Running multiple connections on circuit board ... good or ba

H

Harry Muscle

Guest
Is running multiple connections from one point to another a good or bad
thing to do on a circuit board. I'm working on a layout of a simple
temperature control circuit and I was planning on having the ground run in a
circle, such that almost each point on the circuit would have at least two
different routes back to the ground connection. Is this a good thing to do?
The more routes the better? Or is there a limit? Do the same rules apply
to non ground connections?

Thanks,
Harry




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Harry Muscle wrote:
Is running multiple connections from one point to another a good or bad
thing to do on a circuit board. I'm working on a layout of a simple
temperature control circuit and I was planning on having the ground run in a
circle, such that almost each point on the circuit would have at least two
different routes back to the ground connection. Is this a good thing to do?
The more routes the better? Or is there a limit? Do the same rules apply
to non ground connections?
Click to expand...
This does not normally cause problems, and the full extension of the
idea is to have a ground plane. The exception to this involves either
big or fast currents that will cause voltage drop on their ground
lines or two or more points that need very accurate ground reference
voltages. In the first case, you use a separate ground trace to carry
the current, to keep that drop out of the rest of the grounds,
connecting at a point that does not carry current. In the second
case, you connect those nodes together separately from the rest of the
grounds, connecting them at the quietest point in the ground system.

--
John Popelish
 
"John Popelish" <jpopelish@rica.net> wrote in message
news:3FE8664F.7D833F3E@rica.net...
Harry Muscle wrote:

Is running multiple connections from one point to another a good or bad
thing to do on a circuit board. I'm working on a layout of a simple
temperature control circuit and I was planning on having the ground run
in a
circle, such that almost each point on the circuit would have at least
two
different routes back to the ground connection. Is this a good thing to
do?
The more routes the better? Or is there a limit? Do the same rules
apply
to non ground connections?

This does not normally cause problems, and the full extension of the
idea is to have a ground plane. The exception to this involves either
big or fast currents that will cause vol drop on their ground
lines or two or more points that need very accurate ground reference
vol . In the first case, you use a se te ground trace to carry
the current, to keep that drop out of the rest of the grounds,
connecting at a point that does not carry current. In the second
case, you connect those nodes together se tely from the rest of the
grounds, connecting them at the quietest point in the ground system.

--
John Popelish
Click to expand...
I'm guessing a relay and a fan would fall under the "big current" category.
What about a reservoir capacitor (used to smooth out the DC) of 1000uF?
Should I give it a se te route back to ground?

Thanks,
Harry




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Harry Muscle wrote:

I'm guessing a relay and a fan would fall under the "big current" category.
Click to expand...
They are certainly in the category of noise makers rather than noise
sensitive components. I would give their currents as separate a path
as possible, including cancellation of those current's magnetic
fields, by folding the current path into a parallel pair.

What about a reservoir capacitor (used to smooth out the DC) of 1000uF?
Should I give it a se te route back to ground?
Click to expand...
The currents between capacitor and steady loads is normally part of
the quiet stuff, while the rectifier currents that charge the
capacitors ar part of the noise producing stuff. Treat the rectifier
currents like you do motor and relay currents. Run them to the
capacitors on separate traces than the grid that connects the
capacitor to its loads so that voltage drops caused by the charging
pulses do not get added to the capacitor voltage as seen by its loads.

--
John Popelish
 
"John Popelish" <jpopelish@rica.net> wrote in message
news:3FE8735B.BFA50C3D@rica.net...
Harry Muscle wrote:

I'm guessing a relay and a fan would fall under the "big current"
category.

They are certainly in the category of noise makers rather than noise
sensitive components. I would give their currents as se te a path
as possible, including cancellation of those current's magnetic
fields, by folding the current path into a llel pair.
Click to expand...
You mean by running the + and - lines beside each other, correct?

What about a reservoir capacitor (used to smooth out the DC) of 1000uF?
Should I give it a se te route back to ground?

The currents between capacitor and steady loads is normally part of
the quiet stuff, while the rectifier currents that charge the
capacitors ar part of the noise producing stuff. Treat the rectifier
currents like you do motor and relay currents. Run them to the
capacitors on se te traces than the grid that connects the
capacitor to its loads so that vol drops caused by the charging
pulses do not get added to the capacitor vol as seen by its loads.

--
John Popelish
Click to expand...
Got a quick question about running the connection to my caps. Which of the
following two is better:

RECTIFIER------CAP----VOLT REGULATOR-----LOAD

or

CAP----------|------------VOLT REGULATOR-----LOAD
|
RECTIFIER

The bottom option would provide seperate leads to the reservoir caps, but
I'm not sure if that's the proper way of doing it?

Thanks,
Harry




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http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----
 
Harry Muscle wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:3FE8735B.BFA50C3D@rica.net...
Harry Muscle wrote:

I'm guessing a relay and a fan would fall under the "big current"
category.

They are certainly in the category of noise makers rather than noise
sensitive components. I would give their currents as se te a path
as possible, including cancellation of those current's magnetic
fields, by folding the current path into a llel pair.

You mean by running the + and - lines beside each other, correct?
Click to expand...
Yes. Run a pair of traces from the switching point with a bypass
capacitor across those rails at the switching device, with the catch
diode close to the switch.

The currents between capacitor and steady loads is normally part of
the quiet stuff, while the rectifier currents that charge the
capacitors ar part of the noise producing stuff. Treat the rectifier
currents like you do motor and relay currents. Run them to the
capacitors on se te traces than the grid that connects the
capacitor to its loads so that vol drops caused by the charging
pulses do not get added to the capacitor vol as seen by its loads.


Got a quick question about running the connection to my caps. Which of the
following two is better:

RECTIFIER------CAP----VOLT REGULATOR-----LOAD

or

CAP----------|------------VOLT REGULATOR-----LOAD
|
RECTIFIER

The bottom option would provide seperate leads to the reservoir caps, but
I'm not sure if that's the proper way of doing it?

I like the first one better, because it separates the big charging
Click to expand...
pulses from the steady load currents to the regulator. If you show
all the traces, you end up with the rectifier having two lines to the
capacitor, which is right at the input of the regulator, a second
(smaller) cap right at the output of the regulator, and the common
ground node for these two caps as the tie in point of the regulator to
the circuits that need clean, regulated voltage. That way, the big
charging pulses from the rectifiers cause drops on traces that are not
between any devices that have to agree on what zero volts is.

--
John Popelish
 
"John Popelish" <jpopelish@rica.net> wrote in message
news:3FE8C430.4617AB89@rica.net...
Harry Muscle wrote:

"John Popelish" <jpopelish@rica.net> wrote in message
news:3FE8735B.BFA50C3D@rica.net...
Harry Muscle wrote:

I'm guessing a relay and a fan would fall under the "big current"
category.

They are certainly in the category of noise makers rather than noise
sensitive components. I would give their currents as se te a path
as possible, including cancellation of those current's magnetic
fields, by folding the current path into a llel pair.

You mean by running the + and - lines beside each other, correct?

Yes. Run a pair of traces from the switching point with a bypass
capacitor across those rails at the switching device, with the catch
diode close to the switch.

The currents between capacitor and steady loads is normally part of
the quiet stuff, while the rectifier currents that charge the
capacitors ar part of the noise producing stuff. Treat the rectifier
currents like you do motor and relay currents. Run them to the
capacitors on se te traces than the grid that connects the
capacitor to its loads so that vol drops caused by the charging
pulses do not get added to the capacitor vol as seen by its loads.


Got a quick question about running the connection to my caps. Which of
the
following two is better:

RECTIFIER------CAP----VOLT REGULATOR-----LOAD

or

CAP----------|------------VOLT REGULATOR-----LOAD
|
RECTIFIER
Click to expand...
I was just reading this out of interest, and I am a bit mistified about
this 2nd option. What purpose would a capacitor have before
a rectifier. Surely the capacitor *must* be after the rectifier to make
any sense, and not just a matter of someone's "personal preference" ?


The bottom option would provide seperate leads to the reservoir caps,
but
I'm not sure if that's the proper way of doing it?

I like the first one better, because it separates the big charging
pulses from the steady load currents to the regulator. If you show
all the traces, you end up with the rectifier having two lines to the
capacitor, which is right at the input of the regulator, a second
(smaller) cap right at the output of the regulator, and the common
ground node for these two caps as the tie in point of the regulator to
the circuits that need clean, regulated voltage. That way, the big
charging pulses from the rectifiers cause drops on traces that are not
between any devices that have to agree on what zero volts is.

--
John Popelish
Click to expand...
 
Addie wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:3FE8C430.4617AB89@rica.net...
Harry Muscle wrote:
(snip)
Got a quick question about running the connection to my caps. Which of
the
following two is better:

RECTIFIER------CAP----VOLT REGULATOR-----LOAD

or

CAP----------|------------VOLT REGULATOR-----LOAD
|
RECTIFIER


I was just reading this out of interest, and I am a bit mistified about
this 2nd option. What purpose would a capacitor have before
a rectifier. Surely the capacitor *must* be after the rectifier to make
any sense, and not just a matter of someone's "personal preference" ?
Click to expand...
The point is that the rectifiers, capacitor and regulator share a
couple nodes, but there are several ways to run traces to get them
connected together. If traces had no resistance or inductance, any
way would work the same as any other way.
--
John Popelish
 
"John Popelish" <jpopelish@rica.net> wrote in message
news:3FEDDA4B.BD569563@rica.net...
Addie wrote:

"John Popelish" <jpopelish@rica.net> wrote in message
news:3FE8C430.4617AB89@rica.net...
Harry Muscle wrote:
(snip)
Got a quick question about running the connection to my caps. Which
of
the
following two is better:

RECTIFIER------CAP----VOLT REGULATOR-----LOAD

or

CAP----------|------------VOLT REGULATOR-----LOAD
|
RECTIFIER


I was just reading this out of interest, and I am a bit mistified about
this 2nd option. What purpose would a capacitor have before
a rectifier. Surely the capacitor *must* be after the rectifier to make
any sense, and not just a matter of someone's "personal preference" ?

The point is that the rectifiers, capacitor and regulator share a
couple nodes, but there are several ways to run traces to get them
connected together. If traces had no resistance or inductance, any
way would work the same as any other way.
Click to expand...
o.k. seems like I'm out of my depth on this one. Still remember my power
supply circuit ? I wanted to draw the component names as you suggested
to make the discussion easier, but I haven't done it yet. I didn't quite
understand why we need to guard against oscillation. Is this oscillation
picked up from the air or mains, or is it self generating and can be
calculated. The other thing I/you was not sure about was whether the
resistors near the emitter follower transistors where drawn correctly /
or had correct values. Do you think it is worth while to simply measure
some voltage drops across components for varying load voltages/currents ?

--
John Popelish
Click to expand...
 
Chan wrote:

o.k. seems like I'm out of my depth on this one. Still remember my power
supply circuit ? I wanted to draw the component names as you suggested
to make the discussion easier, but I haven't done it yet. I didn't quite
understand why we need to guard against oscillation. Is this oscillation
picked up from the air or mains, or is it self generating and can be
calculated. The other thing I/you was not sure about was whether the
resistors near the emitter follower transistors where drawn correctly /
or had correct values. Do you think it is worth while to simply measure
some voltage drops across components for varying load voltages/currents ?
Click to expand...
I don't recognize your name. Are you talking about this post?
http://groups.google.com/groups?selm=3FCFA3C6.1D16EE9A%40rica.net&output=gplain

Any time you have gain greater than 1 and feedback, there is a
possibility of oscillations (regenerated echoes) being generated.
Before going further than that, I need to know what you are talking
about.


--
John Popelish
 
"John Popelish" <jpopelish@rica.net> wrote in message
news:3FEE5A02.99D5580B@rica.net...
Chan wrote:

o.k. seems like I'm out of my depth on this one. Still remember my
power
supply circuit ? I wanted to draw the component names as you suggested
to make the discussion easier, but I haven't done it yet. I didn't quite
understand why we need to guard against oscillation. Is this oscillation
picked up from the air or mains, or is it self generating and can be
calculated. The other thing I/you was not sure about was whether the
resistors near the emitter follower transistors where drawn correctly /
or had correct values. Do you think it is worth while to simply measure
some voltage drops across components for varying load voltages/currents
?

I don't recognize your name. Are you talking about this post?

http://groups.google.com/groups?selm=3FCFA3C6.1D16EE9A%40rica.net&output=gplain
Click to expand...

sorry, I forgot to mention which posting, you have guest right.
I will post the circuit again. I think the capacitors around the
op amp are simply standard practice to avoid oscillation, and
are not something in particular for a power supply.

Any time you have gain greater than 1 and feedback, there is a
possibility of oscillations (regenerated echoes) being generated.
Before going further than that, I need to know what you are talking
about.


--
John Popelish
Click to expand...
 
Chan wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:3FEE5A02.99D5580B@rica.net...
(snip)http://groups.google.com/groups?selm=3FCFA3C6.1D16EE9A%40rica.net&output=gplain

sorry, I forgot to mention which posting, you have guest right.
I will post the circuit again. I think the capacitors around the
op amp are simply standard practice to avoid oscillation, and
are not something in particular for a power supply.
Click to expand...
Perhaps, but a power supply regulator is a big, power amplifier with
lots of feedback, whose job it is to hold a voltage stable, or switch
to smoothly and accurately regulated current in the event of an
overload, in spite of all variations in load from any value of
resistor between infinity and zero, inductors, to capacitors, (or
resonant loads made of inductors and capacitors) to pulsing circuits.
Their stability is quite a design problem, especially if there is a
fast spec on how quickly the voltage must get back to setpoint after a
big load current spike.

--
John Popelish
 
"John Popelish" <jpopelish@rica.net> wrote in message
news:3FEF9D31.5A143A49@rica.net...
Chan wrote:

"John Popelish" <jpopelish@rica.net> wrote in message
news:3FEE5A02.99D5580B@rica.net...

(snip)http://groups.google.com/groups?selm=3FCFA3C6.1D16EE9A%40rica.net&outp
Click to expand...
ut=gplain
sorry, I forgot to mention which posting, you have guest right.
I will post the circuit again. I think the capacitors around the
op amp are simply standard practice to avoid oscillation, and
are not something in particular for a power supply.

Perhaps, but a power supply regulator is a big, power amplifier with
lots of feedback, whose job it is to hold a voltage stable, or switch
to smoothly and accurately regulated current in the event of an
overload, in spite of all variations in load from any value of
resistor between infinity and zero, inductors, to capacitors, (or
resonant loads made of inductors and capacitors) to pulsing circuits.
Their stability is quite a design problem, especially if there is a
fast spec on how quickly the voltage must get back to setpoint after a
big load current spike.
You may be right. I have a book (how to use op amps) which says
Click to expand...
on p.9 that it is very unusual for the 741 to "misbehave", so perhaps
the 10nF from negative op amp input to op amp output is to remove
any ac component from the controlling feedback loop.

Zc = 1/jwc = 1/(6.28*10n*f)

I believe you chose f = 20KHz (why?) which gives us
Zc = 8 ohms
Hence Zc << than transistor feedback loop which is at least
hie of 3 emitter followers.

--
John Popelish
Click to expand...
 
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