A Watch

PCB LED Tilt activated watch

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The major flaw with many LED watches is the fact that you have to press a button to see the time, I tried fix that problem by using a tilt switch to active the LED showing the time when tilt your arm to look at the watch.

To see it in action check out:

The watch uses the low power MSP430G2211 MCU from Texas instruments to control the LED and mesure the time with the help of a 32kHz watch cristal. The MCU sleeps most of the time only waking up ones a second to count up the time and check if the tilt switch is active. To show the time the watch uses 12 charlieplexed orange LEDs. When the watch is activated it shows time by lighting up 2 LEDs at different light strength (PWM levels). The bright LED shows the hour and the dim LED shows minutes in 5 minutes intervals.

  • 3D printed Case

    Skoog10/01/2014 at 19:44 0 comments

    I haven't been using my watch for a long time mainly because of the delicate nature of having a exposed PCB as the watch face. To make the watch more practical to wear I designed and 3D printed a case last night :-)

    The PCB is still used as the bottom of the watch and the top case is held in place by looping a "NATO band" trough the case and PCB. The "watch Crystal" is made out of a piece of plexiglass and press fitted in to the case.

    The case was designed in Design Spark Mechanical

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PointyOintment wrote 06/13/2014 at 07:34 point
Doesn't the MSP430 have a built-in low-power RTC? Using that and an interrupt from the tilt switch to wake up and display the time would reduce the power consumption a lot.

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Skoog wrote 09/24/2014 at 21:08 point
The MSP430 I have in this project does not have a RTC from what I can see in the Data sheet but I might have missed it some were I will have to check again. I tried having an interrupt on the tilt switch pin, the problem was that it would wake up the watch way to easy. By only checking the tilt switch one every second and only turning on the screen if the tilt switch has been active for two sample if get some free filtering. Also in between the one second timer interrupts the MCU is in low power sleep mode reducing the power consumption.

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deʃhipu wrote 12/21/2016 at 22:27 point

You can always do the filtering with a capacitor. Or wake up the MCU, but don't display the time until it checks a second time that the switch is engaged after some initial waiting.

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[this comment has been deleted]

Skoog wrote 04/09/2014 at 17:19 point
I used Designspark PCB to design the PCB so you probably need to use that software to open the layout file. Desingspark PBC can be downladed for free on‎

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mpinner wrote 03/10/2014 at 05:27 point
i love the novel pcb design and battery holder

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Skoog wrote 03/11/2014 at 16:27 point
Tacks, I was cutie happy when i figured out that a CR1220 coin cell would fit perfectly with the PCB thickness :-)

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