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FrozenGate by Avery

Tesla Coil Build Thread

Big Green got spun today! :) Motor turned hand guided.


First coat of lacquer down. How many should I do?


Edit nice work on the interrupter!
 
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NICE secondary.

When considering the varnish coat, too much is not an issue. I know the "big boys" varnish them until you can't distinguish the individual turns without a magnifying glass, and that's often on 26ga!

I wish I could coat my secondaries well, but it's -22F outside right now, hit -28F last night. Hell, in my basement it is 37F. I don't think any kind of coating would dry at these temps. I've got three secondaries needing coating atm too.
 
I figure ill put as much on as I can. Im giving each coat overnight to dry. You have no idea how badly I want to put this in the oven at 110 and do them all tonight. Lol.

I have a few questions I guess all ask now. For the toroid im going with the big one from EVR. I know how to physically attache it to the former but how do I make the electrical connection so there is no corona or break out from sharp points. Not a big fan of how oneTesla did it so wondering if there is a more professional way.

Second question is the other end of the secondary. It will be zip tied to the base so I can remove it easily. Is there a HV terminal I can solder to the end of the 28gauge that I can fix to the former? So any plugging unplugging doesnt put stress on that small wire. Will have that wired to some sort of plug on the back of the chassis I can plug in a ground cable.
 
For the toroid terminal connection I use 1/4-20 finishing bolt (the one with the rounded head, not hex, not slotted/screw) with the round side towards the inside of the secondary. There's very little chance of breakout from that smooth rounded exposed area.

For the LV/Gnd connection there are two methods: one is a rounded (to match the curve) copper plate epoxied to the base of the secondary which you then solder the fine wire to. I've never done it as I don't have access to copper plate or the tools to round it to the former, but that's how the big boys do it. The other method is to use another finishing bolt, but much smaller diameter and shorter, perhaps 1/8" x 1/2" long with nuts and washers to hold it in place, and then you wrap the thin wire on it between two washers (which are between two nuts). You repeat that pattern of
[nut][washer]wire[washer][nut] to provide strain relief (no washers = when tightening the nuts you'll pull the wire). I did this on my 3kW coil and it worked out fine.

I just checked my board for manufacturing errors and it came up clean. I think I might be too tired to populate it tonight though, as much as I want to. I got only 3.5hrs of sleep last night and something this important needs me well rested. I had a hard time building the MCU Interrupter. Got the circuitry to where I thought I was done, and wondered why the FB-129 wasn't working.. realized I forgot to solder the connection to the MCU output pin.
 
At one point and what is the best way to get the thin wire from the outside of the former to the inside without creasing it over the top like in the oneTesla set up? I was thinking may a hole drilled in at a shallow angle so the wire just flows through the hole but never bends sharp. Would that method work?

Do you have any pictures of this copper plate method?
 
Yeah the shallow angle hole works but generally one places an end cap on the secondary top which the toroid sits on / is bolted to. This gives it a rounded surface for the wire to be up against so there is no crease.

I'd have to try and dig it up on 4HV or TCML, and I'm not sure exactly what I'd use for search terms. It really is as simple as it sounds. They take a thin copper plate about 1.5" x 0.5" and hammer it until it sits flush on your pvc former, then solder the LV connection to it and epoxy it to the former. Some people then use a pipe clamp (the slotted strap kind) to make connection to the plate, others solder a bolt to the plate, etc. The main idea is to keep all wiring on the outside of the secondary, because having wire on the inside can lead to internal arcing, which can easily destroy a secondary.

Also, here's the code for my interrupter

Code:
/*
  Sigurthr's Digispark SSTC Interrupter!
  By Matt Giordano
  
  Based heavily on ATTiny45/85 code for a simple Solid State Tesla Coil Interrupter
  By Gao Guangyan, <www.loneoceans.com/labs/>
  
  Thank you Gao!
     
  offThresh allows the user to turn off the interrupter
  by turning the potentiometer for BPS to below a certain threshold. 
  E.g. with Threshold set at 5/1023 --> 24mV, the signals will be off.
  Set Threshold to 0 for always-on operation.
  
  Digispark Physical Pinout:
    Pin 5 as Digital Input: CW/Interrupted Mode switch. 
    Pin 4 as Analog Input: Frequency. 
    Pin 3 as Analog Input: Pulse-Width.
    Pin 1 as Digital Output: LED.
    Pin 0 as Digital Output: Fiber Optic Tx.
  For the above analog inputs use a 10k Ohm pot with center wiper to associated 
  pin, one side to 5V and the other side to GND. For Pin 5 use a SPDT On/On 
  switch with center pin to Pin 5 and one side pin to ground, the other side pin to 5V.
*/    

// User Modifiable Variables Here
float maxontime = 5000;     // us - no greater than (32768/5) or 6553us!!
int offThresh = 0;          // Define (offTresh/1023 * 5)Volts as off-threshold
float duty = 0.5;           // Max Duty Cycle desired (here it's 10%)
// User Modifiable Variables End

int vpw;
int vbps;
int vcw;

int critfreq = (1000000*duty)/maxontime;  // Hertz
float ontime = 0;   // always us
float offtime = 0;  // ms or us
float freq;         // BPS Hertz
float period;       // us

int outPin = 0; 
int ledPin = 1; 
int bpsPin = 2; 
int pwPin = 3; 
int cwPin = 5;

void setup() {                
  pinMode(outPin, OUTPUT); 
  pinMode(ledPin, OUTPUT);
}

void loop() {
  vpw = analogRead(pwPin)-offThresh; // read pw voltage
  vbps = analogRead(bpsPin);       // read bps voltage
  vcw = digitalRead(cwPin);       // read cw switch state
    
  if (vcw == HIGH) {
    digitalWrite(outPin, HIGH);
    digitalWrite(ledPin, HIGH);
  }
  
  else { 
    
  if (vpw < 0){
    // Force logic low output when pw voltage is pulled low
    digitalWrite(outPin, LOW);      // Off
    digitalWrite(ledPin, LOW);      // Off
    delayMicroseconds(100);         // Short delay
  }
  
  else {
      
      freq = 1 + ((vbps+2)/2);  
      // sets max BPS to 512.
      // change to ((vbps+4)/4) for 254Hz max.
      // change to ((vbps+1)/1) for 1024Hz max.
  
      /*
        If the period becomes > 2^15 us (T = 32.768ms or f less than 30.51Hz), then
      the period variable runs over! Hence, we make sure this doesn't happen by 
      counting the numbers in milliseconds instead of microseconds. 
        Else, we can be free to count in microseconds
      */
      
      if (freq < 31){
      
        period = (1.0/freq)*1000;               // ms
        
        // Since 31 is a very low frequency, it will not exceed our 
        // pulse width at 10% duty cycle, so we just calc ontime in us.
        
        ontime = 1 + (vpw/1023.0) * maxontime;  // us
        if (ontime > maxontime){ontime = maxontime;}
        
        offtime = period - ontime/1000; // period in ms
        
        // Now send the output signals
        
        digitalWrite(outPin, HIGH);     // On
        digitalWrite(ledPin, HIGH);     // On
        delayMicroseconds(ontime);      // delay in us
        
        digitalWrite(outPin, LOW);      // Off
        digitalWrite(ledPin, LOW);      // Off
        delay(offtime);                 // delay in ms
        
      }
      
      else {
        period = (1.0/freq)*1000000;     // us
        
        if (freq > critfreq){
            ontime = 1 + (vpw/1023.0)*period*duty;    // period in us
        }   
        else{ontime = 1 + (vpw/1023.0)*maxontime;}   // period in us 
        
        // Calculate off-times, capping the on-time to some max

        if (ontime > maxontime){ontime = maxontime;}
        
        offtime = period - ontime;      // period in us
        
        // Now send the output signals in microseconds
        
        digitalWrite(outPin, HIGH);     // On
        digitalWrite(ledPin, HIGH);     // On
        delayMicroseconds(ontime);      // delay in us
        
        digitalWrite(outPin, LOW);      // Off
        digitalWrite(ledPin, LOW);      // Off
        delayMicroseconds(offtime);     // delay in us
      }
    }
  }
}
 
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Is this what you are referring too?



Would this be bent under the former with a hole drilled in it for a bolt or should there be a slot through my base that it slides down through with some sort of clamp/bolt set up below.

Also what is that tape?
 
Similar to that except not protruding past the bottom of the former. No idea what the tape is, probably to hold it on while being epoxied.
 
I guess im still not following then. If its just a curved plate epoxied to the side of the former than how do you connect to it under the chassis?
 
Sigurthr - earlier said:
They take a thin copper plate about 1.5" x 0.5" and hammer it until it sits flush on your pvc former, then solder the LV connection to it and epoxy it to the former. Some people then use a pipe clamp (the slotted strap kind) to make connection to the plate, others solder a bolt to the plate, etc. The main idea is to keep all wiring on the outside of the secondary, because having wire on the inside can lead to internal arcing, which can easily destroy a secondary.

The plate is an intermediary interface between the wire and whatever you're using for the rest of the wiring.
 
Ahh ok I thing I'm getting it. Have it as in the picture but cut off at the base. Have a bolt soldered to that plate and sticking out a little bit over a hole in the base plate. Then come up through that hole with some sort of ring terminal on a wire and bolt it on.

Sorry for the confusion. I was soo lost lol.
 
Np, you got it now. =)

In other news I brute-tested the halfbridge I will be using to test my boards. I pumped 1.5kW through it into an inductive dummy load (BAD!) and it survived just fine. It wasn't too happy, but it is fine.
 
ion: Are those isolated tab FETs? I don't see anything between the FETs and the H/S.

Sig: How did you solve the timing issues?
 
What timing issues?

A solid bridge can hard switch and eat the transients.
 
10MHzcermosc.jpg
 





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