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E-Ink Clock: Hardware

This page gives an overview of the hardware used. You can find the KiCAD files in the GitHub repository. The KiCAD schematic is filled with part numbers and can be exported using KiCAD's BOM functionality.

Attention: The PCB layout in the repository is out of date, since I had some issues in the first PCB. But it should be easy to change the PCB layout in such a way that it fits the schematic again.

Overview

The schematic is divided in four parts: the voltage generation circuits, the E-Ink display, the microcontroller and the DCF77 module.

Voltage Generation

Voltage Generation

The circuit needs six different voltages, of which five are generated here. The sixth voltage is the contrast voltage of the E-Ink display, which is generated in E-Ink part of the circuit.

All this can be achieved much simpler: In my first prototype I used the mother of all switching regulators, the MC33063A, to generate +22 V and -20 V and two linear regulators to obtain the +15 V, respective -15 V. While this is highly inefficient, it is easy and works well, even on a breadboard.

E-Ink Display

E-Ink Display

Not much to say here, the connections are exactly the same as Sprite_tm uses. You can also see that I use his construction to generate the contrast voltage, which happens to be -1.49 V in my case, but can be changed using a trimmer.

To connect the display with the PCB I used a one-sided Hirose FPC-connector with 39 pins and a pitch of 0.3 mm.

Microcontroller

Microcontroller

The LPC1227 was primarily chosen because of the built in real-time clock that is able to wakeup the microcontroller from its Deep Power-Down mode. There is nothing more to say about the microcontroller itself, because this is the standard wiring.

The SRAM module, a Microchip 23LC512, has a capacity of 512 kbit and is used as a 1 bpp image buffer (800 px · 600 px · 1 bpp = 480 kbit). Rasterizing to this buffer is much faster than rendering the image on the fly while updating the E-Ink display. This leads to huge power savings, since the E-Ink display update is — by far — the most power intensive phase.

DCF77 Module

DCF77 Module

This is a standard wiring for most DCF77 modules including a simple filter. Just keep in mind that some DCF77 modules do not work if ON is directly connected to ground because they need a high-to-low edge to start up.