Hard Disk power supply from Notebook Power Supply - Page 1
Forum section: electronics / beginners

author: netdiver_one
author_rank: Newbie
timestamp: January 02, 2020, 05:14:22 pm
content: Dear All,I would ask your advice about a little project I have in mind.I often use a SATA/IDE to USB interface to copy data from old hard disk to new PCs. This interface comes with a black brick with 12v-5v molex connector. For three times this external power supply has failed (once blowing the hard disk it was connected to). I don't want to buy another one to get another piece of junk.As I have a spare notebook power supply (19V - 4.7A output) I think it could give enough power to feed a pair of step down DC-DC converter (two of these:https://www.amazon.com/dp/B008BHAOQO)I can connect the two in parallel to the output jack of the Notebook PSU and feed a molex female connector, stripped from and old PC PSU, setting the outputs to 12v and 5v.I think that the hard disk(s) will draw 1.5A max from both the power lines.Some hard disk have a 2.5A peak in the 12V line. I will connect only one hard disk at a time, and I would like to have a power source that would not blow up any hard disk I connect to it.What do you think about this solution? Will it work? Would you suggest another solution? Do you think I need heat dissipation for the power regulators?Thanks in advance.Best regards.Lorenzo

author: MyHeadHz
author_rank: Regular Contributor
timestamp: January 02, 2020, 05:37:01 pm
content: Those little buck converters won't get near their 3a rating for any longer than a small fraction of a second, if they even manage that. They are only good for a couple hundred ma continuous at 12v.edit: I know because I made the same mistake a while back,in this thread. One common solution is to hack an old desktop power supply into a "bench power supply" (at least that's what youtube calls them). Though limited in features, they are quite robust and stable, and many people have old ones lying around.

author: Wimberleytech
author_rank: Super Contributor
timestamp: January 02, 2020, 05:41:50 pm
content: I have several of these and used them from time to time. Never blew one up, nor destroyed the HD. Hmmm. Have you opened a dead brick to see what failed?

author: tunk
author_rank: Super Contributor
timestamp: January 02, 2020, 05:47:05 pm
content: Here's a test of something similar:https://lygte-info.dk/review/Power%20Adjustable%20buck%20converter%20LM2596%20UK.html

author: netdiver_one
author_rank: Newbie
timestamp: January 02, 2020, 06:10:32 pm
content: Quote from: Wimberleytech on January 02, 2020, 05:41:50 pmFirst one is the original shipped with the interface... I don't remember in which way it failed...The second one arrived DOA: since it came from China, it was very expensive to send it back from Italy, so I opened it and found out that it had a bad soldering. Repaired, after one year it made a bang and the hard disk was burned, all data lost, with a bad smell all around the room - It went directly in the bin, not passing GO.The last one was the most expensive, but now it can't power some hard disks, so I think it is not giving enough amps. I don't want to create another unreliable PSU with my work, I only want a reliable one... but enough "portable" because I often need to make these data transfers outside my lab.Thanks for your reply.Lorenzo

author: netdiver_one
author_rank: Newbie
timestamp: January 02, 2020, 06:18:24 pm
content: Quote from: MyHeadHz on January 02, 2020, 05:37:01 pmThanks for the "heads-up". I will read that topic in detail. For the moment I have an ATX PC PSU with a switch in the green wire to black wire connection, to power up without a motherboard connected to it, but it's not easy to carry in my backpack.All the best.Lorenzo

author: niffcreature
author_rank: Newbie
timestamp: January 03, 2020, 11:00:24 am
content: In my area it wouldn't be hard for me to find a decent 12v power supply with a few amps. Could find one at a thrift store for a few bucks, maybe even in my apartment.But why are you using 3.5" hard drives if you need them to be portable?

author: magic
author_rank: Super Contributor
timestamp: January 03, 2020, 11:08:55 am
content: You may find external HDD power supplies from good brands at electronics recyclers, on auctions sites, etc.Or combine separate good quality 5V/12V wall warts.

author: netdiver_one
author_rank: Newbie
timestamp: January 03, 2020, 12:11:50 pm
content: Quote from: niffcreature on January 03, 2020, 11:00:24 amI work as a Computer Technician and I often make data transfers between old and new PCs directly at the customer's office.BTW, I bought a new sata to USB interface that has a simple 12v wall power supply, but I would like to use also the old interface to not lose the opportunity to work with older IDE drives.

author: David Hess
author_rank: Super Contributor
timestamp: January 03, 2020, 01:34:47 pm
content: I just use a spare ATX power supply to power bare hard drives.I agree with MyHeadHz about current derating the switching modules. I would do so by at least 100% of the worst case surge estimate.