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12v voltage stabilizer?

Discussion in 'General Electronics Discussion' started by wopachop, Sep 10, 2013.

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  1. wopachop

    wopachop

    47
    0
    Jul 22, 2012
    Hi everyone im not very advanced with electronics but hoping and willing to learn. Sorry if i use the wrong terminology at times.

    I have some basic 12v LED strip lighting. Would like to run it off an automotive battery. But the problem is during charging the led strip is receiving around 13.5 volts and that is not ideal for lifespan and heat.

    Im familiar with Constant Current Led drivers. Also familiar with AC to DC Constant Voltage 12v converters. Neither of those work well for this setup.

    But what about a simple 12volt stabilizer? Something that will supply the LED strip with 12-12.5 volts when the input is varying between 12-13.5v?
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    Your 12V battery will vary between 10.5V (dead flat) up to 14.8V (on charge).

    That range is typically VERY bad for cheap LED strips.

    A linear 12V regulator will typically require about 2V more than its output voltage (i.e. 14V, so that's not a good solution). Low dropout regulators may require only 0.5V, but still you have problems as soon as the battery voltage falls below 12.5V.

    This is actually a classically difficult problem where you have a device that requires X volts and the power supply varies from less than to greater than X volts.

    The best solution would be a boost power supply to increase the voltage to (say) 18V, and then a constant current source to supply the correct current.

    If the LEDs are in parallel and have their own resistors then a boost (to 18V) followed by a buck (to 12V) would be an ideal solution.

    For relatively low currents (say to a couple of amps) there are some fairly cheap devices you can purchase
     
  3. wopachop

    wopachop

    47
    0
    Jul 22, 2012
    Love it!! Thanks so much. Im following what youre saying. Physical size of the components matters. Yes the LED strip has the built in resistors, you can cut them every 3 LEDs. They are ready for a constant 12volts. How do i boost it to 18v and buck it down to 12v?
     
  4. wopachop

    wopachop

    47
    0
    Jul 22, 2012
    Alright! Thanks Bob check out that little sucker. Very interesting so you can turn a little screw called a potentiometer and adjust the voltage.

    Thanks for the link is that a friend of the forum or just the first link you found? I would buy one from him to show support. If not i will sniff them down and buy direct from china. Any other places to buy cool little LED drivers? I checked digikey. I know of them and mouser.

    Im open to all info people want to throw at me. Been researching on my own for a couple years. I build lights just for fun to use when we go camping so our trailer batteries last longer. I bought some 12-24 input PWM dimmers to use with rigid 12v led strip. But i was confused, and it turns out the input and output voltage is the same for the dimmer. I thought it was gonna be a steady 12v output that would dim by the PWM pulse.

    I dont mind if the led strip gets below 12 volts. Maybe a low dropout regulator would be a good choice? Does it hurt a low voltage regulator when the battery starts getting closer and closer to matching the voltage of the LED strip?

    Really excited to learn all this stuff is very interesting and extremely useful in the real world.
     
  5. wopachop

    wopachop

    47
    0
    Jul 22, 2012
    Im blown away. Looks like they also sell it as an adjustable step-down power supply. It loses the Boost feature. That might be the one right there.

    Also seeing a mini version the size of a nickel. Just need to learn if they will be ok as the voltage drops down below 12v.
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
  7. wopachop

    wopachop

    47
    0
    Jul 22, 2012
    How would you rate this newer mini dc-dc converter? It says max efficiency is 95%. Wonder what it would get when set to 12.0 volt output and the input is 12-14v.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    That does step down only. It won't work if your input voltage falls below 12V
     
  9. wopachop

    wopachop

    47
    0
    Jul 22, 2012
    Will it stop working completely? Or will the output voltage just continue to drop with the supply voltage?
     
  10. wopachop

    wopachop

    47
    0
    Jul 22, 2012
    Got a reply from the seller on ebay. He said if the Input voltage falls to 11.5v, and my Output setting is set to 12v, i will get nothing.

    Bummer. This is awesome though you guys have helped me a ton! There has got to be a cheap way of knocking that 14volts down to 12v. The buck/boost converters are a little too big and expensive to make it a good choice. Im happy there is a solution at least.

    What else? Have we reached the limits of current technology?
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    It will drop.

    As long as the input voltage is sufficient to power the regulator itself, the output voltage will be only very slightly less than the input voltage.

    At some point it will start to drop further under load, and finally it will turn off. At this point you also risk overheating the mosfet and killing the regulator depending on your load (probably not for a string of LEDs though)

    This regulator will do a reasonable job of coping with over-voltage though.
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    I would be very surprised if this is the case.

    However, maybe you can assume he knows what he's talking about.

    Maybe.
     
  13. wopachop

    wopachop

    47
    0
    Jul 22, 2012
    MAYBE!!!

    Steve thanks so much for the responses.
    I have bought quite a few LED drivers now. Sorta wasting money coming from a guy who does not have much to spare.
    Im going to buy some of the Mini Step Down converters. I can use them on a different project that is running a 9v LED with the same automotive power source. But i really hope they work with the 12v rigid strips.
     
  14. wopachop

    wopachop

    47
    0
    Jul 22, 2012
    I got some of the Buck/Boost voltage converters that Steve Linked. Im using them with a PWM dimmer to power some 12v lights.

    Im getting a pretty loud feedback sound at certain levels. What causes this and is there a way to get rid of that noise?

    My input is around 12.5 and the output around 12v. The noise is loudest when the PWM dimmer is around 75%. If i drop the output to 11v the noise goes away. Im thinking it has something to do with the input and output being close to the same voltage.

    Is there a little electrical component i can solder on to absorb whatever is causing this noise?

    Or does anyone have a link to a different voltage regulator? I dont need the adjustable feature. A constant 12v output would be ideal.

    Thanks again for any help! I've been having a ton of fun playing around with these voltage regulators.
     
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