help! 3mm LED trouble

[Pandawhat]

Recently I have been spending a lot of time attempting to fix and mod my G15 keyboard, at this present time I have repaired the keyboard membrane using 99% ISOPROPANOL, and a silver conductive pen. Now I am attempting to change the built in LED colors. I have removed 4 and changed 4 3mm LED lights. I somehow managed to destroy one connection, and I'm wondering what i did to do this.





Here is a picture of the connector that I screwed up and of what the LED light board looks like.

[Rajagra]

You seem to have something metallic supporting the board while it is powered on...

[Pandawhat]

The "metallic" object you see is simply a parallax view from one of the pins I sniped off an LED I already soldered to the board, it is in no way contacting or supporting the board. I powered the board on to get some extra light for my crappy webcam.

Acctualy the problem is that I have already installed 4 of these lights without error but this 5th one wont work, I removed the original blue one replaced it with a white one, and I burnt the board or something, now any LED i put in that slot doesnt seem to work.

[Rajagra]

Is there any chance you shorted the 2 tracks leading to the resistor? Most other problems would be non-fatal to the LED.

[Pandawhat]

Bingo, after cleaning it up a bit I have with great effect managed to do just that, is there any way i could re-make a connection to the resistor?

[Pandawhat]

Just for the record, this is basically my first time soldering, and 100% my first time doing anything with LEDS. I understood Ripster's last comment, but I am not sure exactly how to go about this, do I just try and solder a connection from whats left of the resistors pad to a point on the LED? If so any suggestions since its so small? I am also collecting tools as I go.

[Rajagra]

Wiring needs to go one of these ways:

+5V line ---> anode of LED
Cathode of LED (shown by a flat spot or short lead) ---> one connection of resistor
Other connection of resistor ---> 0V line

Or


+5V line ---> one connection of resistor
Other connection of resistor ---> anode of LED
Cathode of LED (shown by a flat spot or short lead) --->  0V line

Try to work out the right way from the original parts or whatever is working now, and copy that.



I'm worried about something else now. Once you've got the new LEDs working, will the boards fit back in place? They are a very tight fit as I remember.

[Pandawhat]

The Grey squares are the resistors, and the gold specs are the pin holes for the LEDS.

The LEDs I am installing do fit, except the base of the LED which is a little wider in circumference then the original LEDs, this only requires my shaving a small amount of plastic off the illuminating plastic board they fit into.

I know your explanation should normally cover anyones questions on this topic, but I'm fresh out of the box as far as electronics go, honestly just earlier this month I decided I want to learn about this stuff from scratch, and I'm set on it.

Now when I installed these I did have short and long ends, which I payed no attention to, out of 11 LEDs I fudged up the one I mentioned earlier by burning off the connection to the resistor, and now I have 1 more LED simply not working even tho the connections look fine. Rajagra's explanation was somewhat understood and misunderstood, so I present this diagram of the LED board in hopes of better understanding what I am doing wrong.

[Rajagra]

This is what you need to aim for.


You can solder to the normal spots, or you can add wires to the LED legs that run to alternative spots. The anode can connect to any of the connections along the + line. The cathode can run to its normal pad or be soldered directly to the resistor if necessary (but NOT the side of the resistor that connects to the - line!!)

It's possible the resistor itself is damaged. If so you can buy a replacement of the same value and solder it between the LED's cathode and the - line.

If you connect the LED the wrong way round, it won't light, but it won't cause any damage either.

[Pandawhat]

The extended diagram by Rajagra explains it all to me, its possible just by chance the two LEDs I installed in the "burnt" board were simply the wrong way, secondly the final LED I installed could simply be backwards. Just to test the burnt one what setting should I use on my multimeter?



I used 200 Ohm for my keyboard membrane, and I am in the process of reading.

http://www.allaboutcircuits.com/ and http://www.ladyada.net/library/metertut/continuity.html

P.S. is there any way to donate money to the website? Just curious.

[Pandawhat]

Tested as instructed, everything checks out then my genius self thought, hey! what if I take one of the old blue LEDs and touch the connectors to the 2 not working spots. Yup they light up, I obviously managed to destroy one of the LEDs somehow, and secondly just put 2 LEDs in backwards in the "burnt" connector.

I'm terrible, just plain terrible, I bet I'm the forums most noob poster. THANKS AGAIN, Rajagra, and Ripster. Your like gods to me.

[Pandawhat]

Saw my bro play that game ver.1 he liked it I thought it looked cool but never was interested, when I saw II and 3 I lol'ed.

so.. /agree

[EverythingIBM]

Saw my bro play that game ver.1 he liked it I thought it looked cool but never was interested, when I saw II and 3 I lol'ed.

so.. /agree

All new games are crap, you need to try some MS DOS games. I got a whole shelf full (and all the manuals and such).