Will a white Nichia LED handle 2-CR2 cells?

I just picked up one of the "New" Garrity LED Aluminum spotbeam lights from Walmart (very strong nice bright light). It has a single white Nichia LED. Anyway, I'm thinking of trying 2-CR2 lithium cells in the light instead of the 3 AAA's the light is supposed to run on. Will this likely be OK or will it likely burn out the white LED??

Also, could I directly substitute a green Nichia LED in this light without further modification? The LED's are polarized, is that correct? How do you ID the positive lead and will it burn out the bulb if you get the leads reversed?

Many thanks.

NO... Please Dont Do it.... Unless you use a Current Limiting Resistor... Or else.. use 1 Cr2 with a simple step up circuit (perhaps a Capacitor Switched circuit could give you high eff. @ lower currents of 30 - 60 mA... close to 95%) ....

Normally the Longer LEG is +ve & Shorter one is -ve, Yes (you can substitute white with green without modificaiton ... Green LED's should not be connected in reverse... i dont know why.. but it will burn out (or short the battery) (strange but true) !...

ViReN

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ViReN said:

Normally the Longer LEG is +ve & Shorter one is -ve,

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Yup, and there should also be a flat on the rim next to the minus side.

Doug Owen

Alright, thanks gents. Any suggestions for a good place to buy a few green Nichia LED's, or other good green LED of high quality? It looks like the LED in my Garrity light is 3 mm.

I think.. you should get the LED's in USA from http://order.nichia.thomasregister.com/ .... This link i found from Nicha.Com web site....

A couple of months back .. i had ordered about 500 Nicha's from this shop only...

ViReN

You can also look for Cheap products... but of good quality from Chi-Wing LED Shop @ EBAY....

http://stores.ebay.com/Chi-Wing-LED-product-shop

Nichia's are the BOSS of 5 MM White LED's (30 mA Category)... but they have slightly unconventional shape....

The ChiWing LED's are good enough... 2 ChiWing LED = 1 Nichia ... but color rendering properties of Nichia's match NONE of the other LED's that i have seen so far (we are talking about 5 mm Only) ....

ViReN

ViReN:

Thanks for the excellent info. When I was using a mm ruler to measure the LED, I had some trouble deciding where to measure the LED diameter. Since the LED is domed, is the measurement taken near the tip or at the base? Near the tip it appears to be close to 3mm, but the base of the LED appears wider than 3mm. So, I'm not absolutely sure what size the LED is. Any comment?

Also, how much can one of these white LEDs be overdriven? Do they have to be driven at 20 or 30 mA, or would a higher current provide more output? Any color effects if this is done?

Many thanks.

Here's a pic with measurements on a generic LED to give you an idea on how they measure the dimensions on these things.

http://www.elfa.se/images/highres/h7955.jpg

Thanks, Robban, that was perfect.

Hello Sotto...

Robban's image is self explanatory...

LED's can be over driven till a point that heat generated is dessipated properly... and the Phosper dosent degrade.. atleast till 2000 hours...

In simple terms... you can drive LED's at 40 - 42 mA @ 3.7 or 3.8 Volts ... Please note that these are ABS MAX Ratings...

The More you overdrive, lesser will be LED Life....

If the phospor coting on the LED is thin, very little overdriving will result in more blue tinge in the light... this is primarily due to the construction of LED ...White Phosper... over a blue emmitter...

Even if you measure by a mm Scale, you should get 3 & 5 mm Difference. 3 mm appears like -> o <- from top ..... where as 5 mm will appear like (slightly bigger than .... -> O <- .....

-> o <- 3 mm
-> O <- 5 mm (it should be slightly bigger than this)

Just check it with this. you should get a fair idea...

Thanks & Regards,
ViReN

Thanks ViReN:

Based on your size indicators, it would be a 5 mm then, but it measures more like a 3mm. Guess I need to examine this a bit more carefully. Someday I'll just be able to eyeball it, but I'm just learning about this stuff. /ubbthreads/images/graemlins/thinking.gif

sotto,

Here is the image that might help you out...



Hope this might help you...

ViReN

ViReN:

Excellent, thanks for including the thumb in the shot for size reference. Would you by chance know the size of the LED's say in an Inova X5T? Are they 5 mm?

Oh .. they are (look at the specifications..)

Also Look Here

Thanks & Regards,
Viren

Hello again,

Referring to the original question

"Will the Nichia take two CR (3v) cells in series"

The answer actually is, a little surprising...

"YES", it will work, but the current is something
like 95ma which is way too high. The light will work,
but should only be used intermittently for this purpose
and i dont think it's a very well rounded light for
regular use -- just as a key light where you only
need to see your keys for a few seconds.

Take care,
Al

Wow Mr Al /ubbthreads/images/graemlins/smile.gif

I never thought it could actually work... especially when we are talking of 6 Volts & a Hi-Power CR2 Cell ....

95 mA... and it didnt blow up ???? Kewl....

Thanks & Regards,
ViReN

Hi Viren,

Gee, maybe we're not talking about the same cells?

I meant the CR2016 cell. Is that what you meant?

Sorry if i was wrong about the cell type...maybe
you could post a pic of the cell?

Take care,
Al

PS almost forgot to mention...i've been a little busy
working with my computer system as i was attacked by
several adware and spyware and stuff like that the
other day. Been cleaning it up ever since!

Hello Mr Al,

Sorry to know about the adware... You can install a very good software.... for removal... Lavasoft Web Site http://www.lavasoftusa.com

Also Upgrade to Windows XP SP 2 ... Its just superb... Wont let any Malacious programs in to your machine....

According to my understanding.....sotto is thinking of using 2 x CR2 (more than 1000mAh) & Not CR2016 (110 mAh) or similar button / coin cells .. i am not sure though only sotto can clarify.

Thanks & Regards,
ViReN

CR2 is another "standard-sized" lithium camera cell. It is slightly shorter, but otherwise similar to the CR123 which we are all familiar with. The slight decrease in height does result in a slight reduction in volume and, hence, power capacity. But in all else, it should perform to a similar standard as the CR123 (similar internal resistance, discharge curve, etc.).

So if a white Nichia will not handle 2 CR123 cells, it will not handle 2 CR2 cells. And my experiment way back when I started playing with LEDs suggest that it won't. Not without a resistor in between, which is what the Inova X5 does. So go right ahead and use those CR2 cells, just use a resistor.

Hello again,

Yeah ok, that's not the cell i was talking about,
sorry about that

Those cells will blow the #$(*&% out of the poor little
Nichia :-( without a resistor.

Take care,
Al