Op amps problem Gain Calculation

[default]

On 9 Dec 2005 04:48:50 -0800, sinebar@bellsouth.net wrote:

Does anyone know where I can get a high speed LED for strobing a
rotating q-switch?

Basically you're intent of finding an LED to use as a strobe for a
rotating mirror? How fast is it turning?

"Q-switch" covers a lot of territory . . .
--

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It turns about 30000 RPM.

 

[Simon]

"Simon" <lw004v6382@blueyonder.co.uk> wrote in message
news:CoUmf.6571$iz3.5938@text.news.blueyonder.co.uk...

I'm no electronics expert, thats where you all come into this.............

If I have a electrical device that runs a 2500 mah battery down in 30 mins
say. If i was to put 4 batteries together and place a resistor inline to
reduce it back to 1.25v. Would the item run for 2 hours or considerably
more
than 30 mins anyway? If not how could I do this?


p.s If that would work, what value resistor would I need to reduce 4.8v to

1.2?

 

[Pippa Reeves]

On Sun, 11 Dec 2005 11:50:58 +0000, Simon wrote:

I'm no electronics expert, thats where you all come into this.............

If I have a electrical device that runs a 2500 mah battery down in 30 mins
say. If i was to put 4 batteries together and place a resistor inline to
reduce it back to 1.25v. Would the item run for 2 hours or considerably more
than 30 mins anyway? If not how could I do this?

If you connect 4 identical batteries, with all their Negative terminals
connected to each other, and all their Positive terminals connected, you
will still have the same voltage, but the ability to pull the same current
from the battery for 4 times the length of time.

The load is shared between all the batteries by connecting them in this
fashion, so effectively you end up with a 1.25 volt, 10,000 mAh battery,
(10 Amp Hour battery).

In real life you will probably find that using 4 batteries in parralell to
increase the capacity will make the device run for more than 4 times the
previous time period, as the load sharing between the batteries will have
the effect of slightly reducing the losses in the battery.




Pip

 

[Pippa Reeves]

On Sun, 11 Dec 2005 12:08:48 +0000, Simon wrote:

"Simon" <lw004v6382@blueyonder.co.uk> wrote in message
news:CoUmf.6571$iz3.5938@text.news.blueyonder.co.uk...
I'm no electronics expert, thats where you all come into this.............

If I have a electrical device that runs a 2500 mah battery down in 30 mins
say. If i was to put 4 batteries together and place a resistor inline to
reduce it back to 1.25v. Would the item run for 2 hours or considerably
more
than 30 mins anyway? If not how could I do this?


p.s If that would work, what value resistor would I need to reduce 4.8v to
1.2?

The value of the resistor would need to be damn low..... but it would be
wasting 3/4 of the power stored in the battery if you connect them in
series. So there would be no benefit in using 4 batteries connected in
series.... in fact it would be a waste of energy, waste of 3 batteries,
and a waste of a very high power, low ohms resistor.

Connect the batteries in parralell as suggested in my other reply. There
would be no dropping resistor required by doing it that way.

Pip

 

[John Fields]

On Sun, 11 Dec 2005 13:15:53 +0100, "Alexander"
<electricdummy@hotmail.com> wrote:

"Pippa Reeves" <send_pdreeves_no_spam@bigpond.net.au> schreef in bericht
newsan.2005.12.12.04.12.45.53629@bigpond.net.au...
On Sun, 11 Dec 2005 11:50:58 +0000, Simon wrote:

I'm no electronics expert, thats where you all come into
this.............

If I have a electrical device that runs a 2500 mah battery down in 30
mins
say. If i was to put 4 batteries together and place a resistor inline to
reduce it back to 1.25v. Would the item run for 2 hours or considerably
more
than 30 mins anyway? If not how could I do this?

If you connect 4 identical batteries, with all their Negative terminals
connected to each other, and all their Positive terminals connected, you
will still have the same voltage, but the ability to pull the same current
from the battery for 4 times the length of time.

The load is shared between all the batteries by connecting them in this
fashion, so effectively you end up with a 1.25 volt, 10,000 mAh battery,
(10 Amp Hour battery).

In real life you will probably find that using 4 batteries in parralell to
increase the capacity will make the device run for more than 4 times the
previous time period, as the load sharing between the batteries will have
the effect of slightly reducing the losses in the battery.




Pip



There will always be some current between the batteries.
To prevent this place a schotky diode in series with each battery

---
That's not a good solution, since he wants to pull 1.25 amps out
each of four 1.2V cells in parallel. Even assuming only 0.3V across
each Schottky, that only leaves 0.9V for his load and the Schottkys
wasting 1.5 watts.

Since, with a 1.2V source and the load drawing 5A, the load looks
like:


E 1.2V
R = --- = ------ = 0.24 ohm
I 5A

the circuit will look like:


1.2V
|
[SCHOTTKY]
|
+--->0.9v
|
[0.24R]
|
0V

So, with 0.9V across the load, the load will dissipate:


E˛ 0.81
P = --- = ------- = 3.375 watts
R 0.24R


The Scottkys will be dissipating 1.5 watts and the load 3.375 watts,
for an efficiency of about 69%

Putting the cells in series and using National's LM1770

http://cache.national.com/ds/LM/LM1770.pdf

will get him about 95% efficiency and allow him the full 1.2V into
his load.

On top of that, the design can be done, for free, at:

http://www.national.com/appinfo/webench/scripts/my_webench.cgi

by logging on and following the instructions.


--
John Fields
Professional Circuit Designer

 

[Ron Cook]

On Sun, 11 Dec 2005 12:31:57 GMT, "Simon"
<lw004v6382@blueyonder.co.uk> wrote:

There will always be some current between the batteries.
To prevent this place a schotky diode in series with each battery

schotky diode? Just looked on www.maplin.co.uk. couldn't find one. There
again I wouldn't really know what I was looking for!

You want a Schottky diode.

On the Maplin page, below the listings for 16A devices, are listings
for 10A devices.

30A units

N17CC MBR3035PT 48 in Stock ?1.47
N18CC MBR3045PT 43 in Stock ?1.47
N19CC MBR3050PT 37 in Stock ?1.47
N20CC MBR3060PT 30 in Stock ?1.47


16A Schottky barrier rectifiers
a range of 16a SCHOTTKY barrier rectifiers ideal for use in low
voltage, high frequency invertors, free wheeling and polarity
protection applications. all products are supplied in a to-220a style
case.
N15CC MBR1635 62 in Stock ?0.89
N16CC MBR1645 40 in Stock ?0.89

Ron Cook n1zhi

 

[fritz]

Dan Hollands wrote:

Building a tachometer with readout is a bit of a challanging task

Why not use a laser strobe tackometer:

See Pocket Tach 99 (PT99) for $150
http://www.monarchinstrument.com/Pocket%20Laser.htm#Pocket

Thats probably cheaper - and much much quicker than you can buy the parts
and build one

Dan

Dan,

Thanks for the info. Unfortunately the space available is very
limited and is under the top which would negate the reading of the
display. I looked at the pocket tach and it wouldn't do the job. But
thanks any.

f.

 

[Andreas Rutz]

I don't think it is dying, you just have to go with the technology. Today
you can build electronics at home that haven't been possible for a hobbyist
some years ago. You just have to learn some new things like microprocessor
programming, SMD soldering, high-resolution PCB manufacturing....

Challenge is fun!

 

[Rich Grise]

On Thu, 22 Dec 2005 17:51:45 -0700, Kevin wrote:

I recently bought a very old rotary telephone, and I would like to
hook it up and use it. There are 3 wires in the telephone cord--red,
green and yellow. How do I hook these wires up to a standard RJ11
jack? The phone I have has red, green, yellow and black.

Is there something else I need to modify to get this to work?

First, don't post HTML.

Second, call the phone company and see if they still support pulse
dial.

If so, then connect red to red, green to green, and leave the
yellow and black unconnected. It might not ring, but that's a whole
nother project. ;-)

Good Luck!
Rich

 

[fritz]

Jasen Betts wrote:

On 2005-12-23, fritz <nofritzb@noisland.net> wrote:

Don Kelly wrote:

---------
A white line and a photocell can be made to work at 1 pulse/revolution- feed
it into a counter. Add more lines for more counts/ per rev. A lamp shining
through a film circle with alternating black and clear areas (i.e. a
negative) and a photocell will work (1 transistor amp may be needed). The
number of areas can be adjusted to give multiple pulses per revolution but
at the speed and needed accuracy, this won't be needed. Alternatively, glue
a small magnet on the shaft and pick up magnetic pulses.

So I assume that if the line is reflective enough, the light source
could be right beside the photocell. The distance between the photocell
and the line would be about 1.3 inches but that could be ameliorated by
encasing the photocell in a small tube with a focus on the line. A
magnet wouldn't work because one has to use a wrench on the collet to
remove the bit.


if the shaft is shaped to accept a wrench it's be perfect for a variable
reluctance pickup... it could be positioned behind the shaft where it
doesn't get in the way of the wrench
______
/ _____) _
______/ //~~~\ |o|
wrench //shaft\|~|~|~|___ sensor
______ \\ /|_|_|_|
\ \\___/ |o| mounting
\ ~~~~~) ~ ----- bracket
~~~~~~

shown with a hexagonal shaft but it'll work with round a shaft with two flat
sides or with one or more notches etc too, it'll just give a different number
of pulses per rotation.

"reluctors" are used in electronic speedometer pickups etc once can
probably be had for little cost from an automotive wrecker

I had a car that had one on that sensed the flywheel's (ring gear) teeth
it was only connected to the diagnotic socket.



Bye.
Jasen
What an idea! I assume that it senses more or less metal within it's

sensing range. The way the collet is shaped would give 4 pulses/rotation
or 1600 pps. I assume that since it can sense all the teeth on a ring
gear it ought to be able to do this. Thanks for the suggestion!

f.

 

[Henry]

I think it is. Decades ago when I was young there were several several
electronics supply stores, some like small grocery stores with isles and
isles of parts. Now the only brick&mortar place is Radio Shack where there
is just part of one wall.

I have been getting back into dabbling with some old TTL SN74xxx series
chips I had. I have an od mix. Anyway trying to tinker together some
projects but usually find myself short by one component that is no longer
easy to obtain. And it is not worth the $25 (or more) minimum ordering, S&H,
etc, to buy a $0.99 part. (Like a couple SN7414 that I lack in my box of IC
chips.)

Yes, there is some exciting new things, but we are loosing alot of the
inbetween stuff. But that inbetween stuff is still usable, it still works,
and is still sometimes the best solution for small specialized projects like
what I am doing.

Henry



<sinebar@bellsouth.net> wrote in message
news:1133659328.296648.142930@g49g2000cwa.googlegroups.com...

Is it just me or does it seem like the electronic hobby is dying. I
live in a fairly large city and it is very difficult to find electronic
components now. All the electronic suppliers are gone except for radio
shack and they suck. Am I wrong about this?

 

[Jasen Betts]

______
/ _____) _
______/ //~~~\ |o|
wrench //shaft\|~|~|~|___ sensor
______ \\ /|_|_|_|
\ \\___/ |o| mounting
\ ~~~~~) ~ ----- bracket
~~~~~~


What an idea! I assume that it senses more or less metal within it's
sensing range. The way the collet is shaped would give 4 pulses/rotation
or 1600 pps. I assume that since it can sense all the teeth on a ring
gear it ought to be able to do this. Thanks for the suggestion!

I've got bad news, it might not work - the magnetic field from the motor
might be stronger than the differences caused by the shaft aproaching and
retreating..

I just remembered similar sensors are also used in antiskid breaking
systems ...

but If it works it'll be immune to sawdust and the like....

Bye.
Jasen

 

[Dan Hollands]

"Henry" <henrytj@pghmail.com> wrote in message
news:5cadnTvrJqLH5zPenZ2dnUVZ_vidnZ2d@pghconnect.com...

I am tinkering with some 25 year old TTL logic chips and I need to make a
de-bounce circuit that will stay on for the duration of a the push-button.
I
have several ways already to debounce the button close, but they are
one-shot pulses that have thein own duration. I need both the close and
open
of the push button to be debounced and it to keep the duration of the
button
push. I have seen schmitt trigger circuits (that I have tried to build but
dont seem to work (have to triple check the wiring)), and other RC
variations. What kind of easily accessible parts (like from Radio Shack)
should I be looking for. It all has to run on 4-AA batteries. Looked an
some
op-amp parts at RS but they seem to all require 18v, or more, supply.

BTW, the debouncing solution needs to be acurate to within about 1
milli-second.

Henry

The easiest way is to use a pushbutton with Form C contact (single pole,
double throw) connected to 2 cross connected NOR gates so that when the
moving contact hits one pole connected to one NOR gate the cross connection
latches in one state and when the moving contact hits the other pose
connected to the other NOR gate the cross connection latches in the other
state. Thus you get a latch circuit the follows the pushbutton with no
glitches.

If you don't know how to implement this let me I can give you more details

Dan

--
Dan Hollands
1120 S Creek Dr
Webster NY 14580
585-872-2606
dhollan3@rochester.rr.com
www.QuickScoreRace.com

 

[Dan Hollands]

Henry

Without some knowledge of the type and electrical charactoristis of the
button it is hard to design a debounce circuit. Even with a mechanical
switch are sure that need one - what is the button going to do

--
Dan Hollands
1120 S Creek Dr
Webster NY 14580
585-872-2606
dhollan3@rochester.rr.com
www.QuickScoreRace.com
"Henry" <henrytj@pghmail.com> wrote in message
news:A5qdnYzHhKLWzzLeRVn-ig@pghconnect.com...

"Dan Hollands" <dhollan3@rochester.rr.com> wrote in message
news:qGyrf.55110$XC4.23793@twister.nyroc.rr.com...
"Henry" <henrytj@pghmail.com> wrote in message
news:5cadnTvrJqLH5zPenZ2dnUVZ_vidnZ2d@pghconnect.com...
I am tinkering with some 25 year old TTL logic chips and I need to make
a
de-bounce circuit that will stay on for the duration of a the
push-button.
I
have several ways already to debounce the button close, but they are
one-shot pulses that have thein own duration. I need both the close and
open
of the push button to be debounced and it to keep the duration of the
button
push. I have seen schmitt trigger circuits (that I have tried to build
but
dont seem to work (have to triple check the wiring)), and other RC
variations. What kind of easily accessible parts (like from Radio
Shack)
should I be looking for. It all has to run on 4-AA batteries. Looked an
some
op-amp parts at RS but they seem to all require 18v, or more, supply.

BTW, the debouncing solution needs to be acurate to within about 1
milli-second.

Henry




The easiest way is to use a pushbutton with Form C contact (single pole,
double throw) connected to 2 cross connected NOR gates so that when the
moving contact hits one pole connected to one NOR gate the cross
connection
latches in one state and when the moving contact hits the other pose
connected to the other NOR gate the cross connection latches in the other
state. Thus you get a latch circuit the follows the pushbutton with no
glitches.

If you don't know how to implement this let me I can give you more
details

Dan


Thanks, but I have no control over the push button. Its a camera shutter.
Might be mechanical, might be electronic. Either way it acts like a simple
push button closing a circuit. The mechanical ones, of course have noise.

I have an old camera that I want to try some specialy effects photography
with. I also have a view camera that has a focal plane leaf shutter (built
into the lens) that, in theory, should sync with a flash through its range
of shutter speeds (up to 1/250 of a second.)

Anyway, thanks. I will keep looking.

Henry

 

[newtype]

Maybe this will work ?...

Solving Switch Bounce Problems
http://www.embedded.com/showArticle.jhtml?articleID=18902552

TTL. So use a TTL, 74, LS, ALS, hex inverter for a debouncer?
Your using TTL now so there shouldn't be a problem with
1 milli-second. If not fast enough, look at the ALS, S, AS
TTL logic families ?

"Henry" <henrytj@pghmail.com> wrote in message
news:5cadnTvrJqLH5zPenZ2dnUVZ_vidnZ2d@pghconnect.com...
I am tinkering with some 25 year old TTL logic chips
and I need to make a de-bounce circuit that will stay
on for the duration of a the push-button.
I have several ways already to debounce the button close,
but they are one-shot pulses that have thein own duration.
I need both the close and open of the push button to be
debounced and it to keep the duration of the button
push. I have seen schmitt trigger circuits (that I have
tried to build but dont seem to work (have to triple check
the wiring)), and other RC variations.
What kind of easily accessible parts (like from Radio Shack)
should I be looking for. It all has to run on 4-AA batteries.
Looked an some op-amp parts at RS but they seem to all
require 18v, or more, supply.

BTW, the debouncing solution needs to be acurate to within
about 1 milli-second.

Henry

 

[Pippa Reeves]

On Mon, 26 Dec 2005 03:04:03 +0000, newtype wrote:

Reasons for creating a new newsgroup. From the posts I have
made to alt.binaires.schematics.electronic , the realization
is a.b.s.e is not suited for many multipart files. PDF binaries
are large and have been posted, but I can not u/l large files,
so I break them up to smaller meg files. I am told that
I'm flooding a.b.s.e If this is flooding, then I suggest a
newsgroup aimed specifically at posting electronics related
data. I've been told I'm breaking copyright laws. The data
sheets that I was posting are obsolete, TI, Phillips/Signetics
do not support obsolete devices, they could care less about
obsolete. Othere users have posted manuals and I'm sure they
have also been warned about breaking copyright laws.
If the manufacturer does not exist anymore, who is going to
complain about corporate copyright law? There's no there
at headquarters, it's been turned into a shopping mall?
The main problem is not the copyright issue, it has to do
with users who are complaining about "flooding" a.b.s.e
with so many files. It's about new people introduced to the
internet & don't know how to use/configure their newsreader.

***snip***

This a call for a vote.

Hi Newtype,

I have been a keen viewer of the group alt.binaries.schematics.electronic
for quite some time. Most weeks there have only been 10 or 20 posts, until
you commenced posting the copies of the datasheets.

The problem I have seen with what you have been doing is probably related
to the sudden change in the traffic loading of the group, and the settings
that most ISP's have for a group like a.b.s.e that normally has a low
posting volume, and I would suspect a relatively low number of readers.
The ISP's have the retention on the group set to a low level, this means
that most of the posts you have been putting up are useless from my ISP
(one of the larger ones in Australia!), as there are numerous parts to
each post that have already rolled off the server by the time the last
parts turn up.

I have a suggestion for you, reduce the number of posts you put up each
day, posting about a quarter of the volume each day should cure the
retention problems that most people are upset over. I do not believe there
is a need for another group.


Pip

 

[Henry]

Thanks for the link and I have already been to that site. Great site and I
am using it as one of my references.

Problem is that I dont have any 74 series with schmitt triggers. I looked
thourgh my box of old TTL chips. I have nand gates, counters, flipflops, 555
timers, (plus transistors, resistors, capacitors, etc) but nothing with a
schmitt trigger built in. Being out in a rural area and financially drained
(from caregiving for my mother in her last years) I can not justify $25
minimum ordering with S&H for a $0.49 chip. Radio Shack does not carry
these, and my attempts to build my own from transistors in my
box-o-ole-lectronics seems to have failed. Lacking a scope I cant really
tell if what I assemble is working. So I am continuing by trial and error.
All I know is that with what I have built so far I am getting multiple
triggers from the old camera shutter that I have. That is my noisy switch
that I am using.

Henry



"newtype" <fakeaddress@nowhere.net> wrote in message
news:Xns9737D44792513res808c4earthlinknet@63.218.45.254...

Maybe this will work ?...

Solving Switch Bounce Problems
http://www.embedded.com/showArticle.jhtml?articleID=18902552

TTL. So use a TTL, 74, LS, ALS, hex inverter for a debouncer?
Your using TTL now so there shouldn't be a problem with
1 milli-second. If not fast enough, look at the ALS, S, AS
TTL logic families ?

"Henry" <henrytj@pghmail.com> wrote in message
news:5cadnTvrJqLH5zPenZ2dnUVZ_vidnZ2d@pghconnect.com...
I am tinkering with some 25 year old TTL logic chips
and I need to make a de-bounce circuit that will stay
on for the duration of a the push-button.
I have several ways already to debounce the button close,
but they are one-shot pulses that have thein own duration.
I need both the close and open of the push button to be
debounced and it to keep the duration of the button
push. I have seen schmitt trigger circuits (that I have
tried to build but dont seem to work (have to triple check
the wiring)), and other RC variations.
What kind of easily accessible parts (like from Radio Shack)
should I be looking for. It all has to run on 4-AA batteries.
Looked an some op-amp parts at RS but they seem to all
require 18v, or more, supply.

BTW, the debouncing solution needs to be acurate to within
about 1 milli-second.

Henry

 

[newtype]

Pippa Reeves <send_pdreeves_no_spam@bigpond.net.au> wrote in
newsan.2005.12.26.22.07.15.778339@bigpond.net.au:

On Mon, 26 Dec 2005 03:04:03 +0000, newtype wrote:


Reasons for creating a new newsgroup. From the posts I have
made to alt.binaires.schematics.electronic , the realization
***snip***

This a call for a vote.

Hi Newtype,
I have been a keen viewer of the group alt.binaries.schematics.electronic
for quite some time. Most weeks there have only been 10 or 20 posts, until
you commenced posting the copies of the datasheets.
.... snip ...

I have a suggestion for you, reduce the number of posts you put up each
day, posting about a quarter of the volume each day should cure the
retention problems that most people are upset over. I do not believe
there is a need for another group.
Pip

Reducing the posts wont change the current state of a.b.s.e
The current users of a.b.s.e don't know why there are so many files
to begin with. I want a newsgroup where this will be a problem.
I created a Charter, as per alt.config rules. I state that the new
newsgroup will be for multi-part files. Since there is no charter
for a.b.s.e , no one seems to understand how to use a binary newsgroup.

Even if I post 10 files, that's 10 files too many. That's called
"Flooding" . I seriously doubt it. I posted 1 file and that was
spewed all over. Yet I got response from 5 users for more "You got
anymore..? It dosen't make a difference now, too many hate mongers
out. Too many new users that don't know how to use a newsreader.

 

[John Fields]

On Mon, 26 Dec 2005 01:17:50 -0500, "Henry" <henrytj@pghmail.com>
wrote:

Thanks for the link and I have already been to that site. Great site and I
am using it as one of my references.

Problem is that I dont have any 74 series with schmitt triggers. I looked
thourgh my box of old TTL chips. I have nand gates, counters, flipflops, 555
timers, (plus transistors, resistors, capacitors, etc) but nothing with a
schmitt trigger built in. Being out in a rural area and financially drained
(from caregiving for my mother in her last years) I can not justify $25
minimum ordering with S&H for a $0.49 chip. Radio Shack does not carry
these, and my attempts to build my own from transistors in my
box-o-ole-lectronics seems to have failed. Lacking a scope I cant really
tell if what I assemble is working. So I am continuing by trial and error.
All I know is that with what I have built so far I am getting multiple
triggers from the old camera shutter that I have. That is my noisy switch
that I am using.

---
Henry, please bottom post, since it makes it much easier to follow
the chronological flow of the thread. Thanks.

As for your problem, the only really sensible solution is the one
Dan Hollands offered, using a SPDT momentary switch and
cross-coupled gates to form an RS latch. That way _totally_
eliminates all bounce and the period of the output signal is
_precisely_ equal to the time it takes for the swich's common
terminal to get from one contact to the other.

If you've got a quad NAND (7400, LS00, HC00, etc.) and a SPST switch
you can make a latch, like this:


Vcc Vcc
| |
[1K] [1K]
| |
O-->| <--O---A
|NC | NO NAND Y--+---> OUT
| O +--B |
| | | |
| GND | A--+
| +--Y NAND
| B--+
| |
+------------------+

Now, when you press the switch, the instant the common hits the
normally open contact, OUT will go high and stay high for as long as
you keep the switch pressed. When you release the switch, OUT will
go low the instant the arm hits the NC contact and it will stay that
way until you again press the switch.

Re. your other post, about measuring the actual shutter timing,
what's your idea and what kind of test equipment have you got?

--
John Fields
Professional Circuit Designer