my 1 st mod

This is my 1 st mod. Although it's not a very successful one, i'm still very happy to invite you all to have a look and comment it.
http://hk.f1.pg.photos.yahoo.com/odmqon

Looks pretty successful to me! Nice work. Especially for your first mod /ubbthreads/images/graemlins/grin.gif

Nice!

Good work!!
My first Mods looked pretty much like yours...
And they still work of course /ubbthreads/images/graemlins/grin.gif
It only gets better from here...

Holy cow,

Nice work first mod or otherwise /ubbthreads/images/graemlins/smile.gif

Wilkey

PS, how are things in HK these days. I had a friend go back last year and he said it was quite depressed.

Good first mod. Some details will be good too.

It looks like almost direct drive, just a couple of current limiting resistors. What does it run off? 3C? I'm guessing a couple of really crazy CPFers will be asking why there are gaps between the LEDs, and telling you to cram in more LEDs until there is no more space. /ubbthreads/images/graemlins/grin.gif

Thank you very much for all your replies. My 1 st mod took me nearly 10 hours and finally works after several trials . Actually it is not a very successful one... as i connected the leds in parallel and the 2 resistors in series (it is called direct drive?), the leds are not of uniform brightness. The mod is only nearly as bright as the streamline 4AA led...i think there should be a much better way to connect it and pls kindly tell me if you know.

Hello, Steelwolf,
The mod uses 3D batteries. I prefer D to C while D's mAH doubles that of C's while the price doesn't.

Hi, Ginseng,
Hong Kong's getting better these days but still, finding a good job is a dream for many citizens like me...this is why i have penty of time doing the modding.

It's not direct drive...if you are using resistors.

What are the values of the resistors you are using? With 23 LEDs and 3 D cells, you might be better off just running direct drive (no resistors). Just let the internal resistance of the D cells provide the current limiting. (I'm not sure if you can blow the LEDs if you change from alkaline D cells to NiMH or NiCd D cells though.) I upgraded my old Trek 7 and gave it 14 LEDs. It ran direct drive off 3 C alkaline cells with no problems.

Your LEDs are not uniform in brightness because LEDs, unlike incandescent bulbs are unable to equalise their power usage. While white LEDs have a nominal Vf of 3.6V, it actually varies a little from LED to LED. And a little variation in Vf results in quite a noticeable variation in current. And the current flowing through the LED is the component that determines the LED brightness. So even though you are applying the same voltage across all the LEDs, each LED will be drawing a slightly different current and so will vary in brightness.

There are 2 ways to solve this problem. The first, if you have a large supply of LEDs, is to match them. For this application, you can put them individually across a 4.5V supply and measure the current and so sort them accordingly.

The other method is to use an individual resistor for each LED. This works well only if you use the more precise resistors (1% type). The resistor becomes the main component in each branch to set the current for each LED.

There is a third way, but that involves using a voltage boosting circuit. You wire all the LEDs in series and put in a circuit to boost the voltage until it is sufficient to drive all the LEDs in series, in this case, 23 x 3.6V = 82.8V minimum. The LEDs will distribute the voltage among themselves, but the current running through each will be exactly the same, which results in the same brightness for all the LEDs.

Thank you very much for your advice, Steelwolf. i'm using two 1-ohm resistors in series (with 2.2 ohms measured in total). i did try using no resistors and running direct drive from 3 AA NiMH cells, but the leads of the LEDs made me jump high...they were too hot after just several minutes. i then used 1 ohm and the leads heated up no more but the resistor. Finally i used the present 2.2 ohms. i wonder is it normal to have that heat with no or only-1-ohm resistor? If yes, should i apply heat sinking oil or do something else? i will follow your advice if i can make them as bright as that in my dream!

Great torch for a first mod!
I've had a similar idea myself (the LED matrix!)
I would presume that this torch produces a nice even spread of light!