B
Bob Fraser
Guest
Does anyone have a easy way of adding a 0.20 second delay to a 6 volt DC
control circuit?
control circuit?
T
Terry
Guest
"Bob Fraser" <bfraser1@optonline.net> wrote in message
news:UUcjd.38863$fF6.13003819@news4.srv.hcvlny.cv.net...
news:UUcjd.38863$fF6.13003819@news4.srv.hcvlny.cv.net...
C
ChrisGibboGibson
Guest
"Terry" wrote:
If you'd finished it properly and phrased it as...
"large capacitator on't th'input" it would ha' done't job reet..
Gibbo
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
P
petrus bitbyter
Guest
"Bob Fraser" <bfraser1@optonline.net> schreef in bericht
news:UUcjd.38863$fF6.13003819@news4.srv.hcvlny.cv.net...
(and/or off) delayed? A motor? A microprocessor input? You also have to
realise that *that* long a delay will almost certainly require some
electronics.
petrus bitbyter
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You'd better provide some more information. So what do you have to switch on
(and/or off) delayed? A motor? A microprocessor input? You also have to
realise that *that* long a delay will almost certainly require some
electronics.
petrus bitbyter
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P
PN2222A
Guest
"Bob Fraser" <bfraser1@optonline.net> wrote in message
news:UUcjd.38863$fF6.13003819@news4.srv.hcvlny.cv.net...
news:UUcjd.38863$fF6.13003819@news4.srv.hcvlny.cv.net...
J
James Meyer
Guest
On Sun, 07 Nov 2004 01:15:49 GMT, "petrus bitbyter"
<p.kralt@reducespamforchello.nl> wroth:
fuse lit with a thin piece of nichrome wire. Or a steel ball rolling down a
trough to trip a relay. Or a trained flea.
No electronics at all.
Jim "Rube Goldberg" Meyer
<p.kralt@reducespamforchello.nl> wroth:
I'd use a solenoid connected to a switch through a dashpot. Or a short
fuse lit with a thin piece of nichrome wire. Or a steel ball rolling down a
trough to trip a relay. Or a trained flea.
No electronics at all.
Jim "Rube Goldberg" Meyer
J
john jardine
Guest
"ChrisGibboGibson" <chrisgibbogibson@aol.com> wrote in message
news:20041106195438.07275.00000249@mb-m10.aol.com...
to type?. Get half a gallon of a mans drink like Adnams or Special brew down
yer neck. Guaranteed to close down all higher level functions for at least a
day.
regards
john
news:20041106195438.07275.00000249@mb-m10.aol.com...
Southerners!, gasp!. A belly full of Carling pisswater and you're still able
to type?. Get half a gallon of a mans drink like Adnams or Special brew down
yer neck. Guaranteed to close down all higher level functions for at least a
day.
regards
john
K
Ken Moffett
Guest
PN2222A wrote:
What would be the length of the coax to get a 0.2 second (200 mS) delay?
K
Ken Smith
Guest
In article <418D8C22.6A50@mn.rr.com>, Ken Moffett <KLMoffett@mn.rr.com> wrote:
You would not want to roll it up.
--
--
kensmith@rahul.net forging knowledge
It would be kind of long so you'd better fold it back on its self.
You would not want to roll it up.
--
--
kensmith@rahul.net forging knowledge
P
PN2222A
Guest
"Ken Moffett" <KLMoffett@mn.rr.com> wrote in message
news:418D8C22.6A50@mn.rr.com...
news:418D8C22.6A50@mn.rr.com...
Depends on the velocity factor.
K
Ken Moffett
Guest
PN2222A wrote:
Commercially available options...your design...your choice. ???
P
PN2222A
Guest
"Ken Moffett" <KLMoffett@mn.rr.com> wrote in message
news:418DA18C.10CF@mn.rr.com...
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.
news:418DA18C.10CF@mn.rr.com...
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 $1B. Cheaper than that in Euros.
Since it's 50 ohm cable, the 6V supply needs to supply 120mA, this shouldn't
be a problem.
R
Reg Edwards
Guest
Trained fleas have to be fed at regular intervals with human blood at around
38 degrees Celsius. At a pinch cats' blood will do but then you need a
trained cat able to tell the time. And then you have to feed the cat with
mice.
On balance it would be more economical to use a 2-transistor flip-flop
driving an FET relay.
Can you remember, before the days of television, when side-shows at
fair-grounds had a circus of trained fleas riding bicycles and towing carts.
Entry charge was 2 old pence. Shows began every 10 minutes, most of the time
was waiting for spectators to turn up. Sympathy was shared between the fleas
and circus master. Spectators always felt depressed and robbed when leaving
the tent.
----
Reg
38 degrees Celsius. At a pinch cats' blood will do but then you need a
trained cat able to tell the time. And then you have to feed the cat with
mice.
On balance it would be more economical to use a 2-transistor flip-flop
driving an FET relay.
Can you remember, before the days of television, when side-shows at
fair-grounds had a circus of trained fleas riding bicycles and towing carts.
Entry charge was 2 old pence. Shows began every 10 minutes, most of the time
was waiting for spectators to turn up. Sympathy was shared between the fleas
and circus master. Spectators always felt depressed and robbed when leaving
the tent.
----
Reg
R
Reg Edwards
Guest
Propagation velocity is VERY much lower at frequencies of the order of 1/8th
seconds per cycle. So the cable length and expense will be very much less.
Might amount only to several million Euros using RG58.
seconds per cycle. So the cable length and expense will be very much less.
Might amount only to several million Euros using RG58.
T
Tony Williams
Guest
In article <E9ljd.4657$op3.176055@news.xtra.co.nz>,
Terry Given <my_name@ieee.org> wrote:
Don't laugh, but I did exactly that..... supported a 15KW
drive through 1sec or so browndowns with a hoofing great
big capacitor bank on the 600V dc-link. It was for use in
a factory drawing nylon through constant-speed spinarettes.
Just one twitch of the spinarettes and the whole production
of that shift would be trashed.
I don't remember the exact value of the capacitor bank, but
it was less than 0.5 F and fitted into 3x 19"x6U chassis.
AFAIR total cost to the customer was about GBP15000.
The customer originally wanted to use 600V-worth of Nicads,
but I saw that as a widowmaker.... especially since I would
have been the one to solder up the battery pack.
In anticipation of using a battery pack they paid GBP2000
for a contactor rated to switch 30A at 600Vdc. It's about
2ft long and still down in my shed, never used.
--
Tony Williams.
Terry Given <my_name@ieee.org> wrote:
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 $5 each so theres a hundred
grand,
[snip]
Don't laugh, but I did exactly that..... supported a 15KW
drive through 1sec or so browndowns with a hoofing great
big capacitor bank on the 600V dc-link. It was for use in
a factory drawing nylon through constant-speed spinarettes.
Just one twitch of the spinarettes and the whole production
of that shift would be trashed.
I don't remember the exact value of the capacitor bank, but
it was less than 0.5 F and fitted into 3x 19"x6U chassis.
AFAIR total cost to the customer was about GBP15000.
The customer originally wanted to use 600V-worth of Nicads,
but I saw that as a widowmaker.... especially since I would
have been the one to solder up the battery pack.
In anticipation of using a battery pack they paid GBP2000
for a contactor rated to switch 30A at 600Vdc. It's about
2ft long and still down in my shed, never used.
--
Tony Williams.
T
Terry Given
Guest
Tony Williams wrote:
quid, thats probably comparable to a 15kW UPS, and it'll have much, much
longer service life.
rated for 30Adc. Interestingly enough if you slap a contactor in the
output of a current-controlled drive, it behaves like DC - when you open
the contactor the current decreases so the drive pumps out more volts.
Result = very bright flash of light. I did a set-up once to track down
an EMI problem with a little 70kW drive, by doing exactly that. I
noticed the flash of light from the contactor reflecting off the scope
trolley. It was a new contactor when I started, but was fair rooted when
I finished. But I did track down the problem - a large 3D earth loop
involving 2 PCB assemblies, a ribbon cable, the chassis and 2 0V-Earth
caps. Until you assembled the whole thing there was no loop.....problem
solved with sidecutters (although in production we simply omitted the part)
Cheers
Terry
yeah, going from 1s to 3min makes things a bit worse. But at 15,000In article <E9ljd.4657$op3.176055@news.xtra.co.nz>,
Terry Given <my_name@ieee.org> wrote:
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
[snip]
Don't laugh, but I did exactly that..... supported a 15KW
drive through 1sec or so browndowns with a hoofing great
big capacitor bank on the 600V dc-link. It was for use in
a factory drawing nylon through constant-speed spinarettes.
Just one twitch of the spinarettes and the whole production
of that shift would be trashed.
I don't remember the exact value of the capacitor bank, but
it was less than 0.5 F and fitted into 3x 19"x6U chassis.
AFAIR total cost to the customer was about GBP15000.
quid, thats probably comparable to a 15kW UPS, and it'll have much, much
longer service life.
600A DC rated contactor. And amazement that my 600A ac contactor was
rated for 30Adc. Interestingly enough if you slap a contactor in the
output of a current-controlled drive, it behaves like DC - when you open
the contactor the current decreases so the drive pumps out more volts.
Result = very bright flash of light. I did a set-up once to track down
an EMI problem with a little 70kW drive, by doing exactly that. I
noticed the flash of light from the contactor reflecting off the scope
trolley. It was a new contactor when I started, but was fair rooted when
I finished. But I did track down the problem - a large 3D earth loop
involving 2 PCB assemblies, a ribbon cable, the chassis and 2 0V-Earth
caps. Until you assembled the whole thing there was no loop.....problem
solved with sidecutters (although in production we simply omitted the part)
Cheers
Terry
T
Terry Given
Guest
Reg Edwards wrote:
Why is v much lower at such low F? does Er vary that much with frequency?
Cheers
Terry
Well, lets have 2 then
Why is v much lower at such low F? does Er vary that much with frequency?
Cheers
Terry
J
James Meyer
Guest
On Sun, 7 Nov 2004 09:22:43 +0000 (UTC), "Reg Edwards"
<g4fgq.regp@ZZZbtinternet.com> wroth:
Jim
<g4fgq.regp@ZZZbtinternet.com> wroth:
Where did you pick up that "interesting" tidbit?
Jim
R
Reg Edwards
Guest
It's just elementary electrical engineering, or ought to be.
Lord Kelvin (Transantic telegraph cables) followed by the self-educated
genius Oliver Heaviside (The operational calculus) sorted it all out in the
Victorian Age.
You could try a Google on "propagation velocity" plus "transmission line" or
something like that.
======================================
Reg wrote:
Lord Kelvin (Transantic telegraph cables) followed by the self-educated
genius Oliver Heaviside (The operational calculus) sorted it all out in the
Victorian Age.
You could try a Google on "propagation velocity" plus "transmission line" or
something like that.
======================================
Reg wrote:
J
James Meyer
Guest
On Sun, 7 Nov 2004 17:09:13 +0000 (UTC), "Reg Edwards"
<g4fgq.regp@ZZZbtinternet.com> wroth:
Could you give a web site URL that supports your statement that
propagation velocity decreases as frequency decreases?
Jim
<g4fgq.regp@ZZZbtinternet.com> wroth:
independent of frequency.
Could you give a web site URL that supports your statement that
propagation velocity decreases as frequency decreases?
Jim