Time Keeping

rapscaLLion

Howdy folks,

Plugging away at my project, and thought about adding a new feature.
I would like my DMX controlled LED lights to only turn on between dusk and
dawn, and I do not want to use a light reading to do so, but rather the time.
To this effect I would like some information on keeping track of time with
the propellor: What IC is good for this, which crystal to use with it, etc.
A key interest of mine is how to use this in conjunction with an automatically
recharging battery to maintain time keeping during a power outage, for at least
24 hours.

Another key issue for me: Assuming I solder the ic to the board at the correct
distance, how accurate should the time keeping be? If I'm out by a few minutes
a year, that's fine but much more than that would be pushing it. Any ideas?

Thanks!

Mike Green

Have a look at the Dallas/Maxim DS1302 timekeeping chip (datasheets.maxim-ic.com/en/ds/DS1302.pdf). There's an object to use this in the Propeller Object Exchange (ww1.parallax.com/Default.aspx?tabid=65). The chip provides for a trickle charged rechargable battery or super-capacitor for backup. It can also use a lithium coin cell.

Chris Savage

Agreed...The DS1302 is a fun chip to use...Be sure to follow carefully the crystal capacitance guidelines for accurate timing. There is an App Note on the Maxim website covering this. Take care.

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Chris Savage
Parallax Tech Support