Here is ONE way to keep a LS cool-

LEDBE
Silviron

Silviron

Flashlight Enthusiast
Joined
Jun 24, 2001
Messages
2,477
Location
New Mexico, USA
If worse comes to worse:

keepemcool.jpg


Here is a little 3 CFM - 5VDC ~.250mA fan that fits perfectly under the "heat sink" on an LS module with absolutely no modification. (it will run on 3V at lower speed.)

I have it running on a green LS right now,, both fan and LED powered by 3 C alkalines, and at 340mA draw from the LED, the PCB/ heat sink is staying at room temp... you can just barely feel any extra warmth coming from the negative lead.

Buck ninety nine from Hosfelt; HERE

I kind of started this as a joke, but it may have useful applications, especially in stationary, "mains" powered applications.

And this entire package is actually smaller than an LS on one of those good round heatsinks that I have been using...

The fan is actually running in the pics above, but the camera flash makes it look as if it were stopped..
 
How much power does the entire package use? Is the LS part running on 4.5V 350mA? What about the fan part? There appears to be a resistor in the circuit. What is the value and how does that fit in with the rest of the circuit?

Thanks.
 
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Steelwolf:
How much power does the entire package use? Is the LS part running on 4.5V 350mA? What about the fan part? There appears to be a resistor in the circuit. What is the value and how does that fit in with the rest of the circuit?.<HR></BLOCKQUOTE>

Gee, I didn't expect this kind of interest..

I'll have to re-measure things in the future using fresh batteries and to slightly re-wire it to be able to measure the current draw at both the LED and for the whole package to really answer your question with accuracy... This has been running for 5 hours now, and the batteries are far from their peak, and I'm not really sure what their condition was in the first place.

But, I'll tell you what the circuit is- I have the LS Module in parallel with the fan, then the resistor is a 3.6 ohm that is in series with the LS - just a normal voltage dropping resistor for the LED, to drop the voltage to around 3.3 V and it has nothing to do with the fan.

It never dawned on me until this minute that it MIGHT be possible to use the fan in series with the led AS a voltage dropping resistor... I don't know what the specs on the fan are in that respect, or even if it would be safe or efficient to use it that way even if it does have resistance in the right range...
 
Interesting, 5V fan that draws 210mA in series with a 1W LS. Then you'd need around 8.5V to drive the whole thing; 7 NiMH cells in series. Not the most convenient setup.
 
Too cool Silveron! Next we'll be water-cooling them like my computer /ubbthreads/images/graemlins/grin.gif .

Larry
 
Golly- Just think--- this thread started just a couple of weeks short of two years ago!!

I never did get around to checking out to see how it would work in series instead of parallel.....

I think I still have that thing around here somewhere....
 
I was just thinking. The blades on that fan are so small and the motor/center is so large and it's so close to the heatsink, that I bet it has a rather large dead spot in the middle. I wonder how much good it really does for cooling.
 
I have seen (many years ago) a type of metal/magnet looking thingy that a techie showed me, that if you run a small current through it, one side (bottom) stays cold and the other side (top) hot. Its supposedly able to keep one side cold by transferring/conducting the heat to the other. I am not sure what its called, but it looked just like a black/grayish piece of magnet, except it wasn't magnetic.

Anyone have any idea what that is? If anyone does, I suppose this would help with the cooling process too...
 
It's called a Peltier cooler, named after the guy who discovered the effect. They're often used by CPU overclockers, but they require very good heatsink/fan cooling on the hot side to dissipate the heat, and if your fan fails, your CPU will cook in a matter of seconds.
 
Luke- I did do a little testing back then, and it did keep the LED cool enough to overdrive it significantly (don't remember any concrete figures though). There probably is a "dead spot" in the center, but since the whole thing is pretty compact, it blows enough heat out to make it work, even without a "real" heatsink.

Stanley- We have discussed Peltier coolers around here several times; (Run a search... the topic seems to come up about every six months.) They are incredibly energy inefficient; more of a liability for run-of-the-mill "mobile" lights, although they could be useful in a limited range of permanent indoor applications or automotive....

But as far as I am concerned a good metal heat sink with a lot of surface area (massive or finned) with good "ambient" airflow is by far the most practical way to do anything but the most exotic type of lights.
 
Hmm.. you learn something new every day... and the word of the day is... Peltier!! Thanks a lot guys... /ubbthreads/images/graemlins/smile.gif Not being a modder myself, at least that's one for the knowledge vault in the back of my brains somewhere...
 
What's odd is I like the idea of handing a guy a 3D Mag size light with louvers behind the head just like shark gills that sounds like a miniature turbine when it's turned on, and puts out a 'bar' of light. /ubbthreads/images/graemlins/grin.gif

(Thing is, directing the heat away from both the Luxeon and the user can be a really difficult problem for fan OR Peltier.)
 
I believe, if you already have an adequate metal heatsink, then adding a Peltier cooler doesn't require a fan, and doesn't put you at risk of a meltdown due to fan failure. In this case, the Peltier just causes more heat to move more quickly into the heatsink. If the heatsink can't dump enough heat into the atmosphere, then it will just warm up until a new equilibrium is reached, but the object being cooled will still be at least as cool as using the bare heatsink all by itself. I think it'd be an interesting experiment.

Looking at this background on the original Lithium-Polymer batteries http://www.batteryuniversity.com/partone-5.htm makes me think that a Peltier would have been perfect with these batteries, using the Li-P battery as a heatsink. Of course, there'd be this annoying warm-up time; maybe use a small Li-Ion cell in parallel for fast startup, and then let the main Li-P cell take over as it reaches operating temperature, recharging the Li-Ion at the same time.
 
[ QUOTE ]
highlandsun said:
I believe, if you already have an adequate metal heatsink, then adding a Peltier cooler doesn't require a fan, and doesn't put you at risk of a meltdown due to fan failure. In this case, the Peltier just causes more heat to move more quickly into the heatsink. If the heatsink can't dump enough heat into the atmosphere, then it will just warm up until a new equilibrium is reached, but the object being cooled will still be at least as cool as using the bare heatsink all by itself. I think it'd be an interesting experiment.


[/ QUOTE ]

Peltier cooler's are not a good solution for cooling LEDs.

It takes energy to move heat around. Peltier cooler's use electricity (very inefficiently) to move heat from one side of the device to the other. One side gets cooler and the other side gets the heat taken from the cool side PLUS the energy used to move the heat. Soooo to cool a 1W Luxeon, might take 5-8 watts from the battery and the hot side of the Peltier cooler would need to be heatsinked to dissipate (5 to 8 watts) + 1 Watt. If the heatsink could not dissipate the 6-9 watts, the equilibrium temp would be much higher than using the same sink to dissipate one watt.Talk about a hand warmer!!
 
It is not a joke - even that small fan can make a big difference in the LS functionality. It can avoid excessively massive heatsinks with 5 W LSs.

Once upon a time, incandescent light were throwing away most of the heat they produce via the reflector.
Today, LS produces light from the front and heat from the back. Again, I am not joking: an LS light with a fan, even small, will outperform any other light without it.

There is the issue of water tightness, and may be the noise issue too. Can you imagine a flashlight with a muffler? Because a fan can be replaced by a minuscule electromagnetic driven air pump... Silviron may want to give a try.

Active heatsinks, togheter with optically enhanced LSs may well be in the flashlights of the future.

Anthony
 
Anyone want to donate a pile of 5w greenies? How about 10 mounted in a spotlight body, with a blower to vent hot air. /ubbthreads/images/graemlins/grin.gif

A light-up hair-drier.
 
You must log in or register to reply here.

Latest posts

Back
Top