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Where to find fixed power supplies of: -9V, +9V, and/or -5V

  1. Feb 22, 2009 #1
    Does anyone even make fixed power supplies of these values? I havent been able to find any so far.
     
  2. jcsd
  3. Feb 22, 2009 #2
    What's the application? Do you need bench supplies or something to supply power to a product? Should the +/- supplies be dual tracking? Should it take power from the AC lines?

    What are your current requirements?
     
  4. Feb 22, 2009 #3
    They would be used to power this circuit:

    http://www.tekscan.com/images/flexi-circuit-new.jpg [Broken]
     
    Last edited by a moderator: May 4, 2017
  5. Feb 23, 2009 #4
    I would just use some bench top power supply. You can get cheap ones from radio shack or expensive ones from Agilent.
     
  6. Feb 23, 2009 #5
    I'd use a couple 9 volt batteries. Buy the little snap on leads at radio shack. Apparently, that's why the drawing shows the op amp biased by +/-9V, which is not otherwise a common practice.

    Except for the fact that I took a look at the MCP6001 datasheet. It takes a single ended 5.5V maximum supply.

    There's something fishy about your drawing. It calls a feedback resistor a 'reference resistor'. This is enough to discard it as completely suspect, if you pulled it off a web page somewhere.
     
    Last edited: Feb 23, 2009
  7. Feb 23, 2009 #6

    MATLABdude

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    I second this suggestion (especially given your other thread). Unless you're trying to put this into production or semi-independent prototype, at which point, you might consider getting three regulators: two switching ones to regulate to +9 and -9, and then a linear one to do from -9V to -5V (e.g. LM7905)

    But I'd still use the bench power supply to prototype and ensure that it works. Learning how to (properly) use a bench power supply is an essential skill for an EE, especially an electronics-oriented one. It's also a skill they don't always teach you (or teach you very well in your early years)


    I saw something similar used in a circuit once. The gain equation is -Rf/Rs but since pressure is proportional to the conductance of the sensor (1/Rs), the output voltage (in this configuration) is directly proportional to the pressure on the sensor and Rf acts as a scaling factor (depending on your expected operating pressure range). Don't remember how great it worked out for them, though.
     
    Last edited: Feb 23, 2009
  8. Feb 23, 2009 #7
    k bench top power supply it is (and batteries wont work, I was told by the flexi force engineer).

    I know some of you have seen this, but is this power supply adequate, and are there any less expensive ones available?

    http://salestores.com/pr30trouposu2.html
     
  9. Feb 24, 2009 #8
    Seems pretty decent.
     
  10. Feb 24, 2009 #9

    MATLABdude

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    That's pretty decent. Specs and features look pretty good, though I'm not familiar with the brand. You can try eBay, but that might be hit or miss. Doesn't your school have something like this?
     
  11. Feb 24, 2009 #10
    "The engineer said..." And I say nonsense. Engineers grow on trees. Wait, they swing in trees. No, nevermind. :smile:

    The MPC6001 is a 1.8 to 5.5V device. And the circuit WILL work with +/-4.5 volts from 6 AA batteries. 4.5 volts for the op amp. -4.5V for the reference (the real reference, called V_T). 18 volts will fry it.

    Good grief, go buy a $350 bench supply instead.
     
    Last edited: Feb 24, 2009
  12. Feb 24, 2009 #11
    i would ask where they get their op-amps from. sometimes when one company makes "drop-in replacements" to compete with other brands, the actual product may be quite different.
     
  13. Feb 24, 2009 #12

    berkeman

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    Yabba-Dabba-Doo! That's the first time I've seen bikini models selling power supplies. Yeowza!

    What were we talking about again?.... Oh yeah. That power supply looks good for analog work, for one important reason.

    Quiz Question -- why would them saying it has a fan make me think this supply would be good for analog work? (Well, that plus the physical size for the powers listed....)
     
  14. Feb 25, 2009 #13
    Does the fan regulate the internal temperature within the power supply. Hence the instrument is less prone to temperature drift?
     
  15. Feb 25, 2009 #14

    berkeman

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    Not that. Look at the weight of the supply....
     
  16. Feb 25, 2009 #15
    Hmm perhaps another clue? Based on what I've seen in the past, it seems the fan is to control the ambient temperature within the instrument. Which could fluctuate as much as 30 degrees inside as compared to outside the casing.

    BTW: Have you checked your inbox?
     
  17. Feb 25, 2009 #16
    what do you think would be the heaviest thing in the box?
     
  18. Feb 25, 2009 #17
    I would think its the transformer coils.
     
  19. Feb 25, 2009 #18
    and what sort of DC supply design would use heavy transformers?
     
  20. Feb 26, 2009 #19

    berkeman

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    Only hate mail :biggrin:

    Good Quiz Question clue, Proton....
     
  21. Feb 26, 2009 #20
    I meant your inbox for this forum.

    I'll have to think about this one for a bit.
     
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