Using a Full Sized HDD in a Laptop




In brief: How to wire a regular full sized desktop hard drive up to work with your laptop.

I have had a bunch of times when you need to use a hard drive designed for a Laptop in a desktop system, say for formatting, or copying massive amounts of files. Laptop drives are by spec. 2.5inch wide, while desktop drives are 3.5 inch wide. This isn't a problem for the average user because we have these nice 3.5 to 2.5inch adapters, however what if you wanted to put a full scale drive into a laptop? You're screwed. Of course, in most cases you couldn't even fit the full drive into the laptop just due to it's actual size, not just the different adapter.

But why do this, it's going to be so ugly! Easy... because I have a pile of 3.5 inch drives, and all my 2.5 inch drives are dead. I personally don't care how it looks, assuming it works.

The pinout between a 40 pin ide (standard) and 44 pin ide (for laptops) are identical except for the last 2 columns on the connector:

pin 41 +5v (Logic)
pin 42 +5V (Motor)
pin 43 Ground (Return)
pin 44 TYPE- (0=ATA)

These actually won't be used to power a standard sized drive due to the increased voltage needed over a 2.5" drive, plus 3.5" drives typically require +12v as well. We will just be ignoring these extra pins, and taking power from somewhere else.

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Making the PCB

I had a really basic PCB layout I made in Eagle, but my laser printer ran out of toner, so I ended up having to hand draw out all 80 traces with a sharpie. The 2.5" interface was pulled off of a dead 2.5" disk, this just squeezes over the PCB I burned.

As I recall, the first 20 columns of pins are exactly like the full sized cable, the last two are for the +5v dc for the "fun-sized" drive. Unfortunately, it doesn't have the +12v dc which fill size drives need, only +5v dc. I made solder points for them, but the weren't actually used.

Step 2: Power and Wiring

I butchered a power splitter and put a longer cable in between the ends, so now I use another system to power the drive. Horribly inconvenient, maybe. Horribly effective, you bet.

Step 3: Smoke Test

After crossing my fingers, I turned both the laptop and the PC I was leaching power from.

Hey, my Linux booted! Time to go root you hoes.

Hope you enjoyed reading my instructable!

Be the First to Share


    • Made with Math Contest

      Made with Math Contest
    • Multi-Discipline Contest

      Multi-Discipline Contest
    • Robotics Contest

      Robotics Contest

    35 Discussions


    2 years ago

    I am in need of this. I have a 3.5 drive with all of my family photos and I just gave away my old desktop to a friend's kid building his first machine. The drive is encrypted so external enclosures just don't know what to do with it. I bought a 12" male to female SATA extender, just in hopes, but the computer didn't recognize the drive. It spun up but never registered. None of the other 3.5s I had lying were recognized either. However, a spare 2.5 did. So i'm left to the obvious answer, the laptop can't power the drive. Do you think I could get a desktop power supply just to spin the disk, or is there some feed back loop where the computer is metering power? Can I just plug the 15 pin power from a desktop power supply while plugging the Data port into the laptop?


    1 reply

    Reply 2 years ago

    well That was quick. I remembered I had a dual bay external drive. I literally cut the extension cord in half separating DATA and Power. Plugged the power into the external and the DATA into the laptop. It worked beautifully.


    2 years ago

    I know this is very old instructable but I just have to say I love all the idiot comments like why didn't you get an external drive enclosure or external drives are so cheap or its portability is absolute zero? Why are users like that on this site if they don't understand what this site is about? Tinkering, making stuff, recycling old hardware into something usable or just plain hacking stuff because you can. How would he reuse old junk if he just bought new stuff and how would that be an instructable? It's a proof of concept a just did it because he could kind of thing! Thumbs up guy nice instructable!

    1 reply

    Reply 2 years ago

    Thank you, you nailed it. Yes, my hack was not portable, nor practical, but I never said it was either of those things. As I recall, a big part of wanting to do the write up was because I asked myself "would that even work?", and I could find no documentation of this online.


    3 years ago

    Nice project but this is highly impractical, only due to the lack of power when powering the hdd from the laptop's battery. It is also bulky and it brings the laptop's portability to an absolute zero...


    11 years ago on Step 3

    Cool work. I wonder if you could tap into a 12v connection inside the laptop to run the HDD off the laptop? Or did you decide there was no good way to power the HDD from the laptop? I wonder what kind of effect that would have on the battery life...

    5 replies

    Reply 9 years ago on Step 3

    A) There likely isn't even a 12V rail in the laptop. Even if there is (e.g. for the LCD back-light inverter), there likely wouldn't be enough power left to supply the HDD.

    B) It would have an enormous negative effect on battery life. The drive I happen to have sitting here calls for almost 12W of power.

    You could hack together a power supply that drew straight from the battery, but it would have to be designed to fit in the available space (such as in the place the 2.5" drive used to be).


    Reply 7 years ago on Introduction

    Say you want to power the hard drive from a wall socket, how would you go about that?

    I have a SATA disk I can hook up to my laptop's eSATA port, because it can't get enough power from that port alone I have to (just like you did) hook it up to a molex cable from my (old) PC.

    I would rather have a clean solution and get rid of the old pc altogether.

    I don't want a PSU on my desk (or under it) what I'm really hoping for is a transformer (wall wart) to molex power suply.

    Can that be done? What would I have to look for in volts, watts and amps?
    I have nearly no experience with electrical projects but I am confident of my ability to follow instructions and figure stuff out. And I can connect a couple of wires in a safe manner.

    If there is a store buy able alternative that would be interesting as well.


    Reply 7 years ago on Step 3

    Yes, it can be done, but you will need 2 wall warts: one for 5v, and another one for 12v
    The 5v one must be rated for more than 730mA, and the 12v one must be rated for more than 640mA
    And very important: they must be regulated wall warts, measure their output voltages with a multimeter, and make sure that they are not higher than 5.25v and 12.6v.
    (I just measured an unregulated 12v wall wart, it outputs 18v when unconnected, which wouldn't be good for the drive)

    Then cut a molex plug from your old PSU, and hook the negative cables of both transformers to the black wires of the molex plug (doesn´t matter wich one), the positive 12v cable to the yellow wire, and the positive 5v cable to the red wire.

    (sorry for the not perfect english)


    Reply 7 years ago on Step 3

    Thanks for the reply! English isn't my first language either so no need to apologise!

    I had no idea I would need two voltages... That makes it a bit too complicated (and messy) for me. I guess I'll have to look into something ugly and pricey like this:


    10 years ago on Introduction

    Yeah, it's a nice project, specially when you consider looking into old hard drives, possibly cleaning the all out, I tried this project but in the style similar to using small wires as jumpers using the laptop HDD connector and connecting them to the larger HDD IDE cable, again the jumper connection method, but my laptop (which is similar to the one you used in this instructable: Compaq Presario 1220) only says Operating system missing, I can hear the 3.5 HDD spin but the laptop obviously isn't reading it; if memory serves, I have Windows ME installed in the 3.5 HDD, I am guessing that either the laptop cn't read Win ME or the connections were connected wrong. Do you possibly have detailed wire arrangement(s) between the 3.5 HDD IDE cable and the laptops IDE cable? Oh yeah, I'm using a molex power supply from a pc. See pics for the method i used to connect both IDE cables, note the laptop isn't really using an IDE cable, per se, but a flex cable. See Pics.

    2 replies

    Reply 8 years ago on Introduction

    well if you are still trying to figure it out has the pinouts for 44 and 40 pin ide cables.


    9 years ago on Step 3

    About this 'ible: It's really rather sketchy. It assumes a lot of skills/knowledge that could fill at least five 'ibles on their own.

    It's a good "I did this, so it can be done, so if you need to do it, do it!" but anyone who has the skills to make it based on this description probably already knows it can be done and how to do it... "E" for effort, though! :D


    10 years ago on Introduction

    This works great with SATA drives to, just buy an sata extension cable, or like me take a normal sata cable & solder it into a sata laptop, :)


    10 years ago on Introduction

    well, i already tryed like you said in the last mail, and when i put the mini HDD in the laptop, it says "invalid system disk". i tryed one more make the HDD bootable, copy the system files onto it, and then run install from DOS, and it copyes the system files, and at the first restart, i get a blank screen with a blipping line in the top left corner..and i want to try to connect the regular ATA CDROM, like in the instructable, because my bios says that it can boot from ATAPI CDROM drive, and i might get a chance..anyway, i'll let you know what happened once i get some results


    10 years ago on Introduction

    i want to correct myself for the last post..the IDE cable that i want to make for my thinkpad must have 3 sockets : one in the lappy, one attached to the laptop's HDD, and one attached to a regular CDROM drive

    2 replies

    Reply 10 years ago on Introduction

    I was able to get my laptop to detect a slave device on the IDE cable, when I had a second hard drive installed on it, but I never tried with a CD-ROM. I would imagine that it would be possible to make the laptop access the drive once it's booted, but as for booting from a CD, the bios has to support this. If it won't boot from the onboard CD-ROM, it probably won't boot from the drive hooked up to our hacked cable. What you may want to do instead is take the miniHDD out and get a converter that does the opposite of what this instructable does. Install it into a desktop computer, boot it from a CD, and install windows there. When it wants to reboot for the first time, you can probably put the drive back into the laptop and let it boot for the first time. :) Good luck!


    Reply 10 years ago on Introduction

    yes you can do it, use a regular IDE cable with 3 sockets, one socket connect the hard drive, one socket connect the CDROM, the other will be for the adapter to connect to the laptop, as well you will need a regular PC power supply, to power the hard drive and cdrom, you will need to connect a ground from power supply to laptop