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Registered Member #2273
Joined: Thu Aug 06 2009, 07:02PM
Location:
Posts: 37
Hey guys,
I made a little bit of progress. I removed the zenerdiodes which clamp the voltage after the ct and now i get continuous feedback at a high on time, i get about 15cm sparks into a grounded metal rod. The only problem is that i can't increase the ontime slowly and watch the sparks, i have to start the interrupter with a high on time. This means when i decrease the on time to a specific point, the teslacoil stops working again at it will not start again until i restarted my driver. Maybe its also interesting that the teslacoil starts to stutter when i decrease the on time to much before it completly stops running.
Registered Member #1143
Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721
hm, thats not right. My coil can start resonate even at 0,6% interrupter on time . Can you check Feedback signal at that point when you start to lose the signal, if its below 3V, that means feedback is not strong enough. Even at 0.6% you must get 5V on logic input. One more thing, ar you using right core for CT ? ( best for me is 3E25)
Registered Member #1143
Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721
hv-friekie wrote ...
The core material shouldn't be the problem, i am using a ferrit toroid which is suitable for high frequencies.
I will test this with my scope. When i have this problem that the signal falls below 3V, what am i supposed to change?
Test everything in feedback circuit and maybe change CT. Maybe some how you can't measure primary current because feedback signal can't reach 74HC14 HIGH logic level ( it's the only logic problem, because it works on signal generator )
Registered Member #2273
Joined: Thu Aug 06 2009, 07:02PM
Location:
Posts: 37
I had been testing a 1:1000 Ct, but this made the feedback even worse. It didn't work at all.
I just scoped my feedback signal. There is no sign for that the amplitude goes down when i decrease the on time. The feedback signal is gone from the one to the other second :/
Registered Member #1143
Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721
hv-friekie wrote ...
I had been testing a 1:1000 Ct, but this made the feedback even worse. It didn't work at all.
I just scoped my feedback signal. There is no sign for that the amplitude goes down when i decrease the on time. The feedback signal is gone from the one to the other second :/
Can you remove secondary, and use single core 100T CT ( with 2x 5W 5V zeners ) and show waveform on your 74HC14 input ?
Registered Member #570
Joined: Wed Mar 07 2007, 03:41PM
Location: Winchester Uk
Posts: 42
Is it something to do with C5 and the 1k input resistor time constant? Is C5 needed? With large feedback signals from a long interrupter pulse the diodes on the input gate may clamp and C5 will then charge up and cause the gate output to change state. I think I would try taking this out, or making it larger.
Registered Member #2680
Joined: Wed Feb 10 2010, 09:23PM
Location:
Posts: 45
I have the same problem hv-friekie has. I using primary feedback with a 1:70 CT. The CT outputs a sine wave that is only 40mV peak to peak. I'm quite sure the driver can't pick this up.
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DRSSTC: Feeback problem (Steve's driver)
(~400us)