Small Supply Needed

Discussion in 'General Electronics Chat' started by DC_Kid, May 20, 2008.

  1. DC_Kid

    Thread Starter Distinguished Member

    Feb 25, 2008
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    i am in search for a small kit that produces -+9volt (100ma) from +12v. nothing fancy needed. i need this to fix a goof i made on some boards i have.

    anyone know of any kits out there?
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
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    How about an LM7809 for the + and an LM7909 for the negative?
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    That or 5 diodes in series, something like a 1n4001. They should drop approx 3V.
     
  4. DC_Kid

    Thread Starter Distinguished Member

    Feb 25, 2008
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    regulators? where do i get the - voltage from?

    the Linear LT1054 can give me the negative side, but i would have to make a board for the components. was looking for a off-the-shelf item that i could just pop in the components, solder, done...., etc.
     
    Last edited: May 20, 2008
  5. Wendy

    Moderator

    Mar 24, 2008
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    How much current do you need? The 555 makes a dandy voltage doubler/convertor, if that is what you're looking for. The 78xx and 79xx regulators could take it from there.

    I made the same mistake ThingMaker did, the usual convention for a dual power supply is +/- instead of -+.
     
  6. DC_Kid

    Thread Starter Distinguished Member

    Feb 25, 2008
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    i wasnt really looking for which components, but rather a off-the-shelf ready made pcb.

    i can use the LT1054 in bi-polar supply doubler mode. i can feed it the +5 from my lm7805. i may be able to get the 12 needed components onto a small copper-land perf board, wire it by hand, and then encapsulate it with some MG epoxy i have. it will do the job, but as i mentioned, was looking for a ready-made pcb, perhaps one that has the layout for this LT1054 dupply doubler, etc.

    i goofed on my op-amp power supply, so now i need to come up with a small "daughter" card that can supply +/- 9v (>5v, <-5v)
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Do you need 100 mA at -9 or is the negative voltage just for bias?

    My recent experience with Maxim chips (non-inductor, capacitor switch) is that you can get the -9V at 5 mA (e.g., MAX850 series)or -5 V at 125 mA (MAX 1680 series). If you really need -9 at 100 mA, you can cascade two of the MAX1680s (see datasheet). John
     
  8. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    How many of these pop-in adpaters do you need? Have you seen the SMD-IC adapters that have a bunch of solder pads for adding components. You can also add pins so you get a plug-in device. I can't find a brand on mine. I may have gotten them from Jameco. John
     
  9. DC_Kid

    Thread Starter Distinguished Member

    Feb 25, 2008
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    op-amp(ina114) supply is +/-2.2mA, and i have 6 of them.

    i need 30 "fix that error" boards.

    i know there are those perf boards that have strips of lands connected together and then you just cut across a track to make the circuit, etc, forget its name though.
     
  10. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    They are not perf boards. Jameco part#215491 is just one of many examples. They are 1/32, fiberglass, with a nice pattern for the IC and just lands that you could add the caps too with appropriate shorts (zero-ohm SMDs ?). In catalog 274, it's page 206. I have used a few of them. Of course, making 30 would not be fun. John
     
  11. beenthere

    Retired Moderator

    Apr 20, 2004
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    There was a +DC - -DC converter on the market some time ago I recall it was an ICL7660. The negative voltage got developed on a 10 uF tantalum cap. It mirrored the positive input, with a limit of 10 volts, so you would have to reduce the +12 (assuming you can find one). Jameco is the catalog of last resort.
     
  12. SgtWookie

    Expert

    Jul 17, 2007
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  13. DC_Kid

    Thread Starter Distinguished Member

    Feb 25, 2008
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    you guys are awesome.

    muRata just too expensive at ~$14.

    the LT1054 was about $4 and needed 12 components total to net me 2v and -(2v)

    the ICL7660 for about $1pdip ($0.63 for smt)with a couple of caps and diodes will net me ~2v and -(v) outputs, which will get me ~9v and -5v. perfect.

    thanks guys, you are saving my prototypes from becoming fancy coasters. now i just need to find those strip pc boards. the bottom side has strips of lands all soldered together, then to cut the strips to create the circuit....
     
    Last edited: May 21, 2008
  14. DC_Kid

    Thread Starter Distinguished Member

    Feb 25, 2008
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    now i have to choose diodes and caps.

    1. i have 1N4148's (200mA), are they ok?
    2. caps? i have large supply of 22uF/25V electrolytic? are these ok? i see ripple is a factor of C2 ESR. my IA's are filtered well on the + supply pin, i'll have to add a filter cap to the - supply pin.


    i'm building figure 20, page 10.
    http://www.jameco.com/Jameco/Products/ProdDS/1139469.pdf
     
    Last edited: May 21, 2008
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