Mike's digital clocks

(and other cool homemade stuff...)

On the rare occasions I've got nothing better to do, I like building large and/or unusual digital clocks.  Please note that I cannot provide detailed schematics, PCB layouts etc. for these designs - they are intended to give ideas or inspiration to other potential clock-builders, but feel free to email with any specific queries. See also the Nixie Clock page.
Other interesting clock pages : Propeller Clocks  Electronicsusa - digital clock kits  Cathode-Ray tube clock  Tom McNally's page

Huge countdown clock display built for iPhone launch at three UK O2 stores - more pics here

Custom nixie display built for countdown equences in the UK TV production How not to get on Big Brother (Endemol). April 2002 (To be shown on Channel 4, Mon 20th May 22:00)
Uses Mullard ZM1175 tubes, chosen for their large clear digits and very thin anode mesh. Driven from PC parallel port to display various countdown sequences.

This uses ten 74HC595 shift /latch registers and 80 MMBTA42 driver transistors, as it was done in a hurry and I had to use components which could be obtained and assembled quickly - with more notice I'd probably have used a couple of the  Supertex shiftreg/HV driver chips to minimise component count

Clock built with huge East-German Z568M nixies with 50mm digit height (2001).

Insides - The body is a piece of hardwood, with the inside cut out to house the electronics, and a recess cut into to the top to flush-mount the PCB. Top PCB holds the tube contacts and surface-mounted driver transistors, driven from my nixie clock project PCB, mounted on FR4 baseplate.The tube mounting arrangement is the same as on my B7971 clock below.

Huge nixie clock using Burroughs B7971 alphanumeric tubes (2000)

The PCB forms the top of the case, with  glued acrylic frame and bottom ABS cover. NE-2 bulb inside plastic tube used as flashing hour/minute seperator.

Underside view - PIC16C84 drives modular digit-driver sections, comprising 74HC595 shift-registers and high-voltage driver transistors. Here is a PDF version of the PCB artwork of the driver/socket sections if anyone is interested in driving B7971 tubes - any number of these can be cascaded and easily driven from a PIC etc. or a PC parallel port.

Details showing tube sockets formed from 'D' connector socket contacts, with rings cut from PVC pipe, glued to PCB as surrounds.

Probably the smallest nixie clock in the world (well it was at the time - Jeff Thomas's nixie watch just beats it).... (2000).

After getting hold of some tiny nixie tubes, I decided it would be fun to build a nixie car-clock....

Overall size is 80 x 25 x 45mm, case made from glued ABS sheet.

Construction is mostly surface-mount, on three stacked PCBs.

Rear of front PCB, showing HV driver transistors (FMMTA42)
Middle board, with PIC16F874 processor and 32.768KHz watch crystal

Rear power supply board, containing 5V regulator for PIC, and switchmode converter to generate 200V supply for the nixies. Time-setting buttons on right.
Front PCB with tube removed to show use of  IC socket pins to make tube socket.

Clock built with some old light-guide filament displays, based on a modified version of my nixie clock PCB.

Large clock using Electroluminescent (EL) display, 4.5" high digits (2000). This display is made up from EL strips (originally intended for display backlights in pagers), which give a very nice uniform cool blue-green glow, unlike any LED. They are only about 1.5mm thick, and the whole clock case, made from glued acrylic sheet, is only an inch thick. The EL strips require a high-voltage (200V) AC drive - this supply comes from a standard Pacel EL inverter module. The Inverter chosen is significantly over-rated (it's designed to drive A4 Sheet size panels), to avoid the display brightness varying too much when different numbers of segments are lit. The high-voltage inverter output is switched to the segments using MOC3020 type triac optoisolators, driven by a PIC processor.
A neutral-colour circularly polarised display filter is placed over the EL strips to increase contrast, as the strips are quite light in colour when off - the filter reduces the effect of reflected ambient light. In front of the filter is a black mask with transparent sections for the segments, and the two circular colon dots. The mask is a sheet of typesetting film, produced from a CAD file derived from the display PCB layout to ensure correct alignment.
I found a major problem with the original version of this clock - the display is so bright it lit up the room at night!  I fixed this by adding a light-sensitive brightness control to automatically dim the display at night, by reducing the input voltage to the inverter.

Small dot-matrix clock (~1994). Uses eight 5x7 matrix displays to form a 10 x 28 dot matrix, of which only 8 x 28 are used. Controlled by PIC processor, with HC595 shift-registers as column drivers. Display is proportionally-spaced, and self-centres depending on the width of displayed digits. The hour/minute seperator is a bar which gives an hourglass-type effect, gradually 'filling up' throughout each minute and 'emptying' when the minute rolls over.
Construction is two stacked PCBs, Power is from an external 5V mains adapter.  To avoid the need for unsightly switches, time-setting is done by bringing a magnet near one of two reed-switches. Case is made from glued 3mm ABS sheet.

Second Large clock (1991). Uses 4" high LED displays - the biggest available at the time. Colon is two HP half-inch square bar modules. Driven by a standard 5387-type clock chip, with external ULN2003 drivers. Slim handmade case - consisting of a glued outer frame in 6mm black acrylic, with rear panel glued on, and  front window screwed into tapped holes in frame. Single large 16 x 5.5" PCB (etched with the aid of driptray from Mum's refrigerator!), with components surface-mounted on rear. Powered by external mains transformer. To avoid the need for unsightly switches, time-setting is done by bringing a magnet near one of two reed-switches.

First large clock (~1982). Uses 5mm red LEDs  (3mm for flashing colon), and the (then) standard MM5387 clock chip, with external transistor drivers. Display board is etched PCB for LED locations, but partly hardwired. PCB painted black for contrast. Case is standard plastic project box with lid replaced by red acrylic sheet.