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 but it has an I2C interface. Maxim/Dallas has a bunch of them . 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.


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.

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.