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  • 12V DC Voltage Regulator?

    I have an external hard drive that I hook up to my car stereo that runs off of 12V, rather than using a 12VDC to 120VAC inverter and then the supplied AC->DC converter like I have in the past, could I use a simple Zener Diode circuit to regulate the voltage down to 12V like in first image on this link? Only use a Zener Diode with a forward current of 12V (example)? I'd have to size the resistor accordingly, the HDD states it consumes ~15 watts of power.

    I'd use a voltage regulator like the 7812, but they wouldn't work if the car was off and running close to 12V, they drop out around 13.7V or so.
    ----------------------------------
    Gear:
    Samsung PN50A650
    Yamaha RX-V2500
    Hafler DH-200
    AC130MKII/BG NEO3PDR Two-Ways
    RS390HF-4 w/ HPSA500

  • #2
    Re: 12V DC Voltage Regulator?

    I'd probably be looking for a buck-boost converter with an output set at 12VDC.. this way you wouldn't need to worry about input regulation. An example of one can be seen here: Dimension Engineering.

    The one I linked may just fit your bill @$25. I use their Anyvolt 3 as a benchtop supply for tinkering with the small stuff. These are a hell of a lot more efficient than anything you could do with a zener or something in the LM-78xx realm, and you'd get a solid 12V out even if your battery falls below 9VDC (your HD would run but your car wouldn't start... lol).
    ~Mark

    Stuff I've builded http://techtalk.parts-express.com/co...lies/smile.png

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    • #3
      Re: 12V DC Voltage Regulator?

      While a 7812 will not work, as you've stated... I have used LM317 variable regulators @ 12 volt in car with success. Even with the car off, a healthy battery should be approx 12.6v

      I used these to prevent dimming of LED lighting in vehicles with high draw stereo systems. (Example, LED license plate lights dimming durring a bass note.)

      To power a hard drive however, you might need something larger like an LM150? Having never tried one @ 12v out on a car circuit... I can't say what the working minimum input voltage would need to be...

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      • #4
        Re: 12V DC Voltage Regulator?

        Originally posted by WWWJD View Post
        I'd probably be looking for a buck-boost converter with an output set at 12VDC.. this way you wouldn't need to worry about input regulation. An example of one can be seen here: Dimension Engineering.

        The one I linked may just fit your bill @$25. I use their Anyvolt 3 as a benchtop supply for tinkering with the small stuff. These are a hell of a lot more efficient than anything you could do with a zener or something in the LM-78xx realm, and you'd get a solid 12V out even if your battery falls below 9VDC (your HD would run but your car wouldn't start... lol).
        Thanks Mark, that page states that it has a "1.2V typical dropout voltage, 2.0v maximum at full load" sounds like it suffers from the same problem as the ICs though.
        ----------------------------------
        Gear:
        Samsung PN50A650
        Yamaha RX-V2500
        Hafler DH-200
        AC130MKII/BG NEO3PDR Two-Ways
        RS390HF-4 w/ HPSA500

        Comment


        • #5
          Re: 12V DC Voltage Regulator?

          Originally posted by LSV8 View Post
          While a 7812 will not work, as you've stated... I have used LM317 variable regulators @ 12 volt in car with success. Even with the car off, a healthy battery should be approx 12.6v

          I used these to prevent dimming of LED lighting in vehicles with high draw stereo systems. (Example, LED license plate lights dimming durring a bass note.)

          To power a hard drive however, you might need something larger like an LM150? Having never tried one @ 12v out on a car circuit... I can't say what the working minimum input voltage would need to be...
          Thanks for the tip, what about something like this LM1577-12(.pdf warning)
          ----------------------------------
          Gear:
          Samsung PN50A650
          Yamaha RX-V2500
          Hafler DH-200
          AC130MKII/BG NEO3PDR Two-Ways
          RS390HF-4 w/ HPSA500

          Comment


          • #6
            Re: 12V DC Voltage Regulator?

            Originally posted by JustinG View Post
            Thanks Mark, that page states that it has a "1.2V typical dropout voltage, 2.0v maximum at full load" sounds like it suffers from the same problem as the ICs though.
            "Drop out" doesn't quite mean the same thing here; have a look at the ratings on the DE-SWADJ3:


            You'll get your 12V with an input voltage of 5-36VDC. Their drop out voltage is where the device ceases to operate predictably. Here's my bench supply; fed from a 12VDC meanwell supply, gives me anything I want out 3-24VDC:
            ~Mark

            Stuff I've builded http://techtalk.parts-express.com/co...lies/smile.png

            Comment


            • #7
              Re: 12V DC Voltage Regulator?

              Originally posted by WWWJD View Post
              "Drop out" doesn't quite mean the same thing here; have a look at the ratings on the DE-SWADJ3:

              You'll get your 12V with an input voltage of 5-36VDC. Their drop out voltage is where the device ceases to operate predictably.
              Thank for clarifying, what do you think of the LM2577-12? Looks to be what they are using in that regulator, and this way I might be able to make it a bit cheaper.
              ----------------------------------
              Gear:
              Samsung PN50A650
              Yamaha RX-V2500
              Hafler DH-200
              AC130MKII/BG NEO3PDR Two-Ways
              RS390HF-4 w/ HPSA500

              Comment


              • #8
                Re: 12V DC Voltage Regulator?

                That very well may be the same regulator used in the Dimension piece; I'm betting though that by the time you gather all the other components needed to finish off the supply (flyback trafo, resistors, caps, diodes, etc), you're gonna be at the same price point.
                ~Mark

                Stuff I've builded http://techtalk.parts-express.com/co...lies/smile.png

                Comment

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