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Registered Member #1169
Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251
Wirenut wrote ...
diodes not fitting through the holes of the PCB board? like CR3 and CR4.
Oh yeah, now that you mention it, I did have this exact problem. I just soldered some "posts" out of some of the scrap clipped leads from already-soldered in components, then soldered the leads of the diodes to the posts.
Thats exactly what I did.
This is great stuff Easternvoltage, I don't know how much feedback you get on your book but I promise if I can figure this out then anyone can.
Registered Member #596
Joined: Thu Mar 22 2007, 12:56AM
Location: Columbus, OH
Posts: 2
I'll jump in here with my first post. I just finished building the minibrute as my first tesla coil, it is currently producing 2-3 foot arcs with a 450A limit.
I am using a top mounted breakout (4" of 1/4-20 threaded rod, ground to a point) mainly to prevent arcs to the primary.
I have a question about the feedback transformers, does it matter if they are between the MMC and the primary coil or between the H bridge and the MMC? Does the MMC offset the phase of the current?
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
I have a question about the feedback transformers, does it matter if they are between the MMC and the primary coil or between the H bridge and the MMC? Does the MMC offset the phase of the current?
Review Kirchoff's current law, there *cant* be a phase shift in the current of a series circuit. It does in fact matter because the node connecting L to C has many kV on it. Review ohms law, V = I*Z where I is 450A and Z is the impedance of your MMC or primary at your operating frequency.
Final answer, put the CTs on the output of the H-bridge, not between the MMC and primary because there is HV present there, and you certainly wouldnt want a fault between the primary circuit and the CT!
Registered Member #1169
Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251
I was looking through the schematic and was wondering if C86 was on the Resonat Driver Board? It's in the schematic but it's not on the board that I can find. Another C32?
I also had another question, I couldn't find C7, C8, C62, C64, C66, C68, C81, C83 labeled on the circuit board. My friend had an idea that they were just all of the un-labeled boxes. Is this correct?
Registered Member #141
Joined: Sat Feb 11 2006, 01:14PM
Location: Southern California
Posts: 96
I was looking through the schematic and was wondering if C86 was on the Resonat Driver Board? It's in the schematic but it's not on the board that I can find. Another C32?
Looks like you caught another one - as with c32, I did not include this on mine and it works seemingly fine, but EVR will have to comment on its necessity.
I also had another question, I couldn't find C7, C8, C62, C64, C66, C68, C81, C83 labeled on the circuit board. My friend had an idea that they were just all of the un-labeled boxes. Is this correct?
Yes.
I just finished building the minibrute as my first tesla coil, it is currently producing 2-3 foot arcs with a 450A limit.
Registered Member #154
Joined: Sun Feb 12 2006, 04:28PM
Location: Westmidlands, UK
Posts: 260
Wirenut I see from the layout of your base that you connected your feedback CT on the HV side of your MMC. See Steve Wards post as to why he dosn't reccomend to place the CT on the HV side. Just a thought.
Registered Member #141
Joined: Sat Feb 11 2006, 01:14PM
Location: Southern California
Posts: 96
Wirenut I see from your layout of your base that you connected your feedback CT on the HV side of your MMC. See Steve Wards post as to why he dosn't reccomend to place the CT on the HV side.
Yeah, I see how this could lead to a catastrophic failure. I didn't know there was a difference previously. Just out of curiosity, what is the approximate voltage on the primary? I don't know the primary impedance, but Fres is ~160kHz and pri current is ~1000A max.
Registered Member #1169
Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251
Wirenut wrote ...
Wirenut I see from your layout of your base that you connected your feedback CT on the HV side of your MMC. See Steve Wards post as to why he dosn't reccomend to place the CT on the HV side.
Yeah, I see how this could lead to a catastrophic failure. I didn't know there was a difference previously. Just out of curiosity, what is the approximate voltage on the primary? I don't know the primary impedance, but Fres is ~160kHz and pri current is ~1000A max.
-Does the polarity matter for VR62, VR61, and VR107-VR110 (it says Bi-Directional)
-Are three wires being wrapped around T1? Ie, Wire#1 is (S1/S2), Wire #2 is (G1/G2), Wire #3 is (twisted pair -> Gate DRV/RTN -> from the resonant board)?
Registered Member #141
Joined: Sat Feb 11 2006, 01:14PM
Location: Southern California
Posts: 96
-Just so I understand correctly, The placement of the CT should be placed where I drew the arrow in the image below?
Yes, that is the recommended spot.
-Does the polarity matter for VR62, VR61, and VR107-VR110 (it says Bi-Directional)
Nope.
Are three wires being wrapped around T1? Ie, Wire#1 is (S1/S2), Wire #2 is (G1/G2), Wire #3 is (twisted pair -> Gate DRV/RTN -> from the resonant board)?
Not quite. There are 3 wires, but wire 1 will be s1/g1 and wire 2 will be s2/g2. Wire 3 is correct. I had a hard time finding wire that was small enough to fit 20 turns on the ferrite. What I ended up using was wire from an old parallel cable. I took 2 strands (red and blue in my pic) and twisted them tightly together using a drill. I then wrapped 20 turns on the ferrite. Then I wrapped 10 turns over the top of the red and blue (yellow in my pic) with a third wire. I fed the leads of the 3rd wire through the holes in the board and then twisted them together, holding the ferrite to the board. I could then trim the red/blue wires to the correct length. I'm not sure if it matters, but I put both turn-1-wires to g and both turn-20-wires to s.
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Minibrute Construction Thread / FAQs
