Hi everyone, just thought I 'd sneak in a final project share before G+ shuts down

[G+_Chris O'Riley]

Hi everyone, just thought I'd sneak in a final project share before G+ shuts down. This is something I've been working on for a few months in my spare time. I've made a few electronic gizmos for my son, but wanted to make something he could use every day. So, I thought of a wrist watch with a twist - it's round, and it rounds to the nearest 5 minutes since my son doesn't really need to know the time any more accurately than that (and, of course since I didn't feel like trying to lay out traces for 72 LEDs!). It displays the time in two rings of LEDs - red for the hours and blue for the minutes, in 5 minute increments.

 

Here's a video of it in action:

 

After the light show, all the ICs beside the RTC are powered down or put in sleep mode, and in that state, it only draws about .02 mAh from the battery, which is a 50 mAh cell. It should last months in standby between charges. While the lights are going, it's about 15 mA, so hopefully with "normal" use (not banging the button every 10 seconds), it'll last 1 to 2 weeks between charges.

 

For the components, it uses a M41T62 RTC, an ATTiny841 and an IS31FL3235 28 channel LED driver. Both the RTC and the LED driver communicate over i2C, and there's a lipo charger to handle recharging the cell when USB is plugged in.

 

I'm pretty much down to just finishing up the code and then I'll mill a housing for it from aluminum with a clear acrylic or lexan top. Still debating what style watch band to use, but I'll settle on something soon.

 

Anyway, hope everyone likes it.

[G+_Paul Hutchinson]

Very nice!

[G+_Roger pedrosa]

When is G+ gonna pull the plug on this social media???

[G+_Chris O'Riley]

Update with most of the programming done. Still need to add a battery monitor function, and I have the square wave pin on the RTC routed to a pin on the Tiny841 so I could do calibration... but I'm not sure it's worth the effort. I've been finding these RTCs accurate to about .5 to 1 second per day uncalibrated out of the box, so it would take 1 to 2 months to be off by a minute... and this watch rounds to the nearest 5 minutes!

 

Getting it all working smoothly with just a single button for input was a challenge. I'll be starting on the housing for it soon...