Solid State Tesla Coil Circuit


Similar to the two transistor solid state Tesla Coil
already on this site, this solid state Tesla Coil design uses a normal
flyback transformer to generate it’s high voltage output. Unlike the
other circuit, this one does not use two huge power transistors and high
wattage resistors. Instead it uses a 555 timer to more efficiently
drive a single MOSFET. It’s waveform has adjustable off and on time,
making for an efficient circuit with little waste heat. It can be
adjusted to drive most commonly found flyback transformers and can
operate from a 12V to 18V supply. HV output can reach 60KV or more
depending on the transformer and supply voltage.

Schematic

Schematic of the Solid State Tesla Coil

Parts

Part
Total Qty.
Description
Substitutions
R1, R5, R9 3 180 Ohm 1/4W Resistor
R2 1 10K Pot
R3, R7 2 10 Ohm 1/4W Resistor
R4 1 5K Pot
R6 1 7.5K 1/4W Resistor
R8 1 150 Ohm 1/4W Resistor
R10 1 1 Ohm 5W Resistor
C1 1 0.0047uF 50V Polyester Capacitor
C2 1 0.05uF 50V Polyester Capacitor
C3 1 220uF 25V Electrolytic Capacitor
C4 1 0.01uF 1200V Polyester Capacitor
Q1, Q2 2 2N2222 NPN Transistor 2N3904
Q3 1 SSM5N55 MOSFET
U1 1 555 Timer Integrated Circuit
U2 1 LM7809 9V Linear Regulator
L1 1 100uH Choke Coil
T1 1 Penn-Tran 1-017-5372 Flyback Transformer See Notes
MISC 1 Board, Wire, Case, Socket for U1, Heatsink For Q3, Output Terminal (See Notes)

Notes

  1. T1 as specified in the parts list is going to be almost
    impossible to find, but don’t worry. Penn-Tran was bought by Wiltron and
    no longer exists. However, most any medium to large flyback transformer
    will work as long as it does not have an internal rectifier. Suitable
    units are most often found in TVs made during the 1970s and 1980s. Look
    for the most impressive, dangerous, menacing transformer you can find.
    If you need an idea, a picture of a great transformer for use in this
    circuit:

    Nice flyback tranformer for HV circuit use

    These can be found in a small metal box generally in the corner of
    the TV case, complete with a very handy voltage multiplier unit and
    usually a nice heatsink.

    You will need to either look up the datasheet for the transformer
    you have, or probe it with an ohmmeter to identify the coil
    connections. Most flybacks have a load of taps on the HV side to provide
    focusing, horizontal and vertical signals. These taps are generally of
    no use to you. To find the primary (coil B-A on the schematic) you need
    to find the two lowest resistance connections that are not also
    connected to the HV secondary wiring. Alternately, if your flyback has
    an open frame like the one in the picture, you can wind on 5 or so turns
    of 16 gauge magnet wire as a primary. You will need to experiment with
    the number of turns to get maximum output. The HV ground lead
    (connection C on the schematic) is generally easy to locate. It will
    come from the HV secondary and be tied to the frame of the transformer
    or chassis ground.

    If by some miracle you were able to locate the Penn-Tran
    transformer, then connection B is the red dot on the transformer, A
    corresponds to the black dot, and C matches the orange dot.

  2. If the TV you salvaged the transformer from has a voltage
    multiplier unit (visible slightly at the far right of the above
    picture), then take it as well. It can multiply the output of this
    circuit into very high (over 100KV) DC voltages.
  3. When building the circuit, leave the flyback disconnected.
    Connect a 10 Ohm 10W resistor in place of the primary of T1 and connect a
    scope to the collector of Q3. Adjust R4 to produce an off time of about
    10 microseconds. Adjust R2 for an on time of about 70 microseconds. Now
    remove the scope, 10 ohm resistor, and connect up T1. Power the circuit
    back on and you should have a high voltage available at the output. If
    you do not have a scope, just set both pots in their middle position and
    then adjust them by trail and error until you get the biggest spark at
    the output of T1.
  4. Q3 will require a heatsink.
  5. Needless to say, this circuit can produce dangerous voltage.
    At the very least you are looking at a painful shock. More then likely a
    decent burn will result from contact with the HV output, as well as
    instant and uncontrollable muscle contraction. If you have heart
    problems, don’t build this circuit. Be careful!.

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