TIG Pulser for Miller 180SD

Microcomputers are used in lots of hostile environments. Thing is, getting them bulletproof often takes some development time. For automotive and military stuff, read weeks in the EMI lab. While it's "the right answer" for a product developer, hackers like we would rather just build something that works than make a big project of it. YMMV!

Well, as I should have expected...as soon as I post something in the dropbox, I discoverd the errors in the files. I've sent replacement files today for TIG Pulser.txt and TIG Pulser circuit.gif. The change is to the voltage regulator (U1). It should have been an LM340-15 (or LM7815) instead of a LM7812. Stuff left from earlier prototypes.

Ken

We should perhaps take this offline, though nobody's screaming yet. For DC-DC conversion to get negative bias for opamps, I've used the little chargepumps like the TC7660 -- 88 cents from Digi-Key. I've also done it with the venerable 555, a cap and a couple of diodes. Negative bias usually doesn't need to be regulated. There are also a lot of little switcher chips that can be set up to deliver negative output, and the little red toroidal 35-cent inductors (Hurricane electronics) at Ax-Man work nicely. They're about 220 uH, way more than necessary but I like the 35 cent part!

I think I would use an N-channel MOSFET with a high-side driver. That's partly because I have LOTs of N-channel MOSFETs in my goodiebox

-- and a few IR high-side drivers as well. N-channel devices are cheaper, more readily available, and exhibit lower Rds (on) for given die size.

Some former colleagues, Zoltan Zansky and Norm Planer, once patented a rather clever high-side drive scheme that can work at very low frequencies. (The high-side driver chips rely on the MOSFET switching at a fairly high frequency.) Go to

and search for patent # 4,443,719 This was in 1982 so the patent is expired by now and therefore in public domain.

I'll put a log-taper pot on my list for next Digi-Key order.

Gee, if a guy used a PIC or AVR then any old pot would work. I'm just now getting started with PIC's and AVR's, but I am very familiar with the good ol' LM324! Probably have a dozen of 'em in the linear goodiebox. The LM324 was originally designed to be a rugged automotive/industrial part. It's been around for two decades or more and still is in full production by many vendors.

Use of a uP would enable including more "features", but it's good to learn with a basic and bulletproof device first. As Ernie has observed, there isn't much lore extant about pulsers. I wouldn't know what the hell to do with a CyberTig if I had one.

I did not do much to protect it from EMI aside:

- it is in a different compartment than the HF unit (though the welder currently has its sides open)

- It does not switch any wires (with its internal relays) that go into that compartment. It switches relays that connect those wires.

When I put my inverter into my welder, which I have not done yet, I will not connect it to Cubloc in any way. The inverter will have its own timer.

i

I visited it a little, it is very nice.

i

The modern stuff that is sold these days has some interesting features. One is more analog inputs. Another, is the ability to just connect a keyboard to it. My own control panel has a keyboard (4x4). I plan to use it to program more advanced features like adjustable pulsing. That way I can do all adjustments using software and keyboard input, rather than numerous pots.

i

Not to be to picky, but the Plugs and Sockets should be both Gold or Tin.=

Mixing might - cause corrosion and become faulty.

Martin

Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net=

NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

Ken Moffett wrote:

Ignoramus31273 wrote in news: snipped-for-privacy@news.alt.net:

It's pretty obvious that web design is not my bread and butter. I was doing it mostly to document some of the things I do for the Scicnce Division. I have a workorder system, but visuals are more impressive to the powers that be, than a stack of completed workorders. I've been there for almost 6 years, and started this about a year age. Wish I had been doing it from the start. Years ago, at a former job, I picked up a tech that was let go from another department during a budget crunch. He was very good, and worked very well independently, but never documented what he did. When the crunch came, he couldn't show the administration all the truly wonderful things he did over the years, and what a valuable asset they had. So...

Ken

In years past - the DEC MicroVax workstations - I ran DEC-ELN which was a kernel OS and above a shell was only user code while below it was DEC's. It was MIL Spec.

The interesting thing, being (company was at the time) the world largest buyer of DEC machines - I was also supporting DEC as a vendor. The DEC UVax software team had no idea that the OS was even written for their machine (by a software group in a different division :-)).

But now days - one only has Sun software and Linux.

Martin

Mart> >

If copper/tin or copper/gold or gold/tin junctions set up galvanic reactions then there would be a whole lot more failed electronics out there as how Solder tiself is primarily tin. I hate gold plating since it does not improve the mechanical or electrical characteristics of the joint but has been used more as a marketing tool for making electronics look perttier and fancier

Given the choice pla> Not to be to picky, but the Plugs and Sockets should be both Gold or Tin.

Gold is good in low-current and low-voltage signal connections, particularly those that are frequently connected and disconnected. You're right that there is a lot of absurd hype re gold in audio stuff. Gold-plated line plugs, gimme a break!

Copper tarnishes, tin makes whiskers. Copper oxide can cause partial rectification in a low-current (milliamps or microamps)connection that isn't gas-tight, as in a crimp or sometimes under a screw. Tin is widely used in automotive connectors, but is verboten in aerospace because of the whiskers.