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ARC STARTER AND STABILIZER - COMPLETED

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Newton Brawn

Fri Apr 01 2011, 10:00PM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Hi !

Here the complete arc starter to be attached to a buzzbox, tig, or a plasma cutter.

Description:

]arc_starter_original_complete_w-rev2_in_pdf.pdf[/ file]

Drawings:

]des_arc_starter_and_stabilizer_r2.pdf[/file]
]des_sssg_schematics_r2.pdf[/file]
]des_tungsten_carbide_spark_gap_r3.pdf[/file]
]des_pulse_transformer__coupling_coil_r2.pdf[/ file]
]des_hv_glass_capacitor__r2.pdf[/file]

Pictures:
Parafernalia to measure the HV pulses and spark gap used in begin of project.
Device to wind the pulse transformer - a turn counter and cranckcase. Also a C clamp to hold the device in the table, polyester paper to insulate the layers of the coil, a ferrite core from a tv, a coil after the impregnation.

1301695036 3343 FT0 P Aparatus To Measure High Voltage Spark Gap

[/img]]

1301695125 3343 FT0 P A Cranckcase And Turn Counter Dscf0058

There are more pictures and a video.

Regards

Newton

Ash Small

Sat Apr 02 2011, 06:02AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Very nice work Newton. Do you have any photos of the complete unit?

I'm making some new heatsinks to upgrade my rectifier at the moment and I hope to get my HF arcstarter down here soon (it's in storage 200 miles away at the moment, along with my buzzbox).

Once I've done that I'll post some details of mine, which is simpler, but runs continuously.

Newton Brawn

Sun Apr 03 2011, 11:49PM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Hi Ash Small !

SIm, I have several pictures showing the device under test. It is a assemble not 100% beatiful, but just to put the components together and allow changes in te schematic.

I have a short video, "15+kV in the hands", however I could not attache to the forum. Maybe I can send direct to you

I have tested other circuits simpler tham this one, let me know the schematic of your arc starter.

Regard

Newton

Pictures:

Arc Starter Under Test
Back Picture
Tungsten Carbide Spark Gap

1301874500 3343 FT112240 Arc Starter Under Test Pic2 Dscf0075

1301874500 3343 FT112240 Back Picture Pic2 Dscf0076

1301874500 3343 FT112240 Tungsten Carbite Spark Gap Pic2 Dscf0080

Ash Small

Mon Apr 04 2011, 03:01PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I'll try to draw a circuit from memory later (it's ten years since built it).

In the meantime I'll upload an animated GIF that I created from a basic 3D model I drew when designing a case for it.

(EDIT: Looks like you need to 'click' on the above image to see the animation)

The case is about 12"X12"X18".

I'll start by decribing the layout of components on the front panel.

First, there are the two input and two output glands for the welding current, along with 240V in and argon in/out.

There is the argon flowmeter/controller in the centre, on/off switch on the upper right, and a 'power on' indicator and coloured lens through which I can see the sparkgap, for positive conformation that it is functioning. (the sparkgap is an unsuppressed automotive spark plug).

The three long cylindrical components on the left hand side at the bottom are the hand-rolled HV capacitors. Two of these form part of the HF choke (low pass filter), the other forms part of the spark tank circuit.

Above these are, at the rear, the heatsink cooled by two computer case fans (one blowing, one sucking) which houses the 2N3055 transistor that switches the flyback transformer. (There is a cutout in the back panel for cooling, along with louvres in the sides of the case).

The rest of the switching circuit (two resistors) is housed in front of the heatsink, above the HV capacitors. (along with the flyback transformer, with a ten turn primary and four turn feedback winding)

The box-shaped item at the right lower rear is the 12V wall-wart that privides power to the switching circuit for the flyback, and also powers the cooling fans on the transistor heatsink..

In front of this, (lower right centre) is the choke, which, along with two of the HV capacitors, stops the HF getting back into the rectifier and buzzbox. (The choke is wound on a 50Hz toroidal transformer core)

The component at the left front is the air cored transformer that superimposes the HF onto the welding current. This is arranged in a different orientation to the choke in order to minimize any interference between these two components.

I'll try to provide a circuit diagram and more details later.

(work in progress......)

Newton Brawn

Mon Apr 04 2011, 04:50PM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Hi All

It appears that we can not open the last picture , so I m attaching again.

Regards

1301935785 3343 FT112240 P Tungsten Carbite Spark Gap Pic2 Dscf0080

Newton Brawn

Sat Apr 09 2011, 08:54PM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Ash Small ,

What bring my attention is yours hand made capacitors....Can you provide a good description of its construction ???

Please let me know the schematic of your arc stater, I am really interested on it.

Regards

EDIT: Change of contraction to construction

Ash Small

Sun Apr 10 2011, 02:30AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I'm planning to make some more capacitors this week, so I'll write it up and provide some photos.

Ash Small

Sun Apr 10 2011, 04:45PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

The World's Simplest HF DC TIG welder (schematic).

I built this ten years ago, but I'm pretty certain it is accurate.

(not sure if the second capacitor (50 nano) on the HF choke is required, or if the 'mains protection choke' on the wall wart is required, I added them as a precaution, so, in theory, it could be even simpler.

I've not tried other values for capacitors, or number of turns on air core transformer, as it worked OK first time I tried it (if it ain't broke, don't fix it), but knowing what I know now, I'd probably try some different values. I think the value of the resistor was 330 K Ohms (it was 330 something, I think)

I also might add some protection for the 2N3055 transistor. (I forgot to add the two PC fans cooling the transistor heatsink)

Newton Brawn

Wed Apr 13 2011, 02:24PM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Ash;

Following the World's Simplest HF DC TIG welder (schematic as previous thread ):
I am also not shure about the real need of the iron core bifilar choke on the output of the rectifier ON PREVENTING THE HV molesting the rectifiers.
Following the schema you can see that the HF from the coupling coil can reach very easy the rectifiers and the secondary of welder transformer. This is because the choque capacitance between turns and other stray components.
A capacitor 0.2 ~~ 2uF from the + of the rectifier to ground and other cap of same value from - of rectifier to ground will reduce the HV HF to very low magnitude, avoiding the HF bad effects on rectifies and buzzbox components.
Miller HF15, HF251 and several other machines do not use bifilar choke. Just caps to block the HF.

Note that in the previous thread schema the bifilar choque shall be coiled with wire size suitable for high current.

Also a DC choke just after the rectifier bridge is fine to smooth the rectifier 120Hz pulsing current, giving some help stabilizing the arc.

The values 330Kohms and 0.02uF cap look ok. One discharge evey 5 ~~10 milesecond, controled by the adjustment of gap distance of spark gap. The result is HF pulses not synchronized with the pulsing dc output of the buzzbox... Some misfire during the stabilizing process.

Next time, I wiil show a simpler arc starter ckt

Regards

Newton

Ash Small

Wed Apr 13 2011, 02:43PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Newton Brawn wrote ...

.
The values 330Kohms and 0.02uF cap look ok. One discharge evey 5 ~~10 milesecond, controled by the adjustment of gap distance of spark gap. The result is HF pulses not synchronized with the pulsing dc output of the buzzbox... Some misfire during the stabilizing process.

.

I think the frequency is higher than 5-10 milliseconds. The resistor plays no part in determining frequency, it simply blocks the current circulating in the tank from getting back to the secondary of the flyback. (it follows the path of least resistance).

Frequency is determined by the 20 nano farad capacitor and inductance of the primary of the air core transformer, which I wasn't able to measure when I built it (ten turns 25 mm diameter by ~120 long).

At least, this was the theory I used when I designed it.

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