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I'm looking for a storage solution for small files that would be moved into a small sensor running arduino-like processor.

Ideally the single memory unit would be cheap (in 1-10 cents range), but the memory can be very limited (several megabytes).

The closest I've got so far is small SD Memory card, but the smallest 4GB ones cost several dollars (at least bought in quantities < 100). Anything else I should be looking at?

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    1-10 cents for several megabytes? What is your volume going to be, tens of millions? – Ignacio Vazquez-Abrams Jan 3 '15 at 15:08
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    You can try to find some cheap SPI Flash chips out there. WinBound has one DIP8 of 8MB. The retailer price can be quite high ($2-$3) but I a, sure you can find much better prices in small quantities (findchips.com). – jfpoilpret Jan 3 '15 at 16:49
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    When going for minimal cost it often works the other way around: see what you can get cheapest, then figure out how you can adapt your system to work with it. But I'd probably do my proof-of-concept prototypes with SPI flash too (though in SMT packages). – Chris Stratton Jan 4 '15 at 4:46
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    MicroSD cards are usually made in the tens of millions. But you wouldn't want to interface directly with the flash chip on it though. – Ignacio Vazquez-Abrams Jan 5 '15 at 4:38
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    So all you need is a micro SD of a few GB, a jeweler's saw, and a very steady hand. By which I mean the cost is not a linear function of capacity – Chris Stratton Jan 5 '15 at 4:52
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I assume that, if this is a cost sensitive item, you need a reliable supply of multiples (so looking for small SD cards on e-bay isn't a viable solution).

Does it need to be non-volatile storage? If it does't you may be able to find small 8-bit wide RAM chips at a pretty good price. If it needs to be non-volatile, you might look at individual flash chips. I found this one, an 8-bit by 512 KB Serial-SPI flash chip for £0.19 (about $0.28 US) in single units and £0.176 if you can by 100 at a time. I would expect DRAM chips and chips with a simpler interface to be less expensive (but you might end up spending more on interfacing the chips so it might end up as a wash).

If you're able to consider a variety of processor chips it might be worth looking for something that has adequate storage on chip. That might be the most cost effective way to get the space.

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On ebay you can buy 2nd hand Nokia SD cards from old mobile phones which are 128MB or so and very cheap.

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  • Even though interfacing with a SD card would ramp up the cost a ton... – Anonymous Penguin Feb 3 '15 at 0:27
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    How so? Reliability is a pain, but most SD cards will talk something interoperable with SPI with moderately more software complexity than an SPI flash. – Chris Stratton Feb 3 '15 at 5:19
  • @ChrisStratton SD card readers cost at least $2-3, so it'd be just as easy to use a EEPROM chip. I don't know if the OP wants to be able to have a ton of "disposable" SD cards to use with one device or if he's just trying to minimize the overall cost... – Anonymous Penguin Mar 5 '15 at 2:34
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    @AnnonomusPenguin - No. An SD card reader is useless with an Arduino (you talk SPI directly to the card), so the cost of one doesn't factor into to. Sockets are cheap, and optional anyway, as if you don't intend to move the card to anything else you can just solder directly to it. – Chris Stratton Mar 5 '15 at 14:47
  • Good idea, but won't work in my case. – Marcin Raczkowski Jan 4 '16 at 14:52

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