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Help with voltage regulator circuit, please

Discussion in 'General Electronics Discussion' started by Dust bunny, Oct 4, 2012.

  1. Dust bunny

    Dust bunny

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    Oct 4, 2012
    I have 12 volt lead acid batteries in a sailboat (charged by solar panels - up to 16 volts during equalization) and would like to power a WD Media player and a Wii from the 12 v supply.
    Both devices came with 110v adapters that output 12 vdc. Do I just need a simple 12 v regulator to make this work? (I have seen capacitors and other stuff - to smooth the supply, it said, but isn't the main 12 v batteries enough of a capacitor?
    WD media player needs 12 v 1.5 Amp
    Wii needs 12 v 45 Watts
    What parts do I need to make this work? Thanks for your time.
     
  2. BobK

    BobK

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    You can connect the devices directly to the battery. All you need is the power plugs to match the ones on the adapters.

    Bob
     
  3. robotalk

    robotalk

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    Oct 5, 2012
    Hm, I'll have to disagree with Bob on this one. Household appliances run on 120v AC power and plug into an outlet. Your battery is 12v DC. You need an inverter to change the DC current into AC current, like this one: http://www.cabelas.com/product/Boat...-inverters/_/N-1100565&WTz_l=SEO;cat104465880

    It's specifically made for boats. Hell I've never been on a boat, so it has a plug into a cigarette lighter too, but idk if boats even have those. But if they did, you could just plug it into the cigarette lighter. Otherwise you can attach it to you batteries terminals. If the appliance is more than 120w, it's better to attach it directly.
     
  4. Dust bunny

    Dust bunny

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    Oct 4, 2012
    Thanks Bob.
    What about protecting against over voltage during the day when the solar panels drive the voltage up - usually to 14.4 volts under normal charging and as high as 16 volts when 'equalizing' the batteries?
    I thought a regulator would limit the voltage, but have not seen a 12 v one that handles over 1 Amp at RShack.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    That would be a bad thing to do because Bob is right.

    He's not talking about plugging the adapters into the 12VDC source, but the devices to be powered.
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    That is a concern.

    Depending on your devices, they may be totally OK, or they may be negatively affected.

    The battery could possibly fall as low as 10.5V too...

    One option is one of the many devices available on eBay that do a double DC-DC conversion. Here is one option. If the total current requirements are less than 2A you could possibly get away with just one of these.
     
  7. Dust bunny

    Dust bunny

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    Oct 4, 2012
    I'm only concerned about protection from over-voltage while the batteries are being charged by the solar panels.
    If the voltage drops I can hand-start the diesel engine to charge the batteries - or just not use the devices.
    45 Watts at 12 volts is 3.75 Amps. If a 4 Amp regulator is available, is that all I would need?
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    See if there's a car power adapter for the wii
     
  9. BobK

    BobK

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    Yes, if you really need a stable 12V you would need a buck-boost type of DC-DC converter.

    Bob
     
  10. Dust bunny

    Dust bunny

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    Oct 4, 2012
    A buck boost converter multiplies the input / output value. I think like a transformer of sorts. I have 12.0 to 16 volt input range that I need to regulate an output of 12 volts. Don't I just need a voltage regulator?
    Rshack has 12 v regulators up to 1 amp, but I need about 5 amps (to handle 45watts at 12 vdc)
    Is reference voltage the same as dropout voltage? Is this why I have not found a 12 volt 5 amp voltage regulator?
    I think the Wii car adapter is merely a cigarette plug adapter with 12 v plug on the other end of the cord. Also a car's battery voltage does not go higher than 14.4 volts. I need to protect the circuit from 16 volt solar panels during battery equalization.
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    The 12 volt regulator of which you speak requires a minimum of about 14V (perhaps more at high currents). At the battery voltage falls below this, the output voltage will droop below 12V
     
  12. BobK

    BobK

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    A 12V regulator will not work with 12V in, much less with 11, or 10. A buck boost DC-DC converter can take a voltage lower or higher than 12V and output 12V regulated.

    Bob
     
  13. Dust bunny

    Dust bunny

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    Oct 4, 2012
    Sounds great. Any leads to where I can locate one? All of the buck boost converters I've come across 'step down' 24 volts to 12 or 12 down to 5 etc.
    Can they handle varying input voltages, say, 11 to 17 volts? (Output 12 volts)

    Many thanks for your help!
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Didn't you look at this the first time I pointed it out to you?
     
  15. Dust bunny

    Dust bunny

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    Oct 4, 2012
    Yes, thanks, I did Steve. Two points though; As I stated, I need something that can handle 45 watts, this unit only handles 25 watts. Secondly, isn't part of the objective in electronics tinkering and this projects forum to create solutions that don't cost a ridiculous $60 plus dollars to solve a $10 problem?
    I don't intend to be rude. I very much appreciate your input and time. I just thought there was a 'simpler' method of regulating 12 volts.
     
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Getting a regulated source of 12 volts from a voltage source that is either very close to 12V, or which can range from lower than 12V to higher than 12V is technically quite difficult.

    As for the power required by the Wii, I would check to see if there is a cheap option available on eBay. If there isn't, then we can start talking about how we could put something together.

    Here is an option. I didn't spend too long looking, so there may be cheaper options. I would recommend something capable of 20-30% more current than you require just to keep it operating happily.
     
  17. BobK

    BobK

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    You might try using a low dropout regulator and regulating down to 11V or so. The devices are likely to operate okay at 11V and this would allow your battery to keep powering them down to about 11.5V. You would need a 5A regulator.

    This one might do:

    http://www.datasheetcatalog.org/datasheet/sipex/SPX29503U5.pdf

    Or, if you want real cheap, and don't mind manual intervention, wire up a string of 4 or 5 diodes that can be switched in and out as needed, and a meter to monitor the voltage. Just switch in all the diodes when the battery if fully charged, then switch them out one at a time as it drops.


    Bob
     
  18. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Also, if your battery is also used to supply an electric starter motor and/or an ignition system, you may need some clamping and/or filtering on the 12V supply going into the regulator/charger, to suppress spikes and surges due to load dump and ignition noise.
     
  19. Dust bunny

    Dust bunny

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    Oct 4, 2012
    Thanks for your help. The 60 Watt DC/DC adapter you found, Steve looks like it would work. Ideally I was hoping to make something smaller than the 'brick' this uses. Space on a sailboat is at a premium, so if we could come up with something smaller I'd be very happy.
    I guess from the start I was thinking along the line of a voltage regulator like BobK has found. Thanks Bob. At night the boat's batteries never drop below 12.1 volts. I'll see if I can find out what the minimum voltage the Wii will operate at.
     
  20. davenn

    davenn Moderator

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    Sep 5, 2009
    There are some really nice 12VDC input ATX power supply boards out there
    I use one to power some of my radio equip that requires a fixed 12V even tho the input to the PSU can vary from 10.5 to 15VDC ( or more)

    like this one http://www.mini-box.com/DC-DC

    cheers
    Dave
     
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