Clock Project

My family does a "build a gift" gift exchange for Christmas every year. In short those who participate build something and we do a "white elephant" game to see who gets it. This year I want to build a clock. But I also want to experiment with the Arduino platform. I want to build a clock using Stepper motors that will display: Month, Day, Year, Hour, Minute, Second, Temp. Im thinking of using a RTC and/or a GPS antenna. The problem with the GPS antenna is I would want something powerful enough to work indoors.
So, I'm looking for hardware suggestions, items that would be reliable and long lasting.

Why would you need stepper motors?
Most people display the time on a LCD.

As far as I know you can't guarantee GPS reception indoors. If you want to AC power it, the 50/60Hz power line frequency is super-accurate over the long term and they make little corrections to keep it "perfect" . (If it's been running slightly slow the speed it up a little until the number of cycles is correct, etc.). But of course it's only good until the power is interrupted. Except, there was a [u]problem in Europe recently[/u] and all the AC clocks got slow... :smiley: :smiley: :smiley:

A good RTC module can be as good as a watch. I believe they "trim" the crystals to get better accuracy than the published crystal specs.

using Stepper motors

Standard stepper motors have 200 steps per revolution which doesn't divide evenly by 60, so it can look weird as the hands step unevenly. If that's a problem you can micro-step or gear-down.

And if you are making a clock with traditional hour, minute, and second hands, you need coaxial shafts.

Stepper motors waste an enormous amount of power, so your project won't be battery powered.

DVDdoug:
Except, there was a [u]problem in Europe recently[/u] and all the AC clocks got slow... :smiley: :smiley: :smiley:

Indeed - to the extent that in The Netherlands the monthly air alarm test failed big time, as the clocks were out of sync by too much! (solution: sync the clocks of the alarms and the control centre more frequently).

A good RTC module can be as good as a watch. I believe they "trim" the crystals to get better accuracy than the published crystal specs.

You have to do this by hand: there's a register in the IC that lets you adjust the built-in crystal ballast, and that way you can fine tune the crystal to get down to a few seconds a year.

If there's WiFi available, you can also use NTP to get the time. That's probably the most accurate, together with the GPS signal of course.

I would look at using an ESP8266 module. They are only a few US dollars and include wifi.
By far the cheapest solution for a small project.
You could then use wifi to access a time server with NTP or even one that can provide localtime including DST changes.
For a few dollars more you could add a color LCD and have a fully functional clock and weather station.
Google around for esp8266 weather station, you will find lots of projects.
Total cost is only about $10 USD plus any costs for a case.

— bill

GPS will often work adequately well indoors to get a time sync. It doesn’t take any special receivers. It does help if you’re near a window but even that’s not required.