Voltage Drop?

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protocol6v's picture
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Joined: Apr 22 2006
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What would the best way to drop the 12v supply of power from FireWire to 5v? This is for an external enclosure i bought that needs to be connected to external power to work, but i wanted to mod it so it would run off the FireWire supply like my other case does. This is for a 2.5" HD.

Thanks!

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eeun's picture
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Joined: Dec 19 2003
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Pick up a 12V to 5V regulator

Pick up a 12V to 5V regulator and attach it to an old heatsink.

A quick search for 12V to 5V regulators reveals:
http://www.overclockers.com/tips1095/

...which should at least give you enough info to search further.

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protocol6v's picture
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Joined: Apr 22 2006
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would it stay cool enough to

would it stay cool enough to still fit in the case without a heatsink? I still want to be able to fit it in its origional case so would i be able to lay it flat against the PCB?

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pmjett's picture
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that depends

Pretty much the amount of heat generated by the regulator is proportional to the amount of current you are trying to get through it. A 7805 regulator (super-duper common) is good to 1.5A. It's only good that high with a heatsink. You might get away with just the case of the regulator to dissipate heat, but that might only be at like 100 mA (1/2 watt).

You could try to attach a small square (say an 1" square) of aluminum sheet to the regulator's case, and might be able to make the whole thing pretty flat and manage to move enough heat. How much load are you going to put on your +5? Do watch how you squash the regulator down near the PCB, the tab (and hence the heat sink) on 7805's is ground and easy to short in close quarters.

hope this helps.
mike

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protocol6v's picture
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Joined: Apr 22 2006
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Not worried.

Where I was planning on putting it is a big open spot of grounded metal. So I'm not to worried about shorts. I'll have to pick up a regulator this weekend and see what I can do.

Thanks For the Help!

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Beware that firewire is not a

Beware that firewire is not always 12V. I can be as high as 36V or as low as 9V. Keep that in mind if you want to plug your device into other people's computers.

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protocol6v's picture
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Joined: Apr 22 2006
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I think i'll just buy and act

I think i'll just buy and actual FireWire case.

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You'd be pretty hard pressed

You'd be pretty hard pressed to build one for less money than you could buy one for considering how cheap they are these days.

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