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12v dc to 10v dc converter

Discussion in 'Power Electronics' started by Sich, Oct 1, 2018.

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  1. Sich

    Sich

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    Oct 1, 2018
    Hi
    Please keep answers in plain English, otherwise my understanding is going to run out, long before the answer does!!!
    I want to get a 10v dc supply from a car. Since this seems to be an unusual voltage, can I use two common 12v to 5v converters and just connect the outputs in series? If not, any easy solutions to get the 10v?
    Thanks for looking
     
  2. Kabelsalat

    Kabelsalat

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    Jul 5, 2011
    Good to see someone ask for a clean language, I'm not a native english my self, so urban non-standard expression (like cool words with appearently little or no meaning behind) make it hard to understand, even if the nature of the problem is very simple.

    What is your requirement of amperage and voltage stability? What kind of apparatus are you planning to feed these 10 volts into?
     
  3. Sich

    Sich

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    Oct 1, 2018
    Thanks for getting back so fast.
    It is just the power supply to a battery charger for a handheld radio/walkie talkie.
    The 240v supply that comes with it states 600mA output, so pretty low!
     
  4. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    If current is that low you may be able to do it with resistors, but as long as your above 12v, (12.5v min) I would recommend using a Lm7810 voltage regulator.
    It will give you a regulated 10v at up to about 2amps of current.
     
  5. Sich

    Sich

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    Oct 1, 2018
    Thanks. So a quick youtube search and that linear regulator seems easy to hook up. Do i need the smoothing capacitors i saw in a circuit? If so how do I calculate the size?..... I'm learning fast.....
    I'm guessing the current will vary greatly as the battery charges, so the resistor method might not work?...
     
  6. Tha fios agaibh

    Tha fios agaibh

    2,083
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    Aug 11, 2014
    The soothing caps are used to filter AC out.
    You're using DC.
    I always use a current limiting fuse for safety.
     
  7. kellys_eye

    kellys_eye

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    Jun 25, 2010
    You might struggle with the standard LM7810 regulator as the battery voltage may fall enough to prevent proper regulation. An LDO (low drop out) regulator would be preferred HOWEVER we need more details on the actual charger arrangement as the 10V requirement may not be a strict value.

    Google 10V LDO regulator to find lists and lists of them if you want to go that route.
     
  8. dave9

    dave9

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    Mar 5, 2017
    I wonder if this is worth the bother to make, when you can get a ready made product for about $3 USD delivered, though I don't know if it has the right connector (swapping the connector would definitely be easier than building the whole thing from scratch, plus those parts costs):

    https://www.ebay.com/itm/Car-Charge...Input-12V-or-24V-Output-10V-R7O5/332678364582

    You can find others on ebay by searching Beofeng 10V car charger or change Beofeng to the brand name of your walkie talkie.

    If you do decide to build your own with a linear regulator (whether it be an LM7810, or some LDO, etc), remember that you'd going to need a pretty good sized heatsink to dissipate the potentially 14.4V (engine running) down to 10V at up to 600mA = 2.6W heat. The one I linked "probably" avoids that much loss as heat by being a switching PSU.
     
    Last edited: Oct 1, 2018
    kellys_eye likes this.
  9. Bluejets

    Bluejets

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    Oct 5, 2014

    Attached Files:

    Last edited: Oct 1, 2018
  10. dave9

    dave9

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    Mar 5, 2017
    ^ The larger part of the project is going to be the enclosure, cabling, and connectors on each end, unless Sich happened to already have an adapter and the only problem was it is the wrong voltage so the PCB needed swapped.
     
  11. Bluejets

    Bluejets

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    Oct 5, 2014
    Enclosure problem can easily be overcome by simply encasing in a piece of heatshrink.
    Plenty of sizes available at elcheapo cost from Ebay.
    From memory for tube type they give the size as width = 1/2 circumference.
    Shrink usually about 2:1.
     
  12. dave9

    dave9

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    Mar 5, 2017
    ^ That hardly completes the project as a durable, mobile power solution.

    Yes you can just throw heatshrink tubing on something if you're going to hide it under the dash and put a panel mount socket on the vehicle, since nobody wants a cord permanently attached coming out from under the dash unless they're just trying to do it cheap and dirty and yet, it's not any cheaper in this case.

    You still have to buy wire if you don't have anything suitable (esthetics can come into play here, for example if I were desperate I could take a piece of CAT5 lan cable and use it, but that pales in comparison to the best wire for the job), then there is buying the lighter plug if it's not hardwired, or the fuse & holoder if it is (or if the lighter plug isn't fused) and the plug for the other end.

    It's easy to just say buy some $2 module xyz, and it's easy to do too. The harder part is the finer details of implementation in a mechanical and electrically durable manner. The same is true for most widgets one can buy on ebay/etc for under $10.

    You don't really want something fragile in a passenger vehicle subject to other people being in it that don't appreciate how fragile a heatshrinked blob on a wire is. Life happens, you can't control all the variables of what someone else can do in your vehicle.

    If it were the only way to get the job done, then the course is straight and the choices more narrow. When there are ready made solutions that cost less than the wire and connectors bought separately would cost (delivered), not so much.

    The electronics behind things like this are much simpler, at least to those of us used to doing that, than the entire finished assembly, and thanks to ebay chinese suppliers, cheaper too.
     
    Last edited: Oct 2, 2018
  13. Sich

    Sich

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    Oct 1, 2018
    Thanks all. I have everything i need. I'm going to do both. Buy a finished product for ease and make one for learning. I have two places that i can use. Thanks all for the help.
     
  14. Bluejets

    Bluejets

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    Oct 5, 2014
    One tens to give the Op credit for at least a minute amount of common sense and ability.
     
  15. dave9

    dave9

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    Mar 5, 2017
    ^ IMO this is a pretty common scenario. Many, many times I've considered a project and figured I could bang it out in an evening, but then once you get through all the finer details of implementing it... let's just say I have a lot of projects half finished, that work electrically but aren't cased up and suitable for exposure to any random person trying to use them.
     
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