Impulse DIY fuctions for cordless screwdriver power tools

Discussion in 'The Projects Forum' started by smilem, Jan 5, 2013.

  1. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    Hello, I have an idea to make the impuls function on a makita brand cordless screwdriver.
    It is very handy to unscrew old bolts, or to drill to shiny surfaces like tiles.

    Unfortunatelly the impuls is metabo "inovation" - if you can call pulsed power to the motor inovation. It is available on few cordless drills, and I have one of them that's when I understool how handy this is.

    You can see a video here how the impuls function works
    http://www.youtube.com/watch?v=86l4Ft_xAr0

    Is is possible to design a simple circuit with power fet, etc to pulse the power to the motor?
    I'm sure a power fet, capacitor to select pulse cycle lenght and some other parts would make this doable for DIY project.
     
  2. NFA Fabrication

    Member

    Aug 12, 2012
    104
    3
    Watched the video. I don't see how this is beneficial in any way. I seems like the guy is just making up reasons why it is beneficial as he goes along. I am an automotive fabricator by trade, and this just seems gimmicky to me.
     
  3. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,869
    1,393
    "Impuls" seems like ultra-slow PWM.
     
  4. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    I don't know how it seems it really helps, it is patented so other manufacturers do not want to pay for a patent so they do not have this feature. Before I got the Metabo LTX I have damaged many screws by using regular type makita, bosch screwdriver. At the end I needed to drill the screw head and use pliers to remove it (from wood etc.)

    The Pulsating action makes it easy to unscrew:

    1. screws with damaged head (rusted etc.)
    2. crews with flat type head

    It also helps at drilling holes into tiles or surfaces where drill bit can slip. It's not a gimmick.
     
  5. vrainom

    Member

    Sep 8, 2011
    109
    19
    I agree that there are circumstances where pulsed output is helpful. Even using the torque control can be useful to take out stubborn screws.

    It should be easy to implement, a 555 and a mosfet could do the trick.
     
  6. NFA Fabrication

    Member

    Aug 12, 2012
    104
    3
    I don't see how the pulsing magically gives a screwdriver bit better traction on a questionable screw head, or keep a drill bit in place. But either way, this would be really easy to implement using a 555 as your pulse generator and a FET or something that could handle the motor load.
     
  7. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    I have made this other schematic myself by googling some MOSFET motor control examples and 555 timer circuit. However my simulator just blows everything up ;/ could somebody simulate this?
     
  8. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,869
    1,393
    The schematic looks good to me, except that I don't know what D2 is for. And I don't use simulation software, but I think I have all the parts to breadboard the circuit. What is the pulse rate range you have designed for?
     
  9. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    D3 and R3 combined make the MOSFET turnoff veeerrry slow. How about moving the switch?
    Also, the diode needs to be across the motor, not across the MOSFET.
    You should also add a series gate resistor, as close to the MOSFET as possible, to prevent oscillation.
     
  10. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    D2 is to protech the MOSFET as described here
    Simple Power MOSFET Motor Controller

    http://www.electronics-tutorials.ws/transistor/tran_7.html

    I would be grateful if you could breadboard this :D The pulse range is 2 a second so thats 2hz maybe 4hz
     
  11. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    Yes the diode across the motor before the switch did the trick now the back EMF does not spike and blow the MOSFET on my circuit.

    Your circuit works fine except I want to turn off the 555 timer when pulse is off the batteries would be dead if left on forever.
    My switch position is not optimal, perhaps there is a better place ?
    Perhaps the screwdriver switch would turn off the 555 timer, because i off state the drill is off :confused: so the real switch is not like in diagram it can be off (neutral position)
     
    Last edited: Jan 6, 2013
  12. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,869
    1,393
    I built the breadboard (without the switches) and it functions fine with an LED on pin 3 of the 555 and another LED on the drain of the IRLZ44. However, when I connect the motor, the pulse rate from the 555 runs full speed. I am guessing noise on the Vcc.
     
    Last edited: Jan 6, 2013
  13. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    Every drill I have seen has a power switch and a forward/reverse switch. You have added a function, so it seems like you would need another switch.
    Of course, most also have a speed control built into the trigger, along with the power switch. Not sure how you would incorporate that into the impulse function. It seems like you would want to control the impulse rate, but I don't know how you could do that, and still maintain the speed control function when impulse mode is off.
     
    Last edited: Jan 6, 2013
  14. AfdhalAtiffTan

    Active Member

    Nov 20, 2010
    117
    11
    If memory serve me right, the drill speed control circuit utilises a SCR to control its pulse width.

    So, maybe the 'impuls' function could be added to control the SCR's gate.
    Requiring no further mod...
     
  15. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    I'm not sure what SCR is but I wonder has somebody some example (all drill switches are the same more or less).
    If modded externally the warranty would not be void so that is a plus for external mod.
     
  16. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    When you push the switch you vary the speed and torque (how many amps go to the motor), the MOSFET 555 timer circuit would simply turn on or off the battery pack that would result in pulsing action like in the video.

    If you want slow pulsing you push the switch just a little bit, if you want strong pulses push some more. I would not like to modify the switch if possible because of warranty issues and because the switch is sealed on most models very hard to take it apart without damage. Some are filled with epoxy so once you open it you find out that all the work was for nothing.

    I'm sure fitting SMD style parts for 555 timer and a singe MOSFET in any size screwdriver is possible. You can't use dre drill in pulse mode unless in specific conditions arise that means you will not use it for long periods of time - no overheat to the MOSFET, but small heatsink should be used I think.
     
  17. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    Hmm, what could be done to make the circuit work then?
     
  18. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,869
    1,393
    I added a .1 μF cap across the power pins of the 555 and put 2000 μF across the motor leads, which helped some, but not enough. Separate power supplies would work, but that's not practical.
     
  19. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
  20. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,869
    1,393
Loading...