My mosfet driverless mosfet slayer exciter with adjustable power (not working)

[Jun]

Hi. I'm fairly new to electronics but I decided to try and make a mosfet slayer exciter circuit. Most of the mosfet slayer exciter uses mosfet driver to turn on and off the gate of the mosfet, but since I don't have an access to it, I decided to use BJT(TIP41) to turn on the gate. I came up with the circuit my own and that's probably why it doesn't work :< Anyways, the potentiometer is tuned to 4.2V at mosfet gate and when I turn it on, the mosfet is always shorted and draws about 1A (always shorted). I probed the circuit and noticed that the feedback from the secondary ground is probably not enough to turn off the base of BJT and thats why it's constantly shorting the mosfet. My TIP41 works well with the BJT slayer exciter so secondary feedback should be able to turn off the BJT right?

I spent hours trying to troubleshoot and researching. Please help me out!

[ritaismyconscience]

try it on falstad.com/circuit to see if circuit works as intended.

[Jun]

Ok I'll give it ago!

[Jun]

I've tried, but I still can't get it to resonate. I can't get the transformer to operate right. There's no option to change the secondary.

[SteveN87]

I've never used online simulators before - but it says "3 bad connections" at the bottom!

Re the secondary - you can set the primary inductance, the turns ratio and the coupling coefficient only.
If you know the secondary inductance but not the turns ratio, you can calculate it as follows:

turns ratio = SQRT(secondary inductance/primary inductance)

The coupling coefficient will probably be less than 0.5 for a slayer coil.

[klugesmith]

In that online simulation, mind the polarity of the transformer windings.
I don't see any indicator dots, and am not aware of any convention in the absence of dots.
Not sure it matters in the case you showed, with no feedback from secondary to primary side.

I bet the "3 bad connections" are associated with red dots in the rendering.  One problem with electric circuit CAD in the real world, is connection problems that are invisible in the graphical schematic.  One needs to check the netlist, or in some cases get an acceptable result from simulation that is based on netlist.

Took a look at the falstad.com site, and must applaud the choice to move dots in the direction of conventional current (little positive charges).  Downward in the collector and emitter wires here, following the arrow.  Newbies will find it easier to follow the literature when they let go of urge to think in terms of electron drift, which is a pesky detail discovered long after electric circuit theory.

[ritaismyconscience]

Draw a wire between one of the red dots and one of the other connections to fix it.

It doesn't automatically connect if you just place a component on top of a wire, you still need to connect it manually

[Jun]

Hi guys. Sorry for the late reply. I've been busy with my assignments. And I realised what was wrong with my setup. The secondary was connected to feedback before when I was using regular slayer exciter, but somehow disconnected and that's why it was constantly shorting mosfet. I fixed the connection and changed few things and now it works fine. Thanks for the support on the simulation side. I now know somewhat on how to use circuit simulation.