Minibrute Construction Thread / FAQs / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

Minibrute Construction Thread / FAQs

first previous 44 45 46 47 next

Move Thread

LAN_403

UnionTesla

Wed Jul 13 2011, 05:21PM

Registered Member #2685 Joined: Sun Feb 14 2010, 07:23PM
Location:
Posts: 11

I have ever so cleverly lost page 25 of the construction book which is making completing the addendum difficult. What do C 81 and C82 connect to in the diagram on page 25?

Uspring

Thu Jul 14 2011, 12:18PM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
Location:
Posts: 711

C81 is between the 5V supply (Pin 1 of U81) and ground.
C82 is between Vout of U81 (pin 3) and ground.

UnionTesla

Wed Jul 27 2011, 02:10PM

Registered Member #2685 Joined: Sun Feb 14 2010, 07:23PM
Location:
Posts: 11

I am currently in the testing phase, and we have the Self resonant control board working, but when I test the display board, instead of the LEDs for power and 5V lighting up, the 5V and overcurrent LEDs light up, and I cannot seem to figure out what the problem is. Any suggestions?

Uspring

Thu Jul 28 2011, 03:56PM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
Location:
Posts: 711

Possibly it's the cable. If you put on the
connectors wrong, you might interchange
pin 1 with 2, pin 3 with 4 etc.

Ruben

Mon Oct 03 2011, 01:06AM

Registered Member #3263 Joined: Sat Oct 02 2010, 04:43AM
Location: Sydney, Australia
Posts: 34

Hi all,

I've got my minibrute up and running at last!

First light saw me get about 12" discharges to air -- unfortunately my MMC failed after a 30s run (fan was not connected, I cursed my own stupidity).

MMC is now 5x12 0.047uf polypropylene caps to give 112.6nf (measured) at 7.5kv.

I'd be very great full if anyone could help with the following questions:

1) My LED bar graph works under testing, but not when running. i.e. when I lift one end of R21 and apply a voltage, everything works as it should. When I run the coil with R21 in place, I can scope the primary current waveform, but I get no bar graph led's lighting. The rest of the display board LEDs work as they should.

2) OCD operation: When my OCD activates, I should see the pulse train length decrease, right? (when viewing primary current) this is what I observe.

3) My OCD is set to ~550 A, and it seems to kick in when the signal I scope is ~8 V peak (ie ~5 A across a 1.6 ohm burden resistor) -- unless I'm mistaken this all makes sense. HOWEVER, I'm at this point with just 16" sparks to ground, and 203 V on the DC bus -- is this normal?

Any suggestions warmly welcomed.

Uspring

Sat Oct 08 2011, 09:33AM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
Location:
Posts: 711

Hi Ruben,

Try testing the led bar without the secondary. I've seen
its high voltage field (or ground current) interfere with
the electronics.

Ruben

Sun Oct 09 2011, 12:11AM

Registered Member #3263 Joined: Sat Oct 02 2010, 04:43AM
Location: Sydney, Australia
Posts: 34

Thanks for the suggestion,

In the meanwhile I've made some progress:

*Started plotting primary current vs arc length, and increased my tap point from 4.5 to 5.0 turns -- now able to get 16" arcs at just 174VDC, ~275A

*31" arcs to grounded target with 310V on the bus, and ~375A (increases during ground strike).

After watching a video I captured, I realise that my first graph LED is lighting (Whole board is installed upside down), but it's as if the set point is WAY too high:

I'm still quite confused, as I was quite careful in setting the full scale with R21 lifted.

********************

HOWEVER - after attempting to run the coil at 500A I experienced a semi-catastrophic failure. I've created a separate thread, and would much appreciate any help in troubleshooting!

*********************

johncohn

Sun Nov 06 2011, 03:56PM

Registered Member #1848 Joined: Sat Dec 06 2008, 03:24AM
Location:
Posts: 15

Folks,
A short update after a long silence. Earlier in the year I reported that my MiniBrute self destructed after its first public demo. A primary strike managed to destroy every piece of silicon in the unit. Thank to massive help from my good friend and tesla guru Scot F I've now got it working again. (thanks so much Scott !!!!) We rebuilt the resonator board with new PCB and new components (and sockets !) .. and Scott who's a much cleaner fabricator, helped me re-layout and robustify the HV wiring. The thing came back up fine.. but managed to eat the bottom IGBT (IXGN60N60C2D1-ND's) in the bridge two more times during medium power testing.. We now have the current limit set back to 300A and it seems stable (knock on wood) The disappointing thing is that at the 300A set point I'm getting about an 18" spark instead of the 30+ I was getting when I had it set to 500A.
I'm now interested in making this device work *reliably* at the 500 A set point to get the advertised spark .. Is anyone out there reliably running their device above 300A ? and/or is anyone getting 30"" spark (or so) .. ?

Friend Scott was also wondering if the replacement IXGN60N60C2D1-ND IGBT s were just a little less robust than the original HGT1N40N60's in Dan's kit. . I'm eager to hear if anyone anyone out there experimented with replacing the bridge with more robust devices ?

Very eagre to hear wHat are other people getting out of their Minibrutes !
-jc

ps. One spot of good news is that this morning I rigged up a simple audio circuit in the advanced modulator and now have the coil singing the Jeopardy theme song albet wiht an 18" max spark. Still cool, though

Uspring

Tue Nov 08 2011, 02:20PM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
Location:
Posts: 711

I'm getting about 30" sparks from mine at a 650A setting. I am using a different secondary coil from what Dan is describing and I don't believe my coil is properly tuned to this one yet. I burned up 2 IGBTs from a ground spark. At 500A the coil worked reliably, ground arcs or not.

Apart from using a long extension cord for the variac power (Dan recommends this in the addendum), I have separated the control power ground from the secondary bottom ground. The secondary ground is connected only to the spark rail and then firmly grounded elsewhere. I have also grounded the heatsink to the control ground. I really don't know if that makes sense but my experience is not as bad as yours.

johncohn

Sun Nov 13 2011, 08:01PM

Registered Member #1848 Joined: Sat Dec 06 2008, 03:24AM
Location:
Posts: 15

@uspring... Thanks for the suggestion.. the idea of separating the grounds sounds reasonable as does grounding the heat sink. I'd been wondering about leaving it floating.
Anyone else out there using their coil reliably (eg ground strikes OK) at 500A setting ?
-jc

first previous 44 45 46 47 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob