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A little success

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Ignoramus27362

Jan 1, 1970
0
I bought 10 555 timers to play with, to learn a little bit how to put
real circuits together. At $.25 each, they are cheaper to ruin that
XR2206, at $3.69 each. I finally was able to put an astable oscillator
oscillating at about 200 Hz.

i
 
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Robert Baer

Jan 1, 1970
0
Ignoramus27362 said:
I bought 10 555 timers to play with, to learn a little bit how to put
real circuits together. At $.25 each, they are cheaper to ruin that
XR2206, at $3.69 each. I finally was able to put an astable oscillator
oscillating at about 200 Hz.

i
....and, in the process, you learned a few things electronic.
 
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Rich Webb

Jan 1, 1970
0
...and, in the process, you learned a few things electronic.

Which is A Good Thing. Nobody is born knowing about this stuff and
pretty much everybody has let the Magic Smoke out of a few things along
the way. Hang in there, Ignoramus27362!
 
T

Terry Given

Jan 1, 1970
0
Rich said:
Which is A Good Thing. Nobody is born knowing about this stuff and
pretty much everybody has let the Magic Smoke out of a few things along
the way. Hang in there, Ignoramus27362!

but be *VERY* careful when messing with the big stuff - its the
difference between "oops, there goes a 555" and "Oh ****, where are my
fingers"

Cheers
Terry
 
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John Fields

Jan 1, 1970
0
I bought 10 555 timers to play with, to learn a little bit how to put
real circuits together. At $.25 each, they are cheaper to ruin that
XR2206, at $3.69 each. I finally was able to put an astable oscillator
oscillating at about 200 Hz.
 
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Ignoramus27362

Jan 1, 1970
0
Which is A Good Thing. Nobody is born knowing about this stuff and
pretty much everybody has let the Magic Smoke out of a few things along
the way. Hang in there, Ignoramus27362!

Yep... It is somewhat like computer programming, using logic to debug
things and verify assumptions etc.

i
--
 
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Boris Mohar

Jan 1, 1970
0
I bought 10 555 timers to play with, to learn a little bit how to put
real circuits together. At $.25 each, they are cheaper to ruin that
XR2206, at $3.69 each. I finally was able to put an astable oscillator
oscillating at about 200 Hz.

i

Here is something to implement at the later date in your project. My Lincoln
175 which I use primarily for tig welding has a fixed time for Argon post
weld flow. This can waste a lot of gas if you are stitching and touching up
the welds the do not stay very hot for long time after the arc has
extinguished. The post flow time should be based on the duration and current
used at the time of the last weld. This is a job for a micro but it could be
done with discrete circuitry. Since I still feel very much like a newb at
this, I'd appreciate any comments.


Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

void _-void-_ in the obvious place
 
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Ignoramus4371

Jan 1, 1970
0
Here is something to implement at the later date in your project. My Lincoln
175 which I use primarily for tig welding has a fixed time for Argon post
weld flow. This can waste a lot of gas if you are stitching and touching up
the welds the do not stay very hot for long time after the arc has
extinguished. The post flow time should be based on the duration and current
used at the time of the last weld. This is a job for a micro but it could be
done with discrete circuitry. Since I still feel very much like a newb at
this, I'd appreciate any comments.

I think that what you say makes sense. I would say, go for it, but
have a lower minimum on postflow time to avoid programming bugs
ruining your tungstens.

On my welder, postflow time is settable. I can say that, for example,
postflow should be 8.4 seconds and preflow should be 5.3 seconds and
starting current would be 44.8 amps and the welding current would be
78 amps and the time to reach welding current should be 3.2 seconds
and s0o on and so forth. It is a programmable welding machine, which
is kind of nice.

Later on, when I am done with my current inverter project (whether I
succeed or blow up the IGBTs), I may try to do an automatic welding
setup where the tig torch is moved along a straight line at a
predetermined speed and the welder is controlled from a linux laptop,
let's say. But I should not scatter myself too much, right now I am
focused on the inverter.

i
 
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John Popelish

Jan 1, 1970
0
Boris said:
Here is something to implement at the later date in your project. My Lincoln
175 which I use primarily for tig welding has a fixed time for Argon post
weld flow. This can waste a lot of gas if you are stitching and touching up
the welds the do not stay very hot for long time after the arc has
extinguished. The post flow time should be based on the duration and current
used at the time of the last weld. This is a job for a micro but it could be
done with discrete circuitry. Since I still feel very much like a newb at
this, I'd appreciate any comments.

You want a circuit that models the temperature rise of the tip and
also the cooling time for that temperature rise. An RC time constant
is probably a model that is good enough. Charge a capacitor through a
resistor with a fixed voltage that represents the steady state tip
temperature (this should be higher when the current is higher). When
the current goes to zero, this voltage will also be zxero, and will
discharge he capacitor through the same resistor. When the cap
voltage falles below some fixed threshold, representing the safe tip
temperature without gas, switch the gas off.

In parallel, I would have a single shot that switches the gas on
immediately when current starts (unless you can figure out how to have
it anticipate the current) and holds it on for a minimum time,
regardless of what the cap is doing.
 
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Rich Grise, Plainclothes Hippie

Jan 1, 1970
0
Yep... It is somewhat like computer programming, using logic to debug
things and verify assumptions etc.

But there's a significant difference - if you crash a program, it
doesn't usually let the smoke out - you just edit it and run another
edit/compile/run/debug cycle.

With real parts, when you let the smoke out, you actually _learn_
stuff. :)

Good Luck!
Rich
 
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Rich Grise, Plainclothes Hippie

Jan 1, 1970
0
On Sun, 23 Oct 2005 04:48:02 GMT, Ignoramus27362


Here is something to implement at the later date in your project. My Lincoln
175 which I use primarily for tig welding has a fixed time for Argon post
weld flow. This can waste a lot of gas if you are stitching and touching up
the welds the do not stay very hot for long time after the arc has
extinguished. The post flow time should be based on the duration and current
used at the time of the last weld. This is a job for a micro but it could be
done with discrete circuitry. Since I still feel very much like a newb at
this, I'd appreciate any comments.

Well, obviously, the place to start looking is at the current post flow
timer/regulator. It might even have an adjustment already. But if not,
then find out just exactly what the mechanism does, to figure out what
you need to do to control it. (timer relay? dashpot?)

Please report back here with the results of your investigations. :)

Good Luck!
Rich
 
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Ignoramus5533

Jan 1, 1970
0
But there's a significant difference - if you crash a program, it
doesn't usually let the smoke out - you just edit it and run another
edit/compile/run/debug cycle.

With real parts, when you let the smoke out, you actually _learn_
stuff. :)

It depends on what kind of software you are talking about.
Seriously. Around where I work, software bugs == lost money.

You do have a point though, but these chips are not terribly
expensive. I ruined a $0.29 555 timer, and a $3.59 XR2206, so far, no
big deal.

The amount of time that I spent on this project, already, is enormous
and dwarfs the cost of chips by at least 2 orders of magnitude.

I have piles of used 1960's circuit boards with plenty of free
components too.

i
 
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Ignoramus5533

Jan 1, 1970
0
But there's a significant difference - if you crash a program, it
doesn't usually let the smoke out - you just edit it and run another
edit/compile/run/debug cycle.

With real parts, when you let the smoke out, you actually _learn_
stuff. :)

Good Luck!
Rich

By the way, Rich, do you have any thoughts regarding my XR2206 issues
(see my separate thread on that). The square wave output works, but
has too low voltage.

i
--
 
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Rich Grise

Jan 1, 1970
0
By the way, Rich, do you have any thoughts regarding my XR2206 issues
(see my separate thread on that). The square wave output works, but
has too low voltage.

Well, I've already posted my thoughts, which are, in a nutshell, the
polite way, start small. Get an XR2206 working on a breadboard reliably,
and _then_ start playing with jacking up the output voltage and stuff.

And read.

Good Luck!
 
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Ignoramus5533

Jan 1, 1970
0
Well, I've already posted my thoughts, which are, in a nutshell, the
polite way, start small. Get an XR2206 working on a breadboard reliably,
and _then_ start playing with jacking up the output voltage and stuff.


Getting an XR2206 working on a breadboard reliably is exactly what I
am working on.

It kind of half works.

It produces pulses. I can see them on my scope.

The trouble is that the pulse amplitude is too small. The variable
duty cycle application that makes the chip change the timing resistor
for top vs. bottom of the cycle (which changes their relative
duration), involves sending over 2V to pin 9, from the output on pin
11. My output is about 0.67 volts in amplitude. That's my current
issue.

i
And read.

Good Luck!


--
 
J

John Popelish

Jan 1, 1970
0
Ignoramus5533 said:
Getting an XR2206 working on a breadboard reliably is exactly what I
am working on.

It kind of half works.

It produces pulses. I can see them on my scope.

The trouble is that the pulse amplitude is too small. The variable
duty cycle application that makes the chip change the timing resistor
for top vs. bottom of the cycle (which changes their relative
duration), involves sending over 2V to pin 9, from the output on pin
11. My output is about 0.67 volts in amplitude. That's my current
issue.

May I suggest an experiment? Remove the pull up resistor from the
output and see what the output does. Also, measure the pull up
resistor with an ohm meter (while it is out of the circuit).
 
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Ignoramus5533

Jan 1, 1970
0
May I suggest an experiment? Remove the pull up resistor from the
output and see what the output does.

I will try that. I have a vague feeling that I already tried, but I am
not sure.

I am considering that sticking a comparator chip between 9 and 11, if
all else fails. But I would rather understand what is wrong, rather
than pile up mistakes.
Also, measure the pull up resistor with an ohm meter (while it is
out of the circuit).

Sadly, I definitely did that. It checks out at 5.01 kOhm with my
multimeter. It is a takeout from a '1969 circuit board.

i
 
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John Popelish

Jan 1, 1970
0
Ignoramus5533 said:
Sadly, I definitely did that. It checks out at 5.01 kOhm with my
multimeter. It is a takeout from a '1969 circuit board.

1 down, unknown to go.
 
T

Tim Williams

Jan 1, 1970
0
Ignoramus5533 said:
It produces pulses. I can see them on my scope.

The trouble is that the pulse amplitude is too small. The variable
duty cycle application that makes the chip change the timing resistor
for top vs. bottom of the cycle (which changes their relative
duration) ...

Hey Iggy, if you want PWM, just grab a UC3842 from a dead monitor board, or
at worst, send a buck to a mail order catalog. If you're headed for a half
or full bridge circuit you'll want dead time too, in which case a TL494
might be better. (3524 / TL494 / KA7500 type chips are push pull output,
not overall variable duty cycle, so I don't really know what you could get
that's a cross between them..)

Tim
 
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