Transformer help

[CJP]

Im trying to make a capacitor charger unit that boosts 6v to around 300-400v using a 555 timer chip in astable mode, what sort of transformer core would you recommend plus turns ratio and other little specs? (im not looking for perfection here just something i can work on and tinker with to understand electronics better in that field) i want to put out a reasonable amount of current, ive toyed with camera flash units and they put out about 11µA so im aiming for about nine times that at 100µA, any recommendations? I have an audio transformer that puts out 1-2kv from a 6v battery using a 555 also, would i be able to put my 330v 80µf capacitors in series to meet that voltage with a good voltage share across all capacitors or will that need some messing with?

I practice safety when it comes to higher voltages im not going around shocking people, animals, myself etc with these, i know the charger would put out less than lethal voltage but of course the capacitors (2 x 1mF and 100 x 80µf) know how to kill you.

 

[bountyhunter]

I don't think we are supposed to help people killl themselves......

 

[Reloadron]

Read this link as to capacitors in series, pay attention to the section that mentions "Resistor Network for Series Capacitors" and the logic behind it. Also remember capacitors in series are like resistors in parallel as to the total capacitance. While I do not see a resistor network as a must for your application, it is good material to be familiar with.

That said, if you could fine for example a small 240 VAC to 6 VAC transformer and drive the secondary (6 volt side) with about 12 to 15 volts you would get about the 300 - 400 volts you mention. The 100 uA (.1 mA) is not much at all. A Google of inverters circuits should give you some ideas. There are a number of designs used.

Ron

 

[CJP]

ugh, im not stupid! but if no one will help ill just have to spend a bit of money on different parts to find out what works best. heard of a coilgun? im starting with a small bank of 330v salvaged caps maybe five of those, i can already charge the full bank up with the old chargers i have anyway, i haven't died yet (i have no intention to kill myself), i just want a more effective method.

thanks, i pulled a small charger transformer out of a phone charger but it seems even worse than the micro PCB transformers you can salvage from odd charger circuits, ill give my audio one a go with two parallel sets of five caps in series.

 

[Reloadron]

I gave you a suggestion and answered your question.

Ron

 

[CJP]

the first bit was with reference to bountyhunter, second with reference to you, im kind of multi tasking at the moment so i didnt make that clear, so yeah thanks again Reloadron.

 

[DJDAudio]

Ahh Coil guns are fun projects! I am sure you are well on your way to building it already but from what I have learned in the past the Cap bank is not to picky on how it gets charged as long as it is controlled. For when empty a cap bank will act like a dead short to the charging circuit. A simple way to counter this is a series resistive load. ( I often use Incandescent 300Watt lamps. ) I would simply look for a commercial control step down transformer one that will convert 480 to 120 and just run it in reverse with a series resistive load. And then have an isolation circuit for removal from the circuit. ( this would be for a mains 120V AC feed into the system. )

I am not 100% on what you have planned for your project, this is more along the lines of what I have done in the past.

 

[CJP]

i havent designed it yet, i have yet to design a working charger circuit that doesnt suck, a case and the triggering circuit.
i dont want to use mains because it ruins the fun of having some portable awesome so ill stick with 1.5v, 6v and 9v batteries, ill have a look around for one of those step down transformers, what sort of price range should i be looking for?
you mention that an empty cap bank will behave like a dead short, will this draw too much current too quickly and damage my charger circuit? a 555 will be fine wont it? the 555 will be driving a bu808dfi darlington pair which seems quite beasty in comparison to most, it is able to drive a flyback with relative ease and no heating from a 6v or a 9v battery after 10-20 seconds.

IN ADDITION: my firing circuit involves 5-10 parallel 600v 160A 20ms surge rated triacs, will they be ok? i couldnt find a single large SCR 1600-3000A surge rated for less than £50 which is totally not worth it for what im doing, my triacs costed about £1 each or something , i hope theyll stand up to it.

 

[DJDAudio]

i havent designed it yet, i have yet to design a working charger circuit that doesnt suck, a case and the triggering circuit.
i dont want to use mains because it ruins the fun of having some portable awesome so ill stick with 1.5v, 6v and 9v batteries, ill have a look around for one of those step down transformers, what sort of price range should i be looking for?
you mention that an empty cap bank will behave like a dead short, will this draw too much current too quickly and damage my charger circuit? a 555 will be fine wont it? the 555 will be driving a bu808dfi darlington pair which seems quite beasty in comparison to most, it is able to drive a flyback with relative ease and no heating from a 6v or a 9v battery after 10-20 seconds.

IN ADDITION: my firing circuit involves 5-10 parallel 600v 160A 20ms surge rated triacs, will they be ok? i couldnt find a single large SCR 1600-3000A surge rated for less than £50 which is totally not worth it for what im doing, my triacs costed about £1 each or something , i hope theyll stand up to it.

Portable, that makes allot more sense as to your voltage requirement. I have never built a portable model, for I like to stick with 'Big guns' haha

As long as you size your series resistor or ( current limiting ) resistor accordingly you will not have to worry about over loading your circuit.

As for portable, I have seen this in the past, the Video explains it well,

**broken link removed**

Portable units are out of my comfort zone, so I will leave this to the experts, but I would imagine a DC to DC converter would work well for you something like this,

https://donklipstein.com/rsinvert.html

4-12VDC in 300-400VDC out.

 

[DJDAudio]

Also I have never had good luck with parallel release methods, for if you have any more then one device for the power release, you will find that every unit is slightly different, and one may 'close' 1ms before the rest and will see much more of the load then the rest and may burn it out faster. Unless they are 100% identical I can see you having balance loading problems with that many triacs.

 

[CJP]

i will simply use a microswitch and battery trigger so that the triacs will all certainly stay on for the surge period

i may only need 3 or 4 triacs in parallel, 10 was to be safe it any were damaged with static or something