Power for TTL circuit

Discussion in 'The Projects Forum' started by jgessling, Sep 28, 2014.

  1. jgessling

    Thread Starter Active Member

    Jul 31, 2009
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    I'm gearing up for my second TTL project. One of the issues that bugged me before was power. I had taken a nine (sorta) volt wall wart and ran it through a DM317 to get regulated 5 volts. Never really liked this since it put out a lot of heat, made the heat sink really warm. This time I was thinking that since USB is 5 volt that might be an option. I have an apple iPad charging thingy and it puts out about 5.1V (no load) with up to 2.1A output. That's plenty of amps but I wonder about the voltage regulation. Will this be OK? Sure would be convenient. Thanks for any thoughts.
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Best I can say is to try it. A battery charger may be able to handle more ripple then TTL will, but 5.1V no load is safe for the logic.

    Some extra capacitance may one day be necessary so keep that in mind.
     
  3. ronv

    AAC Fanatic!

    Nov 12, 2008
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    You may be more careful than I am, but I wouldn't let some of my circuits close to my usb port, :)
     
  4. DickCappels

    Moderator

    Aug 21, 2008
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    The +5 on USB is +5V±0.25V, which is compatible with TTL, provided you don't have a significant voltage drop in the cable leading from the USB connector.
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    Think old phone charger.

    Or a 6VDC battery with a silicon diode and Schottky diode forward biased. This will make a 5V source.
     
  6. jgessling

    Thread Starter Active Member

    Jul 31, 2009
    74
    14
    Thanks all. What I've got is an Apple phone charger that also works on iPad so it's got more "oomph" but same voltage. Nice to hear from Bill he's helped me and many others.
     
  7. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Think of a Thrift store as a source of ready-made, cheap, well-regulated wall-wart power supplies. My local Habitat for Humanity Thrift Store sells odd wall-warts for $1. I always check there when I am in town. Bought two just last week...
     
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