Digital Master Clock with 7 Seg LED Displays & Hourly Ch

This cct uses 4026B ICs to drive 1.5" 7 Segment LED Displays. Even at 5volts these are quite bright and require no other components to drive.

There are transistor outputs for the following.
30 seconds to drive 30 second Synchronous clocks.
1 hour for hourly electro mechanical chime.
24 hour for possible calendar drive.
These outputs are controlled by monostables so times can be changed depending on what you want to drive.

Logic is used for clock setting. Seconds can be reset or stopped for precise setting from a time source.

The 30 sec clock pulse can be synchronised with the main display if required (it will then pulse at 00 and 30 secs).

The time is derived from a 32.768Kz quartz crystal.

I have enclosed vero board layouts drawn with LochMaster 3 and cct diagrams drawn with Livewire. I can supply in these formats if required in case you want to mod them for your own use or of course want to make a PCB (the wiring for this project takes a couple of days).

Warning I have designed the vero boards layouts to keep the boards as small as possible this means a lot of wires are crammed into a very small space including both sides of the board.

To fit the cabling in I have used 0.4mm solid wire and have used multiple runs on the Batt & Eth feeds. Not shown on the diagrams are decoupling capacitors of 100nano Farads.

I have not included a layout for the display board as this will depend on the switches and parts of the cct you want to include. I tend to lay the display out depending on what looks best then fit the wiring in around it.

The display lettering is on a second piece of glass set 1mm back from the main glass panel by a rubber spacer (a bit like double glazing).

A full description of this cct can be found here http://uk.geocities.com/brettoliver@btinternet.com/clock_electronic_1a.htm

Brett.

 

Veroboard Layout and Finished project. View a demo movie here only 260k the sound is a bit crap but it gives you an idea anyway

http://home.btconnect.com/brettoliver/Demo.wmv

Also 10 second animation of master driving slave clock. The master can be seen driving the second hand and stepping the min hand at 14:00 hours.

The master also shows the 1 sec pulse along with the 30 sec and 1 hour pulse as the time hits the hour.

The chime display can be seen chimimg down in binary every 2 secs. This drives the chime bell. I have not managed to get sound on this anim as yet so the chime can not be heard.

 

Oscillator Layout and finished wiring.

 

Master Clock with DIY Slave Clock made using 30 sec movement from an old office clock. you can connect as many of these slave as you wish using extra relays or transistors as required.

All slaves can be advanced or retarded from the master clock.

Also 2 large 12" dial clocks with 30 sec and 1 sec syncronized movements. 1 sec quartz clock driver diagram also included.

The clock now chimes via a 4" longcase clock bell and 30sec clock movement(see pic).

 

they seam to be a bit off...

 

that is a really complicated looking clock - is it a prop for a movie or television show?

have you done any figuring as to how accurately it will keep time?

you mentioned adding temperature control to your oscillator... Dallas-Maxim has a unit called the DS32KHZ - temperature-compensated
crystal oscillator

it contains a quarty crystal, and some circuitry for monitoring the temperature and adjusting the crystal's driving properities.

 

I have looked for a device like that in the UK but have not had much luck. I usually buy from Rapid or Maplin but they do not stock them. I have found some places on the net but they do not seem to sell retail or quote for a single item.

Anyone know a supplier in the UK?

Anyway I think I will enjoy the challenge of building my own temp controller. I have most of the parts laying around so it will cost next to nothing to build.

I have tiny 1.5" fan for cooling but just need some ideas for a heater. I am thinking about a resistor of some sort. My room temp is around 17 min in at night in winter to about 28 in summer.

I can get about a second in 5 days in summer without conpensation.
Brett.

 

You don't need both! - the usual technique is to only heat it, using wirewound resistors, and keep it above your highest ambient temperature.

At one time such devices were freely available on the surplus market, they were called 'crystal ovens'.

 

I knew I'd find a use for Photoshop! Just don't look too close.

Brett. :lol:

 

Nigel Goodwin wrote:

Thanks Nigel I'll have to try a few experiments.



I have had a look at the DS32KHZ and at 0-40°C they quote 60 secs a year which is only just better than my uncompensated crystal. If you look at the graph from the datasheet this seems to be very flat at room temperature for uncompensated crystals anyway.


Brett.

 

for room temperature I'd agree, an ordinary xtal is OK

I think the ds32khz (which is expensive) is designed for more industrial or scientific uses, where you're not going to have "room temperature"... like inside the controller for a steel working robot, where the ambient temp might be 50-60C ... or an anarctic data logger with an ambient of -40C

 

Electro Mechanical Clock Chime

Clock chime made using a min 6v relay with 2.5mm copper wire soldered to the armature. The bell is from an old telephone.

 

Brett,

Bravo on a wonderfully crafted project... I love your "contemporary tech' picture frame" style enough to 'borrow' it for a post-card sized project of mine (grin)...

Please take care... Best regards, Mike

 

Hi Oliverb, i like the design of your Digital Master Clock.
I would like to know about the PC Board Layout. Can you buy the Board? Or did you design the Board?
Your response will be greatly appreciated.

 

ngomess
The main board is tri-pad board and is available from Maplin in the UK .

It is strip board with the strips cut into sections of 3 holes. It is designed to make the mounting of ICs easy (no cutting of strips required). The ICs and other components are then wire together using the remaining holes. These wire "link" are not shown on my board layouts.
Link to tripad board at Maplin.
http://www.maplin.co.uk/Search.aspx?criteria=tripad&doy=26m1&source=15

The board layout is designed on a program called Lochmaster.

Hope this helps.
Brett.

 

A quick update on the accuracy of this clock.

The clock has been running now without problems for a couple of months and I have found that I can get it to run within a second a week.

The main problem is adjusting the trimmer capacitor as a fraction of a millimeter will change the clock speed by a large amount.

I have decided to set it to run fast rather than run slow as using the seconds stop switch the time can be reset very quickly.

Brett.

 

If it came down to it, I'd use a PIC/PC and call up time from either an atomic clock station or a sync website...

Just an idea.

-Infamous

 

It would be interesting to see a PIC version of this clock just to see the actual savings in components and time.

There is around 3 days building time in this clock (hard wired without PCB).

I have a PIC controlled atomic clock built from a kit some time back but the LED display is quite dim and is very hard to read in strong light. I had to mount it on a wall facing away from the sun. Also the display seems to flicker a bit.

 

Can you tell us the number of switches being used and their function as well as the number of outputs and their functions? I couldn't quite get a handle on them from your schematics...

Regards, Mike

<added>

I've also experienced fine tuning problems adjusting the crystal oscillator trimmer capacitor... I ended up using my Ham radio transceiver with its built-in 0.5-ppm timebase to monitor the oscillator frequency while I adjusted the trimmer...

My latest PIC clock project (v2) eliminates the trimmer capacitor in favor of a "software trimmer capacitor" function which is more accurate (6.3 seconds/year) and the 'trim' value is much easier to adjust from the front panel... BTW, the v2 clock uses two chips and standard display multiplexing with PWM brightness control which can be adjusted to be "extremely bright"...

 

Milke
There are the following switches

Set Seconds, Mins and Hours these 3 switches just step the digits up to set the time

Sync Seconds stops the clock to enable it to be synchronised with a precison source

Seconds Reset resets seconds to 00

30 seconds pulse sync synchronises the 30 sec clock pulse with the display (you prob won't need this)

30 second clock Advance & Retard for setting slave clocks
note slaves do not step back so retard just stops 30 sec pulse while advance steps the clocks on at 1 second this is about their max speed.

Chime ON & OFF turns chime off for night time

Chime set Used for setting the chime (prob not required on PIC clock)

The clock has the following outputs

30 second (slave drive)

1 hour relay drive

24 hour relay drive

Chime output to drive a relay

Brett.