Electronic – mini Tesla PN2222A transistor getting hot

transistors

I am helping my son make a mini-Tesla for his science fair project and came across a problem I can't figure out. I am following this diagram (pretty much, but without the LED):

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Also, I am not sure of the exact number of windings – around 300 of 27 AWG wire. I have experimented with 2 to 6 primary coil windings and can make this work with 3 windings of the primary coil. My problem is that I have burned up two transistors already – not right away, the circuit works and I can turn a bulb on but the transistor is getting VERY hot. Why? Do I need

  1. fewer or more primary windings?
  2. a different type of transistor?
  3. a heatsink?
  4. a different value resistor or an additional resistor or capacitor (don't ask, but I have seen other versions of this mini Tesla)
  5. just need to buy more tansistors and hope for the best?

Thanks in advance.

LTR

Best Answer

See Understanding the slayer exciter circuit base voltage for a full explanation, but you are basically abusing the transistor in two ways:

  1. By leaving out the diode, you're forcing the B-E junction into reverse breakdown whenever the base tries to go negative.

  2. The 2222 is a small transistor, only good for a few hundred milliwatts of dissipation. It's hard to say what this circuit needs, but it could be considerably more. And issue #1 is only making matters worse.

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