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Topic: DaTajm - A sneak preview of my new homemade wristwatch (Read 42635 times) previous topic - next topic

DaTajm - A sneak preview of my new homemade wristwatch

I've been offline from DP for a while due to a really evil workload.  But I managed to grab a few hours while being a passive participant of some boring telephone conferences so I was able to put a small project together...
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DaTajm is a wristwatch based on a PIC16F1824 powered by a single CR1216 lithium coin cell. I'm using a sandwich of three PCBs.  The topmost pcb (0.8mm thick) have 12 leds and a resistive touchpad on the top side and all the other parts on the bottom.  The middle pcb (1.6mm( is just a spacer for the battery. The bottom pcb have a contact for the positive pole of the battery and a soldered cable up to the top pcb.

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I've uploaded a short video of it in action - when I touch the sensor the time 9:00 is shown (first led 9 (hours) follwoed by led 0 (minutes))

http://youtu.be/HAK1QthG-L8

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #1 –
Awesome!  I really like it.

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #2 –
+1 for awesomeness !!!

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #3 –
Thanks guys. It turned out better than I expected, but the touch sensor is a bit wonky so I'll try to make it a capacitive sensor and see what that does to the power consumption.

Currently I got a 19 uA average draw from the battery using the non-LF chip and sleeping for four seconds before being awakened by the timer overflow interrupt.

Doing a capacities sensor I need to wake up much more frequently and also spend a long time awake while doing the sensing. That will not be good for battery life....
 
Now the watch should last two months on "standby" and likely a few weeks in normal usage. With cap sensing the battery might only last a few days if im unlucky.

I'll also try a version with a pushbutton. A tiny smd button should fit just fine inside the 1.6mm middle pcb having it protruding from the left or right edge like in a real watch.

I know the green color looks a bit shite but  didn't want to spend $60 extra on black soldermask on the prototypes.  I'll probably make a small batch of black pcb with ENIG (gold) finishing when I've got the button/touch issue sorted out.

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #4 –
That's boss

Who made the PCB? Not a lot of places would do internal routing for cheap.

I like the green colour, it gives it that DIY feel because it is the default PCB colour.

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #5 –
[quote author="matseng"]Now the watch should last two months on "standby" and likely a few weeks in normal usage. With cap sensing the battery might only last a few days if im unlucky.[/quote]
Although I like the PIC and especially the PIC32 chips a lot for most of my projects, I regularly turn to the MSP430 value line chips when doing really low power stuff.

The alarm clock I made two years ago [1] awakes 64 times per second, does a little houskeeping and time counting, and draws just 2 uA.  When waking up less often, the power consumption can be reduced further.

Maybe you want to consider using an MSP430 value line chip [2] for this project?  The programmer/debugger [3] costs just $9.99, and the Eclipse based IDE [4] is free for the max. flash size of 16 kB of these chips.

Cheers,
Markus

[1] viewtopic.php?t=2126
[2] http://www.ti.com/lsds/ti/microcontroll ... rview.page
[3] http://www.ti.com/tool/msp-exp430g2
[4] http://www.ti.com/tool/ccstudio-msp430

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #6 –
Frank: The PCBs are made at Seeedstudio and they are actually doing internal cutouts as part of their standard $10 for 10 pcs of 5x5cm PCB service. 

Yes, the green color is making it look like a home DIY project, I want it to become a bit more stylish and then black with gold trims would be better I think. :-)

Marcus: Maybe it's time to broaden my horizons a bit and try the MSP430 series as they seem to be the ruling line of microcontrollers when it comes to low power.  So you can use a Launchpad as a programmer as well or is the one you linked to a specialized Launchpad/Programmer?

What crystal did you run your alarm clock on?  I currently use the 32KHz crystal for both the timer and the cpu.

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #7 –
Yes, I use the Lauchpad as programmer/debugger for my projects.  Simply connect the TEST and RST pins to the chip you want to program.

I use the 32 kHz quarz for the timekeeping ISR (watchdog timer) and run from the internal 16 MHz FRC oscillator when waking up. The wakeup time is 1 us.

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #8 –
Really inspiring project, Mats!

I think it will look great in black & gold! With the resoultion of PCB etching you could make some really intricate designs on the watchface.

How about using a piezo-sensor instead of a touch pad? I recently got some Stick'n'Find devices, and when you get them they're in some low-power mode, and are woken by tapping them a couple of times. I've never used piezo-devices, so I don't know the details, but I think they generate voltage when tapped, so they could be energy efficient.

Another idea would be to have the LEDs on the bottommost PCB facing up, drill holes above the LEDs on the middle layer, and then etch away the copper on the bottom side of the clockface layer below numbers on the clockface to have the LEDs shine through. Would give a very clean dial. Hm, I wonder if light will shine through the black soldermask?

For my own use, I think I'd like more than 5 minute resolution. You could have three rings of LEDs, 60 for 1-minute resolution, 12 or a bit more for seconds and 24? for the hours. 10 pins can charlieplex 90 LEDs according to Wikipedia, so you wouldn't need a huge number of pins. Of course soldering 100 LEDs sounds tedious.

If I didn't have so many active projects of my own at the moment, I'd start making a watch like yours right away ;-)

Greetings from rainy Stockhom!

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #9 –
How do you measure such low currents?, the ucurrent or other tools?

Have been looking a bit on the Silicon labs C8051F9xx series, it supposedly draws about 500nA when sleeping
And it have capacitive sensor.. AND it's so darn small it's a bit fiddly to solder..

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #10 –
Erl: I was thinking for a while to have the leds mounted upside down on the back of the topmost pcb (along with the rest of the parts).  But having it all on the bottom pcb is definitely an option, but I probably have to make the watch slightly bigger do do that.  Having a small piezo that can be tapped to activate the watch would be very nice - it will be hard to fit it though without getting it squished by the battery.

( Stockholm... Lived there for the first 30 years of my life, but for the last 7 years I've only been back there for two days. Too cold ^_^ )

Neslekkim: I used my Agilent 34401A, with 6.5 digits of resolution even the 10mA range gives decent figures.  But I probably should invest in a proper dedicated uA/nA meter or atleast a uCurrent from Dave....

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #11 –
ah, that's something else than my fluke 75 ;)

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #12 –
Congrats matseng, you made HaD ;-)

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #13 –
Hiya,
love it.
One suggestion maybe.
the minute led could blink (minutes % 5 )+ 1 times to signal intermediate minutes (e.g. the 5 minutes led blinks twice when it's 6 minutes past 9).
Keep up the nice work!
Bonghi

Re: DaTajm - A sneak preview of my new homemade wristwatch

Reply #14 –
Very cool!  A couple of suggestions for version 2:

1. I'd suggest adding strap loops on the middle layer too, just to help keep a yank on the strap from snapping the existing single layer right off.  If you left them plated, the copper might add a little strength too, and give room for a soldered support wire for added strength.

2. If you enlarge one of the screw holes in the middle layer, you could use a small spring contacting pads on the top and bottom layers to transfer the positive battery lead.  No soldered wire holding the two halves together makes for easier assembly/disassembly (at the cost of a small loose part).  Or... maybe a top layer solder pad under the screw head and a via where the screw goes into in the bottom layer.

I like the push button idea, as that could be interrupt driven and thus use less battery than either resistive or capacitive.  That said, the cool factor of a touchpad is hard to beat.  Oh, and if you used a piezo sensor, i wonder if it could double as a speaker as well.  That would make it worth the extra battery consumption!

I also like the idea someone else gave of flashing the minute LED to indicate the final digit with more precision.  You could go crazy by putting it in a second mode where the LED chases the second around the face for a while.  If there's room for a phototransistor, you could dim the LEDs according to ambient light too.  Or I wonder if it's possible to use an existing LED to read the ambient light level...  Have a "club" mode where it syncs to the music and strobes.  :p  Or use the LEDs on the front face to set or adjust the time without needing to open it up.