I would like to add LED lights to my childrens ski helmets. Basic idea is to have two small "antennas" (or Mickey Mouse ears or whatever shape they choose), two LEDs on each. Red LEDs directed backwards, white LEDs directed forward. Purpose of LEDs would not be to light up the slope ahead, just to make children happy, so they can see each other during night skiing and to get attention from other skiers on slope as a safety measure. Quick sketches:
Aside from mechanical construction I am more considering the eletrical part. Vision in my mind:
CR2032 battery/batteries(?) for pair of "antennas" (they are small)
Microcontroller would be nice to handle all that operation modes easily but one 3V battery would not be enough.
One 3V battery with 555 chip and voltage booster or joule thief circuit could work for flashing mode for white LEDs as well.
What about 3 AAA recharchables (nice capacity, relatively small)?
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No problem to change specs, I just do not want my children to wear heavy battery packs on their helmets. For safety, no wires from helmet leading under the jacket...
Which way would you go? Any comment appreciated. Thanks
Have you identified LEDs that will actually be visible on the slope? In my experience children tend to be taught in well-lit conditions and milliwatt LEDs would surely not be bright enough to be noticed.
A bicycle front light with LEDs desoldered and moved to "antennas" is one of possibilities - cheap, waterproof housing, included battery holder, limited functions. I am just going through the options list.
What about ATtiny45/85?
two PWM outputs allowing to have separated front and rear LED group
possibility to program any fade in/out effect or flashing sequence
8 MHz running from 2.7 V
3 x 1.2 V AAA rechargables can provide 3.6 V
3 analog inputs; for mode toggle button
LED power - I have seen couple of kids with a common bicycle red rear flasher attached to helmets, no issue with visibility. My kids already ski after sunset without "light helmets", so this would be a funny accessory, surprise. Anyway, this should be a fun project, no a lightning one.
If your using 4 LED's running approx 15mA each then you'll be looking at about 16 to 18 hours from 3 AAA batteries when fully on. I'd deffo look into using an ATTiny45/85 for this project as they are much smaller than the arduino atmega chip (same size as the 555 chip) and they have there own in built crystal (less circuit to build). I've just used the ATTiny85 for a similar LED project utilising the PWM output and creating various flash patterns, easy to program using your Arduino as the ISP.
Maybe thinking of using a rechargable Li-ion battery like a 14500. The're the same size as an AA battery with upto 1200mAh ratings (don't go for higher ratings as sold on ebay, they don't exist) but crucially they already output nominal 3.7v so one battery would be enough.
I forgot to post the image. Kids were happy. It is modified bicycle rear LED flasher. Two red LEDs at back, two organge LEDs at front. Worked in -10 deg. C.
The safety of crash helmets is dependent on the structure not being altered - adding anything on the top that could
catch against a hard object sounds very dodgy to me, instantly splitting the protective shell... Also I can't see how
you can attach without weakening it - glues are out (polycarbonate is utterly weakened by many solvents), and
drilling holes is obviously a no-no.
Tying something soft on seems the only safe method.
If it wasn't for the glue/solvent issue LED strips would be attractive - perhaps these could be tied on rather than
stuck on?
a easy solution to lighted ski helmet is to attach a headlamp to the back of the helmet with zip ties to whatever is available. No glues needed. Then you got AAA batteries so it will last a long time. They are cheap at most hardware stores.
