Help with Drawdio

Discussion in 'The Projects Forum' started by tjb1, Nov 16, 2010.

  1. tjb1

    Thread Starter New Member

    Nov 16, 2010
    Im having problems making this stupid Drawdio. Im currently in school for manufacturing engineering so I know nothing of electronics and im not the best at soldering so I thought I would try this to get a start. Not very happy at this point because I have about $25 in the stupid thing when a kit is $18 but at this point its just about finishing it.

    Here is what I was trying to follow -

    Seems that it is from a british site so many of the items they have referenced cant be found easily in the US but heres what I got

    2 - .0022uf 100V Ceramic Disc Capacitors
    1 - 10k Resistor
    1 - BC559 which translated to a 2n4258 I believe
    1 - 3VDC Mini Buzzer (I think this is the source of many of my problems...I cant find a sounder anywhere)
    and finally I dont know how I screwed this up but I got the US equivalent of the BC548 which should be 2n3906 but I got the 2n3904 which is the NPN version appearently and I have no idea what that means or what effect that would have on this.

    And if you watch the video how they make it sound with pencil lead or by touch or the sink with running water, I can do none of that. The only way I can make the buzzer sound currently is by touching the wires directly to each other. Please help me save this before I destroy it :)
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    Schematic is here

    Do you have photos of what you have so far?

    Do you have a schematic that you are working from different from the one I linked in this post?
  3. Wendy


    Mar 24, 2008
    What is it?
  4. bertus


    Apr 5, 2008
  5. Audioguru


    Dec 20, 2007
    A 2N3904 and 2N3906 transistors have a low max current rating and will probably blow up if they try to drive a speaker.

    Transistors do not work properly if their pins are connected backwards.
    The pins on BCxxx European transistors are reversed on 2Nxxxx American transistors.
  6. tjb1

    Thread Starter New Member

    Nov 16, 2010
    So the middle pin would stay the same and left/right change? Would that be the case on both I mentioned and would the difference in the 2N3904 and 2N3906 make this not work?

    And no I do not have a schematic nor can I really read one at this point, I was just basically copying the solderless plans but soldering them together instead of the screw block.
  7. Audioguru


    Dec 20, 2007
    Simply look at the photo and pinout of the transistor you use on its datasheet.
    A transistor will not work properly and might be damaged if you connect its pins backwards.

    Then you better use exactly the same parts that are shown until you learn how to read a simple schematic.
  8. martinthompson

    New Member

    Nov 20, 2010
    Sorry, yes, it's a UK list of parts. If you do get it working, let me know what bits you've used and I'll update the BOM to have a UK and a US set of bits.

    That last part is probably very significant - you don't want a buzzer - you need a pure sounder. Can you send a link to what you have - see if it *is* suitable or not?

    This part looks like it might do the trick:

    You can see the schematic at I did actually use a 2n3904 and 3906 pair (as my American simulator didn't have any BC548/558s in :) You do need one of each, and they do have to go the right way around. You'll have to get datasheets for all four, and compare them to see which leg is which on the ones you have.

    Hopefully, with all the right bits, you can make it work. It's a lot easier trying things out with screww strip, rather than soldering BTW :)

  9. retched

    AAC Fanatic!

    Dec 5, 2009
    Well that should straighten things out.

    Have you driven yourself completely crazy with the Drawdio?

    I could imagine the number of "pencil stabbings" to go through the roof if too many kids started using drawdios. ;)