Leeching power from a thumb drive

Discussion in 'The Projects Forum' started by cabers, Aug 1, 2013.

  1. cabers

    Thread Starter New Member

    Jul 30, 2013
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    Had an idea for a friends project: to cut it short, he'd like to to incorperate smd leds into the album artwork(on his record sleeve.) Originally thought it may be possible to do this with a button cell battery, but now it was made obvious to me that the current/voltage requirements just don't make this feasible. then i thought, how cool would it be to incorporate a thumbdrive into the album packaging so that he can include a digital copy of his music.

    if at all possible id like to wire the album leds in parallel with the flash drive so they light when plugged in, but im not sure this would leave enough current for the usb drive to function. there's probably a lot im overlooking here, so please chime in if there are obvious considerations that im missing. also anyone have an idea as to how much a typical thumb drive draws during operation? I've been told usb ports can put out 500mA max but they have to be set to do so.

    Thanks!
    Cabers
     
  2. DickCappels

    Moderator

    Aug 21, 2008
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    You will have to measure your particular thumb drive under worst case conditions, which is probably while writing at the highest speed possible (this condition is likely to be when connected directly to the root hub in a fast system while writing a large file from a hard drive and the file is not fragmented, while CPU hard drive, and other USB peripherals are not being used for other things.)

    According to the 2.0 version of the USB standard, USB ports, when used for computer peripherals (for use with phone chargers, the rules are a little different) can supply up to 500 ma from powered hubs or 100 ma from unpowered hubs after they receive permission to do so from the host. Until permission is received, no more than 500 microamps may be driven by the device.

    If you use a thumb drive that meets one of the USB standards, and that thumb drive has a power-on LED, you can use the signal that drives the LED to switch power to your other LEDs on and off.

    In order to determine how much current you may use to power your LEDs, you will have to find out the current requirements the thumb drive reports to its host (this is in multiples of 100 ma from memory) and how much current the thumb drive actually draws (and it might be a good idea to contact the manufacturer and get their specification), then you might be safe to use most of "unused" current allotment.

    I have not read the USB 3.0 specification thoroughly, but I suspect that to maintain backward compatibility with USB 1 and USB 2 devices, power can be handled in the same way.
     
  3. WBahn

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    Mar 31, 2012
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    What kind of "album" are we talking about? A CD? If so, then it is already a digital copy. What are the mechanics of your idea? It would seem that the case would have to have some kind of a USB plug either sticking out of it or have to be retractable in some way. It if is fixed sticking out, then making the package compatible with CD storage systems (even if they are just shelves) hard. Making them retractable increases cost. The the person has to plug the case into their USB port? That's gonna be pretty tricky for many people. You also need to consider the ruggedness of the packaging and how that will affect costs.

    Again, I'm thinking in terms of a CD jewel case because I can't think what other type of album you might be talking about. If you've got something else in mind, please straighten me out.

    It might be better to embed something like a micro-SD card and have a micro-USB device port in the case. Then you can keep the form factor of the CD case intact and compatible with other cases with no moving parts and you can use a standard USB cable to connect to it.

    How many of these do you think will be produced?
     
  4. cabers

    Thread Starter New Member

    Jul 30, 2013
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    album as in record, with cardboard sleeve, asnd yes it will have an extender cable tethering it to the sleeve.
     
  5. wayneh

    Expert

    Sep 9, 2010
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    Depth. You don't have much with an album sleeve. The infamous Sticky Fingers zipper comes to mind. But at least you could avoid the area of the square album cover sleeve occupied by the round vinyl. Still, I'm not sure the thinnest thumb drive guts would fit. I have seen "credit card" USB drives, so maybe.

    Do you hope to have LEDs within the round vinyl region of the album cover? I think this would also be a problem. SMD LEDs are thin, but they're not that thin once they're mounted on a PCB.

    Everything would be WAY easier if you made a fat album, like a double record album without the 2nd record. The thickness of a CD case would be much easier to work with.
     
  6. WBahn

    Moderator

    Mar 31, 2012
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    Well, that pretty much rules out doing custom silicon; you won't have any where close to the market base needed to overcome the non-recurring engineering costs. You may be able to do chip-on-board with off-the-shelf die.

    Depending on how much of the album cover you are hoping to place LEDs in, you have some other problems to consider. If they are over the vinyl itself, you are going to want the sleeve to be extra thick with recesses for the LEDs otherwise you will have pressure points against the record that will damage it pretty easily. Also, the LEDs have to be mounted on something and any something that is large enough to cover a good fraction of an album cover is going to be pretty expensive.
     
  7. trader007

    Active Member

    Feb 27, 2010
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    Just use a button cell battery. The SMD LED's wont light up so bright they blind you, but they will light up.
     
  8. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    They still make vinyl LP records? I had to check the date on the thread.
     
  9. LDC3

    Active Member

    Apr 27, 2013
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    Believe it or not. Some people believe vinyl records produce a better, richer, fuller sound (even with the pops and hiss) than CDs. I think it's a fad (like music on AM radio). ;)
     
  10. WBahn

    Moderator

    Mar 31, 2012
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    But not for very long. And the OP isn't talking about lighting up just one LED, but enough of them to produce something that can be considered "art".

    I did a quick experiment with some brand new Energizer 2032 coin cells. The fresh-out-of-the-package no-load voltage was right at 3.25V. I then took one of them and shorted it with a digital multimeter and initially got 600mA but this started falling immediately and rapidly.

    seconds mA
    0 600
    10 125
    20 96
    60 80
    90 70
    120 63
    150 58
    180 54


    The battery voltage immediately after removing the load was 2.72V and after 3 minutes was 2.86V. After three hours it had recovered only to 2.90V.

    With another battery I connected a green LED and it drew the following currents in the first two minutes:

    seconds mA
    0 53
    30 42
    60 38
    90 35
    120 34


    At the 5min mark it was drawing 33mA and the loaded terminal voltage was 2.22V. Of course, this is principally due to the forward drop of the LED. At the 10min mark it was 2.21V and the current was 23mA. At 15min it was 2.17V and still indicating 23mA. At the one hour mark the voltage was 2.16V and the current was 16mA. I suspect that I was getting influences from the meter when making the current measurements since I had to insert the meter into the circuit. To get minimum series resistance I was using the 10A scale, which has 1mA resolution on the readout. But that last digit is probably pretty shaky.
     
    Last edited: Aug 4, 2013
  11. WBahn

    Moderator

    Mar 31, 2012
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    It's a niche market with a few million sales a year -- worldwide.

    There are self-proclaimed audiophiles who maintain that a physical needle scraping across a piece of pressed plastic produces better audio quality than 16-bit digital does.

    I vaguely remember a story many years ago about a middle school student that did a double-blind study for a science fair project in which she had several people from some audiophile organization listen to a bunch of music. She had them supply the equipment and the records. She also got CDs of the same albums. She had one person from the audiophile group select a song and play both the LP and the CD versions (she had a person from the group do it because of the concerns members had regarding the proper treatment of the equipment and the records). Another assistant would flip a coin and select a switch position that would select which source was sent to the amplifier.

    But there was a hitch. The girl didn't tell anyone that the CDs fell into two catagories. They were all copies (no commercial physical CDs) but some were copies of the commercial CDs while others were recordings of the LPs.

    The results were that the audiophiles did have a pretty decent rate of identifying the true LP sources and the true CD sources as such. But their rate of identifying the CD recordings of LPs as LPs was basically identical to their rate of correctly identifying the true LPs.
     
  12. wayneh

    Expert

    Sep 9, 2010
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    IMHO, if they wouldn't mess around with the dynamic range when they "remaster" CDs, vinyl LPs would disappear because of their clear inferiority. But the music on an LP is different than the "same" music on a CD. A niche for LPs was created by the modern trend to "sausage" the music, reducing dynamic range in favor of loud-all-the-time. You can find plenty of examples where the waveform on a CD is actually clipped where the producer over-cranked the volume. Waveforms on many modern CDs look like a sausage instead of showing the typical ups and downs. Old vinyl LPs DO sound better.

    Some have dubbed this the iPod effect, as producers cater to the masses wearing cheap earbuds as opposed to audiophiles. Who knew that superior technology would lead to an intentional destruction of quality.
     
  13. cabers

    Thread Starter New Member

    Jul 30, 2013
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    Thanks for all the input and the testing you guys have done! Just to clear up the design concept, i was going to adhere the leds to the cardboard and use conductive ink to draw the traces. the leds would then be covered in a thin layer of epoxy to both diffuse the light emitted and to smooth out the surface and prevent snagging the diodes. ill post pictures of the proto when im done!
     
  14. WBahn

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    Mar 31, 2012
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    Have you tried that approach? Namely adhering SMD LEDs to a piece of cardboard and then trying to connect them with conductive ink? I would think that you would have a high failure rate, both initially and as the cardboard is flexed over time. How are you going to adhere them down while still keeping the contacts bare? It's an interesting approach and will be interesting to hear how well it actually works.

    How are you thinking of doing this in production? It sounds quite labor intensive and not too easy to automate.
     
  15. wayneh

    Expert

    Sep 9, 2010
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    You might want to look at something like this for ideas. I have one, and inside it has several LEDs on a flexible tape, including copper tape traces I believe. Might be a better approach than conductive ink.

    Electroluminescent tape would be awesome for your application, if you could solve the circuitry issue - you'd need a very low profile inverter.
     
  16. cabers

    Thread Starter New Member

    Jul 30, 2013
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    Oh cool application for the arm band. yeah i thought about el tape but the inverter would be impossible to size for this. I have a friend who can screen print conductive ink so im gonna use him for getting the traces down.
    caber
     
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