Announcement

Collapse
No announcement yet.

DC power supply

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • DC power supply

    Any recommendations for a 12 volt, 25 amp DC power supply?

    It's to run a DC gear motor with 25 amp max draw.

    Speed control is not a factor, just on/off running.

    TIA.
    Len

  • #2
    If you're not running it full time, a deep cycle battery and a cheap charger could get you there for not too much cash. Otherwise lots of the computer power supplies will supply that.

    Igor

    Comment


    • #3
      That's only 300 watts at 12v...

      John
      My Web Site

      Comment


      • #4
        Pick up a suitable wattage Toroid Transformer from Antek, if they don't have the correct rating, put your own winding on, only ~24 turns needed with 50amp bridge, no capacitor needed to run a DC motor.
        Max.

        Comment


        • #5
          One of the roll around battery charge car starter like the car lots use might do it. Schumacher makes one that advertises 200/100/40/10/2 amp.
          I have one that runs 7 50watt 12v lights on my pier so I didn't have to run 110 in conduit along the water.


          bedwards

          Comment


          • #6
            The thing to watch with battery chargers is only use the most simplest/basic types, controlled charge types, and the ones that sense the charged voltage may not work.
            Max.

            Comment


            • #7
              Even the simplest types may not be a good idea.

              I went through this last year wanting to use my 12v chain saw sharpener (CSS) in my shop and tried using an older battery charger to power it. The motor in the CSS sounded noticeably rough compared to running it off a battery. Don't have an oscilloscope to measure how smooth the 12v supplied was but I suspect it was not a very constant voltage as a battery wouldn't care.


              Steve

              Comment


              • #8
                Originally posted by SteveF View Post
                Even the simplest types may not be a good idea.

                I went through this last year wanting to use my 12v chain saw sharpener (CSS) in my shop and tried using an older battery charger to power it. The motor in the CSS sounded noticeably rough compared to running it off a battery. Don't have an oscilloscope to measure how smooth the 12v supplied was but I suspect it was not a very constant voltage as a battery wouldn't care.


                Steve
                That's why Igor said to get a charger AND A 12 V BATTERY. The battery acts like a filter instead of using capacitors. And besides, battery chargers are designed to ... wait for it ... wait for it ... wait for it ... CHARGE BATTERIES. They are optimized for that task and it should be no wonder that they may not be good at directly powering a motor.

                I also like MaxHeadRoom's transformer and rectifier suggestion, but you will have to package them in something.
                Paul A.
                SE Texas

                Make it fit.
                You can't win and there IS a penalty for trying!

                Comment


                • #9
                  Originally posted by ikdor View Post
                  Otherwise lots of the computer power supplies will supply that.

                  Igor
                  Yep - you can get a cheap or used computer power supplies just about anywhere. However, keep in mind that the wiring harness and connectors may not be rated for 25 amps. Computer supplies have several pigtails coming out and most range from 5v to 12v. The supply is designed to deliver it's power distributed over all of these pigtails so to get one tap at 25 amps, you may have to break into the box and attach heavier gauge wires to the 12 volt rail or make other modifications. I've got a 500 watt computer power supply around here somewhere that has a 12 volt 20 amp pigtail, which would probably get you close enough if your motor is driving a large load continuously.

                  Comment


                  • #10
                    This is usually where I start looking when I need a dedicated power supply.:
                    http://www.mpja.com/Power-Supplies/departments/1/

                    If you want to go cheap though, a PC power supply ought to do the trick with just a little hacking.

                    Comment


                    • #11
                      +1 on the PC power supply. A single rail supply rated for 450 watts should give you between 30 - 35 amps on the 12volt rail.
                      plus give you a source for 5 & 3.3 volt as well. Check the label on the side of the supply - It should give you amperage for the
                      various voltages on the side of the case.
                      As shewlaces said it takes a little hacking (leads/jumper for remote on/off sw.,etc.) but it's not difficult.
                      I cut it twice, and it's still too short!
                      Scott

                      Comment


                      • #12
                        PC power supplies are typically high current for the 5v, the 12 is rated at very much less, typically 8 - 12 amps.
                        Personally I would never use one for a DC motor controller.
                        Max.

                        Comment


                        • #13
                          I think I'd opt for the computer power supply as well. You can take all the 12v output wires and parallel them to get the current. Also parallel the negative wires. You don't have to break into the box at all. But you will need to ensure that the current rating on the 12v output is high enough. Normally you would want a large excess current factor- if the motor is going to draw 25 amps, the supply should be rated at at least 30 amps.

                          You could opt for the brute force, transformer, rectifier, filter approach, but it will take tens of pounds of parts and will certainly cost. It's easy to get various voltage outputs from a power supply, but where the current requirement is more than 5 amps or so, especially in the 20+ amp range, the parts need to be very beefy.

                          I would look at the required duty cycle of the motor first, and base the solution on that. A battery and simple charger could be the most viable way to go.
                          Last edited by darryl; 01-01-2013, 07:47 PM.
                          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                          Comment


                          • #14
                            The power supply I looked at (just an old spare I have kick'n around)
                            is rated 33 amp on the +12 rail, 34 amp on the +5, and 28 amp on the +3.3
                            for a max combined load of 450 watts, and a 60 sec. peak load of 570 watts.
                            It is (or was in it's day) a quality unit. OCZ brand , Single rail supply.
                            The old split rail units have a lower amperage output per rail but have mulitple rails.
                            I cut it twice, and it's still too short!
                            Scott

                            Comment


                            • #15
                              See if you can find some ham radio operators in your area, especially ones that own/operate repeaters. I have 4 12v, 50amp continuious duty power supplies stacked in my shed. If you were closer I'd let you have one for scrap $$, but I think shipping would be prohibitive........

                              Just my $0.02

                              Comment

                              Working...
                              X