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  • Homemade High Voltage Pulse Transformer Video

    Hi, I'm not sure of the exact number but it was a single layer of 40 AWG enamelled coated wire wound on a 15mm diameter 10cm long piece of PVC pipe with a piece of ferrite rod inserted into the pipe as a core. Electrical tape was then wound over it and the primary was a couple turns of thick wire.Short answer: As many as possible but keep it to one layer thick or else it will arc over.

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  • Flyback Transformer Driver for Beginners

    Yep, changing the number of turns on the primary and altering the feedback coil in proportion to match has the most effect. More turns = lower operating frequency = more energy stored in the core per cycle.The transistor selection has a lot more going on than the headline specs such as max voltage and current ratings, some transistors have nasty turn off delay in this circuit which ends up turning a large chunk of the input power to heat and limiting the output from the flyback. 2n3055 and MJE13007 behaved like this whilst MJ15003 worked great, the differences could be seen on an oscilloscope at turn off plus the transistor didn't heat as much and sparks were bigger for a given input power. Unfortunately many transistors don't publish this data in the datasheets, but MJ15003 was designed …

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    Yep, changing the number of turns on the primary and altering the feedback coil in proportion to match has the most effect. More turns = lower operating frequency = more energy stored in the core per cycle.The transistor selection has a lot more going on than the headline specs such as max voltage and current ratings, some transistors have nasty turn off delay in this circuit which ends up turning a large chunk of the input power to heat and limiting the output from the flyback. 2n3055 and MJE13007 behaved like this whilst MJ15003 worked great, the differences could be seen on an oscilloscope at turn off plus the transistor didn't heat as much and sparks were bigger for a given input power. Unfortunately many transistors don't publish this data in the datasheets, but MJ15003 was designed for audio applications.This circuit has been around since the 70's and 2n3055 became synonymous with it as it was widely available at the time, really old versions of the 2n3055 used to perform much better as they were manufactured using a different process, modern ones don't do well with this circuit.As well as the diode and capacitor across the collector to emitter there needs to be something protecting the base to emitter, many transistor can take about 5v reverse before damage starts occurring. In my testing this manifested as the gain permanently reducing. A diode, TVS or Zener to clip emmiter to base voltages under the breakdown level will do.

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  • Flyback Transformer Driver for Beginners

    Its set by the core and number of primary and feedback turns mostly, transistors gain probably has an effect too.

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  • Flyback Transformer Driver for Beginners

    Hi! Use a larger resonant capacitor value (C1) to limit the peak collector voltage along with both protection diodes, also using less primary and feedback turns increases the operating frequency and reduces the peak voltage stress. The diode on the base prevents emitter-base reverse breakdown which slowly degrades the gain.You can use this method to measure the peak voltage spike without an oscilloscope, for 2n3055 the peak needs to stay below 60v (100v for the HV version). Just keep putting suitable capacitors in parallel to C1 or reducing coil turns until the peak voltage stays below 60v, it'll change depending on arc loading too so watch out for that.The side effect of all this is it'll make the arcs small, but at-least it'll save the transistor.Got any other transistors laying around?…

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    Hi! Use a larger resonant capacitor value (C1) to limit the peak collector voltage along with both protection diodes, also using less primary and feedback turns increases the operating frequency and reduces the peak voltage stress. The diode on the base prevents emitter-base reverse breakdown which slowly degrades the gain.You can use this method to measure the peak voltage spike without an oscilloscope, for 2n3055 the peak needs to stay below 60v (100v for the HV version). Just keep putting suitable capacitors in parallel to C1 or reducing coil turns until the peak voltage stays below 60v, it'll change depending on arc loading too so watch out for that.The side effect of all this is it'll make the arcs small, but at-least it'll save the transistor.Got any other transistors laying around? Oddly some of them found in audio amplifier output stages seem to work well for this where's others designed for switch-mode power supplies perform poorly, MJ15003 (designed for audio amps) worked remarkably well and didn't get that warm. 2n3055 gets hot even if the voltage spikes are kept in check, when compared on an oscilloscope the 2n3055 took ages to turn of in this circuit whilst the MJ15003 was really fast.I know this instructable has 2n3055 in the title, but I wrote it as a teen around 10 years ago. During lockdown I've come back and attemptes to tidy up and correct mistakes.

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  • Flyback Transformer Driver for Beginners

    Yeah, looks good! With the switch to LED bulbs those halagen light ballasts are literally being given away for free in some cases.

    Yeah, I just noticed that too. Shame teenage me didn't all those years ago! I've updated the schematic now.

    Hi, sorry I haven't been active in this scene for a very long time but just noticed your comment when I logged in for the first time in years.Your transistor appears to have that diode built in, it's also a horizontal output transistor from the TV and can be finicky to oscillate with this driver. Winding external primary and secondary coils often works better with lower voltages due to the lower inductances, number of turns can be a bit experimental and some transistors work best with more or less.How big are the arcs you're getting? The flyback in that video had something like 20 primary turns and 7 feedback. This allowed the peak primary voltage to reach higher levels and thus give more voltage on the output.Before doing this please see the updated schematic with the capacitor and metho…

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    Hi, sorry I haven't been active in this scene for a very long time but just noticed your comment when I logged in for the first time in years.Your transistor appears to have that diode built in, it's also a horizontal output transistor from the TV and can be finicky to oscillate with this driver. Winding external primary and secondary coils often works better with lower voltages due to the lower inductances, number of turns can be a bit experimental and some transistors work best with more or less.How big are the arcs you're getting? The flyback in that video had something like 20 primary turns and 7 feedback. This allowed the peak primary voltage to reach higher levels and thus give more voltage on the output.Before doing this please see the updated schematic with the capacitor and method to measure peak collector-emitter voltage on the going further page, I know the instructable is a bit messy and inconsistent now and I'm thinking about updating it during the coronavirus lockdown period. Its important the correct capacitor value is selected to prevent the transistor from being destroyed by overvoltage.

    Hi, the 2SA1358 is only rated for 1 amp of collector current and this circuit often draws around 2-3 amps average with peaks much higher. It's also a PNP part (althought that's not a problem if the circuit is adjusted).Are there any other transistors available to you?

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