I and lots of friends have experienced a problem when carrying our bike lights in backpacks-- their on/off switches are often configured so that they are easily turned on while in the backpack... leaving a dead battery come nightfall when needed.

The solution is this Instructable-- constructing guards around the switches to keep them from getting pressed by ordinary jostling in a bag.

Step 1: Version 1: Wire

Construct a guard out of that universal material, paper clip wire. Usually I use jumbo paperclips, unbent, but recently have found high-tech round paper clips very useful (see the alternate photos). For regular jumbo paperclips, straighten out using regular pliers, vice-grips, or a vice, then bend into shape with needle-nose pliers.

Then attach using that other univeral material, 5-minute epoxy.

Note that you need to bend the wire into a shape that will protect the switch from getting pressed by casual contact with stuff, but so that the switch remains accessible to a finger (possibly gloved in winter). Test out angles of vulnerability to contact.

To work with epoxy as an adhesive+structural material:
1. I find 5-minute clear epoxy works better than 2-ton epoxy, since the 5-minute type is slightly ductile when cured and less brittle.
2. Be sure to roughen the to-be-epoxied surface of the light by scratching it with an awl or file, for best adhesion.
3. Rig up some books or paperweights such that the surface on which the epoxy is going is flat with respect to the ground, so that gravity won't cause it to drip or run before it cures.
4. After mixing with a toothpick on a scrap of cardboard, smear a thin layer on the light.
5. Position the wire ontop of that layer. You might need to rig up some supporting bits of cardboard and/or scotch tape to temporarily hold it in place until cured.
6. Dollop a layer of epoxy on *top* of the wire, creating a nice little bubble with the wire encased within.

Here are images of some guards I built, one for a Cateye basic white LED headlamp, one for a Zefal red blinky LED rear light, and one for a Cateye TL-LD-1000 red blinky LED rear light.

Step 2: Version 2: Plastic

For some devices, a piece of plastic makes a better protector.

For example, this Cateye HL-EL500 high-intensity LED headlamp has a funny sliding switch (which, while a lot less susceptible to accidental manipulation in a backpack, of course, occasionally does get tripped... it happened to me!).

Here, in the first photo, I used a piece of 1mm thick polyethelene from some old thing I was throwing out. I cut it into shape, and glued it on using curing cement (Barco or contact cement).
<p>Thanks for the idea</p>
Great idea, I'm always turning my lights on from the light rubbing up against things in my bag. I've just made the modification but using an &quot;alligator clip&quot;, <br/><br/><a rel="nofollow" href="http://dir.coolclips.com/Business/Office_Stationery/A_to_F/Clips/Alligator_or_Bulldog_Clips/Paper_clip,_stationary_vc006468.html">http://dir.coolclips.com/Business/Office_Stationery/A_to_F/Clips/Alligator_or_Bulldog_Clips/Paper_clip,_stationary_vc006468.html</a><br/><br/>This has a couple of advantages: The black base is big enough to fix easily against the light and by removing one of the arms and spreading/bending the other you get a pivoting guard that makes it easier to get at the switch.<br/>
FYI, I had to rebuild this one, since nothing sticks to polyethelene (certainly not epoxy, nor ordinary household cement). The final version is similar to the version for the white CatEye headlamp, except that I used a fancy round paperclip, which was pre-shaped to form a loop protecting the slide switch on this lamp.
If you must attach polyethylene (PE), punch multiple holes in the PE and press PE into the glue, forcing glue through holes and spreading on outer surface. This gives a mechanical attachment to the PE sheet
I had that same problem for a long time and had tried different methods of keeping the button from being pressed in my bag. How long to you expect the epoxy to hold up with constant beating in a bag? I'll have to try this is my current method fails. I did an even simplier fix. I took a 20oz bottle of soda and cut cut out a strip (long enough to cover the button and then wrap around the sides) near the bottom and used many pieces of electrical tape to fasten the plastic over the top of the botton. The nice thing about using plastic near the bottom of the bottle is that it is rounded and provides a bubble over the button. It doesn't get pressed hard enough by anything in my bag to start it, but I just have to press extra hard to light it with my finger. I've been doing that for months, but if for some reason that fails, I'll have to give this a try...
epoxy should last forever; I think you are asking on the small cateye model (shown in the main pic with the loop sticking out in space unprotected), will the wire 'lever' the epoxy loose? answer, unlikely, though epoxy is brittle when cured and if you poke at it hard or pry at it, you can break its adhesion. In this case, the solution would be to shape the wire to prevent any undo stress on the wire, specifically, have the middle of the loop drop down to briefly touch the surface of the light, thus supporting it at the end of the lever arm.
There is a relatively new epoxy called FastCap 2p-10. Bulletproof.
Experience and experiments prove to me that different epoxies have different impact resistance. Counter-intuitively, the quick-set epoxies I buy tend to cure as a slightly ductile slightly rubbery texture (i.e. you can press your fingernail into it and leave a tiny dent). Whereas the 2-ton epoxy cures hard. The difference is that I've had 2-ton epoxied joints fracture or crack. The quick-set styles call themselves "highly impact resistant", which I guess is the key. While static controlled bond strength is important, ability to withstand shock, vibration, and impacts is important too. In fact, in bicycle frames, this difference is the advantage of steel and titanium over aluminum (and even carbon fiber, with regard to impacts) even though the latter are lighterweight per unit strength.
JB weld might be worth a try as well. It is unbelievable stuff. Personally I never take my lights off my bike so this isn't a problem. However, I think if I wanted to do this, I'd cut a piece of something like 3/4" PVC pipe, just maybe 1/4" long, and epoxy that over the switch so in the end the switch was inside a hole that you reached into to push the switch.
iKill, Many bike lights have become bright enough to easily bike with at night on any street. The Cateye HL-EL500 is a great example. It is easily the brightest of the non-competition lights. It's much brighter than my Mag-Lite. It does seem pricey compared to traditional lights ($45) but on the other hand it takes a long time to use the batteries up. Traditional , halogen type lights only last 2 hours while the Cateye featured in the article lasts somewhere around 40 hours on and is much brighter. There are other models that are also very bright, LED driven and are around $30. But I do agree with Vendigroth that the first job is to make yourself seen. The second job is that you can see with them.
i know ill get a few people calling me dumb and such but whats a bike light?
You're dumb. Sorry, couldn't resist. A bike light is exactly that: a light for a bike. the reason that you should use bike lights is no to be able to see where you're going, but to advertise your presence. The lights are there to show off the fact that you're there on a bike, in the dark, at night, rather than for you to see by. Other safety features on bikes include the reflectors set in the wheels themselves, and just above the front and back wheels. How's that for a textbook answer?
I Have had this problem too and I have fixed the switch with a stip of plastic as electricians use to secure wires. It works very well
simple but efficent I love it *****

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