Is this a bad mod? CREE Q5

[NathanH1991]

Hey all thanks for checking out my post I am confused.

I have a Cree Q5 led flashlight that I bought off ebay. I didn't like that the flashlight had 3 modes (HI/LOW/FLASHING). One day I took it apart to see what I can do about it. I found this circuit board (I found out today it is a led driver, probably 3W?) and two simple wires running up to the emitter. I didn't know what anything was except a couple smt resistors. (Scary part) I took the soldering iron and moved the wires so they totally bypassed that whole circuit board and put a 22ohm 1/4 watt resistor on +. It has a power supply of 4.5v (3xAAA). I took it in to a shop that works on circuit boards in television repair to ask some questions. They totally shot me down telling me after a while it will slowly burn out the emitter getting dimmer and dimmer. Now that I think of it, I don't remember what I was thinking of putting a resistor of that ohms in there. Please tell me what you think, how bad did I mess up. What is a led driver for? Can you run a cree or luxeon led directly off a few aaa's?

I would really appreciate it. Let me know if I can help you guys out.

 

[Fichtenelch]

The driver prevents that the led gets too much voltage + current, so it is basically useful. it can also boost voltage if you input voltage is lower than the forward voltage of your led.
So, bypassing is not the way if you want to really improve it. maybe you could swap the driver...

 

[Greg G]

I bet it's not very bright with that resistor in it.

Most likely, you can run that light in direct drive. That 4.5 volts will sag a lot under a load.

It all depends on what the front voltage of the emitter is.

How is the heatsinking on the light?

 

[NathanH1991]

I uploaded some pics of my flashlight:

Before: http://farm5.static.flickr.com/4047/4471855699_b7f334f613.jpg

After: http://farm3.static.flickr.com/2679/4471856249_740487e7fd.jpg

Here is a complete breakdown of the light: http://farm5.static.flickr.com/4070/4472633698_a025d891eb.jpg

And here is the "cree" emitter itself:http://farm3.static.flickr.com/2754/4471855173_12eab12076.jpg

Here is what the flashlight looks like brand new:http://farm3.static.flickr.com/2787/4471847247_ed1d8fc17e_o.jpg

Demo of the light output (with the manufactured driver in it):http://farm3.static.flickr.com/2747/4472626280_55d7b3e75f_o.jpg
http://farm5.static.flickr.com/4017/4472626228_d7aef330e8_o.jpg

I don't know if this has a heatsink or not. What does it look like to you, Greg? It has never gotten hot at all though. Please tell me a little more about the driver and what is the base name of this emitter of light? The BRAND is CREE or LUXEON but is there a name for the actual light? (EX. Incadescent light bulb) I'm trying to find them in bulk on ebay for cheap. I've already gotten a ton of the 5mm red and 5mm white LED lights for a bunch of DIY projects (brake lights right now) I'm really interested in these emitters that I've seen in flashlights such as mine, they are super bright! Thanks

 

[ma_sha1]

The pictures don't work for me as it's asking for log-in info.

Anyway, as the other reply pointed out,
3AAA will not burn out Cree Q5, assume it's heat sinked well.

If if you make sure there's enough heat sink (Or beef it up),
you can run 3AAA DD without the resistor for sure.

You can drive Q5 up to 1.5Amp with good heat sinking,
the 3AAA won't be near 1.5 Amp, I am not sure it'll even go above 1 amp.

 

[CampingLED]

Is your light brighter with the 22 ohm resistor than before the mod? According to my calculations you may only drive the Q5 less than 100mA and it will stay cool with minor heat sinking.

Briefly short out the 22 ohm resistor when it is on and check the brightness and heat. If it get hot fast your heat sinking may not be good. The brightness may wow you. Warm is good, hot is bad, short burst is ok.

 

[yellow]

I agree to very little current with 22 ohms ...
imho it is so little, that the driver still works.
(somehow I calculate lousy 13 mA ... :thinking


everything else is a bit complex:

resistor = "direct drive" ... that means no driver.
the resistor is to fight against too high current.
Problem is - with any means of making light, but with led very obvious - that a slight reduction in voltage leads to a high reduction in current and that means decrease of brightness.
Usually "high" starting brightness, immediately extremely reducing within the 1st few mins, then constant reduction in output, but this reduction gets lesser and lesser. Longer "runtime"
... that is usual for direct drive

driver = regulated light
makes that higher voltage (step down (= buck) converter) or lower voltage (step up (= boost) converter) is "changed" to the voltage the led needs to run.
In general the light stays the same for the whole runtime - which is shorter than with direct drive setup

... 3*AAA and direct drive is mostly used in low, low, low quality lights now, NO comparison to something "real"
(which is also a small light in 2*AA, 2*CR123, 1*18650 size)
the emitter is ok, there are newer ones, but the difference is not this extreme.
What makes a difference is the low current.


heat"sink"
dont let that fool You! What is meant here is, that the led is mounted on an aluminium sheet and this one pressed into housing, so that it makes good contact to the metal outside of the light - which thus forms the heat"sink"
As more power the led gets, as thicker the mounting/thermal plate, as good the contact to housing is, ..., the better for thermal path. To get the heat away from the led and not "cook" it


PS: "Q5" is a Cree XR-E led, "Q5" being the brightness bin (2nd brightest one available)

 

[NathanH1991]

Sorry everyone I'm not good at embedding pictures in these blogs. Tell me if this works:

Before: http://farm5.static.flickr.com/4047/4471855699_b7f334f613.jpg

After: http://farm3.static.flickr.com/2679/4471856249_740487e7fd.jpg

Here is a complete breakdown of the light: http://farm5.static.flickr.com/4070/4472633698_a025d891eb.jpg

And here is the "cree" emitter itself:http://farm3.static.flickr.com/2754/4471855173_12eab12076.jpg

Here is what the flashlight looks like brand new:http://farm3.static.flickr.com/2787/4471847247_ed1d8fc17e_o.jpg

Demo of the light output (with the manufactured driver in it):http://farm3.static.flickr.com/2747/4472626280_55d7b3e75f_o.jpg
http://farm5.static.flickr.com/4017/4472626228_d7aef330e8_o.jpg



Anyway, so I've been reading all your guys' answers and I decided to take the resistor out. Now it's getting 4.5v directly. So from what I understand is, when my batteries start going dead, my light will also get dimmer and dimmer? But with the idea of a "driver" is that the light will never get dimmer it will just one day not work becasue the batteries are completely dead? If you looked at the pictures, what do you think of the flashlight? Is that an "average" low brightness flashlight compared to others similar? Or is my flashlight pretty high quality? I wouldn't mind paying $50 (ebay) for a flashlight but I can't seem to find one that I like better? If you scroll through ebay you will notice my flashlight claims to be the most lumens up until around $120? That is one thing annyoing about ebay, even if the price goes up doesn't mean you will get better quality. So it's really a guessing game if you don't know what you want.

Tell me what you think, what flashlights do you recommend? I'd like one that is about the same size, but more brightness. I need one to carry around but need it to FIT in my pocket somewhat. I think mine is getting dimmer as the guy said at the Television repair shop. Changing the batteries would restore it right? Thanks