Problem with small Tesla Coil

[Luca]

Good day everyone
I am seeing a lot of awesom videos of Tesla Coils playing music on the internet.
I am really fascinated! And want to make one.
I do not have a lot of practical experience with electronics. Especially not with high Frequencies.
A lot of people say i should start small and simple.
So I found a circuit on the internet (Attachment 2) an designed it on EasyEDA and made it into a PCB (Attachement 3).
I have now soldered all the components and it doesn't work
When i power up the circuit with 15V it pulls around 0.06A and no sparks are jumping from the Top of the secondary, which for me would mean that the resonance is not building up correctly ¯\_(ツ)_/¯.
Can anyone help. I have checked all components and i cannot find the problen.
I would be happy for any help.
Thank you

[davekni]

I am seeing a lot of awesom videos of Tesla Coils playing music on the internet.
I am really fascinated! And want to make one.
I do not have a lot of practical experience with electronics. Especially not with high Frequencies.

Yes, musical coils are a lot of fun.  Also require a lot of work, often multiple attempts and iterations of replacing failed parts.  Be prepared for a long path if you proceed.

A lot of people say i should start small and simple.

Yes, generally good advice.  Down side is that really simple circuits tend to be finicky.  Often depend on characteristics of one brand of part or one board layout and wire length, etc.  Once someone gets a simple circuit working, they post it.  A few people will get lucky with copying it and it works immediately.  Many others will give up or get it working only after many tweaks.

Can anyone help. I have checked all components and i cannot find the problen.

First, are you familiar with positive feedback (instability/oscillation) and negative feedback (steady stable current/voltage)?  For oscillation, positive feedback is necessary.  May require reversing primary coil direction (swapping leads).

If swapping phase isn't sufficient, there are many manufacturers of TIP31C.  It is a VERY old part that's been copied many times.  Initially a low frequency low gain transistor.  Some versions are higher gain and faster.  The initial example build may have used a faster higher-gain part.  Also, likely relying on TIP31C capacitance to tune primary.  Parts vary in capacitance too.  May require additional capacitor collector to emitter for tuning.

Circuit has no bypass capacitor.  Makes tuning very sensitive to lead length to power supply.  Circuits should have capacitors across incoming supply voltage, 15V in your case.

Have fun experimenting.

[Rafft]

Good day everyone
I am seeing a lot of awesom videos of Tesla Coils playing music on the internet.
I am really fascinated! And want to make one.
I do not have a lot of practical experience with electronics. Especially not with high Frequencies.
A lot of people say i should start small and simple.
So I found a circuit on the internet (Attachment 2) an designed it on EasyEDA and made it into a PCB (Attachement 3).
I have now soldered all the components and it doesn't work
When i power up the circuit with 15V it pulls around 0.06A and no sparks are jumping from the Top of the secondary, which for me would mean that the resonance is not building up correctly ¯\_(ツ)_/¯.
Can anyone help. I have checked all components and i cannot find the problen.
I would be happy for any help.
Thank you

You could check your primary winding connections?

[Luca]

Good Day
Thank you for your quick reply.
I have now swapped the primary polarity and it now works... kinda.
When i bring an object near the breakoutpoint some verry small sparks start flying.
When taking it away, the sparks stop. Afittionally i have a light in my room which is touch sensitive, and it also started to flicker when playing with the sparks. I did not think such a small coil could do that, AWESOM!
But i see other people in the internet getting about 7-8mm sparks from this circuit.
You mentionned adding a capacitor, how do i determine the capacity and voltage of this capacitor?
Would you just buy a few and try which one works best, or is there another way to determine its value?
Why connect it between collector and emitter? I dont se the purpous there, shouldnt it be between the two primary coil terminals?
I want to experiment with this coil a bit. Do you have any other ideas on how to optimise it?
Could i add a ferrite core to conduct the magnetic field from the primary to the secondary better?
Why doesnt anyone have toploads on such small coils, wouldnt it help?

Yes, i know what positive and negative feedback is and i think i understand the basics of resonance.

I have another question unrelated this post.
Why does the primary current in a spark gap tc not build up so high, that it melts the primary coil?
Shouldnt it theoretically build up into infinity? Why not?

Once again, im thankful for any help.
Im sorry for my ignorence if i dont understand something.
Kind regards
Luca

[davekni]

First priority is to add a capacitor across 15V input (bypass capacitor).  Film or ceramic, 0.1uF or higher.

Then learn about analog circuits.  One good way is through simulation.  There are free online simulators and downloadable ones.  My favorite is LTSpice.  Simulate a spark gap coil to see how it works.