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Electronics USB power --> LCD power?

Discussion in 'Modding' started by bixie_62, 17 Apr 2006.

  1. bixie_62

    bixie_62 Minimodder

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    hey all

    dont know whether or not this has been discussed before, but is it possible to perhaps use a USB port as power for a graphic LCD?

    thank you
     
  2. Confused Fishcake

    Confused Fishcake Minimodder

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    As long as the lcd accepts 5V and draws less than 500ma, then yes. Otherwise, no.
     
  3. bixie_62

    bixie_62 Minimodder

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    how can you work out whether or not it draws 500ma?

    ta
     
  4. Confused Fishcake

    Confused Fishcake Minimodder

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    Power the device from a molex, or from some other high current 5V source, and connect an ammeter in series with the lcd. Do you want this lcd to be generally usb powered, or be able to power it from a specific port on your pc?
     
  5. bixie_62

    bixie_62 Minimodder

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    just generally usb powered, even if it means connecting up to 2 usb ports, im alright with that, as it'l still mean i dont have some nasty cable coming out of my pc powering the damn thing!
    will do the multimeter jobby later on and will post back

    thanx for your help!
     
  6. GuardianStorm

    GuardianStorm Minimodder

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    you coud make a blanking plate with a USB A or similar socket and have that socket hooked up to a molex for power, and a USB B socket on your LCD, cos then you can use a normal USB Cable.


    just dont plug other devices into it or *boom*
     
  7. bixie_62

    bixie_62 Minimodder

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    guardian storm, im intrigued at that idea, simple and effective...

    is it possible to pass 5v through a standard 3.5mm headphone jack without blowing it?! lol

    thanx

    edit:500 posts!! lol
     
  8. Confused Fishcake

    Confused Fishcake Minimodder

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    Easy, they can handle at least an amp or two at 5V.
     
  9. GuardianStorm

    GuardianStorm Minimodder

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    yeah, i have used 3.5mm Jacks to pwovide sockets of the lighting in my cases, and just look at ORAC3, that has more jacks than anything ever.
     
  10. JCG

    JCG What's a Dremel?

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    It's possible but be careful, if you pull it out when the power is turned on it can short.
     
  11. Rod10k

    Rod10k What's a Dremel?

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    Although it looks like you are going away from the idea of USB now I still figured that it would be worth saying.

    USB can supply upto 500ma per port but this is controled by the USB host. As standard a device is only allowed 100ma although it can request more. The host can also request a device to go into low power where is can only draw a few ma's. It seems that most manufacturers don't bother with this and just wire up 5v to the supply but it is worth knowing that plugging something into a USB port without enumerating the device could result in zero power.

    Rod
     
  12. GuardianStorm

    GuardianStorm Minimodder

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    you can disable that in windows, using the device manager and by calling up the properties for the root hub in question.

     
  13. bixie_62

    bixie_62 Minimodder

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    if i do use some sort of 'modular' method of attaching a socket to the front of my computer and a plug on the end of the power wire of the lcd....

    what kind would be most suitable?

    im going to completely rule out anything like a 3.5mm headphone jack as that may cause shorting, which i dont want....

    soo...i was looking at some usb ports ive got that are on the end of a wire, designed to be used as case ports, and was thinking....why not just use that as a power socket, have it wired up to 5v molex.....

    but its too easy for my brother or sister to come in and find a nice convenient USB port on the side my desk and plug their memory key's into that! not nice!

    so what kind of socket/plug design could i use?

    im leaning toward using 3 pin fan headers

    this would mean very little work for me! lol

    well, im going to try that later on tonight/early hours of the night after ive finished my work!
     
  14. GuardianStorm

    GuardianStorm Minimodder

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    why not use a power jack, like you get on all gadgets? there no more difficult to tire up...and you can short them out.

    if you dont know quite what i mean, look on 90% of plug bugs (wall adapters that get very hot) and on the end of their bit of cable...
     
  15. lizard.boy

    lizard.boy What's a Dremel?

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    you could go the 4pin mic jack route like ZapWizard used for his ammolan.. kinda hard to confuse one of those.
     
  16. Confused Fishcake

    Confused Fishcake Minimodder

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    As long as you connect the right usb pins to 5V and ground, it would not break any usb device plugged into it. Really, it won't.
     
  17. SteveyG

    SteveyG Electromodder

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    A standard 2.1mm or 2.5mm power connector would be most suitable for providing external power. Use the correct connector for the right application and you'll never have any problems with people damaging other devices.
     
  18. agent420

    agent420 What's a Dremel?

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    Unless this is a very large display, I wouldn't think the lcd should draw more than 500ma (most power is probably used for backlighting). I'd definitely test with a meter; you'll probably be able to get away with it. I also think that if the usb port can power a 2.5" mobile hard drive (like my WD Passport), it can power an lcd. Certainly this would be the ideal method if you are also communicating with the lcd via usb.

    If you do go the dedicated jack route, I think the power connector mentioned above is the preferred solution.

    I found this interesting article on usb power; specifically, scroll down to the last section 'Theory vs. Reality'.
     
  19. mingingbollock

    mingingbollock Minimodder

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    Hi Bixie , if the lcd you are planning to put onto usb is that 240x128 you got from me ?
    Be carefull because the backlight pulls 900mA :D
    Sorry dont know what the actual lcd pulls though , did i not give you a datasheet ?
     
  20. pccompuman

    pccompuman What's a Dremel?

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    ever think of useing an rca connector??
     

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