What is the best Real Time Clock?

[Saimaster13]

I'm wanting to make a clock or two driven by a microcontroller, and an RTC seems to be the way to go. So, what is the best RTC to get? Anyone have a favorite or most reliable one?

[bitfogav]

The most common one seems to be a DS1307 RTC. a great tutorial Ive used before is here DS1307 tutorial. More info here aswell on the DS1307 RTC RTC digital-DIY. Ive also used the microchip MCP79410 RTC

[Saimaster13]

Thanks! Just what I needed to know, and a tutorial of how to use it, I'll be sure to order some 1307s soon.

[brad]

Youve got me interested. What are you making

[Saimaster13]

Well... I was planning on making a watch displaying time in octal. It would have 6 RGB LEDs, 2 for seconds, 2 for minutes, and 2 for hours. Each color (red, purple, blue, light blue, green, yellow, white) would represent an octal digit.

Also, I was wanting to make a scrolling binary clock. It would have three 16 rows of RGB LEDs, for mins, secs, hours. It would display time in binary, 1s would be represented by a color and 0s would be represented by a color and the colors would scroll across the row of LEDs.

Yup, that would be what I am planning.

[brad]

Sounds very cool - definitely a good conversation starter.

The perfect watch to take to some type of electronics convention!

Have you seen that you can get tiny RGB LED's (1mm x 1mm)


http://au.mouser.com/new/lumex/lumexrgb0404/

(image taken from the mouser site)

[Saimaster13]

And how am I supposed to do anything with them? They are very awesome though, but I do not have the tools for anything that small...

[Chuckt]

And how am I supposed to do anything with them? They are very awesome though, but I do not have the tools for anything that small...

Have you read the datasheet? It might give you some clues.

I haven't played with anything that small but you probably need ESD tweezers, a magnifying glass if you are over 40 and a small soldering iron with a 1/61 inch tip and use solder and flux. It would probably be good to have a circuit board made with one of these programs like Eagle, Diptrace, etc so you can be more exact on placing it.

You might want to investigate GPS for a real time clock. They might be more accurate and you won't have to reset your clock for the right time.

[brad]

Yeah - they're small

But how cool would they look in a watch!

[Garth]

If using a microcontroller, why not just have its clock frequency crystal-controlled, and set up a time to interrupt at every rollover and do the RTC in software instead of using a separate RTC IC.

[Chuckt]

There is a DS1307 sold by Mouser. It is accurate to within 2 seconds a day.

http://www.mouser.com/Search/Refine.aspx?Keyword=DS1307

For something more accurate, there is the DS3231 sold by Mouser:

http://www.mouser.com/Search/Refine.aspx?Keyword=DS3231

There are breakout boards for both of them sold on the internet.