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  • #16
    Originally posted by Mike Amick View Post
    I doubt this is the case but technically it could have been designed to run for 30 min at 14amps.

    The fact that the battery level light is dim is pretty much all the proof you need that the supply you bought isn't making it.

    You can pick up a PC power supply for practically nothing, and have a 12v supply that will put out 20 or 30 amps.
    There is a tiny hack that needs to be made that is silly simple.

    If you don't like doing the small hack needed to the pc supply you can always buy this cool adapter that just plugs in and takes
    care of everything.

    https://www.wish.com/search/pc%20pow...on=0&share=web

    Oh, and I find it coincidental that I have a plug in tennis ball machine that I wanted to make battery powered, but isn't practical so am building my own.
    OK, so what is that tiny hack?
    “I know lots of people who are educated far beyond their intelligence”

    Lewis Grizzard

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    • #17
      You can buy a 12V 25 amp PSU for about $22.

      https://www.ebay.com/itm/153948943767

      A fairly simple and effective surge limiter is a series resistor across normally open contacts of a 12V relay, with the coil across the capacitor. When the capacitor reaches about 10 volts the relay will pull in and short the resistor, so it will not affect further load surges.
      http://pauleschoen.com/pix/PM08_P76_P54.png
      Paul , P S Technology, Inc. and MrTibbs
      USA Maryland 21030

      Comment


      • #18
        Originally posted by PStechPaul View Post
        You can buy a 12V 25 amp PSU for about $22.

        https://www.ebay.com/itm/153948943767

        A fairly simple and effective surge limiter is a series resistor across normally open contacts of a 12V relay, with the coil across the capacitor. When the capacitor reaches about 10 volts the relay will pull in and short the resistor, so it will not affect further load surges.
        Come on P. You know there is no metal in those light weight pieces of garbage.??

        A nice power supply will have some iron in it, no? JR

        Comment


        • #19
          As others have stated, batteries and battery chargers will often produce higher than their rated Voltage. The original battery would have had a low internal impedance so it would have been able to supply enough current at more than 12 V, even under load. And a battery charger must output a Voltage that is higher than that of the battery it is going to charge so it probably has an unfiltered output that reaches well above the nominal 12 V battery rating. This perhaps could be as high as 15 or even 18 Volts or more on the rectified but unfiltered AC peaks. If the machine needs a bit more than 12 VDC to operate, perhaps 13 V or so, then the battery and the charger would have no problem supplying that extra Voltage with full current.

          But the power supply you purchased is probably well regulated very close to 12 V and that may not be quite enough to operate your machine.

          Your power supply may have an internal adjustment which would allow the output to be adjusted to a higher Voltage. I suggest WITH THE POWER DISCONNECTED, you remove the cover and look for an adjustment. It may be labeled "Adjust" or "Out V" or something like that. Crank it all the way up and see if that helps.



          Originally posted by challenger View Post
          I have a tennis ball machine that I purchased a power supply for. The machine is supposed to be battery powered by a 12v 7ah battery. The battery went bad and it's convenient for me to use a cord. I ran the battery wires outside of the unit and powered it with a 4amp,old style, battery charger and it worked fine. I ordered a 7amp power supply and the unit runs but the low battery light glows and the feed tray won't rotate. Any ideas why this isn't sufficient power?
          Thanks
          Paul A.
          SE Texas

          And if you look REAL close at an analog signal,
          You will find that it has discrete steps.

          Comment


          • #20
            Originally posted by J Tiers View Post
            ..........Does the thing work if it has a real 12V battery connected to it?

            If so, can you measure the DC current it draws from the battery?

            Knowing not just the average current draw (is that 7A?), but some idea of how much it varies, would be very helpful in deciding what to do. The bare bones supply MAY be able to handle the load better than what it in the picture. It would still be helpful to know what the maximum draw is, to be sure to allow for that when setting up the supply.

            Yes. Hook it up to a 12V vehicle battery first just to make sure the amperage supply isn't the problem. If it works, check how many amps it draws and go from there.
            Location: Saskatoon, Saskatchewan, Canada

            Comment


            • #21
              Originally posted by PStechPaul View Post
              You can buy a 12V 25 amp PSU for about $22.

              https://www.ebay.com/itm/153948943767

              A fairly simple and effective surge limiter is a series resistor across normally open contacts of a 12V relay, with the coil across the capacitor. When the capacitor reaches about 10 volts the relay will pull in and short the resistor, so it will not affect further load surges.
              I'm under the impression that these switching type power supplies don't behave well in this type of application???

              Originally posted by Arcane View Post


              Yes. Hook it up to a 12V vehicle battery first just to make sure the amperage supply isn't the problem. If it works, check how many amps it draws and go from there.
              The machine runs fine with a lawn mower battery.

              I checked into making my own PS but a step down transformer is more expensive than a heavier duty power supply.

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              • #22
                Bring some potatoes and some vasoline and it becomes a party.

                -Doozer
                DZER

                Comment


                • #23
                  Originally posted by challenger View Post

                  I'm under the impression that these switching type power supplies don't behave well in this type of application???
                  .
                  Depends on the particular switching supply. I have a RF45 mill that is retrofitted to cnc. It has a 48V switching supply (HP server supply, 3KW) and runs all four servo motors just fine Servos are 48V, 750W brushless type.

                  On my bridgeport boss CNC retrofit I have AMC servo drives, BE25a20AC which have built in switching type power supplies, they run the OEM bridgeport servos just fine, those are close to 2HP brush type servos.

                  Comment


                  • #24
                    Originally posted by challenger View Post

                    ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,


                    The machine runs fine with a lawn mower battery.

                    ................................................
                    And there you have it.................

                    The power supply is, as suspected, just not up to the job. We can't be sure if it is voltage or current, but it clearly is not cutting the mustard here.

                    because it ran fine with a "4A old style battery charger", the issue may well be simply voltage, due very possibly to a protector intended to prevent the battery from being run down to zip. You might be able to adjust the PS up in voltage, but that packaged type generally has nothing you can get to without a lot of trouble and possible damage.



                    2730

                    Keep eye on ball.
                    Hashim Khan

                    Everything not impossible is compulsory

                    Comment


                    • #25
                      Originally posted by Dave C View Post

                      OK, so what is that tiny hack?
                      You have to jumper the "POWER GOOD" line to the always on "+5V_STANDBY" line. This tricks the supply into thinking that everything is working properly and drawing power. The pins for these signals varies from brand to brand, but the "POWER GOOD" wire is usually green in color, and the "+5V_STANDBY" is usually purple. It's a simple process to tp locate these wires.

                      Comment


                      • #26
                        Originally posted by SLK001 View Post

                        You have to jumper the "POWER GOOD" line to the always on "+5V_STANDBY" line. This tricks the supply into thinking that everything is working properly and drawing power. The pins for these signals varies from brand to brand, but the "POWER GOOD" wire is usually green in color, and the "+5V_STANDBY" is usually purple. It's a simple process to tp locate these wires.
                        Thanks SLK001, I didn't notice Dave's post. Good explanation of the hack. But I have to repeat that if you don't have a matching plug for the
                        PC supply you have to cut the plug off and handle all those wires separately. I have several of these adapter boards just for the ease of use.
                        You just plug the PC supply into it and your done. It supplies an on off switch. Fuses. And terminal hookups.

                        Click image for larger version

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                        John Titor, when are you.

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                        • #27
                          Fwiw I remember that I had made a bare bones power supply with an ammeter built in. I used this and the machine works great. The initial current is almost 8 amps but comes down to 2.5 running amps.
                          Also fwiw I took the two Amazon power supplies and put them in parallel and the machine still had the low battery light on and no feed tray operation. These are rated at 4 & 7amps for a theoretical 11amps. This "11" amps wouldn't cut it.
                          You may only view thumbnails in this gallery. This gallery has 1 photos.

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                          • #28
                            And you have just discovered one of the reasons why switching power supplies are all the rage.

                            And seriously, as I said in post #19, see if you can crank the Voltage of that 12 V supply any higher. It may only need an extra Volt or two and that can be your cheapest and fastest solution at this time.

                            And if it does not work, it will tell you and us something about the problem.



                            Originally posted by challenger View Post

                            ...<snip>...

                            I checked into making my own PS but a step down transformer is more expensive than a heavier duty power supply.
                            Last edited by Paul Alciatore; 10-17-2021, 08:58 PM.
                            Paul A.
                            SE Texas

                            And if you look REAL close at an analog signal,
                            You will find that it has discrete steps.

                            Comment


                            • #29
                              Originally posted by Mike Amick View Post

                              Thanks SLK001, I didn't notice Dave's post. Good explanation of the hack. But I have to repeat that if you don't have a matching plug for the
                              PC supply you have to cut the plug off and handle all those wires separately. I have several of these adapter boards just for the ease of use.
                              You just plug the PC supply into it and your done. It supplies an on off switch. Fuses. And terminal hookups.

                              Click image for larger version

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Views:	65
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ID:	1966393
                              Thanks for posting that ! I knew you could hot wire a PC supply and they make nice bench supplies BUT that board is so cheap and makes for a nice job. I just ordered 2 on Amazon for $9 total

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                              • #30
                                "But the power supply you purchased is probably well regulated very close to 12 V"

                                Yes they are, to the voltage. Curent output not so much

                                I have many bench power supplies. You wont see them. All on a wood bench.
                                0-550a. Ac and Dc.

                                My 12vdc PS weighs 60lbs. I dont move it anymore. She is set. Well it is not stuck at 12v eigther. Not much leay way on it for frequency.

                                Now? You want to amplify some sighnal at around 10GHz? I can modulate that right in there for you.

                                It will be a short burst you know, make it sweet, and short. We can only compress it so much. JR



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