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Messages - dexter

Pages: [1] 2
1
When buying parts for the driver I couldn't find the UCC27423 chip, so I thought I could use the UCC27424 chip.

i made the same mistake on my first DRSSTC and couldn't get why my coil didn't start

the gates of the p channel mosfets are capacitively coupled so they need a high to low transition in order for one of the p's to conduct

if you use a non inverting driver they'll get a low to high transition and won't turn on

with an external signal the coil will work but you still loose the 1st cycle

2
Solid State Tesla Coils (SSTC) / Re: SSTC not getting interrupted
« on: September 09, 2019, 07:59:23 PM »
single chip double gate drive ic's work well
make sure they are inverting and non inverting
i successfully used MCP14E5 4A gate drivers from Microchip in both half and full IGBT's bridge SSTC's

3
Can someone please recommend good caps to use here, cheaper than Cornell Dubilier? (I'd like to save my extra MMC cap as a replacement part.)

i just bought some of of this caps: https://www.ebay.com/itm/12PCS-0-68uF-680nF-2000V-MKP-TESLA-Pulse-Capacitors-Arcotronics-C4AS-IBGT/173956817574?hash=item2880a262a6:g:37YAAOSw18Jb7q5a
rated for 25A RMS
you can check the seller catalog for other specs

4
What is a good max BPS for music? I think 1500BPS should be enought. Or should I go for more BPS?
I will recalculate the MMC in relation to the new BPS.
depends on the music...
Keep in mind there are pauses and the BPS is not constant so the RMS current will vary quite substantially.
I wouldn't go as far to overdesign the MMC for 1500 BPS but i'd go ~10-20% over the minimum values for normal operation.

Is it now better to have more or less turns on the primary side, or is that completely irrelevant in the case of one turn more or less?
Because I would then choose the MMC accordingly.

read this
https://highvoltageforum.net/index.php?topic=113.0

5

BPS = Basically the Interrupter frequency??
On time = time the coil is on --> on time of the Interrupter signal??
I want to use a Musical interrupter later.
To play different sounds the musical Interrupter changes the frequency of the Interrupter signal? --> different BPS

Yes for all

For your MMC the.0.5 one might suffer when playing music as higher BPS translate to higher rms current. Increase tbe BPS in the MMC calculator and see how much the Temperature rise per cap increases. If you plan to use the coil for sort-ish periods of times (giving the MMC time to cool) it will work fine.

Another thing to consider is impedance matching of the primary and secondary... The primary capacitor plays a role in that and there is a formula but i can't find it right now (on the phone)

6
I had the same price issue with HFBR's when i first moved to DRSSTC's so i tried TOSLINK. Bought a pair of FCR6842032T and R and a TOSLINK optical cable. Maybe breadboard testing wasn't the best idea but i couldn't get them to work. For some reason the output of the receiver could  maintain a stable logic level HIGH for only a few hundreds of ns after which only noise. Tried everything pull up/down resistors comparator bought new receivers and nothing.

In the end i found some OPF2414 receivers on ebay for ~4$ bought a ST Fiber Optic Connector used it to modify the TOSLINK optical cable, replaced the TOSLINK transceiver IC with a high flux red LED and added a LM311 after the OPF2414 because its output was to small (i made my own UD pcb's so adding one more comparator wasn't an issue) and everything works.
Basically from the initial TOSLINK set i only used 1 transceiver (just the plastic part) and the cable which i also modified by changing the connector to a ST connector.


"do you know what type of connector/fiber cable they work with?"
https://www.tme.eu/ro/en/details/avk-216-0200/audio-video-cables/goobay/50447/

7
1. A DRSSTC driver always works at the resonance of the primary LC. The intrerupter doesn't change it.
A problem with the onetesla driver is the lack of overcurrent protection. They get around it by having the coil tuned and by controlling the on time with their intrerupter.
If you use their driver for other coils you risk exceeding the current capabilities of the IGBT's and blow them off.
2. Yes you need to adjust the number of primary turns for a different secondary coil. JAVATC is a great tool but tuning still has to be done manually. Given the lack of overcurrent protection of the onetesla driver you risk blowing the IGBT's when tuning the coil.
3. The bottom of the secondary coil must be connected to earth. For small coils the earth pin of the outlet can be used but for bigger and powerful coils a separate earth ground must be used. Or a sheet of metal could be used but it has to be some distance away from the primary coil and i think it should be at least connected to mains earth.  As for the driver it should be shielded (placed inside a metal box) and connected to mains earth.
4. 5. The polarity of primary coil and feedback transformer have to be in phase. If your coil doesn't starts flip the feedback transformer or the primary coil polarity

8
Capacitor Banks / Re: Bought huge capacitors
« on: June 16, 2019, 08:25:16 PM »
in a 2015 post from 4hv by Kizmo about triggered spark gaps he says it works at any capacitor voltage even as low as 20V
https://4hv.org/e107_plugins/forum/forum_viewtopic.php?p=1&id=171055#post-171722

also saw some russians playing with a homemade taser on the mains wiring of their house which had the same effect as a triggered spark gap

9
I've seen a paper about calculating the self capacitance of a solenoid and in one of the methods they used the self resonance frequency, measured inductance and the length of wire to calculate the self capacitance.
but in their calculation they used l=λ/2 (l= length of wire)

i'm confused... which formula λ/2 or λ/4 describe the self resonance of a solenoid?

10
Its a nice idea, but 50 Hz is not giving the right sound is it? Since its not going positive and negative, but just on/off, maybe 100 Hz is a better emulation of full wave rectified, non-smoothed mains sound.

i used 100Hz because 50 didn't sound right

11
Capacitive and inductive reactances depends on capacitance/inductance and frequency.
Xc=-1/(2pi X f X C)
Xl=2pi X f X L

"Resonance occurs when capacitive and inductive reactances are equal to each other."
that means: Xl=Xc
rearrange the terms and you get: Frez = 1/(2pi X sqrt(L X C))

So whenever you change the capacitance or the inductance the frequency at which Xc and Xl becomes equal (also known as resonant frequency) also changes.

Mads-
   I studied resonant circuits back in the early 1950's.  I vaguely remember that there is some negative "cost" to having L and C too far away from eachother, but I don't know why.
the energy stored in inductor and capacitor is:
Wc=0.5 x C x V^2
Wl=0.5 x L x I^2
At resonance Wc=Wl
For an inductance heater you need high current in the work coil. To achieve this a small inductance coil is used but
 a large capacitor with a high voltage rating is required. So the "negative cost" translate to a monetary cost :)

12
I too didn't understood exactly how UD2.9 works so i made it on a bread board (just the 74HC74 74HC08 74HC14 chips and the passives) feed it signals for FB OCD Interrupter and it works as advertised.
J16 open - works like UD2.7
J16 closed - no output for the duration of the OCD


yellow trace - intrerupter
green trace - output of one of the 74HC08 gates before the UCC

How the driver generate the dead time?
It doesn't. The signal that goes to the GDT comes from the Q and Q- of the comparator which are 50% duty cycle signals and no disproportionate delays seem to be added on the UCC and on the power stage

13
What about the number of series and parallel capacitors?The datasheet doesn't mention the current rating,but in theory the more capacitors in parallel,the less the ESR is or in these applications it makes not much sense?For example at 110kHz,800A which one should I choose, 0.2uF 6kV(more in parallel) or 0.15 8kV(more in series)? (in theory more in parallel)

You can calculate Ipk=C*dV/dT

If 6kV is enough for your coil i'd go for 0.2uF (more capacitance and more caps in parallel)

14
Beginners / Re: SSTC wıth a balast
« on: April 27, 2019, 09:09:31 PM »
connecting the primary coil the other way around even if both coils are turned in the same direction is still the first thing to try on a secondary feedback based SSTC when you get no sparks

15
Beginners / Re: SSTC wıth a balast
« on: April 27, 2019, 08:56:36 PM »
But there are no sparks forming on the tesla coil. What could the problem be?

try connecting the primary coil the other way around

16
Spark Gap Tesla Coils (SGTC) / Re: Question about secondary
« on: April 18, 2019, 09:20:15 PM »
on all my SSTC's i used carbohydrate foam (also known as wood) for the end caps and never had an issue

17
Use a monostable with the time constant a bit higher than the length of the noise or a low pass RC between 2 Schmitt trigger gates with the time constant a bit higher than the length of the noise

18
This thread motivated me to finally make a HV transformer.
The core is the largest TV flyback core i had.
The coil form is made from 2mm thick acrylic glued on a 18mm PVC pipe.
Wound about 2000 turns of 0.25mm wire on six 2.5mm slots by 9.5mm thick and 16 turns primary with multiple taps.
Vacuumed it under oil for a few hours using 2 fridge motors.
Connected it to a full bridge of skm200gb123d bricks running at 30kHz and 130V



/>Here is running interrupted to give it mains humm

19
Solid State Tesla Coils (SSTC) / Re: GDT Experiments
« on: March 28, 2019, 12:37:42 AM »

I am using UCC37322 instead of TC4420, so that might be the reason.
I also wondered what causes the dead time ( well to be honest I would not know what does it even if there was a dedicated component )
What controls the dead time was going to be my next question.


UCC37322 is faster than TC4420...
Given that you got the same deadtime in both cases at different frequencies i'd say the propagation delay from an extra schmitt inverter on one of the UCC's is what produces the deadtime.
What is the part number of U6 (from schematic) that you are using?

20
Solid State Tesla Coils (SSTC) / Re: GDT Experiments
« on: March 27, 2019, 10:52:46 PM »
That waveform confused me a bit until I realized that there is "deadtime" in the signal. Only recently I watched a video on YouTube on that topic - quite glad I recognized it in the waveform.  ;D

You have about 1.8us of deadtime in both shoots and i can't figure it out how...
The Half Bridge SSTC schematic doesn't have any built in deadtime and the TC4420 have delay times less than 100ns and matched Rise and Fall times of 25ns or are you using different IC's?

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