5v to 3v Power Regulation off a Molex connector

Thread Starter


Joined Jan 20, 2012
Hello everyone, this is my first post here, and I appreciate you taking the time to read this.

I am currently working on a project to customize my computer heatsink/cooler. I have a Cooler Master V8 cooler that I plan on adding a 3" plasma disk (the type behind the Borgs heads in Star Trek) to the top of. My ultimate goal is to tap into the harddrive activity LED out pin on my motherboard to activate the plasma disk to give the final impression that I can see the computer thinking.

I have 3 obsticles in front of me:

1) I have to convert the 2 AAA battery opperated plasma disk to run off the 5v molex lead

2) I have to figure out how to make the HDD activity actually activate the disk

3) I have never made an electonic circuit.

I have been researching how to step down the voltage from 5v to 3v (I am assuming since 2 AAAs power it, it must run on 3v) and I have come across many confusing solutions from using resistors, diodes, transformers, and regulators.

Using a regulator seems to be the most reliable option, but I have no idea how to go about doing this, and what regulators (AC or DC -- I assume DC) to use.

I'd appreciate any help be it a suggestion, advice, or even a fully drawn out circuit with a part list (teach a man to fish, I know...).

I wanted to get it powered before I try to tackle the HDD activity portion, but I would definitely appreciate any help there as well.

I have purchased some tools, and I'm not completely useless at being handy, I've just never tried anything like this before. I have an anologue Multimeter I don't know how to use and a soldering iron, as well as a ton of patience and ambition!

Thanks again for reading through this!


Joined Feb 19, 2009
If you are new to electronics, you could just put 3 silicon diodes in series to drop the 5V down to 3.2V (Two AA's would be over 3.2V when brand new). Then use it directly, assuming it is low current (< 1/2 Amp).

Thread Starter


Joined Jan 20, 2012
Thanks for the response--what diode would you recommend? I just built a "test" computer so I won't fry my main pc when I inevitably do something wrong.

Could I just solder the wire to the diodes and then shrink wrap over it, or do they need to be build on a pcb?

Also, I separated the control circuit from the plasma disk itself and added a wire so that the electronics for it can be hidden somewhere off the cooler. I noticed that now when I turn it on, it won't electrify unless I am touching the glass and/or tapping the control unit (where the circuit and batteries are contained). The wire I used I cannibalized from the ground wire in a firewire and is silver in appearance, not copper--could this be the issue? Also, the original wire connecting the disk to the circuit was only about 1/2 an inch long and not insulated. The wire I replaced it with is insulated; could that be the culprit as well?

The wire I added is about a foot long.