PWM [or ANY OTHER] chip that can drive an H bridge?

I was going to suggest an LM339 circuit but, if you're happy, I'm happy ;-)

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Jim Thompson
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I was going to suggest a 555, 50c for one at digikey. But if Jim is happy, then I'm happy too.

Jeff Stout

Reply to
jstout

Don't tell me you designed the xr2206 too?

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 Thanks,
    - Win
Reply to
Winfield Hill

What the #@$% is your problem?

I told you, with at least two options.

Sphero told you, also with at least two options.

Both of us gave you solutions that would be programmable with two pots.

Both of us gave you solutions that will work from 5V to 18V (or more)

Both of us gave you solutions with chips that are in my 1982 National Linear databook, before surface mount was found in anything but weird military systems.

Others chimed in with addenda and cautions &c.

If you can read you already have your answer. If you can't read go back to school.

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Tim Wescott
Wescott Design Services
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Reply to
Tim Wescott

One package of LM339 has 4 comparators... can do both your oscillation AND duty cycle requirements.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

Sure.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

I got you beat on adjustability ;-)

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

No. But I've used it as the core for a super-quality function generator by adding self-tweaking elements around it.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

Gentlemen, I greatly appreciate your help. You helped me with so many decisions already. I would not be where I am without it. However, I am somewhat confused by something.

I am not really asking for very much. I cannot believe that I have to go to great lengths or create esoteric solutions. I suspect (and hope) that we are missing something simple.

Let me make it very clear as to what I want.

I want a IC chip that has the following characteristics:

  1. Generates pulsed, square wave, preferably at 5V above ground alternating with ground.

  1. Can have its frequency controlled by a separate pot and able to function around 30-1000 Hz

  2. Can have its "duty cycle" (percentage of time it spends in the HIGH section) controlled by another, separate pot.

  1. Preferably use about 18VDC power.

  2. Preferably is a DIP.

It may be called PWM or something else. Let's not get stuck on designation here. What matters is that it does what I want.

Is it really true that such chips are nonexistent?

MAX038 does almost what I want, but it is a little expensive, requires a different power supply compared to the gate driver and also amplification of its output. Otherwise it is great.

i
Reply to
Ignoramus30105

I think that I finally found what I am looking for.

XR2206

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$3.59 at Jameco. It fits the bill perfectly.

i
Reply to
Ignoramus30105

Thanks Jim... That IC looks reasonable to you, right?

i
Reply to
Ignoramus30105

You could make one out of a Schmitt trigger. 74HC14 or CD40106. Look at the app notes for "oscilltor" that are often part of the data sheets. Place another resistor across the one from input to output but with a diode in series. Then you can control the duty cycle. That would come to about 10 cents plus some discretes. Oh, and the potmeters.

Regards, Joerg

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Reply to
Joerg

I am happy too. Like I said, I will first make a circuit without the timer chip and will use my wavetek for timing. I will test it without using heavy current or high voltage on the power line.

Once (or if) that works, I will add XR2206 and proper pots and caps, and after testing will try it for real to weld something.

If all works, then I will try to integrate this contraption with my welding machine, by placing it inside the welder and connecting it properly before the high frequency arc start circuit. That way I could use arc start and DC inverter without IGBTs being damaged by high voltage.

My plan for that is to modify that DC electrode negative/DC electrode positive switch to be DCEN/AC/DCEP. If it is in the AC mode, the DC inversion circuit that I built would be powered up.

I would, then, place the adjustment pots on the welder's front panel.

There is plenty of space inside the welding machine.

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I am hoping that if all works, I will convert my $9.99 welding machine (what I paid for it) into a $2,000 welding machine. It would be a perfectly well settable AC/DC welder with digital controls, quite modern in fact.

The only minus of this welding machine would be lack of portability and 3 phase power requirement. I can live with that.

Again, I am doing this for myself, I have no plans to sell this welder.

i
Reply to
Ignoramus30105

Hello Jim,

But the LM339 is 10-12 cents while a 74HC14 is 6-7 cents. And it's a six-pack from which you'd only need one.

Regards, Joerg

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Reply to
Joerg

I read in sci.electronics.design that Ignoramus30105 wrote (in ) about 'PWM [or ANY OTHER] chip that can drive an H bridge?', on Fri, 7 Oct 2005:

If that's REALLY what you want, a 555 will do it. So I guess that ISN'T what you really want.

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Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
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Reply to
John Woodgate

Hello Jim,

Not if I am allowed to use more than one of the Schmitt inverters. Even with just one you can adjust but then it would be an adjustment of low phase and high phase, not the frequency.

Regards, Joerg

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Reply to
Joerg

Yes, we're missing, "What's the goal?" i.e., "What's the application"? "What's the end result you're trying to accomplish?"

You're detailing us to death here - just tell us what you have, what you want it to do, and let the experts figure out how to get from point A to point B.

Thanks, Rich

Reply to
Rich Grise

I did a PWM with a 555 once, and it died first time out. Finally ended up with a pair of MPSU06s in an astable multivibrator.

But this was for a spool gun, that got its power from the welder itself, through the cable. =:-O Very nasty electrical environment!

Good Luck! Rich

Reply to
Rich Grise

$9.99 -- Nice eBay purchase. 300#, have you picked it up yet?

These are also available at low cost on eBay. But I suppose you know that. I assume you have a copy of the datasheet.

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 Thanks,
    - Win
Reply to
Winfield Hill

I will be happy to oblige. I want to thank you for attention and hope that you would be able to provide some expert guidance.

I have a 200A DC Tig welder. Here it is:

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I want to design a device to convert it to a AC/DC welder by means of a H bridge based inverter, to produce square wave AC.

I am going to use Toshiba 200 A IGBTs MG200Q2YS40.

I will drive them using half bridge drivers such as IR21094 chips.

What I need is a generator of pulses to drive the input of IR21094. This generator would send signals to tell IR21094 when to open the high side and when to open the low side.

To be an optimal tig welder, I would like the frequency of pulses to be settable with a potentiometer, from 20 to 400 Hz or so, and to have the width of pulse, as a percentage of pulsing period, to also be settable by a separate pot. That percentage is called a "duty cycle", and I would like it to be relatively wide ranging, say between 20% and

80%.

I apologize if my explanation is unclear and will be glad to clarify it and answer any questions.

As to what I am looking for right now: I am relatively clear as to what to do around IGBTs and gate drivers. I am not as clear as to what is the easiest way to build a generator of pulses that would satisfy the above requirements.

I am looking more for an easy way than for a very cheap way, within reason of course (I did not buy a brand new tig welder, after all). For instance, I would rather buy a $40 "module" that would do what I want, rather than buy a few 50 cent components and spend a week figuring it out.

That said, if figuring out is necessary, I would do it.

So, if you have suggestion for a simple pulse generator, preferably giving 5V pulses and with about 18V power supply, I would be happy to hear from you.

i
Reply to
Ignoramus30105

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