Homemade plasma globe problem.

[Overclocked]

Ive built a Simple 555 Timer (operating in astable mode at appr22kHz) connected to a flyback from a Monitor (A Color Tube mind you) It works, But according to articles on the web, I should be getting 20kV! It seems I am not getting enough since I cant Use a lightbulb as a plasma globe, Yet If I use 2kV at .9A, I get plasma (but then a hole gets burned into the bulb...)

VCC= 10 (Its Supposed to be 12...This maybe because I didnt load down the 5V Rail- Which I have to do in order to use Current above 1Amp) The only thing I can think of is because I am using 10V, Or I am not using a Big enough transistor (currently I am using 2 in parallel each rated at 1Amp each- And they got hot- Intrestingly when one reaches a "max" temp, the other starts to supply more current and gets hot..)

Is there anything else that could prevent me from getting to 20kV? Im thinking I should use a Transistor Astable circuit, since it seems of all the circuits I build, the load is actually getting appr 3V From the transistor (with appr 5-7V coming from the timer).

ADD- Also at one point ( i had used a small neon bulb for the load) the Flyback started making this weird high pitched noise (I was drawing arcs at the time). The timer blew afterwards, and when I replaced it, the noise went away.

 

[HarveyH42]

2kv at .9A is a little bit dangerous, burn through glass... cool. You'll need a schematic to figure much on this. You shouldn't be getting that much current out of the flyback. I haven't messed with high voltage much since my tesla coil years. I did a couple small ones with flybacks and ignition coils, before doing a 250kv. They work on resonance, so maybe it's more in the frequency. Are you ising and protection diodes? Try making the 555 adjustable, 18 kHz-28 kHz.
The high current .9A is confusing, should be under 30 mA. Guarantee you don't want to get zapped.

 

[justDIY]

2kv at 900ma is 1800 watts ... where are you getting that kind of power?

even 20000v at 30ma is 600 watts, no small chunk of power either.

 

[Overclocked]

2kv at .9A is a little bit dangerous, burn through glass... cool. You'll need a schematic to figure much on this. You shouldn't be getting that much current out of the flyback. I haven't messed with high voltage much since my tesla coil years. I did a couple small ones with flybacks and ignition coils, before doing a 250kv. They work on resonance, so maybe it's more in the frequency. Are you ising and protection diodes? Try making the 555 adjustable, 18 kHz-28 kHz.
The high current .9A is confusing, should be under 30 mA. Guarantee you don't want to get zapped.

2kV Is from A different Transformer, not this one...lol. There are no protection Diodes (Although I should Put a one in). Err Dont Darlington pairs have a Diode Installed?

I'll switch the transistors today, I have TIP125 in my box..

Shouldnt I be getting 1-2 Inch Sparks at 20kV?

 

[Nigel Goodwin]

Shouldnt I be getting 1-2 Inch Sparks at 20kV?

In dry air it takes 10KV to jump 1cm.

 

[Blueteeth]

Wow, 2kv @ 900mA???!

In order to use a 'regular lightbulb' as a plasma globe, anything from 12-15kV + would do, like the output from a typical >modified< flyback transformer design. I have no idea why you would want 2kV@0.9A at the output..its not enough voltage for the plasma globe, would kill you, and you won't get it from a flyback. You need maybe 5mA DC at the most, have you tried using a simple cockcroft-walton multiplier? Word of warning, 2kV at anything over 10mA (DC) is dangerous enough.

Heres a link to a legend of the HV world:
www.electricstuff.co.uk

And of course, powerlabs:
http://www.powerlabs.org/plasmaglobes.htm


A regular light bulb wouldn't be a proper plasma globe, different gases at different pressures. And the largest flyback I have from a 22" crt monitor only kicks out 3kV, but it has a built in rectifier diode on the output, and I haven't modified the primary windings at all. Do you have a 12v supply capable of 3A? I would have thought a single 3055 T03 transistor would do (or a mosfet would be waay better) on a fat heatsink.

One way to ensure you get a LOT of voltage on the output (as opposed to just the step-up winding ratio) is to use the flyback transformer in....er..'flyback' If you hand wind a feedback winding, and use that to switch on/off two transistors (LOADS of schems on the web of this) then the primary develops up to 4x the power supply, which in turn is stepped up. Although all these designs rely on the use of an old flyback, without built in diodes, and a custom primary winding.

My two cents,

Blueteeth.

 

[deja_wu]

2kv * 9 a 18 000 watt :

 

[justDIY]

2kv * 9 a 18 000 watt :

what's that got to do with anything?

same as this? 100Mv * 1a = 100,000,000 watt

 

[Hero999]

2kv at 900ma is 1800 watts ... where are you getting that kind of power?.

Perhaps he meant 2kV with a short circuit current of 900mA.

 

[Overclocked]

Perhaps he meant 2kV with a short circuit current of 900mA.

Err Yea. When I make arcs Its Enough to shut off a 15Amp breaker on the primary side of the transformer. I really Didnt measure .9A, but I calculated it Since Vs/Vp = Is/Ip. Since Vs=2kV, and Vp=120v, then N=16.6666667. I then used used Is=Ip/N to get .9A (since its limited to 15Amps thats what I used)

 

[Hero999]

Don't forget that if the transformer is going into saturation you're going to be loosing a lot of power so the output current will be lower than expected.

 

[audioguru]

Imagine getting 1800W out of a puny little flyback transformer.
I am going to tell my electrical utility company to use little flyback transformers instead of the huge transformers they use now.

 

[Sceadwian]

You could if you had a big enough capacitor bank =) For a few ms' at least =) tons of fun surge generators are, I'd build one but I'm too afraid of killing someone. (namely myself)

 

[Overclocked]

You could if you had a big enough capacitor bank =) For a few ms' at least =) tons of fun surge generators are, I'd build one but I'm too afraid of killing someone. (namely myself)

Ive tried. The Caps I have are around 1uF each, 2.5kV (For some reason, Its rated in AC...). I used a HV diode that came with it (guess where it came from!), but I only used one which is probably why when I discharged the cap it didnt work. I'll have to build a Rectifier bridge or a Voltage Doubler (think of it, 4kV @ .45A! I have errr, 7 Sets (7 Caps, 7 Diodes) So I can probably Quadruple the voltage to get around 8kV...

Yes, its dangerous, but I think HV has a certain "mystery" to it that Im drawn too...Or probably the fact that EVERYTHING at high voltage becomes a conductor....

 

[Sceadwian]

Check ebay. Lots of military surplus.
One I looked at real fast was 3kv 100u capacitor for 50 bucks.
Depending on the parasitic values, that's about 4kw's over 500 microseconds. Peaking at near 3k amps. I simulated it with a 1 ohm load.

At those voltages/currents you don't use diodes, you use spark gaps.
High wattage like 1800watts out of a dinky little flyback isn't unusual it's just in tiny little pulses, the average power over time is very very low. Wattage however has nothing to do with time until you tack on seconds/minutes/hours to the end.

 

[audioguru]

High wattage like 1800watts out of a dinky little flyback isn't unusual it's just in tiny little pulses, the average power over time is very very low.

Yes, the max light from a big TV is about the same as a 13W compact fluorescent bulb.

 

[Hero999]

That makes sense, the energy is all stored in the magnetic feild then released in one big high voltage pulse when the current stops flowing, I suppose it's the inductive opposite of discharging a hge capacitor, instead of a huge instantanious current you get a huge instantanious voltage.

 

[Nigel Goodwin]

High wattage like 1800watts out of a dinky little flyback isn't unusual it's just in tiny little pulses, the average power over time is very very low.

Not only 'unusual', but totally impossible!.

The LOPT stage in a TV set is limited to an output of 1mA maximum - at 25KV this means it only supplies 25W. Getting 1800W out of a 25W transformer is completely impossible.

What you could do, for a VERY low duty cycle, is charge a large capacitor with the 25KV at 1mA - then discharge it in a short time to get a very high power pulse - just like a flash gun in a camera.

 

[Sceadwian]

Very low indeed. I didn't mean directly Nigel.
A 25kv 1ma source will charge a 2.5kv 120u capacitor to it's working voltage in about 5 minutes. With a 1ohm load that will discharge to less than 1 volt in 1ms. According to the simulation that's 375 Joules of total power or about 37,500 watts for the duration of the pulse. The peak pulse power is a bit past 6 megawatts. Though I have no idea how real world materials act under these circumstances, that's over 2000 amps peak. I'm sure there are plenty of parasitics involved and many other considerations though.

 

[Hero999]

Apart from resistance, inductance is a large limiting factor in peak current of a discharge from a capacitor and if the system is underdamped the capacitor will charge up in the reverse direction which can ruin a polarised capacitor; a reverse diode in parallel with the inductive load and help this though.