# Is it possible to build homemade storage device?

From what i know, HDD is built on magnetic recording technology. My question is, is it possible to create a storage device from scratch (USB, HDD, etc.)? I'm just eager to try out building some electronic devices...

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You could try making a USB based memory device. For example, get a USB to serial converter chip, a microcontroller and some $I^2C$ memory for it. You could then write a program that will communicate with the micro and write to the memory and read from it. Just don't expect the capacity and speed to be anything close to the one of a commercial USB flash drive. Still, it will give you a starting point. – AndrejaKo May 28 '11 at 11:05
What are you actually planning to do? Build the physical storage medium from scratch, or use preexisting physical storage and just do the interfacing? And what kind of stuff do you want to interface it with? PC or microcontroller or what? – posipiet May 28 '11 at 12:41

Yes, you can do it-- but it's hard and it won't store very much. I think the thing that makes it hard is that you need to know a lot of very specialized areas to make it works. Things like: software, signal processing, electronics, electro-magnetism, metalworking, motors/gears/etc, and materials science (somewhat like chemistry). While not impossible, it is rare to find someone who is proficient in all of those areas.

If you want to make this easier, I would recommend starting with a standard cassette tape player/recorder. Rip out all of the electronics and keep the motors, gears, mechanical stuff, and the read/write/erase heads. Then add back in your own electronics. This still offers a lot of challenges, but the odds of success go way up. Then, if you get that working you can take the knowledge you gained and go on to a hard drive or something.

If you go the cassette tape route, let me mention that if you Google that you'll find a lot of pages that do something similar, but without modifying the player much. They do that by modulating the data into something that resembles audio and can be stored as audio. That's not what I'm recommending. If you rip out the guts of the player/recorder then you can have direct control of the motors and heads, which opens up lots of possibilities.

Hard drives will be harder, mostly because you'd have to figure out how to make the hard drive platters. Meaning, you have to make the magnetic recording medium and somehow spread it out evenly and smoothly on the glass or aluminum platter "base". Making the heads isn't easy either.

I should point out, however, that a clean room is not required. I remember playing with a "removable hard drive" on a DEC PDP-8 computer. Instead of removing the whole drive, you only removed the platters. The platters were about 12 inches across and contained in something like a piece of Tupperware that you'd carry a cake in. About 6 or so platters per carrier. Before putting the platters into the drive you would have to remove them from the Tupperware. It was big, and didn't store a lot, but no clean room either. Don't get me wrong, modern drives do need a clean room. But a DIYer has little or no hope of building a modern drive in his home so it's not really an issue.

Another form of storage that could be interesting is an optical fiber "drive". Light travels approximately 6 inches per nanosecond in a fiber optic. So if you have a fiber that is 100 feet long and you're transmitting stuff at 1 gbps then you're really storing 200 bits of data in that fiber. Make the fiber several kilometers long and you could store a barely useful amount of data. Get a fiber transmitter and receiver set up so whatever is received will be retransmitted and your data will just recirculate endlessly. Some extra stuff will then allow you to read/write the data.

Probably the most useful, and least satisfying, thing to build would be something like a USB thumb drive. Basically you buy the flash chip, and the controller chip, connect them together and you're done. To make it a little harder, replace the controller chip with a microcontroller and write lots of software. It's not super interesting, in my opinion. I don't think it offers the same sense of accomplishment that the other approaches offer-- even though the performance and capacity would be the highest this way.

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about the PDP-8 HDD. That was then, data densities nowadays are much higher, so that the head has to fly much closer to the platter's surface, typically 1 um. A hard dust particle of 1 um may crash the head. – stevenvh May 28 '11 at 14:38
Isn't the index of refraction for fiber (both glass and plastic) about 1.5? That would give a speed of light of 8 inches (20 cm) per nanosecond. – stevenvh May 28 '11 at 16:18
@stevenvh Wow, tough crowd! While data densities of modern drives are high and the head height is super low, we are not talking about a modern drive. We're taking about something that someone built in their home. Using the PDP-8 as a point of reference, I doubt that anyone can build a HDD as good in their home. At least not on their first or second try. So, my point stands. You don't need a clean room when making a HDD from scratch. As for the propagation speed in a fiber: you'r just being pedantic. :) – David Kessner May 28 '11 at 19:31
I'm not sure much is to be gained by replacing the electronics in a tape deck; you are still going to have to modulate and demodulate the data stream, and are still going to be bandwidth limited to probably not much more than audio by the head. You might get a little better with fancier amplifiers and speeding up that tape. Want to store a lot? Use a VCR instead of an audio deck. – Chris Stratton May 30 '11 at 7:39
@Chris Statton By replacing the electronics you can do: Automagic seeking (use one of the channels as an index, store the data in the other channel, then automatically FF and RWD to find where the data is stored). Replace the normal tape bias with your own modulation to increase the storage density. Run the motors at a higher speed for higher data rates. Finer control of the erase head allows more selective writes. Etc. – David Kessner May 30 '11 at 13:19

A ferrite core memory is entirely buidable at home without specialized hardware or electronic parts...

Some kind of low density magnetic media storage could also be built with no custom parts.

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 It's an idea, but I would hate to think of weaving something bigger than an 8 byte memory :-) – Federico Russo May 28 '11 at 16:01 @Federico What about 32 bit on an Arduino shield? :-)) corememoryshield.com/report.html – Axeman May 28 '11 at 18:48 Building a large, low density hard drive could be a fun project. – Chris Stratton May 30 '11 at 7:36 @Axeman: I wonder whether cores could be reliably driven with 2/3 the "switching" current without switching and, if so, whether that's been exploited? It would seem like it should be possible to access 256 bits using 12 wires (4x(4+4)x(4+4)) and "power-of-two" addressing, or 880 bits (four times (12 choose 3)) if one can use arbitrary combinations of drive wires. – supercat Jul 18 '12 at 19:41

A HDD is not a very good idea for a DIY project. You need lots of special parts which aren't available for DIY, like voice coil, the platters and the magnetic head. You'd also need clean room conditions. And of course it's all about high precision mechanics.
Also, if you would succeed in constructing one it would probably cost 10 to 100 times more than what you pay for a commercial product.

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 I once arrived at a friend's while he was doing open heart surgery on a HDD, sitting at the kitchen table with an ashtray next to the open drive :-) – Federico Russo May 28 '11 at 12:15 @Federico - Yeah, so much for clean room conditions... :-( – stevenvh May 28 '11 at 13:31 There are hard drive failures where opening it, fixing the problem, and then immediately imaging it to a good drive is a pragmatically reasonable alternative. Back in the day, I remember running a scrap <20mb drive open, it "seemed" to work for a few hours, but I think not when I tried it again days later. – Chris Stratton May 30 '11 at 7:35

Crazy idea

If you are really really bored. You could delve into organic storage. Slow but huge capacity.

E Coli hard Disk

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You can make magnetic tape from sticky tape and rust.