Rectifier output?

[Gloria West]

120vac input to full-wave rectifier bridge. Without any filtering components
what is the output RMS voltage?

This does not use a center-tapped transformer or such.

Thanks.

 

[John Larkin]

On Wed, 23 Sep 2009 20:12:47 -0700, Gloria West
<gloriasbest22@NOSPAMgmail.com> wrote:

120vac input to full-wave rectifier bridge. Without any filtering components
what is the output RMS voltage?

About 119.

John

 

[Phil Allison]

"Gloria West"

120vac input to full-wave rectifier bridge. Without any filtering
components
what is the output RMS voltage?

** 120 volts, of course.

If you connect a 120 volt lamp to the DC output, it will be the same
brightness as usual.

If you add a filter capacitor, the rms voltage rises up to a maximum of 170
volts DC.



...... Phil

 

[Tim Wescott]

On Wed, 23 Sep 2009 20:12:47 -0700, Gloria West wrote:

120vac input to full-wave rectifier bridge. Without any filtering
components what is the output RMS voltage?

This does not use a center-tapped transformer or such.

Thanks.

Homework?

--
www.wescottdesign.com

 

[Gloria West]

Homework?

No, smart guy.

 

[Gloria West]

120vac input to full-wave rectifier bridge. Without any filtering components
what is the output RMS voltage?

This does not use a center-tapped transformer or such.

Relays run with this rectified supply are buzzing. These are in a 45-year-old
printing press.

I want to replace them with something more modern (the contacts are also
intermittent).

I found some that are rated for 110 dc:

<http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-
1&storeId=10001&catalogId=10001&productId=301209&>

Will these buzz also? Is there a simple way to keep them quiet?

 

[Phil Allison]

"Gloria West"

I found some that are rated for 110 dc:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=301209&

Will these buzz also? Is there a simple way to keep them quiet?

** Yep.

Add a 4.7uF, 250 volt electro across the output of the bridge and put a 4700
ohm, 1 watt resistor in series with the 110 volt relay.

This should give you 160 volts DC average on the cap and 110 volts on the
relay.

I used ohms law and the formula: I = Cdv/dt to get the values.


....... Phil

 

[John G.]

"Gloria West" <gloriasbest22@NOSPAMgmail.com> wrote in message
news:0001HW.C6E05A3F0294CBFEB08A39AF@news.eternal-september.org...

120vac input to full-wave rectifier bridge. Without any filtering
components
what is the output RMS voltage?

This does not use a center-tapped transformer or such.

Relays run with this rectified supply are buzzing. These are in a
45-year-old
printing press.

I want to replace them with something more modern (the contacts are also
intermittent).

I found some that are rated for 110 dc:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-
1&storeId=10001&catalogId=10001&productId=301209&

Will these buzz also? Is there a simple way to keep them quiet?

And who is to say the contact rating will be correct?
Why don't you fix the problem (whatever it is ) rather than trying to
redesign the machine from a position of not enough knowledge?

John G.

 

[Gloria West]

Add a 4.7uF, 250 volt electro across the output of the bridge and put a 4700
ohm, 1 watt resistor in series with the 110 volt relay.

Thank you Phil.

 

[Jon Slaughter]

"John G." <greentest@ozemail.com.au> wrote in message
news:4abb3eb9$0$12718$5a62ac22@per-qv1-newsreader-01.iinet.net.au...

"Gloria West" <gloriasbest22@NOSPAMgmail.com> wrote in message
news:0001HW.C6E05A3F0294CBFEB08A39AF@news.eternal-september.org...
120vac input to full-wave rectifier bridge. Without any filtering
components
what is the output RMS voltage?

This does not use a center-tapped transformer or such.

Relays run with this rectified supply are buzzing. These are in a
45-year-old
printing press.

I want to replace them with something more modern (the contacts are also
intermittent).

I found some that are rated for 110 dc:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-
1&storeId=10001&catalogId=10001&productId=301209&

Will these buzz also? Is there a simple way to keep them quiet?

And who is to say the contact rating will be correct?
Why don't you fix the problem (whatever it is ) rather than trying to
redesign the machine from a position of not enough knowledge?

John G.

Why don't you just fucking answer her question instead of trying to spout
your superiority? If she wants to fuck it up then it's her choice. It isn't
going to cost you anything. You assume she's not intelligent enough simply
because no one could have even close the intelligence you have? Or is it
that you really care about her safety? Yeah.. I bet...

Get over it... you are not the smartest nor ever will be even close. Trying
to keep other people down does not make you more intelligent.

Of course the real reason is you simply don't want any competition.

 

[John Larkin]

On Wed, 23 Sep 2009 23:05:35 -0700, Gloria West
<gloriasbest22@NOSPAMgmail.com> wrote:

120vac input to full-wave rectifier bridge. Without any filtering components
what is the output RMS voltage?

This does not use a center-tapped transformer or such.

Relays run with this rectified supply are buzzing. These are in a 45-year-old
printing press.

I want to replace them with something more modern (the contacts are also
intermittent).

I found some that are rated for 110 dc:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-
1&storeId=10001&catalogId=10001&productId=301209&

Will these buzz also? Is there a simple way to keep them quiet?

Relays coils are inductive enough that they don't follow the ripple
voltage. So the effective (average) DC voltage becomes Vpeak/(2/pi) or
about 108 volts. The 110 volt DC relays should be happy and probably
won't buzz. Try one maybe.

If you add a filter capacitor, you'll get about 170 DC, which won't
buzz but would fry the 110 DC coils. You could add a series resistor
to fix that.

But why not use some nice octal-socket P&B AC-coil relays?

John

 

[John G.]

"Jon Slaughter" <Jon_Slaughter@Hotmail.com> wrote in message
news:h9gh3p$9o1$1@news.eternal-september.org...

"John G." <greentest@ozemail.com.au> wrote in message
news:4abb3eb9$0$12718$5a62ac22@per-qv1-newsreader-01.iinet.net.au...

"Gloria West" <gloriasbest22@NOSPAMgmail.com> wrote in message
news:0001HW.C6E05A3F0294CBFEB08A39AF@news.eternal-september.org...
120vac input to full-wave rectifier bridge. Without any filtering
components
what is the output RMS voltage?

This does not use a center-tapped transformer or such.

Relays run with this rectified supply are buzzing. These are in a
45-year-old
printing press.

I want to replace them with something more modern (the contacts are also
intermittent).

I found some that are rated for 110 dc:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-
1&storeId=10001&catalogId=10001&productId=301209&

Will these buzz also? Is there a simple way to keep them quiet?

And who is to say the contact rating will be correct?
Why don't you fix the problem (whatever it is ) rather than trying to
redesign the machine from a position of not enough knowledge?

John G.

Why don't you just ****** answer her question instead of trying to spout
your superiority? If she wants to **** it up then it's her choice. It
isn't going to cost you anything. You assume she's not intelligent enough
simply because no one could have even close the intelligence you have? Or
is it that you really care about her safety? Yeah.. I bet...

Get over it... you are not the smartest nor ever will be even close.
Trying to keep other people down does not make you more intelligent.

Of course the real reason is you simply don't want any competition.

Actually there is no way to answer her question because she never gave

enough data.
And it has long been proven that the best way to repair a device is to
return it to its design standard rather than redsign it without enough data
or design knowkedge.

John G.

 

[John Larkin]

On Thu, 24 Sep 2009 14:35:08 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Wed, 23 Sep 2009 23:05:35 -0700, Gloria West
gloriasbest22@NOSPAMgmail.com> wrote:

120vac input to full-wave rectifier bridge. Without any filtering components
what is the output RMS voltage?

This does not use a center-tapped transformer or such.

Relays run with this rectified supply are buzzing. These are in a 45-year-old
printing press.

I want to replace them with something more modern (the contacts are also
intermittent).

I found some that are rated for 110 dc:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-
1&storeId=10001&catalogId=10001&productId=301209&

Will these buzz also? Is there a simple way to keep them quiet?

Relays coils are inductive enough that they don't follow the ripple
voltage. So the effective (average) DC voltage becomes Vpeak/(2/pi) or
about 108 volts. The 110 volt DC relays should be happy and probably
won't buzz. Try one maybe.

If you add a filter capacitor, you'll get about 170 DC, which won't
buzz but would fry the 110 DC coils. You could add a series resistor
to fix that.

But why not use some nice octal-socket P&B AC-coil relays?

John

Oops, it's Vp * 2/pi. Still 108 volts.

John

 

[Jon Slaughter]

"John G." <greentest@ozemail.com.au> wrote in message
news:4abbf4c9$0$12695$5a62ac22@per-qv1-newsreader-01.iinet.net.au...

"Jon Slaughter" <Jon_Slaughter@Hotmail.com> wrote in message
news:h9gh3p$9o1$1@news.eternal-september.org...

"John G." <greentest@ozemail.com.au> wrote in message
news:4abb3eb9$0$12718$5a62ac22@per-qv1-newsreader-01.iinet.net.au...

"Gloria West" <gloriasbest22@NOSPAMgmail.com> wrote in message
news:0001HW.C6E05A3F0294CBFEB08A39AF@news.eternal-september.org...
120vac input to full-wave rectifier bridge. Without any filtering
components
what is the output RMS voltage?

This does not use a center-tapped transformer or such.

Relays run with this rectified supply are buzzing. These are in a
45-year-old
printing press.

I want to replace them with something more modern (the contacts are
also
intermittent).

I found some that are rated for 110 dc:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-
1&storeId=10001&catalogId=10001&productId=301209&

Will these buzz also? Is there a simple way to keep them quiet?

And who is to say the contact rating will be correct?
Why don't you fix the problem (whatever it is ) rather than trying to
redesign the machine from a position of not enough knowledge?

John G.

Why don't you just ****** answer her question instead of trying to spout
your superiority? If she wants to **** it up then it's her choice. It
isn't going to cost you anything. You assume she's not intelligent
enough simply because no one could have even close the intelligence you
have? Or is it that you really care about her safety? Yeah.. I bet...

Get over it... you are not the smartest nor ever will be even close.
Trying to keep other people down does not make you more intelligent.

Of course the real reason is you simply don't want any competition.

Actually there is no way to answer her question because she never gave
enough data.
And it has long been proven that the best way to repair a device is to
return it to its design standard rather than redsign it without enough
data or design knowkedge.

So even if it was designed improperly it's still the best to fix it exactly
the way it was? That sounds very intelligent. In any case, that is not the
problem. The problem is that you are assuming she is a moron. That may or
may not be the case but why do you do so? She asked a question and you gave
her a statement. Not just any statement of course but a condescending and
arrogant statement. A common trait among engineers and liberals.

Just because someone does not give enough information does not mean you get
to be arrogant. Either assume what you can or ask for more information but
personal attacks have nothing to do with engineering or helping someone.

 

[Jon Slaughter]

"Gloria West" <gloriasbest22@NOSPAMgmail.com> wrote in message
news:0001HW.C6E031BF028B4E02B08A39AF@news.eternal-september.org...

120vac input to full-wave rectifier bridge. Without any filtering
components
what is the output RMS voltage?

~0.7*Peak. 120V is RMS. The rectified RMS is exactly the same. Think of it
as power. Rectifying it will heat up a resistor jut as much cause the same
amount of power is dumped into it. Mathematically, squaring a the abs of a
function is the same as squaring it.

So |f|^2 = f^2 (assuming f is real)

So it does not effect the result.

(Note that 0.7*Peak is only valid for pure sinusoidal waveforms)

This does not use a center-tapped transformer or such.

Thanks.

There are two main types of rectifiers, AC and DC. AC rectifiers work
directly from AC without the need for rectification(They sorta have it built
in). DC needs dc or you will get "chatter". The chatter is from the contact
in the relay getting turned off and on repeatedly. This is due to the AC
reversing the magnetic field that normally would pull(or push) the contact
closed. What you get then is the ac pushing(or pulling) and then pulling(or
pushing) the contact.

Even if you rectify the AC so it is "DC" the DC relay still will chatter
because the rectified voltage is too low at some points in time. You can
look up on the net exactly how relays work for it to be clear.

So, if they are DC relays, which most likely they are because of the
rectification, then you have to use a filter cap, a cap that "smooths" the
ac to dc like. Basically when the AC goes low, the cap will act like a
battery and supply current to the relay until the AC can get back up. The
cap has to be sized so that it is large enough to handle the current needed.


Generally electrolytic caps are used. It does not hurt too much to use too
large of a cap but using too small will still create chatter. Electrolytic
caps are polar which means you gott hook the + to the + side of the
rectification.

 

[whit3rd]

On Sep 24, 5:11 pm, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote:

"John G." <greent...@ozemail.com.au> wrote in message

news:4abbf4c9$0$12695$5a62ac22@per-qv1-newsreader-01.iinet.net.au...







"Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote in message
news:h9gh3p$9o1$1@news.eternal-september.org...

"John G." <greent...@ozemail.com.au> wrote in message

And it has long been proven that the best way to repair a device is to
return it to its design standard rather than redsign it without enough
data or design knowkedge.

So even if it was designed improperly it's still the best to fix it exactly
the way it was?

It's not 'fix' that's been described, it's 'redesign'. Changing a
branch
circuit from AC to DC might be OK, or (depending on the situation)
might
be disastrous. Switch contacts and fuses that work fine on AC are
unsafe
with DC, for instance.

An acquaintance once had to dismount a 1/4" steel plate to access a
switching SCR, and wasn't keen to lift the plate back into position
when
he was done. He hunted up the original designer, who recalled that
the circuit that SCR was on had a quarter-million joules of stored
energy in a magnetic field. The steel plate went back up that
afternoon.

 

[Peter Bennett]

On Thu, 24 Sep 2009 19:23:03 -0500, "Jon Slaughter"
<Jon_Slaughter@Hotmail.com> wrote:

"Gloria West" <gloriasbest22@NOSPAMgmail.com> wrote in message
news:0001HW.C6E031BF028B4E02B08A39AF@news.eternal-september.org...
120vac input to full-wave rectifier bridge. Without any filtering
components
what is the output RMS voltage?

~0.7*Peak. 120V is RMS. The rectified RMS is exactly the same. Think of it
as power. Rectifying it will heat up a resistor jut as much cause the same
amount of power is dumped into it. Mathematically, squaring a the abs of a
function is the same as squaring it.

So |f|^2 = f^2 (assuming f is real)

So it does not effect the result.

(Note that 0.7*Peak is only valid for pure sinusoidal waveforms)

This does not use a center-tapped transformer or such.

Thanks.


There are two main types of rectifiers, AC and DC. AC rectifiers work
directly from AC without the need for rectification(They sorta have it built
in). DC needs dc or you will get "chatter". The chatter is from the contact
in the relay getting turned off and on repeatedly. This is due to the AC
reversing the magnetic field that normally would pull(or push) the contact
closed. What you get then is the ac pushing(or pulling) and then pulling(or
pushing) the contact.

I hope you meant to type "relays", rather than "rectifiers" in the
first two lines above.

--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

 

[Jon Slaughter]

"whit3rd" <whit3rd@gmail.com> wrote in message
news:6b880847-eed1-48fa-a8c7-4a32dfbe8073@z34g2000vbl.googlegroups.com...
On Sep 24, 5:11 pm, "Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote:

"John G." <greent...@ozemail.com.au> wrote in message

news:4abbf4c9$0$12695$5a62ac22@per-qv1-newsreader-01.iinet.net.au...







"Jon Slaughter" <Jon_Slaugh...@Hotmail.com> wrote in message
news:h9gh3p$9o1$1@news.eternal-september.org...

"John G." <greent...@ozemail.com.au> wrote in message

And it has long been proven that the best way to repair a device is to
return it to its design standard rather than redsign it without enough
data or design knowkedge.

So even if it was designed improperly it's still the best to fix it
exactly
the way it was?

It's not 'fix' that's been described, it's 'redesign'. Changing a
branch
circuit from AC to DC might be OK, or (depending on the situation)
might
be disastrous. Switch contacts and fuses that work fine on AC are
unsafe
with DC, for instance.

An acquaintance once had to dismount a 1/4" steel plate to access a
switching SCR, and wasn't keen to lift the plate back into position
when
he was done. He hunted up the original designer, who recalled that
the circuit that SCR was on had a quarter-million joules of stored
energy in a magnetic field. The steel plate went back up that
afternoon.
----

I haven't seen anything mentioned about a redesign. She wants to replace
components that have failed. Replacing components is not considered a
redesign in my book. There have been many things I've "fixed" by replacing
components that have failed yet it would not even have come close to what I
would call being redesigned.

Obviously one has to have some idea about the circuit involved along with
it's intentions. Replacing relays cannot ever cause any serious harm unless
the design was flawed from the begining. Obviously there is the slight
chance of a catastrophic failure but that can happen even with the original
design. No design is perfect and hence has a redesign that can make it more
perfect(theoretically).

Almost all designs, in the universe of designs, are implemented in a cost
effective way. As you know, this directly competes with a perfect design.
While the best option is usually to replace broken components it is not the
only option. We've all experienced poorly designed systems that could be
redesigned. It's neither her nor there because the origina question had
nothing to do with a redesign. Simply replacing components is not
redesigning the system.

When you replace a battery in your remote did you redesign it? Even if it's
not the same battery? (Maybe if your a pedant)

In any case, it's not up to me, you, or anyone else to decide if anyone has
the right to redesign something unless someone's safety is at issue. But we
shouldn't take this too far since every person has the right to put himself
at danger and even someone other people. Most devices that are in wide use
have the potential to kill people but we don't not complain about such
things and ban them. This is the cost of progress and convienence.

i.e., don't get overboard on such a simple thing. Replacing relays isn't
going to cause a nuclear meldown and kill millions of people. Probably not
even 1. If the wrong relays are used either:

1. They will burn up and need to be replaced again.
2. They will burn up something else.
3. They will not work as intented.
4. The device could work even better. (specially if the device no longer
works)
5. Much progress can be made if the device did not work before or cause
major problems because of the relays.

The probability of Gloria killing herself is pretty low. Probably lower than
the probablity of you dieing from a car wreck tomorrow. (yet you don't
hesitate to drive?) The probability of her killing or injuring someone else
is even much lower. The relays could potentially malfunction at the most
inoppurtune time but the likelyhood of this happening is probably rather
low(mainly because relays don't generally fail in such a way).

This is a printing press and not a nuclear reactor. We see many people
doing stupid things on a local scale and don't complain about it so no need
to do it here. If we woried about what *might* happen then we wouldn't get
much done.

If Gloria wants to redesign it then I'm all for it. Who knows... maybe she
will make the thing work much better. If she kills herself in the process
then at least she tried to do something instead of being paralyzed by fear.
Progress has never been easy and never will be. (well, except if Obama gets
his way)

Of course what you guys are really saying is "All you stupid people gotta
leave it up to the "experts"! Just give me a call and we'll discuss how much
it will cost you for me to redesign it for you."

 

[Jon Slaughter]

"Peter Bennett" <peterbb@somewhere.invalid> wrote in message
news:ts8ob553oenjg678dabgdiq8ku59hqei27@news.supernews.com...

On Thu, 24 Sep 2009 19:23:03 -0500, "Jon Slaughter"
Jon_Slaughter@Hotmail.com> wrote:


"Gloria West" <gloriasbest22@NOSPAMgmail.com> wrote in message
news:0001HW.C6E031BF028B4E02B08A39AF@news.eternal-september.org...
120vac input to full-wave rectifier bridge. Without any filtering
components
what is the output RMS voltage?

~0.7*Peak. 120V is RMS. The rectified RMS is exactly the same. Think of it
as power. Rectifying it will heat up a resistor jut as much cause the same
amount of power is dumped into it. Mathematically, squaring a the abs of a
function is the same as squaring it.

So |f|^2 = f^2 (assuming f is real)

So it does not effect the result.

(Note that 0.7*Peak is only valid for pure sinusoidal waveforms)

This does not use a center-tapped transformer or such.

Thanks.


There are two main types of rectifiers, AC and DC. AC rectifiers work
directly from AC without the need for rectification(They sorta have it
built
in). DC needs dc or you will get "chatter". The chatter is from the
contact
in the relay getting turned off and on repeatedly. This is due to the AC
reversing the magnetic field that normally would pull(or push) the contact
closed. What you get then is the ac pushing(or pulling) and then
pulling(or
pushing) the contact.

I hope you meant to type "relays", rather than "rectifiers" in the
first two lines above.

Yes ;/ Guess I'm starting to get senile.

 

[Ross Herbert]

On Wed, 23 Sep 2009 20:12:47 -0700, Gloria West <gloriasbest22@NOSPAMgmail.com>
wrote:

:120vac input to full-wave rectifier bridge. Without any filtering components
:what is the output RMS voltage?
:
:This does not use a center-tapped transformer or such.
:
:Thanks.

The relays, presumably, did not "buzz" when the system was first designed.
Unless the spring loading on the armature has been increased then the relay
should not buzz when driven from a non-filtered bridge rectifier output. Since
the mains input period is 16.7ms there is only a very brief period (somewhere in
the region of 3-5ms) between the 8.35ms half cycles when the voltage will be
reduced below the holding voltage of the relay and the normal magnetic inertia
of the magnet system should be sufficient to keep the armature from chattering.

The new relays in your link have a nominal release time of 10ms and the 110Vdc
coil has a resistance of 10Kohms - which indicates a large number of turns with
significant inductance. When you replace the relays, and if buzzing does occur,
try connecting a 10Kohm 3 to 5W resistor directly across the relay coil. This
will allow the back emf to "slug" the release time and stop the buzzing.