PRC as a amplifier in GPS question.

I'll have a quick go at explaining. U3B and U5A form an oscillator: note
the feedback from the output of U5A to U3B's non-inverting input ie +ve
feedback. This forms a sawtooth oscillator. U3A is simply a buffer of
half
the supply voltage to set the DC operating point. Probably a single supply
or battery supply. U5B is a comparator without hysteresis. Now, the Delta
P
signal is first amplified by U5C, a DC stage. And no, the 10k feedback
resistor does NOT add hysteresis but simply puts a single pole in the
response to roll off high frequency response, probably pulsations in the
flow or pressure sensor.

The next stage is U5D forming an integrator. Of Course this has open loop
gain at DC which means that the PWM is capable of going to 100% and 0%. I
am assuming here though that the sawtooth amplitude is less than the
supply
rails, you can verify with calcs or simulation. When the system is in
balance, the set point voltage of R28 will equal the value of Delta P
average voltage and there will be a constant duty cycle value. Q2 is
obviously an enable function.

The two 200k resistors in series in the integrator would have been chosen
by the designer presumably because that was an available value, and/or to
minimise the number of different values for a SMT design to minimise the
number of different reels used.
Click to expand...
Geoff,

One more question if I can. Is not U5C a comparator whose output would be
either High of Low depending on the setpoint voltage on its positive input
and the DeltaP voltage. The 10K feedback providing lots of hysteresis.

Greg
 
"Greg Hines"


One more question if I can. Is not U5C a comparator whose output would be
either High of Low depending on the setpoint voltage on its positive input
and the DeltaP voltage. The 10K feedback providing lots of hysteresis.
Click to expand...

** U5C is a unity gain inverting stage formed by R27 and R29 - the
actual gain reducing to zero at some high frequency due to the 0.1uF cap.

Dunno how you get any other idea.



........... Phil
 
"Greg Hines" <greghines@bigfoot.com.NOSPAM> wrote in
news:A9VHe.189$tv6.1039@nnrp1.ozemail.com.au:

I'll have a quick go at explaining. U3B and U5A form an oscillator:
note the feedback from the output of U5A to U3B's non-inverting input
ie +ve feedback. This forms a sawtooth oscillator. U3A is simply a
buffer of
half
the supply voltage to set the DC operating point. Probably a single
supply or battery supply. U5B is a comparator without hysteresis.
Now, the Delta
P
signal is first amplified by U5C, a DC stage. And no, the 10k
feedback resistor does NOT add hysteresis but simply puts a single
pole in the response to roll off high frequency response, probably
pulsations in the flow or pressure sensor.

The next stage is U5D forming an integrator. Of Course this has open
loop
gain at DC which means that the PWM is capable of going to 100% and
0%. I am assuming here though that the sawtooth amplitude is less
than the
supply
rails, you can verify with calcs or simulation. When the system is in
balance, the set point voltage of R28 will equal the value of Delta P
average voltage and there will be a constant duty cycle value. Q2 is
obviously an enable function.

The two 200k resistors in series in the integrator would have been
chosen by the designer presumably because that was an available
value, and/or to minimise the number of different values for a SMT
design to minimise the number of different reels used.

Geoff,

One more question if I can. Is not U5C a comparator whose output
would be either High of Low depending on the setpoint voltage on its
positive input and the DeltaP voltage. The 10K feedback providing
lots of hysteresis.

Greg
Click to expand...
See Phil's answer to this. I think you might be regarding U5C as a
comparator, it is actually an inverting amplifier as Phil says. *If* the
input terminals to the opamp were reversed it *would* be a comparator.
Maybe this has confused you?
 
On , wrote:

[Saved as file: C:\Program Files\Agent\circuit.jpg]
Click to expand...

Hello Greg,
When answering someone, I usually like to leave a
few sentences of their remarks but as you can see
above, your post disappeared when I opened your
diagram and that was all I was left with. Bit of a pain
but never mind.

This circuit for a motor speed control or light dimmer
on this website is similar to yours and simpler.
http://www.solorb.com/elect/solarcirc/pwm1/
There is description on how it works.
Perhaps you can study the diagram with description
and then get a better idea how your circuit works,
since some areas are similar.

I have built that particular controller for a DC motor
in an old mig welder and it works very well. Much
better than the original motor controller which justed
varied the voltage to the motor.
Just thought I would mention that if all you were
looking for was a simple motor controller.

Regards,
John Crighton
Hornsby
 
"Geoff C"<

You have drawn this differently to the first schematic. The feedback
network must go to the inverting (-) input of the opamp
Click to expand...

** Oh deary me !!

The OP has fallen for the old trap of **assuming** that op-amps are always
drawn with the + input uppermost.





.......... Phil
 
I think you are right, I may be colored by bad experiences.

I regret my burst of emotion.

Par.

Spoken like a man !! well done. You can stand tall in this NG.

--
Regards ..... Rheilly Phoull

A man alone in this NG. I am yet to see anyone (myself included)
Click to expand...
apologising for having a rush of blood to the head.

Mike
 
"Phil Allison" <philallison@tpg.com.au> wrote in
news:3lb1gdF11q1d8U1@individual.net:

"Geoff C"


You have drawn this differently to the first schematic. The feedback
network must go to the inverting (-) input of the opamp


** Oh deary me !!

The OP has fallen for the old trap of **assuming** that op-amps are
always drawn with the + input uppermost.





......... Phil
Click to expand...
Yes, a trap for young players that one.
 
"Geoff C"
"Phil Allison"

** Oh deary me !!

The OP has fallen for the old trap of **assuming** that op-amps are
always drawn with the + input uppermost.



Yes, a trap for young players that one.
Click to expand...

** The OP must be off hiding in a corner.

He has pulled his last post from both ISPs I get plus GG.




............ Phil
 
"Geoff C" <notinterestedin@spam.com> wrote in message
news:Xns96A79A8E47F50testnospamcom@61.8.0.29...
"Phil Allison" <philallison@tpg.com.au> wrote in
news:3lb1gdF11q1d8U1@individual.net:


"Geoff C"


You have drawn this differently to the first schematic. The feedback
network must go to the inverting (-) input of the opamp


** Oh deary me !!

The OP has fallen for the old trap of **assuming** that op-amps are
always drawn with the + input uppermost.
Yes, a trap for young players that one.
Click to expand...

You are absolutely correct, my drawing is incorrect. However, I do
appreciate everyones input and time.

Thanks guys.

Greg
 
mikegw wrote:

I think you are right, I may be colored by bad experiences.

I regret my burst of emotion.

Par.

Spoken like a man !! well done. You can stand tall in this NG.

--
Regards ..... Rheilly Phoull

A man alone in this NG. I am yet to see anyone (myself included)
apologising for having a rush of blood to the head.
Click to expand...
Could be that them blokes are too busy enjoying a rush of blood elsewhere in
the body :)
 
On Wed, 03 Aug 2005 08:19:36 GMT, Moses Lim
<hyspeed@zeta.org.au.no.spam.pls> put finger to keyboard and composed:

mikegw wrote:


I think you are right, I may be colored by bad experiences.

I regret my burst of emotion.

Par.

Spoken like a man !! well done. You can stand tall in this NG.

--
Regards ..... Rheilly Phoull

A man alone in this NG. I am yet to see anyone (myself included)
apologising for having a rush of blood to the head.

Could be that them blokes are too busy enjoying a rush of blood elsewhere in
the body :)
Click to expand...
"The problem is that God gives men a brain and a penis, and only
enough blood to run one at a time."

- Robin Williams


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.
 
A man alone in this NG. I am yet to see anyone (myself included)
apologising for having a rush of blood to the head.

Could be that them blokes are too busy enjoying a rush of blood elsewhere
in
the body :)
Click to expand...
Either one usually ends in trouble of one sort or another.
 
I think you jokers know what I am on about, no kneed to play stupid,

e.g. the electric fences is for animals,

e.g. nylon carpets and cars then (damn this dry weather! :) is static
electricity


I am talking about hold on to this .................. ha ha ha I just gave
you a electric shock from this play toy I purchased.






Hmm, better ban electric fences and nylon carpets and cars then (damn this
dry weather! :)

- Daniel
 
"Ben Dover" wrote

I think you jokers know what I am on about, no kneed to play stupid,


***** Hmm! How do you get the bread to rise then??

Brian Goldsmith.
 
Richard Waters wrote:

I need to separate the glass globe from the metal base - does anyone
know a way of doing this while still keeping the 2 halves intact?

I need to be able to separate the glass, from the base, remove the
"guts" of the base and replace it with something else, and then
superglue the glass back to the base so it looks like a normal light globe.

*YES* I know it wont work again after this.

*NO* Im not a bomber or an idiot, but close, Im a Professional Magician!

Cheers, Richard
See if you can source a diamond wire , thats a wire say with abrasive
Click to expand...
impregnated from your local hardware , I used to use mine in a fret saw
30 years ago.
 
"atec" <atec77@xxxhotmail.com> wrote in message
news:430beeb3$1@dnews.tpgi.com.au...
Richard Waters wrote:

I need to separate the glass globe from the metal base - does anyone know
a way of doing this while still keeping the 2 halves intact?

I need to be able to separate the glass, from the base, remove the "guts"
of the base and replace it with something else, and then superglue the
glass back to the base so it looks like a normal light globe.

*YES* I know it wont work again after this.

*NO* Im not a bomber or an idiot, but close, Im a Professional Magician!

Cheers, Richard
See if you can source a diamond wire , thats a wire say with abrasive
impregnated from your local hardware , I used to use mine in a fret saw 30
years ago.
Click to expand...
Easier still, I remember from a kids science show - soak a piece of thread
in methylated spirit, wrap it around the glass, light it, and then dip it
into cold water. It should break in a nice clean line.

*Just like Magic*
 
"Richard Waters" <legerdemain@irimus.com.au> wrote in message
news:430be2e0$1_1@news.iprimus.com.au...
I need to separate the glass globe from the metal base - does anyone
know a way of doing this while still keeping the 2 halves intact?

I need to be able to separate the glass, from the base, remove the
"guts" of the base and replace it with something else, and then
superglue the glass back to the base so it looks like a normal light
globe.

*YES* I know it wont work again after this.

*NO* Im not a bomber or an idiot, but close, Im a Professional Magician!

Cheers, Richard
Click to expand...

Richard - do you want to get inside the glass envelope or just separate the
parts?

To separate, start with two - break the glass out of one, cut / grind / saw
or etch the base off the second one.

rob
 
On Wed, 24 Aug 2005 13:00:44 +1000, Richard Waters
<legerdemain@irimus.com.au> put finger to keyboard and composed:

I need to separate the glass globe from the metal base - does anyone
know a way of doing this while still keeping the 2 halves intact?
Click to expand...
Many years ago I had a bad batch of globes that separated in normal
usage. It was quite disconcerting to be watching TV and have a hot
globe shoot past your head. I think the adhesive must have been magic.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.
 
I guess you read the post in a different way - I thought he wanted to just
separate the base from the globe, alter the base, then reassemble - not break
the glass

David - who would suggest the OP try soaking the whole globe in something like
actetone to try and dissolve the glue that holds the base and glass together -
or phone the mfg and ask what glue they use

"NetPlus Micro Computers (Shaw Goh)" wrote:

Easier still, I remember from a kids science show - soak a piece of thread
in methylated spirit, wrap it around the glass, light it, and then dip it
into cold water. It should break in a nice clean line.

*Just like Magic*
Click to expand...
 
"Jasen Betts"
use a propane blow torch (or gas flame etc) to heat the base of the
bulb until the adhesive in there lets go.
Click to expand...

** That is just what I said earlier in this thread !!

I have used very hot air to release octal valves from their hard plastic
bases.


That'll get you an intact glass part. and a metal part with melted solder,
Click to expand...

** Yep - I wind up with a perfectly intact glass envelope and a slightly
frazzled bakelite base.

Have managed to "repair" numerous expensive valves ( KT88s etc) where
internal flashover had occurred.





........... Phil
 
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