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Simple flyback driver Help please!

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Niykon

Sun Apr 25 2010, 09:05PM

Registered Member #2826 Joined: Sun Apr 25 2010, 08:21PM
Location:
Posts: 6

Hello all,

For the past month I have been messing around with flyback drivers, the ultimate goal being a DIY Jacob's Ladder. At the start of the project, based off the circuit diagrams, available knowledge, etc this seemed a simple and relatively straightforward proposition. That was a month ago.

I began by ripping the flyback drivers out of a CRT Monitor, and a small 20" tv.

First Driver:
I started with this driver:

Not having any 2n3055 transistors, I made use of some surplus 2n3773 transistors.

After identifying the sense coil, primary coil, and HV pin, I fired the driver up using a 12v Car battery charger. I burned up my first transistor, as I failed to identify the correct polarity on the primary. But after the transistor was replaced, limited success was mine! I was awarded with a measly .25" arc. Clearly this was a successful trial run, but most assuredly not a successful Jacob's Ladder.

The reason for this, in my mind: The sense coil was external, so I could see that it was in the realm of 20-30 windings. This means that the primary had many more windings then this. With so many windings in the primary, no wonder I was getting lousy results.

Second Driver:

After messing around with capacitor and resistor values, I finally got a square wave. The results, with a 24v input? A .5 mm arc. Again, measly, but this was using the internal primary winding. So I cut off the external sense coil, and rewound on a primary of 10 tuns. The results: a .25" arc. Again, not good enough.

Third Driver:
For this driver, I went back to the first driver circuit, and rewound my primary and secondary. I used 3 turns for sense, and 5 turns for primary, of .43mm dia magnet wire. This is 26-24 gauge wire. I know this is too small, but its what is on hand. After hooking up the circuit, this time with a 2n5880 transistor, the results: A burned up resistor. I had been using the fattest resistor i could find in my piles of junk, without knowing its power rating. So, I went down to my stores again, and using 1/2 watt resistors, rigged up a serious series/parallel resistor combo, getting me up to roughly 5 watts on each resistor combo. The new results with 24v: NOTHING, except the heating of my 2n5880.

SO, my question is this. What am I missing?! I see people on YouTube, this forum, countless websites, even some 12 year old kid on Instructables getting much more impressive results then I am, and I am doing exactly as they are doing.

When I get home tonight, I can upload photos of my flybacks, setups, etc if need be.

hboy007

Sun Apr 25 2010, 09:12PM

Registered Member #1667 Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 373

Hi there and welcome to the 4hv community.
Deja-vu, anyone?

Antonio

Sun Apr 25 2010, 09:42PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Possibly your power supply has not enough current capability. Anyway, a regular flyback transformer will not produce a spark much longer than 0.25" between smooth terminals, or 3 times this between points. Using the internal primary coil you need at least 50 V to get significant output, switching at a few kHz. To switch at tens of kHz, obtaining the full power that the transformer can handle, you need a higher voltage power supply, possibly more than 100 V (this is what is used in TVs and monitors). With an external primary you essentially trade less voltage for more current, and your power supply must be able to handle it.

cjk2

Sun Apr 25 2010, 09:50PM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263

Yes, post pictures.

Random suggestions:
Don't even consider using the built in windings. They are junk, you don't know the turn count, wire awg, etc. Just forget about it. The one transistor drivers are junk. Anything 2n3055 based (or whatever random transistor you use) is just a bad design. Build a ZVS royer style driver. Do not use bipolar transistors with a 555 driver. If you do insist on doing this, use a dralington transistor. Your problems are likely caused by the transistor having a low gain, maybe 10-50. And it is difficult to drive them hard enough with a 555. Use a darlington arrangement or a MOSFET to solve your problems. Also stick a snubber across the switch so the inductive kick does not destroy it.

Or just build a ZVS driver and don't worry about any of these problems.

Niykon

Mon Apr 26 2010, 07:31AM

Registered Member #2826 Joined: Sun Apr 25 2010, 08:21PM
Location:
Posts: 6

It seems that both of you are saying, boiled down, that I need a higher voltage power supply. I totally agree on that point. However, the point behind this is a form of cool, cheap gift for 3 friends. They are all engineers and would absolutely love it :p And yes, I do know that Jacob's Ladders are dangerous. This is why I have 10ft of clear 5 inch pipe in my garage. This is to go over the electrodes, and prevent unwanted hands getting into the arc.

So with this in mind, my goal is to produce a Jacobs ladder with a moderate gap at the top. Maybe 1.5"-2"

What kind of driver should I go with, to achieve this. My goal is to keep the cost for this project under 50$. I KNOW that the simple 2n3055 driver can get some results. Why is mine currently getting NO results.

Also, im considering giving this one a go:

But, with such measly performance from ANY driver ive tried... I dont think its quite the drivers fault? Im not sure if its the power supply, as the battery charger provides just over 12v a 9 amps. As far as the 24v supply, im not sure what its rated for. But hey, it was around :P

Besides, this guy is using a 9v battery:

And hes also getting way better performance.

GhostNull

Mon Apr 26 2010, 12:51PM

Registered Member #2648 Joined: Sun Jan 24 2010, 12:45PM
Location: Australia
Posts: 291

Niykon wrote ...

This is why I have 10ft of clear 5 inch pipe in my garage. This is to go over the electrodes, and prevent unwanted hands getting into the arc.

beware of ozone build up

radhoo

Mon Apr 26 2010, 03:22PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699

You can use the the 555 timer chip , but you'll need to add a totem pole made of transistors to control the mosfet. The schematic you've posted is incomplete, and the author highlighted that in his webpage, so extra care when choosing your schematics.
Here is my page with quite a few high voltage power supplies:

In order, you have the simple 2n3055 oscillator, the dual 2n3055 for more power, the 555 driver, the ZVS, etc etc, with some pics and vids to aid the construction.

Regarding th epower supply, 24V is enough for some remarkable sparks
(here's my marx generator using 12V @ 10Amps max:

)

But in case you'll need to build your Own high power lab supply, this approach works good:

quicksilver

Mon Apr 26 2010, 09:05PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

I've experimented w/ the ZVS driver, a 555 design and the simplistic single TO-3 x-ister designs. The ZVS driver needs some amps. If you don't feed it at least 8, I wouldn't bother as the sparks are similar to most others @ low current levels. That being said, it's just about the best design available (ZVS).
The trick w/ the simple single x-ister designs is that they are short use only. Limit them to a few seconds and work with your feedback & primary coil windings and you may be surprised. I've gotten 2-3 cm sparks from them w/ 12Vdc & 3A.
The 2N3055 is not a good idea. The 2N3773 is a good choice as is the MJE19003. IF you're going to go with a simplistic design look at your transistors and pick high energy switching transistors and high wattage resisters (even as high as 10W).
If you do build a ZVS, buy quality Zeners & pay strict attention to the choke (wind it well: test it prior if you can).

Niykon

Mon Apr 26 2010, 11:08PM

Registered Member #2826 Joined: Sun Apr 25 2010, 08:21PM
Location:
Posts: 6

Hey again,

I gave the dual 2n3055 circuit a go, this time on the monitor flyback. Still nothing accomplished, except heating up one of the transistors significantly.

I used my car charger again as the power supply. Its being drawn down to 8.9 volts. Across the primary, im only reading .03v.

What am I doing wrong here. Ive triple checked the circuit, and tried both the sense and primary coil both ways (As in, I hooked up to both ends of the coils) to see if perhaps there was a polarity issue. No difference.

The only difference between my driver and the one on your website, radhoo, is that I have a different flyback, as well as using a diff. transistor. I am making usage of a 2n5880 transistor, as opposed to a 2n3055. I looked at the datasheets, and the only difference i notice is that mine is rated for more power and voltage....

So is the transistor the issue?

cjk2

Tue Apr 27 2010, 04:52PM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263

Perhaps a transistor is bad. Maybe one of your windings is out of phase. Maybe your power supply voltage is too low. Post some pictures if you can.

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