Powering 3.5" ext HD off auto

**infinitiqx4** · 03-31-2006, 11:28 AM

Hey, any 3.5" external HD enclosures that I can power off my car's unregulated power? I am using a laptop so no computer PS on board (lots of posts on how to do that). 2.5" drives are too small, I'm looking for 300gig. I don't mind chopping the cables on a cheap enclosure.

http://www.newegg.com/Product/Produc...SubCategory=92

Could I use any of the ones with AC-DC converters that output 12V like these:

http://images10.newegg.com/NeweggIma...186-206-04.JPG

http://images10.newegg.com/NeweggIma...155-501-03.JPG

Thanks!

**infinitiqx4** · 03-31-2006, 11:56 AM

Should I just get this DC-DC converter?

http://www.mp3car.com/store/product_...roducts_id=138

I hope I don't start regretting buy a laptop instead of building a computer/ power supply for this install... (Got a new Dell 600m for 500 w/ 1gig ram, 80gig hd, and 64meg video-- couldn't resist!)

**2k1Toaster** · 03-31-2006, 01:20 PM

Hello. 3.5" HD's use the 12v rail to regulate everything in a matter of speaking. The 12v is used to spin the drive up, and also to power the head that goes back and forth. If it is unregulated, you will get random misalignemnts with the rest (ie. spins too fast/slow, misses data, or head isn't in the right spot over or under shot it). Basically you need it regulated. You can get that one you mentioned in the link that is variable, or you have other options. You could build one, I guess... but save yourself the headache and spend the 30 bucks.
As for the external enclosure, I have no idea whether the 12v regulator is built into the transformer area, or onboard. I guess if onboard, then I don't see why not, but too much or too little voltage might really mess something like that up.

**infinitiqx4** · 04-02-2006, 10:35 PM

Okay so maybe with http://www.mp3car.com/store/product_...roducts_id=138 this might work? Can you suggest which of these enclosures should work simply by slicing the cord to 12V and ground? http://www.newegg.com/Product/Produc...SubCategory=92 Thanks!

**2k1Toaster** · 04-02-2006, 11:13 PM

yes the mp3car product will definately power it because it regulates it. Any of the enclosures will work that transform the power to 12v.

**RawsonDR** · 04-03-2006, 12:58 AM

I don't mean to throw a wrench in the works at this point but there's one thing I should mention. On the description page of the DC-DC converter:

note: input voltage must be greater than output voltage by approximately 1.5V, for example the 12v output won't work with 12v input, see one of our other power supplies for that application

This means, with the car running and a healthy alternator providing 14+ volts, your hard drive will run great. With the car is off, however, and everything running on 12-13V battery power, your 12V output may be a bit weak. The drive may still operate around 11.5volts though, but who knows how low it will go. That risk is up to you if it is important.

**infinitiqx4** · 04-03-2006, 08:30 AM

Originally Posted by RawsonDR

I don't mean to throw a wrench in the works at this point but there's one thing I should mention... With the car is off, however, and everything running on 12-13V battery power, your 12V output may be a bit weak. The drive may still operate around 11.5volts though, but who knows how low it will go. That risk is up to you if it is important.

Doh. Beginning to think I should go with an internal 2.5" in my DVD bay for more storage instead.

**DarquePervert** · 04-03-2006, 08:36 AM

Originally Posted by infinitiqx4

Should I just get this DC-DC converter?

http://www.mp3car.com/store/product_...roducts_id=138

Yes, it's semanitcs and yes it's probably damn nit-picky.

It's not a DC-DC converter. If it accepts DC power input and provides DC power output, it doesn't convert anything!!!!

I know that's how it's listed in the store here. I'm going to point this out to them as well.

**infinitiqx4** · 04-03-2006, 08:49 AM

It is not nit-picky, its pretty relevant!!! I had ordered a 300gb 3.5" drive that I luckily was still able to cancel a few minutes ago.

Now I need to decide for a 2.5" if I'm going external powered off USB or I'm going DVD bay...

Thanks you guys, you saved me a lot of future headaches there!

**shotgunefx** · 04-03-2006, 09:17 AM

Originally Posted by RawsonDR

I don't mean to throw a wrench in the works at this point but there's one thing I should mention. On the description page of the DC-DC converter:

This means, with the car running and a healthy alternator providing 14+ volts, your hard drive will run great. With the car is off, however, and everything running on 12-13V battery power, your 12V output may be a bit weak. The drive may still operate around 11.5volts though, but who knows how low it will go. That risk is up to you if it is important.

It may work, the voltage drop across a regulator usually is a function of the current draw. I'm using a DIY once based on a ld1084v12 and still getting the same voltage with the current off, but currently, not drawing much current from it.

There's also the MIC29xxx adjustable series
These regulators feature 300mV to 370mV (full load) dropout voltages. Bit more expensive though.