Instructables
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Here is how to add safety LEDs to your bike helmet using conductive paint. I was always losing those lights you clip on to your bike, and they're not cheap or good quality.

Materials:
conductive paint
conductive epoxy
5-minute epoxy (hot glue for grownups) or hot glue and gun
wooden sticks or plastic coffee stirrers for mixing and applying epoxies
9-volt battery
magnetic reed switch
magnet(ring-shaped for tethering)
LEDs(white and red if law in your state mandates, or your choice)
clear spray enamel(for coating circuit to protect from rain-shorts)
wire
solder
moist paper towel
bike helmet

Tools:
pencil
soldering iron
wire cutters/strippers
needlenose pliers
masking tape
paint brush
fine grit sandpaper or sanding block
solderless breadboard for prototyping (optional)

Flickr set available.

Project home page on Sternlab.
 
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Step 1: Prep your materials

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Prototype your circuit:
Test your LEDs to make sure they work, and work out what your circuit will look like. Since I'm using a 9v battery, I'm using three white LEDs for the front in series wired with four yellow in-series LEDs, and the two sets are wired in parallel (see circuit diagram). See what works best for you, and try it out on the breadboard before you commit to the design on your helmet.

Prep the helmet:
Lightly sand the surface to allow the paint to bond more easily. I also took this opportunity to sand off brand logos from my helmet. Follow the sanding with a thorough wipedown with a damp paper towel or cloth. I'd avoid using any cleaner here, since who knows what chemicals are in it and what they might do to your circuit. Water does just fine. Be sure the helmet is completely dry before doing any painting.

Step 3: Paint the conductive traces

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Pretty self explanatory:
Paint inside the stencil you've just made. Make sure to stir the paint thoroughly and often, as the particles have a tendency to settle. I applied two coats. Refer to manufacturer's instructions for optimal paint thickness.

Touch ups:
Let it dry a little, but not all the way, and peel the tape off carefully. I took the tape off before the paint was dry to make sure none had bled under the paint, shorting the circuit. I touched up any bleeds with my damp paper towel.

Let the paint dry for at least two hours before attaching components. My paint's instructions said that it reaches full dryness (and therefore highest conductivity) after 24 hours.

Step 4: Prepare components

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Solder leads from your battery. I already had a wired-up magnetic reed switch, but you really could use whatever switch you want. I chose not to use a toggle, as it would be difficult to waterproof. I solderd one regular wire and the wired switch to my battery since my switch was already wired, but you could just as easily work it into your conductive trace circuit.

Lay out your LEDs and trim their leads (but make sure you keep track of the cathode and anode orientation). Mix some 5-minute epoxy and affix the battery and switch to the helmet. Allow to dry. position wire ends on paint traces and lay out ALL LEDs before mixing the conductive epoxy (so as not to waste time once its mixed)

Step 5: Affix LEDs and wires with conductive epoxy

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Mix the conductive epoxy and attach LEDs and wires to the paint traces. Since the helmet is not a flat surface and I wanted to attach everything at once, I used a large piece of tape to gently provide support to the LEDs while the epoxy dried. Once it's dry (or mostly dry), test your circuit to make sure the LEDs light up. If they don't, you may just need to let it dry more. Let everything dry for 24 hours, then use some more 5-minute epoxy to reinforce the conductive epoxy and seal around the bottoms of the LEDs (for waterproofing and extra strength).

Step 6: Seal and wear with pride!

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Take your helmet outside or to a well-ventilated area, and spray the outside with clear spray enamel. Tape off areas you don't want to cover like the strap and bulbs of the LEDs. This will protect your paint traces from wear and water.

I affixed my magnet to the strap with a cord, so it's always with the helmet. I simply reach up and touch it to the switch to turn it on!

Design note: I avoided placing traces or components on the top of the helmet, as that is the surface on which it rests when the helmet's not on my head, and I didn't want to risk scratching up my circuit or damaging the components.

Flickr set available.

Project home page on Sternlab.
leona9125 months ago

Wow, just find a nice article here, although I got professional LED headlamp already, still want to try this! But I think I will use LED strips because it's more beautiful like this http://goo.gl/zWLR8Z

Love this article, let me know more!

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This is awsome, but I don't wear a helmet lol
bekathwia (author)  TheCheese99217 years ago
Then perhaps you could affix the LEDs straight to your brain, which will soon be splattered across the road. You should always wear a helmet!!
Hahaha funny! Side note, Conductive paint is kinda expensive and in this economy? Might be a little overboard for just a helmet. Why not just use aluminum tape? It would be reflective too which would help drivers see you.
My god that was funny. :)
My education was three orders of magnitude more expensive than a bike helmet. And besides who are you without your brain?
I always wear my helmet,at first I didn't really think of the helmet much but after a fall top of head first I leared its allways good to wear a helmet.
This thing is very cool, but you should seriously use some resistors to limit the current through them.
iv seen ur comments on a ton of instructables, r u an administrator or something?
Even I post everywhere I feel it's needed or necessary. I'm no Admin, but I like leaving comments on how to help someone out. Or just complimenting on a good design.
No. There are many others here on instructables that posts more comments than me.
Shredman5 years ago
I tried this several months ago. It is still workig really well. http://forums.mtbr.com/showthread.php?t=464791&highlight=blinking+pet+collar
Asbestos6 years ago
Just as a note, many state laws (MA, for example), require that the bike have a light at car head-lamp height, which the helmet light wouldn't satisfy. This actually makes sense in terms of safty -- when I bike up behind another bike at night and all they have is a helmet light, I often don't see them until I'm barely ten feet away: you just don't expect to find tail lights at that height, and at that height there are usually a lot of other distracting lights around, from signs and traffic lights and whatever. But as an ADDITION to your regular tail light, their just great! Thanks for the instructable.
I didn't know that about the car-headlight height! How interesting. Personally, I have noticed that cars noticed me better when I wore a headlamp, compared to a handlebar-mounted light -- I ride on roads with many parked cars, which tend to block the handlebar light... but with a headlamp I can peer over parked cars and look in the direction of the stopped cross-traffic car (residential) and they tend to see me much more readily! perhaps I will use a combination :) thanks for that heads-up though! getting a ticket for minutiae like that... would suck.
dlfynrdr6 years ago
What I like about this idea is since you've done away with wires, you've eliminated the need to drill holes in the helmet (a common mistake I've noticed) Since any holes weakens an already weak safety item.
bekathwia (author)  dlfynrdr6 years ago
Yeah, that's what I was after! I knew I couldn't put any holes in the thing, for my own safety, so the paint works great.
whoa! That is definitely the helmet to sport a skate park. I love how the conductive paint appears like a graphic design. +
Next time just use pressure sensitive flat wire for your circuit, maybe on the inside of the helmet instead of the outside. Conductive paint is not designed to carry electricity, it's designed to dissipate static charge (high volts, but very low amps).
bekathwia (author)  TogetherinParis6 years ago
That's funny, it seems to work fine for me!
stasterisk6 years ago
Fabulous instructable! I really like the big honking LEDs, and your method of making traces!!
mrtfor20087 years ago
You might wanna be careful with the spray paint, petroleum distillates tend to weaken the foam used in helmets (and that foam is weak enough as it is). You might want to try to protect the exposed foam to overspray.
bekathwia (author)  mrtfor20087 years ago
Thanks! Yeah, I taped over the foam when I sprayed it, but not because I knew the paint would weaken the foam... thanks for the info!
Great instructable! Wow that paint is really expansive. 5 gallons for $2000 bucks.
jpb7 years ago
Nice work! Have you had a chance to do some rain-testing?
carlos66ba7 years ago
Very very nice. I like the use of the conductive paint so that you don't have pesky cables around. The only thing I'd like different is the placement of the battery (it looks odd sticking out that way. Anybody with good ideas on this?
bekathwia (author)  carlos66ba7 years ago
You're right, the battery sticks out funny, but at least it's out of the way. Perhaps coincells would be better, although they wouldn't last as long. Thanks for the comment!
lemonie7 years ago
Rear LEDs should be red(?)
Otherwise this is pretty cool. You're going to wear you helmet, and you're not going to leave in on the bike = always have your lights.

L

(learn to smile)
bekathwia (author)  lemonie7 years ago
My model doesn't know how to smile for pictures. LEDs on the internet are obviously serious business. =]

And to be honest, I just happened to be out of red LEDs when I made this.
nagutron7 years ago
Cool idea! I love apparent the design is. Function made beautiful. An artist could get pretty intricate with the conductive paint.