The About-o-Clock

The About-o-Clock is a word clock that tells the time in words. It shall show the time, and do nothing else. Therefore, it has no buttons. When switched on, it shows the time.

It knows the time exactly from the ether, but it tells us only roughly. To not forget the time, it has a small battery.

The clock has a nice font, so that it is a pleasure to read. With natural letter spacing, untracked, in monospace with serifs. For German time, no decenders are necessary.

The colour is important, too. A bright orange, which the photo camera does not like, but the clock is not for the camera but for our living room. The colour is 595nm, a wonderful orange, but the camera insists that it is yellow.

To adjust the brightness it observes the environment. It turns darker when we watch a film and the living room becomes cosy. If that is not enough, its brightness can be turned up and down with an infrared remote control, or be switched off completely.

Small Versions:

[ 100 | 150 | 200 | 300 | 450 | 600 ]

Building Details

• CPU: Atmel AVR Atmega644 (an Atmega164 would have been enough) @ 2MHz
• DCF77 receiver: ELV with individual voltage regulator LD1117V33
• Real-time clock: Maxim DS1307, battery buffered
• IR receiver: TSOP1740
• LEDs: 595nm highflux LEDs, driven with ~30mA
• Voltage: +5V, regulated with efficient Recom R-785.0-1.0
• Matrix: 8 vert, 11 horiz, fully encapsulated in copper foil to minimise DCF77 disturbance
• Dimming: 255 step PWM at ~1MHz; ~4kHz line frequency; ~500Hz display refresh
• Drivers: PWM capable constant current source, linewise common anode, manually built from transistors (next time: use Max7221)
• Casing: aircraft plywood 4mm + white, glossy acrylic ink spray
• Front: CNC cut 4mm acrylic glass into layer of lamp black acrylic ink
• Mounting: iron sheet + 8 neo magnets 20x2mm
• Glue for iron and magnets: 2 component acrylate glue
• Diffusor: thin plastic bag from farmers market
• Programmed in GNU assembler (under Linux)
• IR reception, DCF reception, brightness control, second pulse from RTC, I2C communication, and display refresh are all in an interrupt
• TIMER0 for PWM (phase correct PWM mode)
• TIMER1 for global system time @ ~1MHz, used for measurements in IR and DCF reception

Other Word Clocks

There are some other variants of the word clock below. There are also software-only implementations, but below, only hardware implementations are listed.

Hobby

• Large (248 LEDs) in Croatian
• Small variant based on PIC
• First prototype of Doug's commercial ones
• In an IKEA frame
• Wooden frame with a colour birthday message
• German with different dialect modes
• German, multicolour
• Polish version
• Another one in an IKEA frame
• With serif font; hand-carved, it seems

Commercial

• Dougs Word Clocks
• QlockTwo