CO2 Power Supply Schematic Help

[The Lightning Stalker]

Series ballast for limiting current through
the tube? You would have to play with
different resistor values until it reaches
22mA for your particular setup. It may not
even need a resistor at all.

 

[Sigurthr]

With such a small filter capacitance you might not need a ballast resistor since the plasma impedance may be significant enough. If you use a doubler you're already limited to 17.5mA steady state at best (Pout = Pin - Ploss; Vin x Iin = (Vout x Iout)- loss). Typically you can overdrive tubes a bit too, so you'd really need an ammeter and to play with various resistances. If you do this, mind the power dissipation in the resistor.

 

[upaa27]

Ok. The ballast resistor would be just to prevent spikes but I'm guessing the cap and nst handle those pretty well.

 

[Cyparagon]

Resistors do not filter spikes.

 

[upaa27]

Resistors do not filter spikes.

Resistors can prevent current from getting to a certian point(limit to maybe 20ma so that current spikes won't do any damage)

 

[Polonium210]

Resistors can prevent current from getting to a certian point(limit to maybe 20ma so that current spikes won't do any damage)

I don't think you understand what a CURRENT limiting resistor is for.

It limits the current across the bore to prevent you from burning up the tube.

As Cyparagon said, resistors do not filter spikes.

 

[Sigurthr]

If I knew the plasma impedance I'd do the math (would have to look up the formulae first) on the peak current of dumping a 2200pF cap into the bore, to get your initial striking current, but... yeah, not gonna happen. A ballast resistor is a good idea. Is it totally necessary? Don't think so. I don't think we'd be anywhere near the explosion energy for such a large tube anyway.

 

[upaa27]

I don't think you understand what a CURRENT limiting resistor is for.

It limits the current across the bore to prevent you from burning up the tube.

As Cyparagon said, resistors do not filter spikes.

Ah I see. I did not know about those specific type of resistors.

If I knew the plasma impedance I'd do the math (would have to look up the formulae first) on the peak current of dumping a 2200pF cap into the bore, to get your initial striking current, but... yeah, not gonna happen. A ballast resistor is a good idea. Is it totally necessary? Don't think so. I don't think we'd be anywhere near the explosion energy for such a large tube anyway.

Ok. I don't think I will use one then. I am just new to gas and didn't know how much you could push the tube compared to the standard diode lasers

Just tryin' to be safe

 

[upaa27]

Hey guys.

For resistors with a psu, does the formula v/I=R still apply when the input has a set current? ie. A psu with 15ma 30kv to 60ma at 15kv by using resistors in parallel how would you find the first resistor's value?

Sorry for the stupid question, I have just been looking forever for an answer and couldn't find one

 

[Sigurthr]

No worries.

It's still a voltage source, it isn't a constant current type device, so Ohm's Law still applies.

I'm not sure what your second question is asking, sorry.

Since you're rectifying and filtering the AC power you get a different voltage out: Vpeak (Vpk or Vdc) = 1.414 x Vrms (Vac). So use the Vpk voltage when figuring out the resistance you need, not the Vrms on the label. Also, NSTs (at least the transformer type) are rated by short circuit current and open circuit voltage; i.e. a 15k 30ma NST is 15kVrms when not connected to anything and 30mA when shorted with a piece of wire, never 15kV AT 30mA draw.

 

[Cyparagon]

It's still a voltage source, it isn't a constant current type device

I don't think so. From what I understand, it's more like 30mA constant current with a voltage limit of 12kVRMS. It'll send roughly 30mA into 100kΩ load, it'll send roughly 30mA into a 1KΩ load, and it'll send roughly 30mA into a short. That's why it's good for powering weird loads like a long neon tube.

I'll try to remember to test that when I get home.

A psu with 15ma 30kv to 60ma at 15kv by using resistors in parallel how would you find the first resistor's value?

You want to use a pair of resistors as a 200% efficient transformer?

I'm sorry man, but if you don't know what a resistor is, you should NOT be playing with high voltage.

PLEASE, for your own safety, start with a project that isn't lethal if you screw up.

 

[Sigurthr]

I don't think so. From what I understand, it's more like 30mA constant current with a voltage limit of 12kVRMS. It'll send roughly 30mA into 100kΩ load, it'll send roughly 30mA into a 1KΩ load, and it'll send roughly 30mA into a short. That's why it's good for powering weird loads like a long neon tube.

I'll try to remember to test that when I get home.

Interesting. The one I had played with a while back was just a simple current limited - voltage source inverter. Above 12mA (one I had was small) draw it would simply cut out from an internal protection circuit, so it couldn't be used for low impedance loads. This certainly changes things then.

 

[Things]

Never had much luck with using inverter NST's for drawing arcs - the plain ol transformer types are so much more forgiving and no protection crap either

 

[DashApple]

Never had much luck with using inverter NST's for drawing arcs - the plain ol transformer types are so much more forgiving and no protection crap either

You can get round that on some of them by removing the feedback winding , it just then drives the flyback inside at full power .

 

[upaa27]

You want to use a pair of resistors as a 200% efficient transformer?

I'm sorry man, but if you don't know what a resistor is, you should NOT be playing with high voltage.

PLEASE, for your own safety, start with a project that isn't lethal if you screw up.

Thanks for your concern cyp. I don't really want to cram all that equipment into a drawer though.

I was just curious to how to get 60 ma at 15 kv from a 30 am 15 kv transformer and wondered if it was possible to do with resistors. I guess not

Maybe just voltage double it then use a step down transformer

@Sigurthur
Thanks for the response man, as for my example, as cyp stated is not feasable

 

[upaa27]

Made the rectifier in 2 different ways both full wave. Now tube isn't igniting how is this not enough voltage?