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Registered Member #1361
Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305
Hey guys, Well i built the 555 flyback driver, and everything works, but the arc output is tiny. The arc can barely even be strecthed 1cm. Its only a little tiny purple arc, and has the usualy high pitch squeal. I have tried varying the windings and changing from 12V @ 4A to 12V @ 8A, and the arc hasn't changed much at all.... Anyone know how you increase arc length?? Also is the output supposed to have a crackly squeal to it? Do i have to tune it in any way? The circuit works, i just need to get a bigger arc.
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
How did you change from 4A to 8A? Anyway at 12V I doubt it would even draw much more than a few amps, regardless of power supply capabilities. You need to increase the voltage, and/or use fewer turns to get more power. The squeal is absolutely normal. To remove it increase the operating frequency of the 555, a 555 calculator can be used to find new component values. 1 cm isn't terrible for your setup though, my first sparks were that small too.
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
A normal flyback will not really produce arcs much longer than 1 cm, if you want it to last more than a few seconds. You can eliminate the squeal by increasing the frequency, but then you have to increase the input voltage to have the same output voltage. This also increases the available average current, resulting in more powerful arcs. Always connect some resistance in series with the fyback output (at least several tens to hundreds of kOhms, several resistors in series to avoid arcs over the resistors), or the flyback will be quickly destroyed.
Registered Member #1361
Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305
i have used a flyback using a single transistor driver, and the arc output on that was good, i am using the same power supply i used on that here. by the switching current thing, i meant changing PSU's. i have been mucking aroun with the frequency of the 555 timer, but it kinda depends on wether the 555 can handle the frequency. The driver i made was this one
Right now, the audio can be heard better when there is NO arc, but just a slight corona. The circuit says 6-12V, so i dont think i should use any more than that. Instead of the said transistor, i used a TIP41C, which is an equiv. of it. Anyone know the safe resistances i could change on the circuit, but so the 555 or TIP41C doesnt let out the smoke?
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Antonio wrote ...
A normal flyback will not really produce arcs much longer than 1 cm, if you want it to last more than a few seconds.
Really? 95% of the flybacks I had could produce 10cm arcs and get just warm after a minute. It's usually in the 15-25cm range when they destroy the diodes/fry internally (we are talking about approx. 400-800W of real power when they go).
To the OP, you should run the 555 from separate supply, then you can use as much voltage as you want for your FET (well anyway, the transistor rating should be at lease 5-10 times the power supply voltage). A small foil cap (50-200nF) of sufficient voltage rating across the primary helps a lot sometimes.
Registered Member #1361
Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305
I have tried varying the frequency, removing the core spacers, varying amount of windings, and only got a little difference. Theres gotta be something else going on here, i only get a small amount of carona at 1cm!
Registered Member #1370
Joined: Mon Mar 03 2008, 09:01AM
Location: Finland
Posts: 56
How about the whole driver? Does it provide enough power for the flyback? I am currently playing with audio modulated one, and my supply gives maybe around 35Vdc at several amps (2-7). Output voltage is higher with lower frequencies, and input current is lower. I think that 100W is enough to give 5-6cm arcs. Frequency addition makes system to take more current, and therefore arcs are lots of hotter and thicker.
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
Plasmaddict wrote ...
Antonio wrote ...
A normal flyback will not really produce arcs much longer than 1 cm, if you want it to last more than a few seconds.
Really? 95% of the flybacks I had could produce 10cm arcs and get just warm after a minute. It's usually in the 15-25cm range when they destroy the diodes/fry internally (we are talking about approx. 400-800W of real power when they go).
To the OP, you should run the 555 from separate supply, then you can use as much voltage as you want for your FET (well anyway, the transistor rating should be at lease 5-10 times the power supply voltage). A small foil cap (50-200nF) of sufficient voltage rating across the primary helps a lot sometimes.
You can stretch an arc for a few cm, between points, after it starts. I measure the output voltage by the spark length between balls, and 1 cm or a little more appears to be the limit. 10 cm I would say that is plainly impossible without destroying the insulation of the flyback or making it arc to the core. The output voltage that I measure is just above 20 kV. Far insufficient for this. In most of the flybacks that I have here the point where the output cable enters the transformer is not completely sealed and the distance from there to the exposed core is of just 2 or 3 cm. I am using a 50 V power supply for the flyback, of course separated from the 12 V for the 555, and a 1500 V transistor that is operating completely saturated. I have some larger units with enough insulation for more voltage, but to drive them I need more input voltage, or an extra input winding (I am using the normal input winding).
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
An important thing to remember is that there are huge individual differences between flybacks. Some will spark readily and give huge arcs, while others just give wimpy arcs no matter what.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Well I have the same driver and i use 50v in and have 2-3 inch arcs. Use a better transistor and put at least 24 volts into it for good output. I use an irfp460 and it made a HUGE difference from what a 2n3055 could do. I of course have a great flyback though as it can withstand about 30kv indefinitely without heating much even though the arc is white hot. With the 555 running an irfp460 i can get as much as 210 watts from the flyback! If the voltage is 30kv than 210/30000= 7 milliamps!
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Another thread about singing arc...
