life was the most important factor to me. My goal was to be able to take FeatherQuill with me on a weekend trip and have enough batter life to write for a couple of full days without needing to recharge it. I think I've achieved that. Below are the various measurements I took and conclusions I came to regarding battery life. Keep in mind that 18650 battery cells come in various capacities, and the models I used for this project are 3100mAh each.
Measurements:
LCD Only: 1.7W (5V 340mA)
LCD Only (Backlight Off): 1.2W (5V 240mA)
Everything On (No Keyboard LEDs): 2.7W (5V 540mA)
Keyboard Disconnected: 2.3W (5V 460mA)
USB Hub Disconnected: 2.3W (5V 460mA)
Raspi Only: 0.6W (5V 120mA)
Raspi + Keyboard: 1.35W or 1.05W ? (5V 270mA - 210mA, average: 240mA)
Everything Connected (Backlight Off): 2.2W (5V 440mA)
Conclusions:
Raspi: 120mA
Keyboard: 80mA LCD
(minus backlight): 240mA
LCD backlight: 100mA
LCD total: 340mA
USB Hub: No power used
Normal Use: 5V 540mA Standby
(Backlight Off): 5V 440mA
Standby (LCD Off Entirely): Readings inconsistent, but 5V ~220mA
Battery Life with 8 x 18650 3.7V 3100mAh cell battery pack (total: 24,800mAh):
Normal Use: 34 Hours Standby
(Backlight Off): 41.5 Hours
Standby (LCD Off Entirely): 83.5 Hours
Additional Information and Explanations:
Measurements were taken using a cheap energy monitor and probably aren't completely accurate or precise. But the readings are consistent enough that we can assume they're "close enough" for our purposes.
Everything runs at 5V (nominal). Power for testing was coming from a standard USB wall wart power supply. Power for the actual build will be coming from an 18650 LiPo battery pack via a LiPo charging/booster board.
These measurments were taken while running DietPi (not the Raspberry Pi OS) with both WiFi and Bluetooth disabled. Bluetooth utilities/services were entirely removed. 267