Will this timer work?

Greetings All,
I have a wire feed welder that I would like to add a stich timer to.
The way it works is when the trigger on the welding gun pressed the
welder turns on for a short time, then turns off for a short time, and
so on until the trigger is released. So I thought I would use a 556
timer because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556
and a solid state relay makes me wonder if the 556 circuit is
appropriate.
Thanks,
Eric

 

[Tim Wescott]

On Thu, 19 Mar 2015 10:43:58 -0700, etpm wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to. The
way it works is when the trigger on the welding gun pressed the welder
turns on for a short time, then turns off for a short time, and so on
until the trigger is released. So I thought I would use a 556 timer
because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556 and
a solid state relay makes me wonder if the 556 circuit is appropriate.

Hey Eric:

Without seeing the circuit I can't say, but to just do what you want a 556
should be adequate (at least if you can trigger one section with the other
-- I can't remember offhand if the 555 polarities work out).

The four possibilities that I can see for your board being different are:
(A) the original designer just didn't like the 555, had his head up his
ass, or both; (2) the 555 causes some problem that neither of us is
foreseeing; (third) For some reason the 555 solution was more expensive at
the time of manufacture; (finally) the board does more than just
controlling stitching, perhaps being used with more buttons and knobs in a
fancier accessory controller.

I presume that you would prefer to have a stitch period knob and a stitch
duration knob rather than a stitch-on duration knob and a stitch-off
duration knob. The former is easier with a 556, the latter can be done
with a 555.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

On Thu, 19 Mar 2015 12:53:34 -0500, Tim Wescott
<seemywebsite@myfooter.really> wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to. The
way it works is when the trigger on the welding gun pressed the welder
turns on for a short time, then turns off for a short time, and so on
until the trigger is released. So I thought I would use a 556 timer
because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556 and
a solid state relay makes me wonder if the 556 circuit is appropriate.

Hey Eric:

Without seeing the circuit I can't say, but to just do what you want a 556
should be adequate (at least if you can trigger one section with the other
-- I can't remember offhand if the 555 polarities work out).

The four possibilities that I can see for your board being different are:
(A) the original designer just didn't like the 555, had his head up his
ass, or both; (2) the 555 causes some problem that neither of us is
foreseeing; (third) For some reason the 555 solution was more expensive at
the time of manufacture; (finally) the board does more than just
controlling stitching, perhaps being used with more buttons and knobs in a
fancier accessory controller.

I presume that you would prefer to have a stitch period knob and a stitch
duration knob rather than a stitch-on duration knob and a stitch-off
duration knob. The former is easier with a 556, the latter can be done
with a 555.

Greetings Tim,
I want the stitch on and stitch off situation. I thought that a 556
would be needed for this. It seems the circuits I have made with a 555
wouldn't let me do this. I guess I need to look some more.
Thanks,
Eric

 

[Bob Masta]

On Thu, 19 Mar 2015 12:53:34 -0500, Tim Wescott
<seemywebsite@myfooter.really> wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to. The
way it works is when the trigger on the welding gun pressed the welder
turns on for a short time, then turns off for a short time, and so on
until the trigger is released. So I thought I would use a 556 timer
because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556 and
a solid state relay makes me wonder if the 556 circuit is appropriate.

Hey Eric:

Without seeing the circuit I can't say, but to just do what you want a 556
should be adequate (at least if you can trigger one section with the other
-- I can't remember offhand if the 555 polarities work out).

The four possibilities that I can see for your board being different are:
(A) the original designer just didn't like the 555, had his head up his
ass, or both; (2) the 555 causes some problem that neither of us is
foreseeing; (third) For some reason the 555 solution was more expensive at
the time of manufacture; (finally) the board does more than just
controlling stitching, perhaps being used with more buttons and knobs in a
fancier accessory controller.

Regarding (2), I have never been a big fan of 555s due to
the huge current spikes they introduced on the rails. (Not
to mention the plethora of supporting parts required for
even the simplest timing jobs.) I have read (somewhere)
that the spike problem has been solved (maybe only in the
CMOS versions?), but maybe that was what the original
designer was concerned about.

Best regards,


Bob Masta

DAQARTA v7.60
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE Signal Generator, DaqMusiq generator
Science with your sound card!

 

[Tim Wescott]

On Thu, 19 Mar 2015 12:59:34 -0700, etpm wrote:

On Thu, 19 Mar 2015 12:53:34 -0500, Tim Wescott
seemywebsite@myfooter.really> wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to.
The way it works is when the trigger on the welding gun pressed the
welder turns on for a short time, then turns off for a short time, and
so on until the trigger is released. So I thought I would use a 556
timer because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556
and a solid state relay makes me wonder if the 556 circuit is
appropriate.

Hey Eric:

Without seeing the circuit I can't say, but to just do what you want a
556 should be adequate (at least if you can trigger one section with the
other -- I can't remember offhand if the 555 polarities work out).

The four possibilities that I can see for your board being different
are: (A) the original designer just didn't like the 555, had his head up
his ass, or both; (2) the 555 causes some problem that neither of us is
foreseeing; (third) For some reason the 555 solution was more expensive
at the time of manufacture; (finally) the board does more than just
controlling stitching, perhaps being used with more buttons and knobs in
a fancier accessory controller.

I presume that you would prefer to have a stitch period knob and a
stitch duration knob rather than a stitch-on duration knob and a
stitch-off duration knob. The former is easier with a 556, the latter
can be done with a 555.
Greetings Tim,
I want the stitch on and stitch off situation. I thought that a 556
would be needed for this. It seems the circuits I have made with a 555
wouldn't let me do this. I guess I need to look some more.

I just think of a 556 as two 555's, so I tend to use "555" where I mean
"two 555's".

If you want to control stitch-on and stitch-off duration, then you bypass
one of the resistors in a 555 astable circuit (I can't remember pin
numbers off the top of my head, but it's the one that goes between the
discharge pin and the cap, and you want the diode cathode toward the cap.
IIRC. YMMV. AODA (all other disclaimers apply)).

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[John Fields]

On Thu, 19 Mar 2015 10:43:58 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to.
The way it works is when the trigger on the welding gun pressed the
welder turns on for a short time, then turns off for a short time, and
so on until the trigger is released. So I thought I would use a 556
timer because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556
and a solid state relay makes me wonder if the 556 circuit is
appropriate.
Thanks,
Eric

---
Trying to do the whole thing with a single 555 is pretty nasty since
even with a variable duty cycle used to control the weld time, as
far as I know there's no easy way to change the frequency without
causing interaction with the pulse width.

Using a pair of 555s or a 556, both in monostable mode, would be
appropriate, since you'd use one to determine the time between
stitch welds and the other to determine the weld time.

In use, what you'd do would be to start one of the one-shots when
the trigger was pulled, and then, when that one-shot timed out it'd
trigger the other one which, at the end of its cycle, would start
the cycle anew, generating another round, forever, until the trigger
was released.

Would you like a schematic?

John Fields

 

[Tim Wescott]

On Mon, 23 Mar 2015 14:55:12 -0500, John Fields wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to. The
way it works is when the trigger on the welding gun pressed the welder
turns on for a short time, then turns off for a short time, and so on
until the trigger is released. So I thought I would use a 556 timer
because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556 and
a solid state relay makes me wonder if the 556 circuit is appropriate.
Thanks,
Eric

---
Trying to do the whole thing with a single 555 is pretty nasty since
even with a variable duty cycle used to control the weld time, as far as
I know there's no easy way to change the frequency without causing
interaction with the pulse width.

Using a pair of 555s or a 556, both in monostable mode, would be
appropriate, since you'd use one to determine the time between stitch
welds and the other to determine the weld time.

If you wanted separate frequency and duration controls, I'd implement it
with one working as an astable, triggering the other as a one shot.

In use, what you'd do would be to start one of the one-shots when the
trigger was pulled, and then, when that one-shot timed out it'd trigger
the other one which, at the end of its cycle, would start the cycle
anew, generating another round, forever, until the trigger was released.

That does exactly what you say you don't want -- it makes the pulse width
settings interact with frequency.

But somewhere in this thread Eric says that he doesn't want to control
frequency and duration -- rather, he wants to control the duration of the
on and off times individually.

In that case, a single 555 would work mighty well, and has the advantage
that in the event of some oddball occurrence the system wouldn't stall
out, with each timer waiting for a trigger from the other. Given that
you've got a circuit with mA currents at 5V sitting next to one with 60A
at tens of volts, I think that "oddball occurrences" should be planned for.

Would you like a schematic?

John Fields

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[John Fields]

On Mon, 23 Mar 2015 17:38:30 -0500, Tim Wescott
<seemywebsite@myfooter.really> wrote:

On Mon, 23 Mar 2015 14:55:12 -0500, John Fields wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to. The
way it works is when the trigger on the welding gun pressed the welder
turns on for a short time, then turns off for a short time, and so on
until the trigger is released. So I thought I would use a 556 timer
because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556 and
a solid state relay makes me wonder if the 556 circuit is appropriate.
Thanks,
Eric

---
Trying to do the whole thing with a single 555 is pretty nasty since
even with a variable duty cycle used to control the weld time, as far as
I know there's no easy way to change the frequency without causing
interaction with the pulse width.

Using a pair of 555s or a 556, both in monostable mode, would be
appropriate, since you'd use one to determine the time between stitch
welds and the other to determine the weld time.

If you wanted separate frequency and duration controls, I'd implement it
with one working as an astable, triggering the other as a one shot.

In use, what you'd do would be to start one of the one-shots when the
trigger was pulled, and then, when that one-shot timed out it'd trigger
the other one which, at the end of its cycle, would start the cycle
anew, generating another round, forever, until the trigger was released.

That does exactly what you say you don't want -- it makes the pulse width
settings interact with frequency.

But somewhere in this thread Eric says that he doesn't want to control
frequency and duration -- rather, he wants to control the duration of the
on and off times individually.

In that case, a single 555 would work mighty well, and has the advantage
that in the event of some oddball occurrence the system wouldn't stall
out, with each timer waiting for a trigger from the other. Given that
you've got a circuit with mA currents at 5V sitting next to one with 60A
at tens of volts, I think that "oddball occurrences" should be planned for.

---
How would you do it with a single 555?

 

[Tim Wescott]

On Mon, 23 Mar 2015 21:54:57 -0500, John Fields wrote:

On Mon, 23 Mar 2015 17:38:30 -0500, Tim Wescott
seemywebsite@myfooter.really> wrote:

On Mon, 23 Mar 2015 14:55:12 -0500, John Fields wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to.
The way it works is when the trigger on the welding gun pressed the
welder turns on for a short time, then turns off for a short time, and
so on until the trigger is released. So I thought I would use a 556
timer because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556
and a solid state relay makes me wonder if the 556 circuit is
appropriate. Thanks,
Eric

---
Trying to do the whole thing with a single 555 is pretty nasty since
even with a variable duty cycle used to control the weld time, as far
as I know there's no easy way to change the frequency without causing
interaction with the pulse width.

Using a pair of 555s or a 556, both in monostable mode, would be
appropriate, since you'd use one to determine the time between stitch
welds and the other to determine the weld time.

If you wanted separate frequency and duration controls, I'd implement it
with one working as an astable, triggering the other as a one shot.

In use, what you'd do would be to start one of the one-shots when the
trigger was pulled, and then, when that one-shot timed out it'd
trigger the other one which, at the end of its cycle, would start the
cycle anew, generating another round, forever, until the trigger was
released.

That does exactly what you say you don't want -- it makes the pulse
width settings interact with frequency.

But somewhere in this thread Eric says that he doesn't want to control
frequency and duration -- rather, he wants to control the duration of
the on and off times individually.

In that case, a single 555 would work mighty well, and has the advantage
that in the event of some oddball occurrence the system wouldn't stall
out, with each timer waiting for a trigger from the other. Given that
you've got a circuit with mA currents at 5V sitting next to one with 60A
at tens of volts, I think that "oddball occurrences" should be planned
for.
---
How would you do it with a single 555?

Look in the data sheet for the usual astable circuit. Replace each
resistor with a pot + series resistor (and short, shielded leads given
the environment!). But I'm not done.

If left at this point, then the pot from the discharge pin to the cap
will have current flowing through it in both directions, and will affect
both the on and off times. So, bypass it with a Schottky diode going
from the discharge pin to the cap -- now each pot will independently
adjust it's own time.

Ta da.

I can't remember where I learned the diode trick, but it was decades ago
-- I think I was still in school, and may have picked it up from one of
my profs at Portland State.

--
www.wescottdesign.com

 

[Jasen Betts]

On 2015-03-24, John Fields <jfields@austininstruments.com> wrote:

On Mon, 23 Mar 2015 17:38:30 -0500, Tim Wescott
seemywebsite@myfooter.really> wrote:

On Mon, 23 Mar 2015 14:55:12 -0500, John Fields wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to. The
way it works is when the trigger on the welding gun pressed the welder
turns on for a short time, then turns off for a short time, and so on
until the trigger is released. So I thought I would use a 556 timer
because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556 and
a solid state relay makes me wonder if the 556 circuit is appropriate.
Thanks,
Eric

---
Trying to do the whole thing with a single 555 is pretty nasty since
even with a variable duty cycle used to control the weld time, as far as
I know there's no easy way to change the frequency without causing
interaction with the pulse width.

Using a pair of 555s or a 556, both in monostable mode, would be
appropriate, since you'd use one to determine the time between stitch
welds and the other to determine the weld time.

If you wanted separate frequency and duration controls, I'd implement it
with one working as an astable, triggering the other as a one shot.

In use, what you'd do would be to start one of the one-shots when the
trigger was pulled, and then, when that one-shot timed out it'd trigger
the other one which, at the end of its cycle, would start the cycle
anew, generating another round, forever, until the trigger was released.

That does exactly what you say you don't want -- it makes the pulse width
settings interact with frequency.

But somewhere in this thread Eric says that he doesn't want to control
frequency and duration -- rather, he wants to control the duration of the
on and off times individually.

In that case, a single 555 would work mighty well, and has the advantage
that in the event of some oddball occurrence the system wouldn't stall
out, with each timer waiting for a trigger from the other. Given that
you've got a circuit with mA currents at 5V sitting next to one with 60A
at tens of volts, I think that "oddball occurrences" should be planned for.
---
How would you do it with a single 555?

use diodes to steer the current.



----+--- vcc (+12V)
+---v |
off time +-[VR1]--->|--|--------+
| | |
| | |
+---v | |
on tine +-[VR2]---|<--|--------+
| | |
| +--------+ |
| | | |
| | . . . .|. . . . |
| | . VCC(8) . |
| | . . |
| +--RES(4) OUT(3)--+--> out1 (totem pole)
| . LM555 .
+-------TH(6) DIS(7)-----> out2 (open collector)
| . .
+-------TR(2) CV(5)--
C1 | . .
===== . GND(1) .
| . . . .|. . . .
| |
+-------------+
|
---+-- gnd


VR1 sets the "output low" time
VR2 sets the "output high" time

If you use a bipolar 555 (NE555, LM555) the discharge pin can sink
200mA which at 12V is enough to drive a mid-sizd relay.

--

Bye.
Jasen


--
umop apisdn

 

On Mon, 23 Mar 2015 14:55:12 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to.
The way it works is when the trigger on the welding gun pressed the
welder turns on for a short time, then turns off for a short time, and
so on until the trigger is released. So I thought I would use a 556
timer because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556
and a solid state relay makes me wonder if the 556 circuit is
appropriate.
Thanks,
Eric

---
Trying to do the whole thing with a single 555 is pretty nasty since
even with a variable duty cycle used to control the weld time, as
far as I know there's no easy way to change the frequency without
causing interaction with the pulse width.

Using a pair of 555s or a 556, both in monostable mode, would be
appropriate, since you'd use one to determine the time between
stitch welds and the other to determine the weld time.

In use, what you'd do would be to start one of the one-shots when
the trigger was pulled, and then, when that one-shot timed out it'd
trigger the other one which, at the end of its cycle, would start
the cycle anew, generating another round, forever, until the trigger
was released.

Would you like a schematic?

John Fields

Greetings John,
I think you have hit on exactly what I want to do. Yes, please, a
schematic would be great.
Thanks,
Eric

 

On Mon, 23 Mar 2015 17:38:30 -0500, Tim Wescott
<seemywebsite@myfooter.really> wrote:

On Mon, 23 Mar 2015 14:55:12 -0500, John Fields wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to. The
way it works is when the trigger on the welding gun pressed the welder
turns on for a short time, then turns off for a short time, and so on
until the trigger is released. So I thought I would use a 556 timer
because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556 and
a solid state relay makes me wonder if the 556 circuit is appropriate.
Thanks,
Eric

---
Trying to do the whole thing with a single 555 is pretty nasty since
even with a variable duty cycle used to control the weld time, as far as
I know there's no easy way to change the frequency without causing
interaction with the pulse width.

Using a pair of 555s or a 556, both in monostable mode, would be
appropriate, since you'd use one to determine the time between stitch
welds and the other to determine the weld time.

If you wanted separate frequency and duration controls, I'd implement it
with one working as an astable, triggering the other as a one shot.

In use, what you'd do would be to start one of the one-shots when the
trigger was pulled, and then, when that one-shot timed out it'd trigger
the other one which, at the end of its cycle, would start the cycle
anew, generating another round, forever, until the trigger was released.

That does exactly what you say you don't want -- it makes the pulse width
settings interact with frequency.

But somewhere in this thread Eric says that he doesn't want to control
frequency and duration -- rather, he wants to control the duration of the
on and off times individually.

In that case, a single 555 would work mighty well, and has the advantage
that in the event of some oddball occurrence the system wouldn't stall
out, with each timer waiting for a trigger from the other. Given that
you've got a circuit with mA currents at 5V sitting next to one with 60A
at tens of volts, I think that "oddball occurrences" should be planned for.

Would you like a schematic?

John Fields

Greetings Tim,
I must be confused or confusing or both. What I want to do is control
each function independent of the other. So if I increase the weld
pulse time I don't want the non-weld time to change. And the other way
around. So let's say I'm welding a 1 inch long bead and then leave a 1
inch space, and then weld a 1 inch bead and so on until I let go of
the trigger. But then I decide I want 1/2 inch long beads. I change
the welding pulse so that it is only half as long as before but the
non-weld time stays the same. Isn't that what John Fields is
describing? Or am I just confused and confusing everbody else with
illiterate posts?
Thanks,
Eric

 

[Tim Wescott]

On Tue, 24 Mar 2015 16:22:44 -0700, etpm wrote:

On Mon, 23 Mar 2015 17:38:30 -0500, Tim Wescott
seemywebsite@myfooter.really> wrote:

On Mon, 23 Mar 2015 14:55:12 -0500, John Fields wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to.
The way it works is when the trigger on the welding gun pressed the
welder turns on for a short time, then turns off for a short time, and
so on until the trigger is released. So I thought I would use a 556
timer because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556
and a solid state relay makes me wonder if the 556 circuit is
appropriate. Thanks,
Eric

---
Trying to do the whole thing with a single 555 is pretty nasty since
even with a variable duty cycle used to control the weld time, as far
as I know there's no easy way to change the frequency without causing
interaction with the pulse width.

Using a pair of 555s or a 556, both in monostable mode, would be
appropriate, since you'd use one to determine the time between stitch
welds and the other to determine the weld time.

If you wanted separate frequency and duration controls, I'd implement it
with one working as an astable, triggering the other as a one shot.

In use, what you'd do would be to start one of the one-shots when the
trigger was pulled, and then, when that one-shot timed out it'd
trigger the other one which, at the end of its cycle, would start the
cycle anew, generating another round, forever, until the trigger was
released.

That does exactly what you say you don't want -- it makes the pulse
width settings interact with frequency.

But somewhere in this thread Eric says that he doesn't want to control
frequency and duration -- rather, he wants to control the duration of
the on and off times individually.

In that case, a single 555 would work mighty well, and has the advantage
that in the event of some oddball occurrence the system wouldn't stall
out, with each timer waiting for a trigger from the other. Given that
you've got a circuit with mA currents at 5V sitting next to one with 60A
at tens of volts, I think that "oddball occurrences" should be planned
for.

Would you like a schematic?

John Fields
Greetings Tim,
I must be confused or confusing or both. What I want to do is control
each function independent of the other. So if I increase the weld pulse
time I don't want the non-weld time to change. And the other way around.
So let's say I'm welding a 1 inch long bead and then leave a 1 inch
space, and then weld a 1 inch bead and so on until I let go of the
trigger. But then I decide I want 1/2 inch long beads. I change the
welding pulse so that it is only half as long as before but the non-weld
time stays the same. Isn't that what John Fields is describing? Or am I
just confused and confusing everbody else with illiterate posts?
Thanks,
Eric

John is describing (I think! Maybe I'm the one reading it wrong!) a
system where the start of each bead is a constant distance from the start
of the last, and you can adjust the length of the bead.

I.e., you set the cycle length to two inches, then choose a weld length
within that.

I could see wanting to do it either way, and possibly giving the user a
switch to do so -- this starts getting difficult with 555 timers, which
may be why you have something entirely different.

At any rate, both the circuit that I describe and the one that Jason Betts
posted will work -- I think Jason's is a bit better than mine, frankly.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[Tim Wescott]

On Tue, 24 Mar 2015 05:40:57 +0000, Jasen Betts wrote:

On 2015-03-24, John Fields <jfields@austininstruments.com> wrote:
On Mon, 23 Mar 2015 17:38:30 -0500, Tim Wescott
seemywebsite@myfooter.really> wrote:

On Mon, 23 Mar 2015 14:55:12 -0500, John Fields wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to.
The way it works is when the trigger on the welding gun pressed the
welder turns on for a short time, then turns off for a short time,
and so on until the trigger is released. So I thought I would use a
556 timer because I want to be able to adjust each interval
independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch
of other components. Such a complex circuit compared to one using a
556 and a solid state relay makes me wonder if the 556 circuit is
appropriate. Thanks,
Eric

---
Trying to do the whole thing with a single 555 is pretty nasty since
even with a variable duty cycle used to control the weld time, as far
as I know there's no easy way to change the frequency without causing
interaction with the pulse width.

Using a pair of 555s or a 556, both in monostable mode, would be
appropriate, since you'd use one to determine the time between stitch
welds and the other to determine the weld time.

If you wanted separate frequency and duration controls, I'd implement
it with one working as an astable, triggering the other as a one shot.

In use, what you'd do would be to start one of the one-shots when the
trigger was pulled, and then, when that one-shot timed out it'd
trigger the other one which, at the end of its cycle, would start the
cycle anew, generating another round, forever, until the trigger was
released.

That does exactly what you say you don't want -- it makes the pulse
width settings interact with frequency.

But somewhere in this thread Eric says that he doesn't want to control
frequency and duration -- rather, he wants to control the duration of
the on and off times individually.

In that case, a single 555 would work mighty well, and has the
advantage that in the event of some oddball occurrence the system
wouldn't stall out, with each timer waiting for a trigger from the
other. Given that you've got a circuit with mA currents at 5V sitting
next to one with 60A at tens of volts, I think that "oddball
occurrences" should be planned for.
---
How would you do it with a single 555?


use diodes to steer the current.



----+--- vcc (+12V)
+---v |
off time +-[VR1]--->|--|--------+
| | |
| | |
+---v | |
on tine +-[VR2]---|<--|--------+
| | |
| +--------+ |
| | | |
| | . . . .|. . . . |
| | . VCC(8) . |
| | . . |
| +--RES(4) OUT(3)--+--> out1 (totem pole)
| . LM555 .
+-------TH(6) DIS(7)-----> out2 (open collector)
| . .
+-------TR(2) CV(5)--
C1 | . .
===== . GND(1) .
| . . . .|. . . .
| |
+-------------+
|
---+-- gnd


VR1 sets the "output low" time VR2 sets the "output high" time

If you use a bipolar 555 (NE555, LM555) the discharge pin can sink
200mA which at 12V is enough to drive a mid-sizd relay.

If you use a bipolar 555 you can't be sure the output goes high enough.

If you use the discharge pin straight to a relay, then even with a diode
across the coil (which slows down the relay opening) you'll be abusing the
555's protection diodes.

I only use this arrangement with a CMOS 555, and I'd drive a relay with a
separate transistor, using a resistor in series with a diode, or a zener
diode, to make sure that there's a hefty voltage across the coil on turn-
off, to speed up the current decay and make the relay turn-off quicker and
more positive.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

On Mon, 23 Mar 2015 14:55:12 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to.
The way it works is when the trigger on the welding gun pressed the
welder turns on for a short time, then turns off for a short time, and
so on until the trigger is released. So I thought I would use a 556
timer because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556
and a solid state relay makes me wonder if the 556 circuit is
appropriate.
Thanks,
Eric

---
Trying to do the whole thing with a single 555 is pretty nasty since
even with a variable duty cycle used to control the weld time, as
far as I know there's no easy way to change the frequency without
causing interaction with the pulse width.

Using a pair of 555s or a 556, both in monostable mode, would be
appropriate, since you'd use one to determine the time between
stitch welds and the other to determine the weld time.

In use, what you'd do would be to start one of the one-shots when
the trigger was pulled, and then, when that one-shot timed out it'd
trigger the other one which, at the end of its cycle, would start
the cycle anew, generating another round, forever, until the trigger
was released.

Would you like a schematic?

John Fields

Greetings John,
I though I posted a reply to your message above but when looking for
it I don't see it. So, yes please I would love a schematic since it
looks from your post that you are describing what I want. I think.
Thanks,
Eric

 

[Jasen Betts]

On 2015-03-25, Tim Wescott <seemywebsite@myfooter.really> wrote:

On Tue, 24 Mar 2015 05:40:57 +0000, Jasen Betts wrote:

On 2015-03-24, John Fields <jfields@austininstruments.com> wrote:
On Mon, 23 Mar 2015 17:38:30 -0500, Tim Wescott
seemywebsite@myfooter.really> wrote:

On Mon, 23 Mar 2015 14:55:12 -0500, John Fields wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to.
The way it works is when the trigger on the welding gun pressed the
welder turns on for a short time, then turns off for a short time,
and so on until the trigger is released. So I thought I would use a
556 timer because I want to be able to adjust each interval
independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch
of other components. Such a complex circuit compared to one using a
556 and a solid state relay makes me wonder if the 556 circuit is
appropriate. Thanks,
Eric

---
Trying to do the whole thing with a single 555 is pretty nasty since
even with a variable duty cycle used to control the weld time, as far
as I know there's no easy way to change the frequency without causing
interaction with the pulse width.

Using a pair of 555s or a 556, both in monostable mode, would be
appropriate, since you'd use one to determine the time between stitch
welds and the other to determine the weld time.

If you wanted separate frequency and duration controls, I'd implement
it with one working as an astable, triggering the other as a one shot.

In use, what you'd do would be to start one of the one-shots when the
trigger was pulled, and then, when that one-shot timed out it'd
trigger the other one which, at the end of its cycle, would start the
cycle anew, generating another round, forever, until the trigger was
released.

That does exactly what you say you don't want -- it makes the pulse
width settings interact with frequency.

But somewhere in this thread Eric says that he doesn't want to control
frequency and duration -- rather, he wants to control the duration of
the on and off times individually.

In that case, a single 555 would work mighty well, and has the
advantage that in the event of some oddball occurrence the system
wouldn't stall out, with each timer waiting for a trigger from the
other. Given that you've got a circuit with mA currents at 5V sitting
next to one with 60A at tens of volts, I think that "oddball
occurrences" should be planned for.
---
How would you do it with a single 555?


use diodes to steer the current.



----+--- vcc (+12V)
+---v |
off time +-[VR1]--->|--|--------+
| | |
| | |
+---v | |
on tine +-[VR2]---|<--|--------+
| | |
| +--------+ |
| | | |
| | . . . .|. . . . |
| | . VCC(8) . |
| | . . |
| +--RES(4) OUT(3)--+--> out1 (totem pole)
| . LM555 .
+-------TH(6) DIS(7)-----> out2 (open collector)
| . .
+-------TR(2) CV(5)--
C1 | . .
===== . GND(1) .
| . . . .|. . . .
| |
+-------------+
|
---+-- gnd


VR1 sets the "output low" time VR2 sets the "output high" time

If you use a bipolar 555 (NE555, LM555) the discharge pin can sink
200mA which at 12V is enough to drive a mid-sizd relay.

If you use a bipolar 555 you can't be sure the output goes high enough.

it seems reasonable to expect 11V with a 12V VCC. Why do you think that's
not enough?

If you use the discharge pin straight to a relay, then even with a diode
across the coil (which slows down the relay opening) you'll be abusing the
555's protection diodes.

there's no protection diode on the discharge pin (what would be the
point).

but yeah you need parallel diode on the relay. the relay's internal
resistance will turn it off fast enough, I doubt we need to be faster
than 100ms in this application. but if speed is needed a parallel RC
in series with the diode can expedite turn-off withput incrasing the
stand-off voltage.




--
umop apisdn

 

[John Fields]

On Wed, 25 Mar 2015 12:53:38 -0700, etpm@whidbey.com wrote:

On Mon, 23 Mar 2015 14:55:12 -0500, John Fields
jfields@austininstruments.com> wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to.
The way it works is when the trigger on the welding gun pressed the
welder turns on for a short time, then turns off for a short time, and
so on until the trigger is released. So I thought I would use a 556
timer because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556
and a solid state relay makes me wonder if the 556 circuit is
appropriate.
Thanks,
Eric

---
Trying to do the whole thing with a single 555 is pretty nasty since
even with a variable duty cycle used to control the weld time, as
far as I know there's no easy way to change the frequency without
causing interaction with the pulse width.

Using a pair of 555s or a 556, both in monostable mode, would be
appropriate, since you'd use one to determine the time between
stitch welds and the other to determine the weld time.

In use, what you'd do would be to start one of the one-shots when
the trigger was pulled, and then, when that one-shot timed out it'd
trigger the other one which, at the end of its cycle, would start
the cycle anew, generating another round, forever, until the trigger
was released.

Would you like a schematic?

John Fields
Greetings John,
I though I posted a reply to your message above but when looking for
it I don't see it. So, yes please I would love a schematic since it
looks from your post that you are describing what I want. I think.
Thanks,
Eric

---
Hi Eric,

I'm off to a doctor's appointment for a while, but I'll post the
schematic and an LTspice simulation for you some time today.

John

 

[John Fields]

On Wed, 25 Mar 2015 12:53:38 -0700, etpm@whidbey.com wrote:

On Mon, 23 Mar 2015 14:55:12 -0500, John Fields
jfields@austininstruments.com> wrote:

On Thu, 19 Mar 2015 10:43:58 -0700, etpm@whidbey.com wrote:

Greetings All,
I have a wire feed welder that I would like to add a stich timer to.
The way it works is when the trigger on the welding gun pressed the
welder turns on for a short time, then turns off for a short time, and
so on until the trigger is released. So I thought I would use a 556
timer because I want to be able to adjust each interval independently.
The intervals are pretty short, from maybe a half second to a few
seconds. I first thought a 555 would work but it seems to me a 556 is
better for adjusting the intervals independently. There used to be a
circuit board available as an option for this welder but it no longer
is. I have the schematic for that board and it used a programmable
timer, the 4536B, and an LM2901 quad comparator, along with a bunch of
other components. Such a complex circuit compared to one using a 556
and a solid state relay makes me wonder if the 556 circuit is
appropriate.
Thanks,
Eric

---
Trying to do the whole thing with a single 555 is pretty nasty since
even with a variable duty cycle used to control the weld time, as
far as I know there's no easy way to change the frequency without
causing interaction with the pulse width.

Using a pair of 555s or a 556, both in monostable mode, would be
appropriate, since you'd use one to determine the time between
stitch welds and the other to determine the weld time.

In use, what you'd do would be to start one of the one-shots when
the trigger was pulled, and then, when that one-shot timed out it'd
trigger the other one which, at the end of its cycle, would start
the cycle anew, generating another round, forever, until the trigger
was released.

Would you like a schematic?

John Fields
Greetings John,
I though I posted a reply to your message above but when looking for
it I don't see it. So, yes please I would love a schematic since it
looks from your post that you are describing what I want. I think.
Thanks,
Eric

---
Here's a link

https://www.dropbox.com/sh/yikxzbjuncr1v6l/AACoSK5d_R2YsKxZTIPGBY4Oa?dl=0

to a schematic and to the .asc file that'll let you run an LTspice
simulation, if you care to.

I opted for a single 555 running as an astable because Tim Wescott
was right; my original dual one-shot circuit could have entered a
hang state with no output without a manual re-start, while this one
is inherently unstable and _MUST_ run, barring some major disaster.

One caveat is that its first output pulse will be about twice as
long as the others, and another is that there's a very slight amount
of interaction between the times when they're being set.

That is, if you set the weld ON time for, say, 100ms and then the
OFF time for 1 second, the ON time will change a tiny bit. Less than
1% as I recall, but you can see it for yourself if you run the sim.

If you decide to use the circuit, make sure that C2 is wired right
at the package, directly across pins 1 and 8.

John Fields

 

[Owen Cook]

What would the purpose of that 1000 ohm resistor (R1)be? It is in series with a 1 meg ohm resistor so would seem to be unnecessary?


Owen

 

[John Fields]

On Fri, 27 Mar 2015 22:16:22 -0700 (PDT), Owen Cook
<xemoth@gmail.com> wrote:

What would the purpose of that 1000 ohm resistor (R1)be? It is in series with a 1 meg ohm resistor so would seem to be unnecessary?


Owen

---
When U1-7 (DIS-) goes low in order to discharge the timing cap, C1,
it'll also sink the current from the 12 volt supply through R1 and
R2.

As a consequence, if R1 wasn't there and R2 somehow wound up at zero
ohms, the 12 volt supply would be connected directly across U1-7 and
GND.

Depending on whether it's a bipolar or CMOS chip, U1-7 will be
internally connected to either the open collector of an NPN or the
open drain of an N-channel MOSFET, resulting in the supply positive
being connected to ground with only Rce or Rds limiting the current
through the device.

If you run the sim with R1 and R2 shorted you'll see that, for the
NE555 with U1-7 low, current into U1-7 will limit at 2 amperes,
which means that Rce(sat) is running about 6 ohms and the package
will be dissipating 24 watts.

Not a Good Thing, and the magic smoke will probably escape.

John Fields,
Professional Circuit Designer.