Need help fixing Multi-LED flashlight

[S_Bodi]

Hiya there, hoping someone can help me

My 128-LED flashlight stopped working recently, and it must have been whacked around a little as I determined the problem to be that the wire carrying the negative charge from the batteries has disconnected from the battery side, while the wire carrying the positive charge has disconnected from the matrix side.

I've attached a pic - the yellow wire is the negative wire which I'll solder back to the battery end. My question is: does it matter exactly where the positive cable is soldered to on the PCB shown - I just can't figure out where it has disconnected from. Cheers for any help

 

[csshih]

hm, looking at the photo, it appears that all the LEDs are hooked up in parallel..

the PCB looks like it's in sets of 2, right? side by side, it should be either +, then -, or the opposite.. not sure from those pics.
It does matter which side you hook the wire up with, LEDs only function in one direction, but if you have the correct side hooked up,the entire thing should light up. (not sure if my wording will confuse or not)

have you ever considered going into Cree "Power LED" flashlights? They come in much smaller packages.. while still being pretty darn bright.

 

[S_Bodi]

Thanks for the reply.

Indeed the contacts are in pairs.

From what you say - so long as I connect the positive wire to a positive contact then the whole thing should light up seeing that it's in parallel - is that what you mean?

If I mess it up would I kill the whole matrix?

.. And yes I have considered a Cree power-LED but I'll see if I manage to fix this one first

Cheers

 

[Moonshadow]

Looks like your other wire needs to go to the larger of the two semi-circular pads at the centre - on the right in your picture.

This will then connect up all of the alternate 'C' shaped rings via the zig-zag conductor running radially towards the right hand edge.

Reminds me of one of those mazes where you have to start at one edge and work your way to the middle.

 

[csshih]

you probably wont kill it if you hook it up wrongly.. just short circuit the batteries.

if it starts smoking.. turn it off!!

 

[adder]

well on the other side of the pcb there should be a resistor u should connect the + side to it,since i have a similar 9 LED light.if the positive wire from the battery does't go via the resistor then leds will mostly die.

 

[JBorneu]

Just connect the positive wire to a positive contact point on the PCP. It's easy to see which ones are positive and which are negative in the middle. Make sure the (uninsulated parts of the) positive and negative wire can't touch any other contact points and you'll be fine.

The light clearly does not use a resistor. Don't worry about that. It's not a design that will last thousands of hours, but there are enough LED's in there to handle quite a bit of current for quite some time without killing them. Yes, there are lots of better lights, but this one is so simple that it's a very good starting point to learn about LED lights and to practice your soldering skills and electronics knowledge. And, whatever happens, as long as at least one of the LED's still works and you have cells delivering the correct voltage, you'll be able to get some light out of this thing all by yourself.