# Need some electrical help please



## Maju (Jun 5, 2008)

Hello.

I am hoping to wire all of my lighting up to one illuminated master switch. This will probably consist of 2 Cold Cathode Tubes/1 inverter, 3 pre-wired 5mm LED.

After looking at the molex plugs I see that the LED's connect to the 12v wire and the inverter connects using the 7v wire.

Would you have a look at the wiring diagram below and tell me if it would work (and be safe)
Also, i'm not to sure of how to wire up the LED in the switch and where to power it from plus whether i'd need to put a resistor in the power line to it? The spec's for the switch are below







Here is the back of the switch ... +'ve terminal shown on the right






spec from the data sheet

Contact Configuration	  SPST-NO-DB
Switching Action	    Latching

*SWITCH*
Dielectric strength 1000V a.c.
Insulation resistance 1GΩ
Contact resistance (initial) 50mΩ
Current rating (typical) 400mA at 32V a.c. resistive
100mA at 50V d.c. resistive
125mA at 125V a.c. resistive
Switching power (max) 16VA a.c.
*LED*
Typical fwd voltage (Vf at I operating) 2,2V
Max fwd voltage (Vf at I operating) 3,0V
Forward current (I operating) 20mA
Luminous intensity (Iv at lopr) Green LED – 160mcd

Hoping that you can help and that I haven't bitten off more than I can chew

Maju


----------



## rigelt (Jun 8, 2008)

*it won't work like that*

you need to do some more research first.
it's not 12v and 7v but 12v and 5v. 
connect pin4 to pin3 you get 5V
connect pin1 to pin2 you get 12V
connect pin1 to pin4 you get 7V

iportant - use the 5V connnection that way the resistor will heat up less.

LED Typical fwd voltage 2,2V 
Forward current 20mA

Resistor for the green LED >>   R = (5V - 2.2V) / 0.02 A = 140 Ohm    

your wiring diagram won't work as desired separate the 12 and the 5V circuits. Good Luck


----------



## Maju (Jun 8, 2008)

Thankyou very much rigelt

I shall have another go at figuring out the wiring and see how I get on.
Bit of a bummer about using the 5v line for the resistor as I've gone and bought a 470ohm resistor. Oh well,13p wasted 

Thanks again


----------



## Chryonn (Jun 8, 2008)

Let us rephrase all this: the *potential difference (PD)* between pin 1 and 2 is ~12V.  The PD between pin 3 and 4 is ~5V.  The PD between pins 1 and 4 is 7V, and there's been some discussion as to whether this is actually detrimental to the PSU or not.  Go to www.ledcalc.com to work out what resistor you need for the LEDs you're using.   if you forget about the lit-part of the switch and just use the switch itself, i don't see anything wrong with the diagram, though perhaps as rigelt says, you need to separate out the 5 and 12V lines.  you should wire up a test circuit first. 
i use a breadboard for plugging in the LEDs and modded my own 5V supply (from a USB cable) and a 12V supply (from a modded female Molex), then i plug in the resistors that i think will give best illuminosity.
i've been messing around in order to mod my desk and bookcase with LEDs.


----------



## MKmods (Jun 8, 2008)

also can you link us to the cathode and inverter. (most that I have seen use 12V for inputs)

(on your original diagram you show the voltages as yellow=12V and red=7V (on a comp PS the red=5V)


----------



## rigelt (Jun 9, 2008)

Oh!  if you already own a 470 Ohm resister, then give it a shot and try the 12V supply. Yeah then there's not much wrong with the diagram and it should work.
Myself however, I would not mix pin3 and 2 together. I think there's a reason, that all the cables in the case carry on the 4 cables instead of just pin1, 2 and 4. Can a pro modder tell us more about this??
Thanks for mentioning the url: www.ledcalc.com


----------



## MKmods (Jun 9, 2008)

On your PS inside the computer the red wire is 5volts, yellow wires are 12V, orange wires are 3.3 volts and the black ones are grounds.

careful when adding accessories (fans,lights etc) as they use a different color code than the computer.


----------



## Maju (Jun 9, 2008)

Well that's a pleasant surprise waking up to lots of helpfull replies. Thanks all

Yep, my bad re the cable voltages. Doubly glad that i posted here now and have not fried anything.
Here is a shot of the molex for the inverter









sometimes it is embarassing just how much of a dunce you can be - or rather I can be.
Have just noticed that the voltage for the inverter is in fact 12v and that I was in fact looking at the rear end of the pass through molex and that it was in effect upside down.
Bloody idiot seems to fit the bill here.

So in a revised light this should simplify things greatly.
If I get stuck then rest assured you'll see me posting again.

Thanks All


----------



## Maju (Jun 9, 2008)

*sensitive electicians look away now !*

Hoorar !

Thanks for your help people. Have achieved what I wanted to do. Have yet to install it into my case but waiting for other parts to arrive.

The test set up isnt pretty but at least it works.






Right. Next up modding the Sythe Kama meter to replace the volume knob with a heftier potentionmeter - or whatever they're called for the rad fans.

Cheers Again


----------



## MKmods (Jun 9, 2008)

good job.


----------



## rigelt (Jun 9, 2008)

Thanks for your feedback - great to see that green LED lit!  hehe


----------



## lemonadesoda (Jun 10, 2008)

Dont leave those molex connectors with snipped leads dangling. Remove the snipped lead completely. Get pliers and pull them out like rotten teeth.


----------

