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LED matrix timer display - brush your teeth for two minutes kids!

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Might be a bit math intensive to determine if the brush is being moved correctly. If you could get it to determine the motions are correct, you could have a little panel with LED's that progress to show what they should be doing- top-left-inside, top-front-inside, top-right-inside, and so on, giving them 10 seconds on each part before moving to the next. Combine that with stopping the timer if the brush isn't moving, and resetting the timer if the brush doesn't move for a long time, and you might be half-way there to clean teeth. ;-)


Clean teeth, or a new video game.  (Better not make it too entertaining though, too much brushing can damage teeth/gums).

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  • 2 weeks later...

Having done quite a bit of work in the past with inertial sensors, I can say that it's next to impossible to distinguish one type of motion from another using accelerometers & gyros. Especially with the kind of cheap accelerometers that would fit on the back of a toothbrush. So although it's a pretty nice idea, I think in the end I'll have to trust them. I'll probably be behind them in the bathroom policing the whole thing anyway, and the timer is as much for me as it is for them. AND of course the whole thing is only an excuse to play with electronics and spend some cash of parts and PCB manufacture :smile:


But in any case, the components turned up, I soldered them on & it worked first time - so I've attached some photos and a couple of grabs from the scope to show what the power supply looks like. I have another filter before the power gets to the MSP, which I've got on the scope traces separately. More by luck than judgement, this filtered power happened to max out at 3.6v!


So: Populated board front & back:




Scope trace of filtered & unfiltered power: 



& The same (except the traces are swapped) after I added a couple of extra thousand microfarads of capacitance to the power supply. This has a different time scale too, but you can see the min & max of the supply voltage at the bottom of the snap.



& Again, just because I only just found out how to get my scope to upload screengrabs to my laptop, here's one of those spikes zoomed in. Presumably, when the power supply load changes as a new set of LEDs are switched on, the regulator reacts with this little short wobbly spike thing that lasts just under a microsecond. Hopefully this won't cause any issues with the serial communications between the shift registers (running off this noisy supply), and the micro (running off comparatively clean power).



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Also, one more pic I forgot, here's everything plugged together showing some text. After reading something about how the text needs to be antialiased to allow for smooth scrolling, I modified the text rendering code to allow the characters to be placed by quarter pixels. This made a huge difference to the readability of text on such a small display, but makes it look a bit weird in photographs.


The idea is to intersperse the timer display with occasional inspirational/subliminal messages :smile:


Well, actually probably just stuff to entertain a bit - although I've not really had any good ideas on this. At the moment it just scrolls Robert Frost's 'Fire and Ice', which is a bit over their heads and perhaps a bit apocalyptic for bedtime anyway. I thought perhaps knock-knock jokes would be pretty fun.





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