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.
|R1, R5, R9||3||180 Ohm 1/4W Resistor|
|R3, R7||2||10 Ohm 1/4W Resistor|
|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|
|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)|
- 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
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.
- 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.
- 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.
- Q3 will require a heatsink.
- 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!.