Dangerous LED Flashlights Warm The Heart


You may, or may not have read on January 7 that Target is starting off the year on a noble foot by recalling around 55,000, ± a few, six-piece LED flashlight sets that could, or could not, pose a fire hazard. Ranging in length from about 3” to 7.5”, each set costs $10 and packs two small, two medium, and two large size LED-based flashlights. These sets were selling exclusively in Target’s Minneapolis stores.

Apparently Target, the Chinese manufacturer of the dangerous components, the US Consumer Product Safety Commission, all three, or any combination thereof believe that “the flashlights can heat up enough to pose a fire hazard”. If true, good idea; let the recalling begin. Anyone who bought a set with UPC code 490021010049 printed on the back of the package can return it for a full refund. Or keep them and take one or two on your next camping trip to keep warm or start up the old camp fire. Beats rubbing two sticks together.

All seriousness aside, there is something fishy going on design wise. Now correct me if I’m wrong, but are not flashlights one of the simplest things one could design, even using LEDs?

In the dark ages of technology, flashlights consisted of only two or three C or D batteries (rechargeable a luxury), a filament bulb rated at about 9 Vdc, an on/off sliding switch, and some kind of metal or plastic housing with a round, clear cover for the bulb. The batteries lined up in series across the bulb terminals and the switch opened and closed the series circuit. There were never any overheating issues unless one may have reversed a battery or two and even then nothing occurred because the lamp stayed dark and the user almost always corrected the problem immediately. In those days ‘immediately’ was usually the only time one needed a flashlight. Also, any heat generated by these relics was not enough to warm your hands in August.

So how much more complicated can an LED flashlight be? Unless the component in question employs some bold and radical design solution, which is usually a cause for failure, how much heat can one of these modern simpletons generate? Most consumer LED flashlights I’ve seen use one or two AA, or even AAA batteries.

Now I’m not taking into consideration those larger units that come with a bar handle and can sub for a spotlight on a Warner Brothers film shoot. We’re talking enough to get you up the dark stairway and around your house for a while until the power comes back on kind of flashlight.

So what could cause enough heat in an LED flashlight that would, in turn, cause a fire? Faulty rechargeable battery, maybe. If the unit uses a step-up or step-down dc/dc converter that’s pulling too much current, or is poorly designed, sure. Enough heat for an exchange or refund, not enough to cause Smokey the Bear to start recording PSAs again (now that smoking is nearly illegal). Although LEDs run pretty cool, perhaps these units employ some five-and-dime components fabricated from weasel dust? Maybe.

In general, I don’t think the design would be that sophisticated, using even simple converters in a six pack of flashlights from China selling for $10. In fact I wouldn’t be surprised if these units use the old “indicator light” approach: a 330Ω resistor in series with the batteries and the LED(s). Probably the resistor or other resistive element is heating up and warming up the flashlight handle. Other than that, got any clues?

Please or Register to post comments.

Commentaries and Blogs
Guest Blogs
Apr 8, 2016

Confabbing on the Fabless Fad 2

High capital and maintenance costs, and EDA advances along with abstractions to deal with chip complexity, have been leading contributors to the fabless migration....More
Mar 2, 2016

Home or Very Small Office Electronic Circuit Prototypes, Part 4 5

Part 4 focuses on testing for a reflow oven and build of a mixed SMT/through-hole board....More
Jan 4, 2016

Building Home or Very Small Office Electronic Circuit Prototypes, Part 3 11

Part 3 delves into critical equipment for testing today's electronics, and provides updates on circuit-board designs from Part 1....More

Sponsored Introduction Continue on to (or wait seconds) ×