Split DC input into three voltages

Discussion in 'The Projects Forum' started by tonewill, Nov 12, 2010.

  1. tonewill

    Thread Starter New Member

    Nov 12, 2010
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    Hello to you, I have an old circuit (drum machine salvaged from an old organ) that I'd like to get working. It requires three voltages: +15v, -28v and -14v. Ideally, I'd like to use something like a 30v DC adaptor/wall wart and make a circuit using vero-board to convert it to these voltages (or thereabouts). Is this feasible? If so, any suggestions, books, websites, online circuit diagrams that would show how to do this? I'm not very knowledgeable about electronics though I've built several projects over the years. Any help appreciated, Barry.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Do you have an idea of the power requirements of this circuit?

    You don't have your location in your profile. It will help us to help you, if you provide at least your country and state or province.

    Click on the "User CP" link on the menu bar, scroll down to "Location", type in your location info, and click the "Save" button at the bottom.
     
  3. tonewill

    Thread Starter New Member

    Nov 12, 2010
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    Thanks SgtWookie, The only power requirements I know are the voltages mentioned; I don't know how much current it uses although I imagine if I assume 1A then I should be well within requirements. I've just been looking at circuits for +15v and -15v using L7815CV and L7915CV regulators, however, they all use a centre-tapped mains step-down transformer where I'd like to keep the step-down isolated in a wall-wart for safely. I'm just not sure if it's possible using, say, 30VDC input (or maybe 30VAC are available if that helps). Thanks for trying to help, much appreciated.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Is this a transistorized circuit, or does it use valves/tubes?

    Since you're in the U.K., electronic components will be rather pricey.

    You might be able to use a discarded ATX or ATXplus12 computer power supply to get +12v and -12v; which is fairly close to the +15/-14 supply - still need the -28 though.
     
  5. tonewill

    Thread Starter New Member

    Nov 12, 2010
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    Thanks SgtWookie, It's a transistor circuit. The cost of parts aren't the problem (a few diodes, capacitors and regulators aren't that much here), the problem is knowing if and how to get the three voltages from a wall transformer. If anyone can offer advice on that it would be much appreciated.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Well, standard linear regulators just won't work very well with a single 30v wall-wart. You'd need to use switching regulators, and I don't know how much experience you have.
     
  7. tom66

    Senior Member

    May 9, 2009
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    Components are very cheap here in the UK, Wookie. Not much more than in the USA. I order from Farnell and Rapid Electronics.

    You could also try my ATX power supply mod (on this forum) which converts a +12V ATX into +28V -28V or thereabouts. Then, some regulators could be used to step the voltages down to +15/-14.

    Or you could try a buck-boost converter. The MCP34063A may be an option, for inverting the voltages.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    Well, the ATX mod is dicey at best; not something I'd recommend for a "n00b" to attempt. You're bypassing some of the internal protections, and operating the supply at beyond it's design limits. Unless someone has an identical power supply, their results will vary widely.
     
  9. tom66

    Senior Member

    May 9, 2009
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    Yes - I know that. However, any non-standard power supply is dicey at best, because we do not know requirements like output current, transient response, ripple voltage and so on.
     
  10. tonewill

    Thread Starter New Member

    Nov 12, 2010
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    Okay chaps, not to worry, I'll investigate more. Doing a computer power supply mod is okay if you have an old supply lying around, but I don't unfortunately. Thanks again, Barry.
     
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