SD Memory options / other options

Discussion in 'Embedded Systems and Microcontrollers' started by spinnaker, Nov 6, 2011.

  1. spinnaker

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    Oct 29, 2009
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    I am looking at building a temperature logging device.

    Since I am familiar with and have the programming tools I'd like to stick with the PIC 18F family.

    I have the temperature sensor part working with a PIC I have on hand.

    I want to add logging so that I can take an SD chip or thumb drive and plug it into a PC for analysis.

    At first I thought I could log to a thumb drive but after I looked into it, I found that the USB enabled PICs can only be a device and not a host. Is this true?

    I could also write to an SD memory card. But all of the sockets I have seen are surface mount. My soldering skills might not be up to surface mount. Are there other options for SD memory sockets? But I suppose if I am going to get started on surface mount a socket is a pretty good way to do it. :)

    One thought I had was maybe get a large capacity EEPROM and transfer the data via RS232 to the PC but that is a bit cumbersome.

    Any other ideas?
     
    Last edited: Nov 6, 2011
  2. thatoneguy

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    PICs in the 16F/18F series are only USB devices, not hosts or hubs.

    For the SD card, you could order a PIC Dev board with an SD Card and LCD Display, I forgot where I saw that one, but it was the size of a 16x2 LCD, had an SD card slot, a USB jack for power, and the rest of the I/O along the edge.

    As for soldering a surface mount, it isn't as hard as you'd think. Have a good, clean iron, and a Flux Pen (Very Important). Put flux on the PCB and a small amount of solder on the pads. Then use the flux pen and make sure the SD socket "pins" are well coated with flux. Align and heat one pin, then reheat for perfect alignment. After that, just go down the line heating up all the connections and the solder you added at the beginning will be enough to make the bond.

    For SMD work, the two biggest problems are A) Putting too much solder on, often caused by using far too large diameter solder, Get 0.020" diameter or smaller, and B) Not enough/No flux prior to application of heat/solder.

    Solder wick is handy to clean up if you put on too much solder, often salvaging something that looks ruined.

    Practice is a big part of it, especially in knowing how much solder to put on the pad prior to the component for the first bond. If you watch some youtube videos from sparkfun about SMT soldering it will be more clear.
     
  3. ErnieM

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    I actually prefer surface mount parts (especially resistors and caps) over leaded devices. I've mounted a few SD card sockets, once a replacment on a dev board and the others just on breadboards with just holes and pads on 01." centers.

    Most of the pins of an SD card are on 0.1" centers. The few (1 or 2) can be jumpered over to other pads.

    You can get breakout boards for SD cards, but I think these are too expensive.
     
  4. spinnaker

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  5. spinnaker

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    I hope you at least get the socket with that? :)


    So the SD sockets are actually through hole? Or at least some?

    Like this one?

    http://www.ebay.com/itm/Reverse-Mou...886?pt=LH_DefaultDomain_0&hash=item336d605906


    Nope wait it says surface mount but how do you solder from underneath?
     
  6. spinnaker

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  7. spinnaker

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    After looking at it again you would not need a micro SD adapter the way he did it. But I think it would be a heck of a lot easier to just solder a single row header to the adapter and just use micro SDs.
     
  8. thatoneguy

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    From another ebay listing, here is the way I've seen them:



    [​IMG]



    The "Reverse Attachment" flip which side is "up" when inserting a card, but you need a reflow oven or hot air pencil to solder.
     
  9. nerdegutta

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    Dec 15, 2009
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    You tin the pad with just about enough tin, place the component, and use a hot air gun.

    It's a risky business, but it works.
     
  10. ErnieM

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    THIS is the type I use, is is NOT for a micro card, it is a full size SD card. I believe the Indestructable article uses this too. These cards have pads on 0.1" centers making them very useful for hand soldering as you can get solder type breadboards with 0.1" pads & holes.

    Looking at this image you can see "most" of the lower tabs are about 0.1" apart. These can be soldered to pads with a regular iron using the smallest tip you have. For the tabs not on centers I pull them up and use jumper wires to other tabs.

    You probably don't need all 11 pins either, there are pins there to detect the card is there, the write protect tab setting, and some other card digital functions a micro usually doesn't need. The Indestructable gets along fine with only 7 connections.
     
  11. thatoneguy

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    In Post #16, he stated he didn't want to be limited to Micro SD cards, So a standard SD card slot would work for any SD card, since there are adapters for mini and micro to plug into a standard SD slot.

    The pins on it are easy to solder, as well. On the similar socket for Micro SD, the pins are TSSOP spaced, which is a bit harder to solder.
     
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