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2.4v PSU for electric screwdriver

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    2.4v PSU for electric screwdriver

    My sis gave me a cheap B&D cordless driver a few years ago. It never would hold a charge for long even on the shelf but I used it anyway for a couple of years. I like the size and weight of it and having pretty bad arthritis in my hands it was sorely needed.

    First the spring for the ac prong release button broke and started poking out, which I removed before it had the chance to short the ac main. Then the batteries died and wouldn't charge.

    I removed the batteries and charger board and soldered two wires directly to the direction/power switch and the motor works fine although a bit fast from two 1.5 flashlight cells as the motor is rated for 2.4v. I want to convert it to a corded driver. I don't need cordless while working on my bench and don't want to have to wait for batteries to charge in order to use it either.

    I tried a few different PSUs, wall-warts, etc. but nothing would supply enough stall current to get it turning. I did some current readings, it pulls over 3 amps at stall and 1.5 amps free running. I use an old Delta 145w ATX PSU on my bench for powering drives etc. and decided to try the 3.3v output to run the screwdriver, which worked.

    I don't want to burn the motor out with over voltage so I connected a 3 amp silicon diode in series and it dropped the voltage near perfect to 2.45v. This is fine for the time being but I'd like to build a PSU into the handle of the driver and just run an ac cord to the outlet but haven't had luck finding an appropriate circuit.

    #2
    Re: 2.4v PSU for electric screwdriver

    Maybe try to find a 5V, 2A, 2.5A, or 3A AC power adapter. Those should be somewhat more common (usually they are for some modems and routers). Most regulate the output voltage with a 431 shunt and opto. Just remove bottom resistor in the 431's feedback network, and that should give you 2.5V. You may also have to swap the output rectifier, though.

    3A @ 2.5V is 7.5W, so an adapter like that should have no problem.

    Comment


      #3
      Re: 2.4v PSU for electric screwdriver

      http://www.dx.com/p/lm2596-digital-d...rk-blue-360654

      Comment


        #4
        Re: 2.4v PSU for electric screwdriver

        Thanks for the tips guys.

        The LM2596 looks good, the only concern I have is the stall current going over 3A.

        Comment


          #5
          Re: 2.4v PSU for electric screwdriver

          i'll go look for something more powerfull then

          Comment


            #6
            Re: 2.4v PSU for electric screwdriver

            The inrush current will be a lot higher than 3A.
            Never stop learning
            Basic LCD TV and Monitor troubleshooting guides.
            http://www.badcaps.net/forum/showthr...956#post305956

            Voltage Regulator (LDO) testing:
            http://www.badcaps.net/forum/showthr...999#post300999

            Inverter testing using old CFL:
            http://www.badcaps.net/forum/showthr...er+testing+cfl

            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
            http://s807.photobucket.com/user/budm/library/

            TV Factory reset codes listing:
            http://www.badcaps.net/forum/showthread.php?t=24809

            Comment


              #7
              Re: 2.4v PSU for electric screwdriver

              10A
              http://www.dx.com/p/10a-dc-cnoverter...-supply-214277

              15A
              http://www.dx.com/p/15a-dc-4-32v-to-...gulator-219807

              Comment


                #8
                Re: 2.4v PSU for electric screwdriver

                Bud: Exactly. I know the meter can't show the inrush current fast enough so it's got to be well over the 3A I saw. I could lock the screwdriver and measure it but don't want to burn anything out.

                stj: I need to go ac to dc, not dc to dc. Using one of those I'd still need to run it off a separate PSU. So I may as well run it off the ATX PSU with the diode It's just a little clumsy is all. I'm not sure if a transformer to work that will fit in the handle exists.
                Last edited by SteveNielsen; 12-15-2014, 10:26 AM.

                Comment


                  #9
                  Re: 2.4v PSU for electric screwdriver

                  I think by the time you get all the parts, it will be a lot more than that B&D is worth.
                  Never stop learning
                  Basic LCD TV and Monitor troubleshooting guides.
                  http://www.badcaps.net/forum/showthr...956#post305956

                  Voltage Regulator (LDO) testing:
                  http://www.badcaps.net/forum/showthr...999#post300999

                  Inverter testing using old CFL:
                  http://www.badcaps.net/forum/showthr...er+testing+cfl

                  Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                  http://s807.photobucket.com/user/budm/library/

                  TV Factory reset codes listing:
                  http://www.badcaps.net/forum/showthread.php?t=24809

                  Comment


                    #10
                    Re: 2.4v PSU for electric screwdriver

                    well i have a really nice electric screwdriver with lithium-ion battery's that cost me £15

                    Comment


                      #11
                      Re: 2.4v PSU for electric screwdriver

                      My desire is to not use batteries at all.

                      Anyway, thanks for the input guys, you've helped me realize doing what I want is not practical nor cost effective.

                      I'll just use it as a "screwdriver workstation" using the small ATX PSU and diode. I can put the PSU out of the way.

                      Comment


                        #12
                        Re: 2.4v PSU for electric screwdriver

                        That's similar to what I did with a cordless 9.6V drill I had. Except I wired it to a Xbox 360 PSU. Still works fine, though I could have used thicker wire (20 AWG wire actually heats up a bit with a few amps of continous load on it). Link of the ugly mess here:
                        https://www.badcaps.net/forum/showth...705#post294705

                        Anyways, I'm pretty sure the 5V adapter will work. Most will shut down and restart if your stall current is too high, so no need to worry about the inrush current too much. If you really are, just add a 2200 uF cap or two in there, and that will do it.

                        Or you can use the setup you have now. In that case, I'd say just run it straight up on 3.3V. Pretty sure the little motor will take it just fine. Most can take up to 4 to 5 times their rated voltage and they will still work. Post a picture of it if you want.
                        Also, run a 3rd extra wire to your desk (or to the screwdriver) and hook it up to PSON on the PSU's end. On the screwdriver's wire, put a little switch between that wire and ground. Now you can turn ON the PSU easily as you pick up the screwdriver and then turn it OFF when you are done using it.
                        Last edited by momaka; 12-17-2014, 12:12 AM.

                        Comment


                          #13
                          Re: 2.4v PSU for electric screwdriver

                          Not sure what 5v adapter you mean.

                          Here's a pic of the motor.
                          Attached Files

                          Comment


                            #14
                            Re: 2.4v PSU for electric screwdriver

                            looks just like the one in my old bosch screwdriver - RIP.

                            Comment


                              #15
                              Re: 2.4v PSU for electric screwdriver

                              Jeez, I took the thing apart again to get that picture and had pita experience getting it back together. I have no idea why as I had zero problem with that before. Plus I put the motor in backwards so the polarity reversed at the switch! I guess I'm getting dumber by the day now Actually the trick I finally figured out was having the pinion in the gear cluster, not on the motor shaft.

                              It's ok tho' I have to take it apart again to replace the short leads with a cord.
                              Last edited by SteveNielsen; 12-17-2014, 03:38 PM.

                              Comment


                                #16
                                Re: 2.4v PSU for electric screwdriver

                                Originally posted by SteveNielsen View Post
                                Not sure what 5v adapter you mean.
                                I meant you can use a 5V power adapter rated for 2A to 3A. 2A and 2.5A adapters tend to be somewhat common. Look in a pawn shop or yard sale next time and you might just find one.

                                Originally posted by SteveNielsen View Post
                                Here's a pic of the motor.
                                Typical 380-size motor (you can see that on its label). Those can usually take A LOT more than 2.4V. Well, I guess it depends on what size of wire they used for the rotor inside (the thicker the wires, the rated voltage would be lower and stall current current). But these tend to be quite common in bigger toy RC cars that run on 7.2V and 9.6V batteries. So up to 12V will likely give it no problems. You'll just have a supper fast screwdriver .
                                Last edited by momaka; 12-17-2014, 10:32 PM.

                                Comment


                                  #17
                                  Re: 2.4v PSU for electric screwdriver

                                  dont overdrive it unless it has a variable clutch, you'll just end up stripping threads!

                                  Comment


                                    #18
                                    Re: 2.4v PSU for electric screwdriver

                                    Thanks for the info guys. I'm just going to use it 2.4v, normal speed is fine for me. Even at 3.3v it seems nearly twice as fast, too fast for what I want.

                                    Comment


                                      #19
                                      Re: 2.4v PSU for electric screwdriver

                                      use this power supply and adjust the voltage to that what you exactly need. The power supply has a voltage adjustment.
                                      http://www.dx.com/p/5v-3-8a-regulate...41#.VJNd7ZACDA
                                      here is another one:
                                      http://www.aliexpress.com/item/5V-10...508775940.html
                                      Last edited by CapLeaker; 12-18-2014, 05:17 PM.

                                      Comment


                                        #20
                                        Re: 2.4v PSU for electric screwdriver

                                        if you back up and read the thread you will see we did the DX stuff.

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