Need help with transistor problem!

Discussion in 'The Projects Forum' started by learningslowly, Aug 8, 2010.

  1. learningslowly

    Thread Starter New Member

    Aug 8, 2010
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    Hello, i have been reading this forum for a while but decided to finally sign up because im in a bind. I am building this as a portable HV power source.
    http://www.555-timer-circuits.com/stun-gun.html

    It says i need a BD679 but unfortunatly the only place around here to get components is the local radioshack, or some old gutted electronics. I managed to get everything for this project together but i cannot find the transistor. The local radioshack had a TIP3055 so i grabbed it. Would this work? Thanks you for your help.
     
  2. learningslowly

    Thread Starter New Member

    Aug 8, 2010
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    0
    I actually stumbled upon this schematic, its similar but without the voltage multiplier. It uses a TIP31 which i can probaly get at radioshack. Would that work in place of the BD679?
     
  3. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    The TIP3055 has a much lower gain than the BD679. For this reason it might not be able to drive the transformer. Try one but replace the base resistor with a 100 R one. If it doesn't work, connect two of them in a darlngton arrangement.
     
  4. mik3

    Senior Member

    Feb 4, 2008
    4,846
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    The TIP31 comes with the same scenario as the TIP3055.

    Also, you have to place a diode in parallel with the transformer's primary winding to absorb the back EMF after the the transistor switches off. Do not use an ordinary rectifier diode but a fast recovery diode or a schottky one.
     
  5. learningslowly

    Thread Starter New Member

    Aug 8, 2010
    5
    0
    Alright ill give it a try, thanks for the help.
     
  6. bertus

    Administrator

    Apr 5, 2008
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    2,346
    Hello,

    For what are you going to use the circuit?
    Keep in mind that we want to keep stuff safe over here.
    The circuit can be dangerous when used in the wrong way.

    Bertus
     
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