Hello helpful all.

I'm starting the last stage of a project which needs two synchronised

count-down clocks. Think I know how I'd like to do it but would appreciate

any thoughts members have.

Each clock is built around an F84. Readout is a 4-digit 12mm LCD,

showing either Hh:Mm or Mm:Ss. The two clocks are separated by 30

feet. They are identical except that one is a master, the other a slave.

The slave needs to start with whatever time is set on the master. It

should also Pause/Unpause or Reset when told to by the master. The

necessity is for one-way IR communication from master to slave. One

possibility which may foul this up from time to time is coinciding IRQs.

The plan is to have the master enable its Timer0 IRQ first and the slave

only enable its IRQ after receiving the first pulse of IR from the master. The

slave would delay about 1/2 an IRQ period, so that the IRQs of the master

and slave are well and truly separated in time. As each digit is in the range

0-9 I could send a wake-up pulse of 2 IRQs length and then 4x4-bit nybbles,

using 1bit per IRQ. Both clocks would then start their count-down as soon

as the IR transmission had finished. The time difference between the displays

would be the 1/2 IRQ. Pause/Unpause and Reset could be 1010 and 1011.

Is there anything glaringly obvious I've overlooked ?

The IR receiver has been taken from a trashed VCR. I've tried a few discrete

designs in the past but never managed to come up with anything as effective.

Although the power consumption is sort of OK at 1.5mA at 5V (the slave

clock is on battery power), if anyone knows of a circuit as good as a VCR

receiver at lower power I'd be interested.

regards, Joe

PS there's a printer utility called FinePrint that will condense several pages

onto one sheet. I've used it for a while to save paper when printing listings. 4

pages per sheet is about the limit of readability. I found it at download.com

under Utilities / Printer.