Need Help on a Throwie Driver

Discussion in 'The Projects Forum' started by Scrixx, Jan 20, 2010.

  1. Scrixx

    Thread Starter New Member

    Jan 19, 2010
    Hello there I wanted to create LED throwies which are wirelessly powered.. power

    I found this and have been wanting to make one, I'm new at electronics and a bit confused on the driver schematic..

    Not really sure which components to use and how to connect them together =/.
    Here's a few questions:
    What is the U1 at the bottom left?
    What is the 10n at the bottom of the schematic?
    What is the 1n that is right on top of it?( 1microfarad capacitor? )

    I'm very confused and if anyone could help explain the connections of the components and which ones they are I'd really appreciate it. Thank you.
  2. SgtWookie


    Jul 17, 2007
    U1 is the 555 timer.
    That is a 10 Ohm resistor.
    That is a 1 nanoFarad capacitor.
    1nF = 0.001uF (microFarad)
    1nF = 1000pF (picoFarad)

    Hopefully, the information provided is sufficient. If not, don't be afraid to ask more questions.
  3. Scrixx

    Thread Starter New Member

    Jan 19, 2010
    Thank you, it helped, But I'm still confused about the U1.. so is it the type of 555 chip?

    And also the zigzag lines represent resistors right?

    5k Ohm?

    27k ohm?

    Then I searched the IRF540 and mosfet. I'm not quite sure how to attach that.. Does the middle pin attach to the 10ohm resistor and the left pin to negative part of the supply and the right pin to the positive terminal of the supply?

    I attached a redo of the schematic into more of something I could understand. Is it connected alright?

    All the +5vs in the original means they all connect to the positive end of the supply and the three lines mean that it's connected to the negative end?

    Thank you for helping.
  4. Chris15

    Active Member

    Apr 15, 2009
    OK throwies are fun with slingshots i admit it

    If you want your throwie to flash it is a bit more complex but possible of course

    The simplest form of throwie is just a 10mm led connected directly to a 3v button cell battery with tape or watever (dont solder to the battery)

    Or if you want to use a 555 timer to oscillate you can but i beleive this circuit is simpler an maybe more efficient

    The fuzzy lines are resistors when there is a 'R' at the end of some numbers this means the resistance in ohms (Ω) if there is a K e.g '100K' this means 100 k ohms 1Kohm is 1000 ohms

  5. Wendy


    Mar 24, 2008
    The 555 timer generates a square wave, an AC signal. This in turn drives the transistor, which in turn drives the coil. The coil has an AC magnetic field around it.

    555s are pretty simple to use, but if you make a mistake you can let the smoke out. They are also pretty cheap, Radio Shack marks them up pretty dramatically.

    If you do use a battery with this circuit make sure it is a big one, it will get sucked dry pretty quickly. You'll note the links you used use a computer power supply, which is major overkill (but cheap to run).
  6. SgtWookie


    Jul 17, 2007
    With the MOSFET oriented so that the writing on the face of the package is visible, pins towards you:
    Left pin is #1, gate
    Middle pin is #2, drain
    Right pin is #3, source
    The tab is #4, also connected to #2, drain

    The gate (left pin) gets connected to the 10 Ohm resistor.
    The drain (middle pin and/or tab) gets connected to the coil.
    The source (right pin) gets connected to ground.

    5k Ohms is not a standard value of resistance. However, you can use a 4.7k or 5.1k resistor; it will work just fine.
    A table of standard resistance values is here:
    Bookmark that page. The E12 and E24 values are most commonly used by hobbyists.

    You can order the E48 through E192 values if you really need them, but you'll usually pay more for the extra precision.
  7. Scrixx

    Thread Starter New Member

    Jan 19, 2010
    Thank you, but my goal was to power the throwies wirelessly via the driver circuit. So I guess it's not really throwie..

    I pretty much have it worked out thank you everyone.

    Two questions though.

    Would it be possible to combine resistors to get a 27k Ohm? Radioshack doesn't have 27k Ohm resistors =/

    Would it be possible to use a IRF510 mosfet instead of the IRF540 mosfet? Radioshack doesn't have the IRF540 but they have IRF510..

    And could someone verify if I connected the wires alright in the redo of the schematic? ( I just redid it so that it's easier for me to follow )

    Thank you for your help everyone.

    EDIT: Would 22k Ohm resistor work in replacement of the 27k Ohm?
    Last edited: Jan 20, 2010
  8. SgtWookie


    Jul 17, 2007
    You could use a 22k and a 4.7k resistor in series to get 26.7k.
    You could also use a 4.7k resistor for the 5k, which is not a standard value.
    A 5.1k would work too, but you might not be able to get those at Radio Shack.

    The notebook you linked to didn't give much of an idea about the "work coil" - no dimensions, number of turns - nothing. Radio Shack does sell 100uH RF chokes that might work, though.

    I simulated the circuit; see the attached. I re-drew it because your connections to pin 3 and pin 4 were a bit muddled in your drawing. I added S1, a power switch (you might want to add one as well).

    The IRF5x0 series are rated for a Vdss of 100v. The original circuit did not have any reverse-EMF protection diode; the inductor would quickly exceed the breakdown voltage of the MOSFET and could destroy it.

    D1 is a 12v Zener diode; the exact voltage is unimportant. Radio Shack used to sell both 5.1v and 12v Zeners; don't know if they still stock them in stores.

    The 1N5401 is a 3A power rectifier diode. You could use any 1N400x series diodes if you have them. A 1N914/1N4148 would not work, though.
  9. Scrixx

    Thread Starter New Member

    Jan 19, 2010
    Thank you!

    Everything is cleared up :D

    I really appreciate the help.