AVR-Chat

AVR-Chat@yahoogroups.com wrote:
> G'day all
> 
> I'm looking into a project for an outdoor time/temp/date
> giant display (20" high possibly).
> 
> As the unit will be mounted on the side a multistory building
> as I understand, I don't think the client will want to get a
> cherry picker or climb a window washing lift to reset the
> time twice a year to cater for the dreaded daylight time changes.
> 


This is not answering your time question at all, but a word of advice
about the display itself - make sure you pick the beam angles of the
LED's you use for the display very carefully.

I built something exactly like this for the side of a nightclub and we
used 20 degree LEDs. At a distance, 20 degrees is a lot narrower than
you think, and you could hardly see it unless you were dead in line.

We eventually had to rebuild it with 40 degree LEDs which worked much
better, but we still had to angle the sign downwards.

My sign has an RS485 link to the manager's PC inside the building where
he can correct the time. It uses a Philips PCF8583 real time clock and
hardly ever needs correcting. It does daylight saving adjustments
automatically (add 1 hour at 1am on last Sunday in March, back 1 hour at
2am on last Sunday in October). However if I was doing it now I would
include a GPS time module as others have suggested. But I'm not sure how
fixed your daylight saving times are - I was in Oz during April and they
changed end of daylight saving by a week to allow the Commonwealth Games
to occur in summer time. Not sure GPS would help with that.

-- 
Tim Mitchell
tim@sabretechnology.co.uk
http://www.sabretechnology.co.uk