E-Paper Clock Displays Things In A Battery-Friendly Manner

Clock builds are a hacker staple, and many overflow with power-thirsty LEDs and network features. This build from [mattwach] takes quite the opposite approach, sipping away at its batteries thanks to an e-paper based design.

The build relies on a small Waveshare e-paper module which only requires power when the display is actually changing. When static, the display needs no electricity, and this helps save a great amount of power compared to OLED or LCD-based clocks.

An Atmega328p is the heart of the build, running off a 32.768 KHz clock crystal for a combination of precise timekeeping and low power draw. Time is ensured to be both precise and accurate thanks to a GPS module which allows the clock to sync to satellite time when powered up. It’s a common way to sync clocks to a high-quality time source. Most of the time, though, the GPS is kept powered down to save the 30-100 mA that the module typically draws when in use.

Other features include a temperature, humidity, and pressure sensor, with ambient pressure graphed over time. There’s also notification of sunrise and sunset times, along with the current phase of the moon. It’s all wrapped up in a case tastefully manufactured using 3D printed parts and some wooden CNC-cut panels for a nice rustic look.

With the e-paper display and the microcontroller configured for low-power operation, the clock will run for around 6 months on four AAA cells. Overall, it’s a nifty little clock that will provide the time, date, and other information without the need for an Internet connection. Video after the break.

20 thoughts on “E-Paper Clock Displays Things In A Battery-Friendly Manner

    1. That will depend a great deal on the quality of the antenna and the building you are in – large reinforced concrete or steel frame forget it, brick probably ok, wood very likely ok at least if the antenna is better than my CF-H1’s – that thing doesn’t even work with unobstructed view to the sky very well.

      Does seem to me though that using a network time server would make more sense, as a house without sufficient wifi to handle that request quickly in the modern world is going to be rather rare – heck we have ethernet fun all through the house and still have to have wifi on – largely for guests, but also for our own portable gizmos.

      1. A clock that doesn’t require an internet connection is infinitely more useful than one that does, IMHO.

        In the US, a clock that can be turned on and is instantly accurate can be based on GPS or WWV/WWVH, and GPS seems ‘easier’ than WWV/WWVH reception.

        1. Really depends on what you are using it for doesn’t it – looks like a desktop clock to me, which means good wifi signal is almost a certainly where GPS is not.

          1. For “me” a clock is only for a time indication and nothing more (have no need to be accurate than within 5 minutes. (ok every body relacks.. ;)

        2. If you’re using a radio signal, WWVB at 60KHz is reliable. WWV fades and comes and goes on a given frequency.

          Heathkit had “The Most Accurate Clock” that did use WWV. But I gather it could switch frequency, and made adjustments to the clock so it stayed “accurate” even without reception. WWVB has really taken over for that.

          It’s a sad thing the the New Heathkit sells “A Most Reliable Clock” to harken to the previous product, except it’s nothing special.

        3. Have a look at the EverSet ES100 receiver and the WWVB-BPSK radio signal. The ES100 receives and decodes, the output (I2C) is a time stamp containing every available information (UTC, DST, leap second etc.). Very easy to work with. The receiver chip and some kits are exclusively available from UNIVERSAL-SOLDER (Canada). I would love to see someone using this for an e-paper clock!

      2. It also depends on the module firmware whether it gives time information before catching multiple satellites. Seeing just one satellite is enough to obtain time reference to about 100 ms accuracy. But some modules only report time after they have a full fix.

    2. I’d swap the GPS for for LoRaWAN. There’s a time sync protocol with it that’s plenty accurate for a desktop clock. It’s cheap enough to set up a LoRaWAN server if you don’t have one within range, it’s extremely low power, and doesn’t require an active antenna.

  1. So depending on your building and window position, changing the batteries outside could be the thing to do. A note inside informing you of such would be a nice touch. Another way would be to create a warning in software, if batteries changed and no gps fix – push warning msg to screen – I looked on the github repo but could not spot it. Nice project.

  2. Nice setup but I do question the GPS usage for keeping time when a DS3231 is smaller and cheaper and if you want to save power further a FET could be put on the VCC power input to the module letting the coin cell do the work of keeping the RTC accurate. e-Ink is a great low power display and perfect for this type of project which only changes a few pixels every 30 seconds.

  3. There are, IMHO, multiple manners of synchronization. From the Sundial-esque to more advanced. Each probably has a valid use-case/application. What was chosen here is fine. I really like the display of information!

  4. This is really cool. It begs the question, why is ePaper not used in more commercial products such as clocks, weather stations, thermostats, etc. that have low update rates.

  5. Cool, but 6 months with 4AAA batteries is not “a long time.” My alarm clock has been going for 1.5 years with 3 AAA batteries. Of course it’s not synced with GPS time, but it drifts so slowly i only need to ajust it every half year or so.

    1. My cheap DCF77 LCD alarm clock runs on a single AA cell. The one it now has been in there longer than I can remember. Several years, at the least.

      No drift, always correct – and it automatically adjusts for daylight savings time.

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