magnetic field

[Gene S. Berkowitz]

In article <1117427404.112130.302520@g14g2000cwa.googlegroups.com>,
siliconmike@yahoo.com says...

I've developed a small device that trips a circuit if its power
consumption goes outside a bound.

There are quite a few machines (for example - pumps) whose power
consumption depends on the input voltage.

Such machines may get damaged in case the external conditions go
berzerk. (example when there is no input to a submersible pump). In
such cases the power input fluctuates. (The current input fluctuates,
but unpredictably in many cases)

My device is initially programmed with 2 graphs:

1: of Maximum Power versus Input-Voltages of the machine it intends to
protect.
2: of Minimum Power versus Input-Voltages of the machine it intends to
protect.

The device interpolates and makes this graph smooth.

When the power consumption of the machine goes out of bounds for a
given input voltage, it trips the machine.

First, does such device exist in the market ? If yes, what is it called
?
What are the other uses one could contemplate for this device?
(It was originally made for pumps)

Thank you
Mike

Yes, it exists, and I have one in my basement, to protect my well pump.
http://www.franklin-electric.com/Prod_text/item8.htm

--Gene

 

[Charles Jean]

On 29 May 2005 18:44:10 -0700, "James" <lpln117@yahoo.com> wrote:

I have a car battery 12 volts. I wanna run a 7A load at
6 Hz. Does anyone know a way for me to oscillate the
output of the car battery at 6 Hz??

I can't use a function generator and plugging it into
a power amplifier because the freq response of most
power amplifier is 20Hz - 20Khz. I need 6 Hz output
with current capacity of 7A.

Thanks.

James
___

If you don't have to be real tight on frequency, how about this:
7805 regulator and caps to supply a low-end PIC with internal
oscillator. PIC programmed to output a 6 Hz square wave that drives
the gate of a MOSFET? One of the IRF series would work for 7A @ 12V.
What is the load and temperature range?

 

[Pat Flannery]

Robert Clark wrote:

Key for lifter drive becoming a generally useful propulsion method is
an electrical power source lightweight enough to be lifted by the
lifter dirve. Electrostatic high voltage generators may prove to an
answer for such a power source.

I'd still just generate the energy on the ground, and beam it to it as
microwaves; the wide flat shape of the lifter would make an ideal shape
for a rectenna.

Pat

 

[exxos]

<cheian07@yahoo.com> wrote in message
news:1117522568.470512.316980@g43g2000cwa.googlegroups.com...

hi good day!
i am installing my sis6215c display card with its driver but whenever
the computer starts up, it always says incorrect display adapter. can i
find a better display driver here on the net? pls give me some link.
tnx, ian

a simple google search finds many links

http://www.driverfiles.net/Video-Adapters/Vision-Graphics/page,level2,783,5,resultpage1.html

http://www.driverfiles.net/Video-Adapters/Vision-Graphics/sis6215c/download/page,show,12978,783,5,.html


and if your clever you could just goto sis.com and download the drivers from
the huge list they have there.

Chris

 

[sds]

cheian07@yahoo.com wrote:

hi good day!
i am installing my sis6215c display card with its driver but whenever
the computer starts up, it always says incorrect display adapter. can i
find a better display driver here on the net? pls give me some link.
tnx, ian

Hi.
http://www.driverguide.com not bad either.
One of the funny things i have seen with SIS graphics is that sometimes the
small heatsink stuck on the chip has the wrong number on it. (seen that on
6326 i think...)
But just try a few different drivers you should get there in the end.

 

[John Muchow]

Cross-posted...

I have 3 Radio Shack 13.8V, 25A power supplies (model #22-510,
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F009%5F001%5F005%5F000&product%5Fid=22%2D510
) which are working great.

But, I need to get up to 40A output though by hopefully paralleling
two or three of them. Can this be safely done using either or both of
the following methods?
- Series resisitance on the output of each unit to act as a ballast to
help balance the out puts (similar to what's done to help balance
current thru paralleled MOSFETs)?
- Series diode (probably paralleled 6A diodes) on the outut of each
supply to prevent the unit with a slightly higher voltage output from
causing unwanted current flow back into the slightly lower-voltage
unit? The voltage drop across these diodes wouldn't be too much of a
problem but I'd love to avoid it if I could.

I'm guessing that I'd need to adjust the output voltage of each power
supply to be as close to each other as possible and use short,
large-gauge, identical length connections from each supply.

I hesitate to start experimenting without knowing a bit more of what
the possible options are for paralleling these power supplies. IMHO,
I probably wouldn't have too many problems until I reached higher
current levels, but by then any problems would be pretty nasty and
probably happen too quickly for me to do anything about.

Thanks for any info you can offer!

John Muchow
-- remove SPAMMENOT for e-mail responses --

 

[The Real Andy]

On 27 May 2005 17:35:03 -0700, john.ruckstuhl@gmail.com wrote:

Sneaky scales fudge weights deliberately.

I suspect that many modern, microprocessor -controlled bathroom scales
have programmed in hysteresis to increase user confidence in the
scale's accuracy. The scale remembers fresh measurements, say 166.2#,
and if it next measures same weight +/- a little (within a short time),
say 166.8#, then the scale decides to report the *original* measurement
166.2#. Neat. Sneaky. User believes the scale is highly repeatable.

On such a scale, I weigh myself multiple times and get the same reading
(to the 0.2#) each time. 166.2#, 166.2#, 166.2#, 166.2#, ...
Then I weigh something different (myself holding a load), to reset the
memory.
Then I weigh myself again... Now, get something like 166.8#, 166.8#,
166.8#, 166.8#, ... very solid again, but 0.6# different from 1st
series of measurements.

I tried 6 models (2 or 3 brands) at a retail store display and find
this "feature" common.

Is it important? Maybe yes in the following scenario -- in some sports
like wrestling, boxing, judo, you have multiple competitors weighing in
at the same time, same scale, with possibly very similar weight. Some
competitors are concerned with as little as 0.25#. In this case it
seems one competitor could inherit the weight measurement of the person
in front of him.

In a perfect world, competition weigh-in equipment should be
certified/calibrated. But since the bathroom scale appears so
repeatable, some competitions now use modern, microprocessor
-controlled bathroom scales.

Somebody's going to say... "you shouldn't do that". Right, I agree.
But (a) it's happening, because (b) this hysteresis (memory)phenomenon
isn't widely known, I suspect.

Anyone care to confirm? Contradict? Repeat the experiment on their
own scale? Comment? In my experiment I didn't bother to determine
what weight difference resets the memory -- 1#? 1.5#?

Regards,
John Ruckstuhl

Having spent some time in the weiging industry, i can assure you that
the cheap portable bathroom scales that you buy are neither:
a. repeatable
b. accurate
c. linear

In fact, most will become more innacurate in the most common weight
ranges.

In AU, a cheap set is $20, a good repeatable set is $400. The
expensive scale can be recalibrate and remains linear. Should it not
be linear a multi-point cal can be done. The cheap set can only be
thrown.

Most cheap sets are innacurate of the shelf as they are made in china
and fail to take into account local gravitational constants

 

[mike]

John Muchow wrote:

Cross-posted...

I have 3 Radio Shack 13.8V, 25A power supplies (model #22-510,
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F009%5F001%5F005%5F000&product%5Fid=22%2D510
) which are working great.

But, I need to get up to 40A output though by hopefully paralleling
two or three of them. Can this be safely done using either or both of
the following methods?
- Series resisitance on the output of each unit to act as a ballast to
help balance the out puts (similar to what's done to help balance
current thru paralleled MOSFETs)?
- Series diode (probably paralleled 6A diodes) on the outut of each
supply to prevent the unit with a slightly higher voltage output from
causing unwanted current flow back into the slightly lower-voltage
unit? The voltage drop across these diodes wouldn't be too much of a
problem but I'd love to avoid it if I could.

I'm guessing that I'd need to adjust the output voltage of each power
supply to be as close to each other as possible and use short,
large-gauge, identical length connections from each supply.

I hesitate to start experimenting without knowing a bit more of what
the possible options are for paralleling these power supplies. IMHO,
I probably wouldn't have too many problems until I reached higher
current levels, but by then any problems would be pretty nasty and
probably happen too quickly for me to do anything about.

Thanks for any info you can offer!

John Muchow
-- remove SPAMMENOT for e-mail responses --

There are a bunch of issues.
Where is the current limit set? Is it set at a level that the PS can
tolerate at 100% duty cycle?
What's the shape of the current limit? If it's foldback, you've got
problems.
Is there overvoltage protection? If one crowbars it has to take all
three down. Probably in a puff of smoke.
Can they tolerate voltage at their output when turned off?
Even if you switch them with a power strip, they'll come up differently.

What's the cost of the thing you're powering? How does that compare
to the savings on the power supply? Is it worth the risk?

Once you get all that sorted out, you have three choices.
Resistors to force load sharing, give up on low output impedance and
hope the settings are stable enough to stay where you balanced it.

Redesign the supplies to put one regulation loop around the whole thing.

Sell the two and buy one good one.
mike

--
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
..
Wanted, PCMCIA SCSI Card for HP m820 CDRW.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Wanted 12" LCD for Compaq Armada 7770MT.
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/

 

[GaryG]

"The Real Andy" <will_get_back_to_you_on_This> wrote in message
news:q51r91h5e2idh6i0vgiu4q2u7kk6c4mmcf@4ax.com...

On 27 May 2005 17:35:03 -0700, john.ruckstuhl@gmail.com wrote:

Sneaky scales fudge weights deliberately.

I suspect that many modern, microprocessor -controlled bathroom scales
have programmed in hysteresis to increase user confidence in the
scale's accuracy. The scale remembers fresh measurements, say 166.2#,
and if it next measures same weight +/- a little (within a short time),
say 166.8#, then the scale decides to report the *original* measurement
166.2#. Neat. Sneaky. User believes the scale is highly repeatable.

On such a scale, I weigh myself multiple times and get the same reading
(to the 0.2#) each time. 166.2#, 166.2#, 166.2#, 166.2#, ...
Then I weigh something different (myself holding a load), to reset the
memory.
Then I weigh myself again... Now, get something like 166.8#, 166.8#,
166.8#, 166.8#, ... very solid again, but 0.6# different from 1st
series of measurements.

I tried 6 models (2 or 3 brands) at a retail store display and find
this "feature" common.

Is it important? Maybe yes in the following scenario -- in some sports
like wrestling, boxing, judo, you have multiple competitors weighing in
at the same time, same scale, with possibly very similar weight. Some
competitors are concerned with as little as 0.25#. In this case it
seems one competitor could inherit the weight measurement of the person
in front of him.

In a perfect world, competition weigh-in equipment should be
certified/calibrated. But since the bathroom scale appears so
repeatable, some competitions now use modern, microprocessor
-controlled bathroom scales.

Somebody's going to say... "you shouldn't do that". Right, I agree.
But (a) it's happening, because (b) this hysteresis (memory)phenomenon
isn't widely known, I suspect.

Anyone care to confirm? Contradict? Repeat the experiment on their
own scale? Comment? In my experiment I didn't bother to determine
what weight difference resets the memory -- 1#? 1.5#?

Regards,
John Ruckstuhl

Having spent some time in the weiging industry, i can assure you that
the cheap portable bathroom scales that you buy are neither:
a. repeatable
b. accurate
c. linear

In fact, most will become more innacurate in the most common weight
ranges.

In AU, a cheap set is $20, a good repeatable set is $400. The
expensive scale can be recalibrate and remains linear. Should it not
be linear a multi-point cal can be done. The cheap set can only be
thrown.

Most cheap sets are innacurate of the shelf as they are made in china
and fail to take into account local gravitational constants

Do you have any experience with the newer digital models? Not the low-end
ones, but ones like the Tanita with ostensible 0.2 lb resolution, priced
around $50-90 (US).

For instance, http://tinyurl.com/49swe, or the more expensive German-made
Soehnle brand http://tinyurl.com/3t6kt.

GG

 

[Vidar Lřkken]

log wrote:

Supposed our alternating current jumps from 60 Hz to
1 khz or 1 Mhz. What would happen?

Well, as a motor is a inductance, it'd not work. Higher frequency means
bigger "resistance" in the windings, so there'd be less current. From
50/60Hz to 1kHz, the motor would stop working. The current would be so
small it would probably not work at all, at least have much lower power.

What appliances would be damaged? Or would the fast
fluctuations average to a DC such that the electric
fan would no longer run? Suppose you increase the
frequency of the AC to just say 200 Hz. Will the
electric fan still run? Or will it run so much faster?
How about light bulbs and flourescents?
The electric fan would not work, because it has a inductance, which

would pass no current at higher frequency. Not because it would average DC.
Most appliances would probably not be damaged, since the current decreased.
Transformers *might* work , but would have different characteristics on
higher frequencies.

So most of the things that use electricity, except lightbulbs and
heaters would stop working. I don't know about fluroscent lights, but I
guess they'd stop working, since they're commonly in parallell with a
inductance, which would pass no current, and thus not work as expected.
Maybe someone else can eleborate on the fluorescent lights?

Just want to understand the significance of
frequency in power lines. Thanks.

log

--
MVH,
Vidar

www.bitsex.net

 

[GaryG]

<john.ruckstuhl@gmail.com> wrote in message
news:1117637715.868408.257540@z14g2000cwz.googlegroups.com...

Hi,
Thanks to all who took time to reply.

Yesterday I went to a Bed, Bath, & Beyond store where there were
several models on display.

I brought with me several 0.5 liter water bottles (approx 1 lb.) and
half-consumed one (approx 0.5 lb.) so that I could adjust my weight in
0.5 lb. increments. I tried 3 models and found two that I think
exhibited this programmed hysteresis, and one that did not.

The $40 Thinner TH300 uses load cells and reports to 0.5 lb.
Holding an empty shopping basket and full pockets, I measured at 181.0
six times in a row. Then, holding ~0.5# in my basket, I still measured
181.0. Again, holding ~1#, I still measured 181.0. Then, when holding
~1.5#, apparently past the programmed hysteresis threshold, scale
reported 182.5.

The $50 Tanita BF679 reports to 0.2 lb. It did not have hysteresis.
Each measurement was independent, reporting like 178.2, 178.4, 178.6,
178.4, ... (I wasn't holding an empty shopping basket for this one).

The $60 WeightWatcher WW60 (Scales by Conair) uses load cells and
reports to 0.1 lb.
I (plus basket) measured 180.7 six times in a row. Then holding ~0.5
lb., I measured 180.7 again. Then, holding ~1#, I measured 181.9 .

So, I see this programmed hysteresis in some models, with a breakaway
delta of ~1#.

I had thought I originally noticed this two months ago in several
Taylor models and a Tanita, but I wasn't able to test any Taylors
yesterday and my one Tanita test didn't show it.

Best regards,
John Ruckstuhl

Outstanding report...thanks!

My experience with Tanita has been the same - no hysteresis noted.

Consumer Reports magazine tested several models of body fat scales in the
last year or so. As I recall, they liked the Tanita the best - they warned
that body fat was quite variable, and probably not very accurate, but that
the body weight reported by Tanita was better than most other units (not
sure if they tested for hysteresis).

GG

 

[Louis Scheffer]

"log" <logansummersh@yahoo.com> writes:

Supposed our alternating current jumps from 60 Hz to
1 khz or 1 Mhz. What would happen?

First, our power grid would not work so well. The inductance of the lines
is already bad at 60Hz, and would be 16 times worse at 1 khz.

Probably nothing will work at 1 Mhz, except maybe heaters, and even this
depends on the reactive component - 1 MHz is just too far from the normal range.

What appliances would be damaged? Or would the fast
fluctuations average to a DC such that the electric
fan would no longer run? Suppose you increase the
frequency of the AC to just say 200 Hz. Will the
electric fan still run? Or will it run so much faster?
How about light bulbs and flourescents?

If you can get it to your house, some stuff will work at 1 khz and some
not. Incandescent lights and heaters should work fine. Stuff with simple
switching supplies (laptops and other things with power warts) may work.
There is no problem in theory (they do AC->DC->AC->DC) but the input filters
might be tuned to 50/60 Hz. Stuff with transformers may well work depending
on the exact construction. (At HP, back when most instruments had transformers
we tested almost all our products at 400 Hz, and they worked well in general.)
Flourescents might come on but will be dim since their ballasts are
inductive. Most motors will not work at all for two reasons; they depend on
the frequency to set their speed and cannot run 16 times as fast, and the
inductive winding will let less current through. Basically you would need to
look at each piece of equipment to see if it would work, or be damaged.

Finally, the audible noise will be horrible. The ear is much more sensitive
to 1 khz than to 60 Hz, especially at low volumes.

Just want to understand the significance of frequency in power lines. Thanks.

It's a tradeoff; higher frequencies can use smaller and lighter power equipment
such as transformers, filters, and capacitors, but low frequencies are easier
to ship long distances, and more convenient for rotating machinery such as
motors and generators. So airplance, were weight is important and wires are
short, use 400 Hz. Spacecraft, where weight is really important, use 2.4 khz.

 

[CWatters]

<doransignal@gmail.com> wrote in message
news:1117552951.154646.293980@g14g2000cwa.googlegroups.com...

I have a lot of old circuit designs that require a crystal for ham
radio. Is there some circuit that I could build to emulate a crystal.
So it could be a direct plug in? Just wondering
Lee

Whats the spec on the crystal you need?

 

[Antti Panula]

Just want to understand the significance of
frequency in power lines. Thanks.

The most part of digital clocks would run 16,7 times faster at 1kHz. So the
normal day would be just under 1,5 hours at this frequency of mains power.

Antti
OH7GLS

 

[John Muchow]

There are a bunch of issues.
Where is the current limit set? Is it set at a level that the PS can
tolerate at 100% duty cycle?

PS turns off at 25A, 100% duty cycle, after a few seconds. Runs
forever at 22A, 100% duty cycle. Seems to be thermally activated.
Not sure where the current limiting is set but it does reliably shut
down if output is shorted.

Is there overvoltage protection? If one crowbars it has to take all
three down. Probably in a puff of smoke.

Don't know...no reference other than "electronic overload protection"
in the instructions, but's that's probably for current.

Can they tolerate voltage at their output when turned off?
Even if you switch them with a power strip, they'll come up differently.

Hmm...good point. I can make sure that the load is off until I
manually turn it on after the PS's have settled. Wouldn't diodes in
series with the outputs prevent any problems with this though?

What's the cost of the thing you're powering? How does that compare
to the savings on the power supply? Is it worth the risk?

That's the big decision. I have three perfectly good PS that I still
need for other uses and would prefer not to buy a 4th, if possible.
Especially since I don't have much room on the bench.

The device(s) I'm powering are fairly inexpensive. There's a lot of
deciding to do on whether it's worth the time to try to parallel the
units I have or just bite the bullet and buy a hi-amp unit.

Once you get all that sorted out, you have three choices.
Resistors to force load sharing, give up on low output impedance and
hope the settings are stable enough to stay where you balanced it.

The load is stable at one current value for the entire time it's on
but it will be turned off while the PS's are running. I was *hoping*
that would be a better situation for them to deal with.

Redesign the supplies to put one regulation loop around the whole thing.

Good idea, IMHO, probably not worth doing since choice #3 is easy to
do.

Sell the two and buy one good one.

Yea, might just have to do this one (but keep all the units). Just
hate to have to fit another unit in somewhere.

Thanks for the info/ideas Mike!

John

John Muchow
-- remove SPAMMENOT for e-mail responses --

 

[The Real Andy]

On Wed, 1 Jun 2005 06:26:55 -0700, "GaryG" <sorrynoemail@NOSPAMX.com>
wrote:

<snip>

Having spent some time in the weiging industry, i can assure you that
the cheap portable bathroom scales that you buy are neither:
a. repeatable
b. accurate
c. linear

In fact, most will become more innacurate in the most common weight
ranges.

In AU, a cheap set is $20, a good repeatable set is $400. The
expensive scale can be recalibrate and remains linear. Should it not
be linear a multi-point cal can be done. The cheap set can only be
thrown.

Most cheap sets are innacurate of the shelf as they are made in china
and fail to take into account local gravitational constants

Do you have any experience with the newer digital models? Not the low-end
ones, but ones like the Tanita with ostensible 0.2 lb resolution, priced
around $50-90 (US).

For instance, http://tinyurl.com/49swe, or the more expensive German-made
Soehnle brand http://tinyurl.com/3t6kt.

GG

The high end Soehnle scales can be calibrated, but the ones show look
like you standard cheap crap. I could well be wrong here. Some Soehnle
stuff is quiet good.

Tanita, never seen anything but cheap crap.

The good scales I am familiar with are manufactured by a company
called AND. Try do a google for AND though!!

 

[The Real Andy]

http://www.andweighing.com/and.nsf/html/UC+Series

 

[John Fields]

On 1 Jun 2005 16:19:53 -0700, "log" <logansummersh@yahoo.com> wrote:

For those experts in the timer ic LM555. What value of
potentiometer should I use for Ra, Rb, and C so I can
vary the frequency from 0.1 to 100Khz. What combination
did you use and why?

---
Unless you have some overriding reason for wanting to use a bipolar
555, you should use a CMOS 555 in this configuration:

7555
+-------+
+--|TH |
| |__ OUT|--+---->OUT
+-O|TR | |
| +-------+ |
| |
+----[R]------+
|
[C]
|
GND

That way can get about a 50% duty cycle output, get rid of one of the
resistors, use smaller valued capacitors and larger valued resistors,
and generally make your life simpler since for an astable you can
write, for the period:


T = 1.4RC

or, for the frequency,

1
f = -------
1.4RC

You state that your frequency range is 0.1 to 100kHz, which is 100Hz
to 100kHz. That's a frequency range of 1000:1, so the change in
resistance will also have to be 1000:1.

One problem you will have is trying to get 100kHz with the pot at the
low resistance end of its travel, so the thing to do there is to
assume that the pot's end resistance is zero ohms and insert a fixed
resistor in series with it so that when the pot is up against the
stops you'll still have that fixed resistance in there. Like this:


+-------+
+--|TH |
| |__ OUT|--+---->OUT
+-O|TR | |
| +-------+ |
| |
+---[R1]-+->[POT]
| | |
[C] +----+
|
GND

Now, if you consider some reasonable value for R1, like 1000 ohms,
then the pot needs to be 1 megohm in order to get the 1000:1 frequency
spread you need.

So, if you've got 1000 ohms in there with the pot cranked all the way
down to to zero ohms, your capacitor has to have a capacitance of:


1 1
C = ------- = --------------------- = 7.14E-9F ~ 7nF
1.4Rf 1.4 * 1000R * 1E5Hz


7nF isn't a standard value, but off-the-shelf pots are available in
resistance steps of 1-2-5, so for half the resistance (500k) the
capacitance would increase by a factor of two to 14nF. 15nF is
available and it's pretty close, so with R1 equal to 499 ohms and a
500k pot that might work for you. If it didn't, then you'd have to
fiddle with series and parallel combinations of caps to shift the
frequency range to where you wanted it to be.

--
John Fields
Professional Circuit Designer

 

[Jamie]

Vidar L?kken wrote:

I'm programming a atmel Tiny 2313, and have to use the "ret"
statement.
The problem is that ret simply jumps to the top of the program, not
the location it was called from. I'm prorgramming in assembler (of
course...).

Does anyone know how to "enable" ret call?
make sure you cleaned up your stack.

using the RET is simply popping things off the
stack to generate a return address.
overflow of the stack or writing 0's on the
stack i guess could cause it also :_)

 

[Don Bowey]

On 5/31/05 8:22 AM, in article
1117552951.154646.293980@g14g2000cwa.googlegroups.com,
"doransignal@gmail.com" <doransignal@gmail.com> wrote:

I have a lot of old circuit designs that require a crystal for ham
radio. Is there some circuit that I could build to emulate a crystal.
So it could be a direct plug in? Just wondering

Many oscillator circuits intended for a crystal, will work well using a
parallel LC in series with a DC blocking cap.

Don