Simple Slayer Exciter DIY

Hello Ladies and Gents, this is the first part of the Tesla coil series, in which you'll learn how to build a Slayer Exciter, which is one of the simplest feedback driven solid state Tesla Coils.
*Important*, the bottom wire for some reason in the circuit diagram is extremely thin, a proper schematic can be found here platinumboi.wi...
The circuit is simple to build and has great room for modification. Feel free to play around with it.
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Disclaimer: high voltages and radio frequencies involved. Act accordingly and don't blame me for injuries.

[@krizzrojas5037]

Excelent... hi from from Peru ;D

[@acmdq2007]

1:43: The current in L2 does not turn the transistor off. It turns it more on. Look at the dots. The transistor is turned off just when the current in L2 changes direction, half cycle of the oscillation later. R1 is not critical. Anything that does not burn the transistor works. R1 can be even removed. Just touch the circuit and it starts. In your simulation, K should be much smaller than 1. Something as 0.2 is realistic. To run the simulation a load capacitance is required.

[@ivanrodionov9724]

Antonio, thanks for your detailed reply! Please correct me if I am wrong, but as I understand it R1 is used for two things:
Firstly, if the transistor is assumed to be an ideal linear amplifier, it is used to provide an initial condition to the circuit so as to prime it from the unstable equilibrium point about 0 current 0 voltage and move it to a stable limit cycle in which it will oscillate.
Secondly, as you are well aware the BJT exhibits some nonlinearities. with this circuit, we want to get maximum power output from it, and this goes down to having more current flow through the primary coils. Now sure, as you have pointed out, in your comment, this circuit can indeed be removed from its unstable equilibrium point by any nudge "even touching". However, without a fixed bias, if too much load is applied to the circuit, the dynamic equilibirum point will shift, eventually converging towards 0,0 as there wil not be enough energy going back to the transistor to maintain the oscillation, and due to aforementioned non linearities, as the equilibrium shifts, efficiency I am assuming will also decrease to due a distorted waveform, hence causing heating and other problems such as voltage spikes.
Here, the R1 helps avoid these problems by maintaining a fixed initial condition, that is time invariant!
As for the L2, fair enough, the transistor indeed does not truly get turned off and on in this circuit due to it being in the linear region, and R1 maintaining a bias current.
As for the simulation, fair enough, a lower coupling value would yield more realistic results, but I doubt that would change much in terms of conceptual behavior, as as far as I know LTspice uses linear coupling loss models.
Lastly, I included the parasitic capacitance in the coils in the simulation, however, I am unsure about a load capacitance being mandatory for the simulation to run, as it ran with and without one.

[@acmdq2007]

@@ivanrodionov9724 The transistor operates linearly just in the first cycles. In steady-state in operates as a switch, open when the current through L2 is going through the LED and saturated when the current goes to its base. What heats it is essentially the interruption of the collector current when the current in L2 starts to go "up". Without the resistor the circuit easily stops when the load is excessive. With the resistor the oscillator restarts when the load is removed. In a simulation a capacitor from the open top of L2 must be added, chosen so the oscillation frequency is correct. K=1 produces very unrealistic waveforms.

[@johnpap350]

Hey what did you probe with your oscilloscope to get the sine wave?

[@ivanrodionov9724]

you mean to test the circuit? I used a 1x probe from KKmoon. cant post links on yt comments but you'll find it if you just search kkmoon probes.

[@johnpap350]

@@ivanrodionov9724 No, I mean which part of the circuit did you probe? Thanks.

[@ivanrodionov9724]

@@johnpap350 ohh it was freehanging (capacitively coupled to the secondary coil) at least for when I measured the sine wave

[@spcraftsman2656]

N-Ice

[@nguyendesign4517]

what is D1?

[@ivanrodionov9724]

The diode used to prevent negative voltage.

[@nguyendesign4517]

@@ivanrodionov9724 IK BUT WHAT IS IT? sorry for caps

[@ivanrodionov9724]

@@nguyendesign4517 ohh, no problems! Honestly any shottky type diode will be fine for this, even works with an LED. I think I used a uf4007 for this.

[@nguyendesign4517]

@@ivanrodionov9724 ohhh okay great thanks man

[@nguyendesign4517]

and can i use tip31c instead?