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Alex1M6

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  • Flyback Transformer Driver for Beginners

    Hey there, put the transistors in parallel with one another (leg to leg assuming the transistors are the same pinout). If one transistor heats up more than the other add emitter current sharing resistors of about 0.1-0.2 ohm in series with the emitter legs of each transistor. If possible mount the transistors on the same heatsink so they stay at the same temperature. Let me know if you want diagrams or more information.As for output current it's probably going to be in the region of about 5-20mA. When the arc is thin and blue then there's probably a couple milliamps at most, purple there's probably more like 10mA and when it starts to look like a yellow-white flame then the current is probably around 15mA and above. The arc current will change depending on arc length however, you can meas…

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    Hey there, put the transistors in parallel with one another (leg to leg assuming the transistors are the same pinout). If one transistor heats up more than the other add emitter current sharing resistors of about 0.1-0.2 ohm in series with the emitter legs of each transistor. If possible mount the transistors on the same heatsink so they stay at the same temperature. Let me know if you want diagrams or more information.As for output current it's probably going to be in the region of about 5-20mA. When the arc is thin and blue then there's probably a couple milliamps at most, purple there's probably more like 10mA and when it starts to look like a yellow-white flame then the current is probably around 15mA and above. The arc current will change depending on arc length however, you can measure it using a current meter in series with the high voltage and watch it change depending on loading.

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  • Flyback Transformer Driver for Beginners

    No problem, good luck with your model railroading.

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  • Flyback Transformer Driver for Beginners

    In that case I'd swap out the HV return wire to one rated for high voltage such as in the links I posted previously so it doesn't eat away at the insulation where the brown return cable goes through the enclosure. Then add some big scary warning labels to the enclosure with usage instructions.I'd also recommend a TVS diode across the transistor collector to emitter since a floating flyback relative to the driver is riskier on the transistor.

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  • Flyback Transformer Driver for Beginners

    The only way to stop the spark between the high voltage return and housing is to connect the high voltage return to the housing, but only do this if you're 100% sure you can't come into contact with the high voltage at the applicator (arcs can punch through glass and epoxy).It's arcing because of capacitive coupling between the metal housing and flyback, the high voltage is really pulsed high frequency DC and at high voltages small capacitances can let significant currents pass.What's your reason for not wanting to ground the high voltage return pin? If everything is grounded correctly and the house wiring is good then the metal enclosure and probe will be at 0v and shocks from touching it will only be from static effects of the applicator.

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  • Flyback Transformer Driver for Beginners

    Hi, for MJ15003 those voltages are ok. Does the transistor heatsink get too hot to touch? Getting toasty after several minutes is fine, getting hot after a minute or so isn't. If it's the latter then it may run cooler with just one transistor as the base drive may struggle with two of them (causes more switching losses).Do you still get a shock from the grounded case when the high voltage is forming a continuous arc? As its a static applicator the high voltage could be charging your body up like static electricity, when you touch the grounded case your body capacitance is discharged to ground with a zap.Would connecting the high voltage return pin to mains ground prevent the applicator from working? As I think that connecting it to circuit ground would reduce risk of static shocks by prev…

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    Hi, for MJ15003 those voltages are ok. Does the transistor heatsink get too hot to touch? Getting toasty after several minutes is fine, getting hot after a minute or so isn't. If it's the latter then it may run cooler with just one transistor as the base drive may struggle with two of them (causes more switching losses).Do you still get a shock from the grounded case when the high voltage is forming a continuous arc? As its a static applicator the high voltage could be charging your body up like static electricity, when you touch the grounded case your body capacitance is discharged to ground with a zap.Would connecting the high voltage return pin to mains ground prevent the applicator from working? As I think that connecting it to circuit ground would reduce risk of static shocks by preventing potential between you and circuit ground from appearing. Maybe with some distance between the applicator and enclosure the grass won't be attracted to the side of the enclosure, or connecting the HV return pin to ground via a resistor would reduce the strength of the loop between the applicator and metal case of the enclosure.The 22 ohm resistor getting hot is normal, the price to pay for a simple circuit ( :

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  • Flyback Transformer Driver for Beginners

    Hi, is that transistor heatsink electrically connected to the metal box? The case of the transistors are internally connected to the collector so the entire heatsink will have high voltage on it, you have two options here one is to use isolators between the transistors and heatsink whilst the other is to electrically isolate the heatsink from the rest of the metal enclosure (I can see metal screws in your picture). Is the enclosure connected to mains earth ground and is the earth ground at the outlet in a known good condition? The return pin of the HV flyback transformer needs grounding too.Also is that heatsink getting hot? It should run just warm with one transistor but may end up running hotter with two as it could struggle to correctly switch both transistors fast at the same time.

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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

    Hi, I haven't been active here in years. Please see the updated schematic and section on how to measure peak transistor voltage. Sorry it blew a transistor for you, but I originally published this instructable as a teen and didn't know better.

    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?

    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.

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