0.2 second delay ciruit design

[Winfield Hill]

Terry Given wrote...

Capacitance does vary with frequency, and may do so "in a spastic
manner". Most especially as frequency goes up...

It should be noted that over the range of mundane frequencies, such
as 100Hz to 10MHz, readily measured to 100ppm accuracy with standard
precision LCR meters, capacitors vary only slightly with frequency.
This is due to the dielectric absorption effect, sometimes called
soakage, which says that in some dielectrics, given time, additional
dipoles flip in response to an electric field. We discuss this in
AoE page 220, with some data from a Hybrid Systems HS9716 datasheet.


--
Thanks,
- Win

 

[Ian]

"ChrisGibboGibson" <chrisgibbogibson@aol.com> wrote in message
news:20041106195438.07275.00000249@mb-m10.aol.com...

"Terry" wrote:


"Bob Fraser" <bfraser1@optonline.net> wrote in message
news:UUcjd.38863$fF6.13003819@news4.srv.hcvlny.cv.net...
Does anyone have a easy way of adding a 0.20 second delay to a 6 volt
DC
control circuit?


A large capacitor on th input!


Are you in northern UK?

If you'd finished it properly and phrased it as...

"large capacitator on't th'input" it would ha' done't job reet..

Gibbo

Rubbish - that's the northern *English* accent.

Regards
Ian

 

[ChrisGibboGibson]

"Ian" wrote:

[snip]

Are you in northern UK?

If you'd finished it properly and phrased it as...

"large capacitator on't th'input" it would ha' done't job reet..

Gibbo

Rubbish - that's the northern *English* accent.

Northern UK *is* Northern England. There's nowt above us worth discussing so it
meet as well not be there.

Further, as they have their own government, they can hardly be considered part
of the "United Kingdom"



Gibbo

 

[Rich The Philosophizer]

On Mon, 08 Nov 2004 14:01:33 +0000, Ian wrote:

"ChrisGibboGibson" <chrisgibbogibson@aol.com> wrote in message
news:20041106195438.07275.00000249@mb-m10.aol.com...
"Terry" wrote:


"Bob Fraser" <bfraser1@optonline.net> wrote in message
news:UUcjd.38863$fF6.13003819@news4.srv.hcvlny.cv.net...
Does anyone have a easy way of adding a 0.20 second delay to a 6 volt
DC
control circuit?


A large capacitor on th input!


Are you in northern UK?

If you'd finished it properly and phrased it as...

"large capacitator on't th'input" it would ha' done't job reet..

Gibbo

Rubbish - that's the northern *English* accent.

Do they maintain all those weird accents in an attempt to mask the

inbreeding?
;^j

Thanks,
Rich

 

[Ian]

"Rich The Philosophizer" <null@example.net> wrote in message
newsan.2004.11.08.17.50.49.970652@neodruid.org...

On Mon, 08 Nov 2004 14:01:33 +0000, Ian wrote:


"ChrisGibboGibson" <chrisgibbogibson@aol.com> wrote in message
news:20041106195438.07275.00000249@mb-m10.aol.com...
"Terry" wrote:


"Bob Fraser" <bfraser1@optonline.net> wrote in message
news:UUcjd.38863$fF6.13003819@news4.srv.hcvlny.cv.net...
Does anyone have a easy way of adding a 0.20 second delay to a 6
volt
DC
control circuit?


A large capacitor on th input!


Are you in northern UK?

If you'd finished it properly and phrased it as...

"large capacitator on't th'input" it would ha' done't job reet..

Gibbo

Rubbish - that's the northern *English* accent.

Do they maintain all those weird accents in an attempt to mask the
inbreeding?
;^j

Thanks,
Rich

It comes from watching too many Monty Python sketches.

;-)

Regards
Ian

 

[glen herrmannsfeldt]

Winfield Hill wrote:

Terry Given wrote...

Capacitance does vary with frequency, and may do so "in a spastic
manner". Most especially as frequency goes up...

It should be noted that over the range of mundane frequencies, such
as 100Hz to 10MHz, readily measured to 100ppm accuracy with standard
precision LCR meters, capacitors vary only slightly with frequency.
This is due to the dielectric absorption effect, sometimes called
soakage, which says that in some dielectrics, given time, additional
dipoles flip in response to an electric field. We discuss this in
AoE page 220, with some data from a Hybrid Systems HS9716 datasheet.

The dielectric constant of water at low frequencies is about 80,
for an index of refraction of about 9. At optical frequencies its
index of refraction is about 1.33, so its dielectric constant
is about 1.77. The dipoles can follow the field at low frequency,
but not at higher frequencies.

-- glen

 

[Terry Given]

PN2222A wrote:

"Ken Moffett" <KLMoffett@mn.rr.com> wrote in message
news:418DA18C.10CF@mn.rr.com...

PN2222A wrote:

"Ken Moffett" <KLMoffett@mn.rr.com> wrote in message
news:418D8C22.6A50@mn.rr.com..

PN2222A wrote:

"Bob Fraser" <bfraser1@optonline.net> wrote in message
news:UUcjd.38863$fF6.13003819@news4.srv.hcvlny.cv.net.

Does anyone have a easy way of adding a 0.20 second delay to a 6
volt
DC
control circuit?



I like to use a coaxial delay line.

What would be the length of the coax to get a 0.2 second (200 mS)
delay?

Depends on the velocity factor.

Commercially available options...your design...your choice. ???


OK. I'll pick RG213. I've got some out in the garage.
VF = 65.9%.
velocity 234 meters per microsecond.
So we need 989 x 10^6 M of cable.
$0.37 per foot. But in this quantity, a discount should be available.
Call it $1B. Cheaper than that in Euros.

Since it's 50 ohm cable, the 6V supply needs to supply 120mA, this shouldn't
be a problem.


ROFLMAO!

Reminds me of an applications dept. question we got one friday
afternoon: a customer wanted to back up his 6kW ac drive for 3 minutes -
power outages caused problems with glass solidifying and taking hours to
clean up. So our apps engineer asked if we could add a few more caps to
the DC bus, to run the drive for 3 minutes. Initially we just said "piss
of dave" or words to that effect, but it was beer o'clock and dave
wanted an answer, so we did a few calcs. Thats 1MJ, but alas the DC bus
can only collapse from 600V to 500V, ie need C = 20F or so. As we used 2
caps in series, we needed 40F worth of 2.2mF caps, ie 18,200 capacitors
(and they were about $5 each so theres a hundred grand , We kinda got
all silly, and worked out how big the box would need to be, how many km
of cable, the 36,400 crimp terminals etc etc. Then we gave him a cheaper
alternative, which was another 6kW vector drive with a common DC bus. A
bicycle wheel with 12 XXXX beer cans (it was the aussies who asked the
question) cable tied to it, spinning at a quite reasonable speed
(because we could slow it to a standstill). We also priced a whole bunch
of batteries, and a UPS, and a small hammer & brush & dustpan from RS,
which was the cheapest option at around $30. They bought a UPS.

Cheers
Terry

 

[Terry Given]

Reg Edwards wrote:

"Terry Given" wrote

Reg Edwards wrote:


Propagation velocity is VERY much lower at frequencies of the order of

1/8th

seconds per cycle. So the cable length and expense will be very much

less.

Might amount only to several million Euros using RG58.


Why is v much lower at such low F? does Er vary that much with frequency?


======================================

Yes it does. It can't help itself. It just follows the laws of nature
according to well known physical principles involving inductance,
capacitance, resistance and conductance, the properties of all transmission
lines.

L,C,R and G depend on a line's dimensions and the materials from which it is
made. All except C vary with frequency from zero to infinity.

L,C,R and G are known as a line's 4 primary constants. Velocity, or phase
shift per unit length, is one of the 4 secondary constants derived from the
primaries.

But at the age of 79 I havn't the time to spend on a 6-months, personal
course of instruction on transmission lines. So I suggest you begin with a
Google on "propagation velocity" plus "transmission lines". You will find
it a fascinating, both a practical and academic subject.
----
Reg.

Sometimes I ask questions because I dont know the answer. Sometimes I
ask questions because I think others might want to know. You might be
surprised what I know. And perhaps how quickly I learn. Alas the
guild-like attitude of "I'm not gonna share my hard-earned knowledge" is
all too common. When you add to it the propensity of employers not to
hire older engineers (in favour of kids who can code HTML), small wonder
so many skills are lost, and people like me seek knowledge in old books.

In general, the phenomena is brought about by dispersion - of which
there are two kinds:

Normal dispersion, which is quite uncommon, in which phase velocity
decreases with increasing frequency

Anomalous dispersion, which is almost always the case, in which phase
velocity decreases with decreasing frequency, as reg stated.

Assuming Ur = 1 (not always the case, but just about) then V is
proportional to 1/sqrt(Er). For many materials Er increases with
increasing frequency, albeit in a somewhat spastic (read as
non-monotonic, just trying to inject a little flavour) manner.

The slope of the Er-vs-frequency curve dictates the mode of dispersion;
-ve slope means anomalous dispersion, but at the varying frequencies it
may become normal.

Just about any lossy line is anomalous. Data taken from IEEE Press
reprint of Richard E. Maticks excellent book, Transmission Lines for
Digital and Communication Networks.

Cheers
Terry

 

[Reg Edwards]

Could you give a web site URL that supports your statement that
propagation velocity decreases as frequency decreases?

Jim

====================================

You must be misreading Google. In any case Google should not be taken as
always telling the gospel truth. I must admit I've never searched Google
myself.

Any text book which treats transmission lines in an elementary mathematical
manner will tell you how to calculate propagation velocity from a line's 4
primary constants of Inductance, Capacitance, Resistance and Conductance,
and of course frequency.

Velocity always decreases with frequency.

On all air-insulated cables, at radio frequencies, velocity is very nearly
the velocity of light, 186,000 miles per second. Insulating materials slow
it down a bit by increasing capacitance between wires.

At audio frequencies, on the same cable, velocity is much lower.

For example, at 1000 Hertz, a standard telephone cable with a capacitance
between wires of 0.065 microfarads per mile, and a wire resistance of 83
ohms per mile, has a velocity as low as 48,000 mile per second.

But this same cable, when used on the Internet Broadband, has a velocity
roughly 120,000 miles per second.

At frequencies of 50 and 60 Hertz, on power distribution lines, propagation
velocity is only about 10,000 miles per second.

Different velocities at different frequencies over long cables cause
distortion of television wideband video-frequency pictures. Special networks
have to be used at cable ends to correct such distortion.

The formulae used to calculate the electrical properties of transmission
lines are not very complicated. Only simple algebra. Look on the electrical
engineering shelf of your local library.

To calculate to engineering accuracy, from power frequencies to UHF, all
properties of transmission lines and their performance, download programs
RJELINE4 and COAXPAIR from website below.

Single file only. Download in a few seconds. Not zipped up. Run immediately.
----
Reg

 

[Jim Meyer]

Rich Grise <rich@example.net> wrote in message news:<pan.2004.11.14.17.13.44.169468@example.net>...

On Sun, 14 Nov 2004 13:29:41 +0000, Reg Edwards wrote:

Could you give a web site URL that supports your statement that
propagation velocity decreases as frequency decreases?

Jim

====================================

You must be misreading Google. In any case Google should not be taken as
always telling the gospel truth. I must admit I've never searched Google
myself.

Any text book which treats transmission lines in an elementary mathematical
manner will tell you how to calculate propagation velocity from a line's 4
primary constants of Inductance, Capacitance, Resistance and Conductance,
and of course frequency.

Velocity always decreases with frequency.

Well, I, for one, just now, upon reading this sentence in this context,
had a sort of mental "ding!" - Of course! That's how prisms work!
(or maybe, 'why' . )

Thanks!
Rich

Reg meant to say, "Velocity always decreases as frequency
decreases."

As for light through a prism, violet light is bent more than red
light because violet light (higher frequency) is slowed more than red
light. Your analogy between prisms and transmission lines doesn't
work.

Jim