TIG HF circuit earthing opinions

Discussion in 'Hobby Electronics' started by Mark Harriss, Jul 23, 2004.

  1. Mark Harriss

    Mark Harriss Guest

    Hi people, I've just built an arc stabiliser circuit for TIG welding
    based on the first schematic at:

    http://www.geocities.com/CapeCanaveral/Hangar/6160/welder/arcstarter/hf.html

    My circuit is actually this:

    http://members.dodo.net.au/~ningauble/

    I have used a 10A mains filter unit (centre right of lower pic) with an
    earthing point and one half of a 10KV neon sign transformer which has the
    centre tap internally connected to earth. My query is this: is the earthing
    of this circuit acceptable or have I got some problems on my hands? even
    though the output is transformer isolated.

    I've tested the circuit and it runs fine when welding aluminium with a small
    AC stick welder and produces a small amount of screen noise on the TV set 3M
    away.

    tia
    Mark Harriss
     
    Mark Harriss, Jul 23, 2004
    #1
    1. Advertising

  2. On Fri, 23 Jul 2004 05:48:38 GMT, Mark Harriss <>
    wrote:

    >
    >
    > Hi people, I've just built an arc stabiliser circuit for TIG welding
    >based on the first schematic at:
    >
    >http://www.geocities.com/CapeCanaveral/Hangar/6160/welder/arcstarter/hf.html
    >
    >My circuit is actually this:
    >
    >http://members.dodo.net.au/~ningauble/
    >
    >I have used a 10A mains filter unit (centre right of lower pic) with an
    >earthing point and one half of a 10KV neon sign transformer which has the
    >centre tap internally connected to earth. My query is this: is the earthing
    >of this circuit acceptable or have I got some problems on my hands? even
    >though the output is transformer isolated.
    >
    >I've tested the circuit and it runs fine when welding aluminium with a small
    >AC stick welder and produces a small amount of screen noise on the TV set 3M
    >away.
    >
    >tia
    >Mark Harriss



    Hello Mark,
    congratulations on a fine looking arc starter.
    I like it! Good for you!

    I could see the picture OK but the circuit diagram did not
    appear for me, could you send me the circuit via e-mail please.

    I started collecting bits to make an arcstarter myself and
    then an old Lincoln unit fell at my feet for next to nothing.

    The high voltage capacitor associated with the spark gap
    is hard to find. I am assuming your capacitor is made up
    of many caps in the white tube. What types are they, where
    did you get them and how much did they cost?
    Tell me about your spark gap. What is the base made
    out of? I am assuming tungsten tig rods for the gaps,
    what diameter?
    You found a nice little neon sign transformer too. The one
    I was going to use is enormous. I didn't come across any
    small ones when I was looking for them. What are the
    dimensions of your cabinet so that I can estimate the size
    of the bits and pieces?

    Back to your question. I can't see any problem having
    one side of the secondary earthed. It would be nicer
    for us if one side the secondary wasn't earthed but we
    have to use what we can find. :)

    Funny how we have different takes on what is important,
    I haven't worried about noise filters but plastered my rectifier
    unit with heaps of capacitors to protect the diodes. I use
    O.1mfd caps across the welder terminals and to ground also.
    I can't see a High Freq by pass capacitor in your picture on
    the welder side terminal inside your arc starter. Maybe it is
    there but I cant see it. I just want to make you aware of adding
    protection for your welder or rectifier or nice inverter tig welder
    should you connect one up to your arc starter. I am probably
    over cautious here, but couldn't give a monkeys about the
    electrical noise. :)
    The heavy current black coil to front panel studs, how
    is that done? Is it a copper tube?

    Excellent job Mark!
    Regards,
    John Crighton
    Sydney

    PS
    Here are some pictures of my old Lincoln arcster
    http://users.tpg.com.au/john_c/
     
    John Crighton, Jul 24, 2004
    #2
    1. Advertising

  3. Mark Harriss

    Mark Harriss Guest

            Thanks for the feedback John, I've fixed a mistake in the page so the
    schematic should now load ok and added some extra text and photos to provide
    more detail about the unit, if you'd care to take another look at it, I can
    answer any more questions.

    Thanks
    Mark
     
    Mark Harriss, Jul 24, 2004
    #3
  4. Mark Harriss

    Mark Harriss Guest

    Thanks for the picture of your Lincoln John.
    It's the first look inside a commercial unit I've seen so far.

    Mark Harriss
     
    Mark Harriss, Jul 24, 2004
    #4
  5. On Sat, 24 Jul 2004 04:58:40 GMT, Mark Harriss <>
    wrote:

    >
    >        Thanks for the feedback John, I've fixed a mistake in the page so the
    >schematic should now load ok and added some extra text and photos to provide
    >more detail about the unit, if you'd care to take another look at it, I can
    >answer any more questions.
    >
    >Thanks
    >Mark



    Hello Mark,
    that is brilliant mate!
    You even made your own capacitor. WOW!
    I was thinking it was probably a bunch of regular
    1000 volt polywhatevers in series parallel to acheive
    around 2000pF 10KV rating stuffed in the tube and here
    you have made one single capacitor. That is great!

    You mentioned Aluminium solder. I want to know all
    about that. Where did you get it?

    You have plenty of room in the box to build a gas flow timer
    to keep the gas flowing after you stop welding for several
    seconds and upwards. Protects your cooling tungsten and
    your cooling weld from contamination.

    For DC welding steel, once the arc has started you don't
    need the HF to run continuously as you do with Aluminium,
    so you might look into fitting a sensor circuit to switch
    the neon sign transformer supply off after the arc has started.
    This will save wear and tear on the spark gap points and
    your capacitor.
    I press a button on my tig torch handpiece, well, it is just
    a taped on microswitch which causes a relay to switch
    power to the high voltage transformer. Another relay
    drops out or clicks in, I cant remember, when the welding
    transfomer or DC supply open circuit voltage drops from
    about 50/80V to around 25V. Meaning heavy current is
    now flowing so there is no more need for the HF high voltage.
    For Aluminium welding I can switch to continuous HF high
    voltage.

    Have you told "Bill the Arcstarter" about your project?
    I am sure he will be delighted that you used his notes
    and achieved success.
    There is a DIY Welder mailing list that has been out of
    order for a while but is just starting up again now.
    http://www.diywelder.com
    http://forums.diywelder.com/forum/index.php
    I am sure the people there will be delighted to see
    your arc starter also. They are all struggling with this
    stuff. You would give them inspiration Mark.

    I can't quite see from the pictures how you joined the
    heavy black cable to the studs.It looks very neat How
    did you do that?
    You have inspired me Mark, I will have to join the list
    again. :)

    So many hobbies and so many things to do.
    Lifes Good.

    Regards,
    John Crighton
    Hornsby
     
    John Crighton, Jul 24, 2004
    #5
  6. Mark Harriss

    Mark Harriss Guest

    Hi John,
    I did try multiple 630VDC capacitors up to 40 KV in
    series/parallel arrangements but they all died in under 5
    seconds no matter what. The aluminium solder was bought ages
    ago from Dick Smith and is made by Multicore. It needs a hot
    tip which will suffer corrosion from the flux (it stripped
    2mm of scale from a 150W Birko iron in minutes.

    The gas timer will be next cab off the rank for my unit.
    I still need to get my own handle yet though buying one from
    the states looks to be about 30% of the local price.

    Does TIG welding aluminium require actual high current HF
    power or is 50Hz good enough?.


    Thanks
    Mark Harriss
     
    Mark Harriss, Jul 24, 2004
    #6
  7. Mark Harriss

    Phil Allison Guest

    "Mark Harriss"
    >
    > Does TIG welding aluminium require actual high current HF
    > power or is 50Hz good enough?.
    >



    ** Ask 2GB if you can borrow their 873 kHz transmitter for a small welding
    job - should work a treat.


    What macaroon !





    .......... Phil
     
    Phil Allison, Jul 24, 2004
    #7
  8. Mark Harriss

    Mark Harriss Guest

    Funny you should mention that,but a friend of mine
    qualified as a broadcast engineer while working at 2GB in the
    sixties. I have personally seen a tech strike a small welding
    arc across the bottom egg insulator of a guy wire at the Bald
    Hills shortwave transmitter in Brisbane.

    Regards
    Mark Harriss



    Phil Allison wrote:

    >
    > "Mark Harriss"
    >>
    >> Does TIG welding aluminium require actual high current HF
    >> power or is 50Hz good enough?.
    >>

    >
    >
    > ** Ask 2GB if you can borrow their 873 kHz transmitter for a small
    > welding
    > job - should work a treat.
    >
    >
    > What macaroon !
    >
    >
    >
    >
    >
    > ......... Phil
     
    Mark Harriss, Jul 24, 2004
    #8
  9. On 24 Jul 2004 03:12:54 -0700, (Mark Harriss)
    wrote:

    >Hi John,
    > I did try multiple 630VDC capacitors up to 40 KV in
    >series/parallel arrangements but they all died in under 5
    >seconds no matter what. The aluminium solder was bought ages
    >ago from Dick Smith and is made by Multicore. It needs a hot
    >tip which will suffer corrosion from the flux (it stripped
    >2mm of scale from a 150W Birko iron in minutes.
    >
    > The gas timer will be next cab off the rank for my unit.
    >I still need to get my own handle yet though buying one from
    >the states looks to be about 30% of the local price.
    >
    > Does TIG welding aluminium require actual high current HF
    >power or is 50Hz good enough?.
    >
    >
    >Thanks
    >Mark Harriss



    Hello Mark,
    thanks for the info on the solder. Pity about the multiple capacitor
    bank. I think the Tesla coil boys use a particular polycarbonate
    type that are more rugged than normal polycarbonates for pulsed
    use and have some slight self healing ability. I remember checking
    them out price wise and they were about four or five dollars each from
    a mob called Crusader or a name something like that down at Padstow.
    The Tesla group have all the details on this capacitor. Anyway, they
    were too expensive for me. Did you use resistors (in the megohm
    range) across each cap in your original multiple mini capacitor bank.

    Yes, 50 Hz is fine for welding aluminium using an ordinary common
    transformer machine. Some welders have a "balance control"
    that can bias the AC current waveform to be slightly more positive
    or negative as required.
    Electrode negative heats the job more than the tungsten electrode.
    Electrode positive heats the tungsten electrode more than the job
    but has a nice cleaning action on the aluminium. So playing with
    the balance control allows the operator to have more, or less
    cleaning action, according to what the job requires.
    People have being using plain ordinary transformer welders
    with no balance control for decades. You'll be fine.

    With the expensive inverter machines full of bells and whistles
    the AC welding current can be varied from 20 Hz to a few
    hundred Hz. The higher the welding current frequency the
    narrower the heat cone becomes. One of the students
    at the Meadowbank Tafe welding night class brought
    in his new $6000 suitcase size inverter tig machine and
    let us all have a play with it. At 20 Hz the heat cone was
    fluttery and wide. At the higher frequencies, I noticed a definite
    narrowing of the heat zone. Good for penetration on thick material.
    I only had a five minute play but it was great.
    We all wanted to play with it. Variable pulse settings, variable
    background current settings, adjustable sequences, for heating
    up and gradual cool down to avoid craters and memories for
    recalling the settings for particular jobs. What a machine!

    I bought a cheap auto darkening helmet which helped me
    enormously but later I found out that the view through it was not
    as clear as other students autodarkening helmets. I paid $200
    for mine, I have seen the same model go for $100 new on
    ebay. Try a few on the job before you buy one. The one I
    liked owned by a fellow student was a $300 Preditor brand.
    To me, the clarity of this student's Preditor helmit was
    as good as our teachers expensive Speedglas helmet.
    Avoid this one. AG3 (AG111)
    That is the model I have It is not good.
    http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&category=633&item=3829460081&rd=1
    Give that brand/model a miss.

    Hey Mark, you still haven't told me how you joined the
    heavy black cable to the front panel studs. :)

    You mentioned buying a tig torch from the USA.
    Silverwater welding down here in Sydney have a
    small tig torch, 100 amps max for short periods for $110.

    Have you bought stuff from the USA? Any problems with duty
    or customs? I have been looking at used electronic test equipment
    from the USA on ebay and it looks so good, price wise.

    Regards,
    John Crighton
    Hornsby
     
    John Crighton, Jul 24, 2004
    #9
  10. Mark Harriss

    Mark Harriss Guest

            Hi John, sorry about the delays but the news server I'm using hardly
    updates these days. The cable is joined to the 1/2" threaded brass rod with
    1mm tinned copper sheet that is formed on a round mandrel and soldered to
    the brass rod, then the narrower copper cable is inserted and crimped closed
    with pliers. The copper does not closed at the top and solder can be fed
    through to completely fill the voids. The outside is wrapped in the scotch
    23 tape (butyl?) which eventually fuses into a single mass.

            My cap banks did have multiple series parallel units of four parallel
    and about 40 series units but no equalising resistors as I thought they
    would average out over multiple parallel units. They were no-name mains
    suppression caps and I think they just weren't of a suitable quality for the
    job.

            So the switchmode TIGs only go up to a few hundred Hz?. It should be
    possible to make a controller for a conventional welder but switchmode
    welders are getting cheaper every day. The TIG handles here:

    http://www.welding-direct.com/

    sell for US$57 for a 200A unit with a 4m cable but need all of the
    accessories bought to go with it such as collets and nozzles.The same unit
    from BOC Australia is A$480 so as you can see it's a fair bit cheaper.
    As far as getting the stuff into the country I just get it posted and have
    had no problems so far.


    Mark Harriss
     
    Mark Harriss, Jul 25, 2004
    #10
  11. "Mark Harriss" <> wrote in message
    news:...
    > Hi John,
    > I did try multiple 630VDC capacitors up to 40 KV in
    > series/parallel arrangements but they all died in under 5
    > seconds no matter what.


    Yes that would be right !! DC Capacitors can fail due to ionisation between
    the plates known as the corona effect destroying the Dielectric at Voltages
    Higher than around 100V AC ...
    Try again only using Capacitors specified for High voltage AC and you should
    have a much lower Failure rate

    Some references :
    http://www.sbelectronics.com/cterminology.htm
    http://www.azom.com/details.asp?ArticleID=1266
    http://www.avxcorp.com/docs/Catalogs/cdesc.pdf

    > The aluminium solder was bought ages
    > ago from Dick Smith and is made by Multicore. It needs a hot
    > tip which will suffer corrosion from the flux (it stripped
    > 2mm of scale from a 150W Birko iron in minutes.


    I purchased some for a job a few Months ago so afaik DSE still stocks it
    .....

    Regards
    Richard Freeman
     
    Richard Freeman, Jul 29, 2004
    #11
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. siliconmike

    Earthing in TV

    siliconmike, May 21, 2005, in forum: Electronic Basics
    Replies:
    22
    Views:
    2,242
    Ken Taylor
    May 24, 2005
  2. Replies:
    10
    Views:
    925
    Fred Bloggs
    Jun 19, 2005
  3. Ignoramus24693

    TIG inverter: schematic of the timing circuit

    Ignoramus24693, Oct 16, 2005, in forum: Electronic Design
    Replies:
    0
    Views:
    683
    Ignoramus24693
    Oct 16, 2005
  4. Ignoramus26745

    Snubber circuit design -- max voltage (TIG welder)

    Ignoramus26745, Nov 2, 2005, in forum: Electronic Design
    Replies:
    5
    Views:
    775
    Winfield Hill
    Nov 3, 2005
  5. Ignoramus17256
    Replies:
    0
    Views:
    597
    Ignoramus17256
    Nov 5, 2005
Loading...

Share This Page