alarm clock

we’re planning on programming an alarm clock to make the arduino output change a numerical LED display. after reading the post about the GPS clock, we were wondering if there are any other suggestions for calibrating the arduino using an external device (ie - stopwatch) or if there is a way to program the arduino to accurately keep its own time.

also, as we are new at coding, any thoughts/suggestions/nudges in the right direction would be very much appreciated - we’re driven mostly by design concepts and this is our first venture into the land of robotics.

GPS is a smart idea, becuase if the power crashes and the machine comes back up again, the GPS knows what the real time is.

There are real-time clock IC's, but they have to generally be set again-- like old IBM computers that think it's Jan 1, 1961.

Sparkfun in the US has a GPS module that can be hooked up to the serial port of the Arduino.

Unless you've got a GPS lying around or lots of money to buy one just to make a clock, what you want is a real time clock. It's a clock, typically with a 32.768kHz crystal and a battery backup (typically a lithium coin cell).

Sparkfun has a module http://www.sparkfun.com/commerce/product_info.php?products_id=99 but it has an I2C interface. Maxim/Dallas has a bunch of them http://www.maxim-ic.com/rtc.cfm . I'm sure other vendors make them, too. I'd look for one with an SPI interface, since the Arduino's Atmel has SPI built in.

-j

There are state operated time transmitters which are very accurate and reliable. Many countries have them. You can usually get the required hardware for pretty cheap.

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1162986904

http://www.npl.co.uk/time/ http://en.wikipedia.org/wiki/DCF77 http://tf.nist.gov/index.html http://en.wikipedia.org/wiki/Radio_clock

If you just want a steady seconds pulse, why not use a el cheapo penlight analog clock and pick the pulse from the coil inside? check if it runs without the coil, then you save yourself changing the battery every year. :-)

I am doing the same thing. but i have 2 12" led displays to use. everything is wired up i just need to write the software. To drive the LED displays, i am using the same IC's that spark fun used in their Wall Clock except mine are the DIP versions not surface mount.