El Cheapo Flashlight Doubles as Paper Clip Holder
Brit John Goldsmith sent in this example of an el cheapo shake-to-light flashlight he purchased at a filling station - it was a discounted offer if you bought enough petrol. Well, he got what he paid for, though given the price of petrol in the UK, the station probably could have given away a Surefire flashlight.
“As the closeup photo shows, the power comes from a magnet and coil, being stored in a 0.22 Farad (not microfarad!) capacitor on the PCB. The on/off switch has a little magnet on the slider and a reed switch on the PCB. This maintains the integrity of the watertight housing. The operating magnet is actually some small powerful magnets embedded in a larger lump, presumably steel. A nuisance as it drags all the recent UK coinage out of your pocket. I’m sure the unit would be more efficient with metal springs as end stops - the rubber used seems to absorb all the energy. I recently bought a wind-up 3 LED unit which is much brighter and much longer running (and less embarrassing to operate).”
Having looked closely, John also discovered a problem with the magnet. Like most high strength magnets, it is plated for corrosion protection, but the plating is peeling off. So far it is not impeding operation.
Note this post originally appeared on Made by Monkey’s British cousin (twice removed) Electronics Weekly.
David commented:
I teach map and compass to the boy scouts, and all of a sudden we started finding compasses with the poles reversed. In other words they were off exactly 180 degrees. Sure enough,the compass was in the same pocket as one of these "shaker" lights.
There was also a recall on a cheap survival kit in a water bottle that contained various gadgets including a "shake" light that disabled the compass.
Richard in NJ commented:
I have seen these "shake and shine" LED flashlights at local flea markets here in NJ for $2.00 Their really more of a novelty item not worth the time to re-engineer to work better. I still like my old reliable 2x D-Cell Eveready incandescent model. Just more plastic and metal for the landfill in a few months time.
John commented:
I picked one up in a dollar store it came in a great looking box but it was not a real one. It had a slug of metak in place of a magnet and just a small amount of wire. The switch and led were there, I can only guess that the importer was ripped off.
Sparky commented:
Oh- and keep it far away from your credit cards or it might wipe out the info on them!
Mark Weiss commented:
Didn't bring any of my work magnetometers to the home flashlite (or vice versa), but with a probably huge magnetic field (Guessing 800 Gauss -- a PURE GUESS), I wouldn't feel safe taking this thing anywhere. In car? Perhaps I'd mess up car speakers. Perhaps I'd mess up car compass. Perhaps I'd mess up audiocasettes (yes my car is all high tech Audi A4 2006, but has both CD and audiocasette player which sounds very nice actually). Has anybody measured the magnetic flux emanating from this flashlight gizmo?. I just threw mine in the dumpster (was a gift is why I had it) so I didn't have to worry about car speakers, compass, audicassettes, home videotapes or my credit cards in my wallet which I keep in my briefcase.
Brad commented:
I think you have missed the mark with this one.
Did an engineer write this article?
Who Knew commented:
As you say, replacing the rubber bumpers with metal springs might improve the rebounding of the magnet. Perhaps just using better rubber would help? The bumpers shown in the photo also look too big, as if they're taking up some of the overall travel of the magnet. At any rate, I've found the better shake flashlights use opposed polarity magnets at each end. They work as well, perhaps better than springs, and don't wear out.
Ajax 4Hire commented:
I bought 2 dozen of these last year for Christmas presents ($0.80 each). They still work and yes you must have a permanent magnet back-and-forth in a coil to generate power. I was skeptical about their operation but they appear to work and work well.
This is an example of new and better technology (White LEDs) being used to replace old flashlight lamps. The much lower power required by the LEDs allow for something like this to work.
Joel Hacker commented:
Not to mention, please check for a Schottky Diode versus a regular diode. Knock-offs normally use the latter leading to higher losses in the "generator"
Dan commented:
I have one of this. For the 1 Dollar I paid, I though it was a good deal. I guess that if you want to pay 300 Dollars, you can get aa SST50 with 99% more lumen output and the magnetic problem solved.
