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Main => Main Forum => Topic started by: thatdecade on June 01, 2008, 09:17:45 am

Title: Step up to 12V from num/scroll/caps
Post by: thatdecade on June 01, 2008, 09:17:45 am
Just thinking out loud, bear with me.

I'm looking to connect a Cold cathode fluorescent lamp to my ipac's LED harness.  Problem is that the light tube is 12V 700mA.

I know the ipac's LED connections are 5V and can only source 10mA, but I think I would be safe stepping up the voltage and using the pc power supply to source the current needed.

(http://img230.imageshack.us/img230/2616/transistorccfltz8.jpg) (http://imageshack.us)

The only thing that worries me is the start up time lag (their not instantly on with power).  The bars do have a switch that makes them sound sensitive, but it looks pretty lame with the arcade but proves that the light bars can have fast reaction/start up times.
I may ditch the whole 12V problem by leaving it always powered with the pc and rewiring the sound portion of the tube's inverter circuit so it switches on/off with the keyboard's LEDs.
Title: Re: Step up to 12V from num/scroll/caps
Post by: SirPeale on June 01, 2008, 09:59:08 am
How about some background as to *why* you would want to do this.
Title: Re: Step up to 12V from num/scroll/caps
Post by: abzman2000 on June 01, 2008, 12:11:02 pm
presumably he wants to use something like scroll lock as an output pin, and use it to control the lights with software, or at least that's what I would do. 
Title: Re: Step up to 12V from num/scroll/caps
Post by: hanelyp on June 03, 2008, 07:51:37 pm
(http://img230.imageshack.us/img230/2616/transistorccfltz8.jpg) (http://imageshack.us)

Not quite.  That will only feed ~4.3V to the CCFL, the remainder on the 12V being lost in the transistor.  You want the CCFL on the collector (+12V side) of the transistor with the emitter (leg with the little arrow) going to ground.
Title: Re: Step up to 12V from num/scroll/caps
Post by: abzman2000 on June 03, 2008, 08:40:14 pm
you mean put the ccfl between 12v and the transistor, and hook ground directly into the transistor?