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Did any one read the article in Nuts and Volts by Chris Savage about Mixing Voltage — Parallax Forums

Did any one read the article in Nuts and Volts by Chris Savage about Mixing Voltage

sam_sam_samsam_sam_sam Posts: 2,286
edited 2011-04-09 05:50 in General Discussion
Systems - Interfacing 5 volts and 3.3 volts Devices

Very well writen article

Please make a link to this info when you can Thanks

Comments

  • PublisonPublison Posts: 12,366
    edited 2011-04-01 11:25
    Yes, That article should be added to the interface Sticky. Nice one Chris!!
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-04-01 13:01
    There's a thread in one of the stickies that talks about 3.3V to 5V interfacing. It kind of rambles and it's hard to know which of the ideas are good ones. It leaves the impression that a 1K resistor is all that is needed to interface with a 5V circuit. I'm pretty sure the recommended resistor value is closer to 3K (for the Propeller).

    Chris's article is much nicer. It should take the place of the thread used in the sticky.
  • wmosscropwmosscrop Posts: 409
    edited 2011-04-03 00:29
    Duane Degn wrote: »
    It leaves the impression that a 1K resistor is all that is needed to interface with a 5V circuit. I'm pretty sure the recommended resistor value is closer to 3K (for the Propeller).

    Duane, I've been using a 1K resistor on a 5V input (from a GPS receiver) for several months... no problems.

    I believe that somewhere in the previous discussions the issue is not voltage but current... and a 1K resistor is sufficient for keeping the input current at "safe" levels.

    In any case, a clear and consise guide on this subject would be welcome!

    Walter
  • tonyp12tonyp12 Posts: 1,951
    edited 2011-04-03 10:54
    I think it should be mentioned that they make IC that take care of this problem.
    http://www.mouser.com/ProductDetail/NXP-Semiconductors/74AHCT245D118/?qs=sGAEpiMZZMs9F6aVvY09bk%2ffb8R74De%2fPssnRSrNzv4%3d

    smaller 2bit
    http://www.mouser.com/ProductDetail/NXP-Semiconductors/GTL2002DP118/?qs=sGAEpiMZZMsty6Jaj0%252bBBr%252ba7pY41EA16CnqyfpH0m4%3d
  • Beau SchwabeBeau Schwabe Posts: 6,566
    edited 2011-04-03 12:25
    Great job Chris!
  • $WMc%$WMc% Posts: 1,884
    edited 2011-04-05 17:24
    This was a great write-up.
    '
    I printed this down and added it to my Engineering/hobby note book.
    '
    Great info Mr.Savage, Well done.
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2011-04-05 17:57
    I went out and a copy to read the article. Good job Chris!

    I came across another IC that can be used 74HC4050 (or CD4050)
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2011-04-06 08:34
    I haven't had a chance to get to the store to grab this... It is posted online somewhere yet?

    OBC
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2011-04-06 09:26
    Jeff,
    I doubt that it is available online since it is in the April issue but I too would like a digital copy for posterity...

    $WMc% said he printed it - maybe he found it or scanned it.

    <edit>
    Even thought I don't subscribe, I managed to view it on line http://nutsvolts.texterity.com/nutsvolts/201104/?folio=46#pg46
  • PublisonPublison Posts: 12,366
    edited 2011-04-06 09:39
    Jeff,

    Try this:

    http://www.nutsvolts.com/index.php?/magazine/article/april2011_Savage

    I don't know if it just works on my machine, because of the memorized Digital Issue login.

    Oldbitcollector (Jeff) wrote: »
    I haven't had a chance to get to the store to grab this... It is posted online somewhere yet?

    OBC
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2011-04-06 10:39
    I'm thinking that Parallax has the authorization to post these on their website, perhaps it will be there soon. I was able to see the first couples pages. This could very well be the best article I've seen in N&V this year. I'll definitely pick up a copy on my next trip out to Akron. Silly to keep buying it off the stand 20 miles away, bit it does give me a good excuse to hit the bookstore. :)

    OBC
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2011-04-09 05:50
    I was reading over this article again. Chris mentioned that when using a series resistor:
    If your device does not include clamping diodes, you should not use a series resistor to interface to the 5V signal. While the 3.3V device may appear to function, it will eventually fail from electrical stress.

    Does a voltage divider circuit provide more protection than just a simple series resistor?
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    Ron,

    This message is old, but I just ran into it looking for something and thought I would go ahead and answer that for anyone else who may stumble across this and wonder the same thing.

    The single series resistor is designed to limit the current, not the voltage of the signal. The voltage divider is dividing and therefore limiting the voltage of the signal.
  • RS_JimRS_Jim Posts: 1,764
    edited 2016-12-06 14:26
    Any chance of getting a link to the article?
    Jim
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    You have to be a subscriber to view the online edition of the magazine, however I had this article on my website until the fall of the vBulletin software. Once I get the new site populated it will be available from www.savagecircuits.com again. Just been moving and still have so much packed.
  • RS_JimRS_Jim Posts: 1,764
    let us know when Savagecircuits.com goes live again!
    Jim
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    The website is live, just not fully populated. When vBulletin failed for Parallax they migrated the database to this software. I didn't even know what I was going to do, so I manually backed up all my information by copying and pasting the text into notepad documents, saving the images and attachments and taking screenshots of the various pages.

    I have been slowly putting stuff back up using Joomla, but ran into a snag when some hacker found a way to shut down my website. Now I'm moving, but should be able to get back to it slowly over the next couple of months in between repacking things.

    http://www.savagecircuits.com
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