Morse Key Contacts?
On 18 Nov 2017 18:00:54 GMT
Stephen Thomas Cole wrote:
rickman wrote:
Jerry Stuckle wrote on 11/18/2017 10:50 AM:
On 11/17/2017 11:20 PM, rickman wrote:
Jerry Stuckle wrote on 11/17/2017 11:00 PM:
On 11/17/2017 6:57 PM, rickman wrote:
Jerry Stuckle wrote on 11/17/2017 3:23 PM:
On 11/17/2017 3:37 AM, rickman wrote:
Jerry Stuckle wrote on 11/16/2017 10:34 PM:
On 11/16/2017 9:17 PM, rickman wrote:
Jerry Stuckle wrote on 11/16/2017 9:02 PM:
On 11/16/2017 7:28 PM, rickman wrote:
Gareth's Downstairs Computer wrote on 11/16/2017 4:01
PM:
On 16/11/2017 20:04, rickman wrote:
Gareth's Downstairs Computer wrote on 11/16/2017 12:55
PM:
On 16/11/2017 17:07, rickman wrote:
Bob Wilson wrote on 11/7/2017 9:47 PM:
On 11/4/2017 5:42 AM, Gareth's Kitchen Komputer
wrote:
On Mon, 21 Dec 2015 23:33:17 +0000, gareth wrote:
For those who make their own Morse Keys, what do
you use for the
contacts,
for
I have found the phosphor bronze pillar for the
dot contact on my
ersatz
Vibroplex
to be very noisy and scratchy?
I'm fairly sure that I asked this question before,
but it has been a
habit
of never put off till
tomorrow what you can put off till the day after.
I chose phosphor bronze because in the days of
making one's own
electronic
organs, phosphor bronze was suggested as a
suitable keying matreial
for
the
keyboards.
If a question's worth asking, Gareth...
I have not made lots of keys, but when I do I use
contacts from old
relays.
I still have some relays I bought as WWII surplus
when I was in my
teens,
back in the 1950's. They have strange coil
parameters, weird mounting
arrangements, etc., but nice little silver contacts.
Bob W, WA9D
Why use a mechanical switch? There are magnetic hall
effect switches
around. Or a mercury wetted switch can be operated
by a magnet. Are the
magnetic switches too sloppy?
Perhaps you confuse mercury wetted with reed relays?
I am thinking of reed relays, so I guess I used the
wrong name, but aren't
they wetted with mercury to prevent corrosion building
up?
In the closed atmosphere of the glass tube, there should
not be any corrosion, I think. ISTR some gas in there,
but don't know about mercury wetting.
Call it what you want, corrosion, oxidation, just plain
pitting. The point is a solid surface will wear from the
arcing that happens when contacts break connections
(which also happens on initiating connection
because of switch bounce). Mercury doesn't have this
problem as it is a
liquid and reforms the layer every time it is "pitted".
Mercury also does not make a "clean" break. It "puddles"
as the contacts
are pulled apart due to surface tension. It leads to
irregular break timing. This isn't a problem at low
switching speeds as you have in regular
switches and relays, but can be at higher rates as in CW.
Additionally a
magnetic field for switching accentuates this problem.
Reed relays are good
for things like security system contacts, but not a CW
key.
I haven't timed such switches. What is the timing precision
requirement
for CW? Does optical satisfy it?
Never tried optical but as long as you can get a clean
make/break of the beam it should work. The problem as i see
it would be that clean make/break; the beam will fade in and
out. Probably not as bad as a reed
switch - but for high speed CW you need clean operation.
That's why many keys use brass contacts or similar; the have
a clean make/break. And even if they get pitted they are
soft enough to burnish rather easily and thick enough to
last for years.
So no numbers? Let's try to make some.
According to Tom - W4BQF, "All high speed code (above about
55 wpm) is sent with a keyboard/keyer or a computer
keyboard". So we can use 55 WPM as an upper limit for using
a manual key.
Dot length = 1.2 seconds / WPM = 1.2 / 55 ~= 22 ms
Switch bounce time for many switches is some single digit
ms. So I'm not sure what "clean" make/break means. The
bounce time for reed switches is about the same as other
switches I found.
No, it is not bounce time - "clean" is how quickly it
makes/breaks. Brass contacts are virtually instantaneous.
However, reed switches operate via a
magnetic field. This field is not a simple make/break - it
gets stronger and weaker depending on the distance from the
magnet. IOW, brass contacts are digital but the magnet field
is analog. The actual switching does not necessarily always
occur at the same magnetic field strength. Additionally,
switching off to on requires a stronger magnetic field than
the release. The two combined can result in varying width
pulses at high speed. Optical
is also analog and can have similar problems.
And before you dismiss all of this - why don't you see any
paddles with reed
switches or optical? If these methods are so good, why aren't
they in the high-end paddles/keys?
Whether or not reed switches are used in keys is not related to
your understanding of electronics.
It is. That is the context in which they were brought up. But
I know you'd rather change the context than admit you are
wrong.
There is nothing going on here except that you are mistaken about
the functioning of switches. How about you address the issues
rather than diverting the discussion.
I'm not diverting the discussion. You just don't understand how
magnetic and optical sensors work. That is very obvious.
Go back and read. I didn't say anything technical you said was off
topic. I was pointing out that what others do is not limited by you
lack of understanding.
Reed switches are *not* analog any more than mechanical
switches in that they don't vary the connection continuously.
They are still metallic switches and make or break when the
metals touch. The fact that the magnetic field varies
continuously is no different from the pressure from the paddle
varying the position of the mechanical switch contact
"continuously". I found no information indicating significant
variations in the action of reed switches. The variation in
pull-in and release field strength gives a small amount of
hysteresis which is desirable in any switch. It is not enough
to distort the key times from one character to the next.
Reed switches are not - but the magnet field which triggers them
are. And there is a huge difference between the magnetic field
and finger pressure on a paddle. That's exactly why reed
switches are not used on paddles.
"There is a huge difference"... but you can't say what that
difference is. The motion of the key paddle is analog which
results in an analog displacement of the mechanical switch until
contact is made or in the case of a reed switch, results in the
analog change in field strength until the threshold is reached
where the switch pieces are pulled together. All analog until
the switch pieces make contact which results in a discrete output
change.
The real difference is in the bounce time. A mercury wetted reed
switch has no bounce time, contact is singular and certain. A
mechanical switch has a variable resistance until the point of
contact stops moving and settles down. That's the bounce time.
I did tell you the difference. But you called it off-topic. This
is not related to bounce time. But you can't get over that fact.
And you have failed to explain what *is* the problem. Rather than
discuss the issue you are diverting. Is there something you would
like to understand better?
Likewise optical is only optical in the movement of the paddle
and the signal seen by the detector. Once the signal passes
through a threshold detector with hysteresis the signal is
purely digital. The strong suit of optical is that it
eliminates all mechanical issues of wear and failure.
The same is true for optical - except that optical can also be
affected by ambient light, making the switch even less
reliable.
Lol. It is easy enough to exclude ambient light.
And how are you going to do that without restricting the motion of
the paddles? Oh, I know. You have this magical whatchamacallit
that creates a black hole around the sensor and doesn't let any
light in, while not restricting any motion.
Right.
The mechanical force can be conveyed without light entering. I
guess you've never used a camera with a mechanical shutter? This
wouldn't require anything nearly as complex as that, but you do
need to understand the principle before you can see how it might be
done.
I did a bit of reading about reed switches yesterday and they
have much less bounce time than other switches and the mercury
wetted types have virtually no bounce time. In fact while
looking for info on typical bounce times one of the pages I
found showed a rather elaborate circuit to debounce the two
mechanical switches in a keyer. If the switches were so
instantaneous, why would they need a debounce circuit?
Once again it isn't the bounce that causes the problem.
Bounce is a problem that makes the timing of the switch closure
uncertain and must be eliminated. Compensating for the
uncertainly can't be done. So what is the problem in mechanical
switches if not bounce? If a switch bounces for 5 or 10 ms, that
is a significant portion of time for a 22 ms dot.
THIS IS NOT RELATED TO BOUNCE! GET OVER IT!
Actually, it *is* related to bounce as a debounce circuit is
required and typical debounce circuits create delay with undefined
delays. Instead of yelling what the issue isn't, how about you
explain what it *is*?
Your analysis above shows a complete lack of understanding of
how switches in general work and not just reed switches. Try
reading about switches a bit. You will quickly find that
metallic switches do not make or break cleanly with an
"instantaneous" connection. Just use google or any other tool
to find some info on this and read it.
Nope, my analysis is right on. And it is exactly why reed and
optical switching is not used in keys and paddles.
You actually haven't analyzed anything. You just keep repeating
the same unsupported conclusions ignoring the way mechanical
switches operate.
I have, but you call it "off-topic".
You have not explained anything and I said nothing technical you
said was off topic. You simply incorrectly stated that a magnetic
switch is analog (which actually makes no sense) because the field
at the switch varies in a continuous manner until the threshold is
reached. You erroneously stated the mechanical switch (which a
reed is also) is "digital" because it is either open or closed,
totally ignoring the fact that a reed relay is uses mechanical
contacts as well. Both devices have an analog input, the range of
motion/force for the mechanical switch and the magnetic field for
the reed/Hall switch and a digital output, closed or not closed.
So if your ideas are so great, why
aren't there any high end manufacturers which have keys or paddles
with reed or optical switches? If they are as good as you say, I
would expect to see dozens of them on the market. Or maybe they
know I'm right and you're wrong.
Have you done a survey of all keys on the market? I haven't.
Maybe I'll patent the idea if no one is doing it.
Why don't you come up with your own paddles using them and market
them? If they're as good as you say, you should make a fortune.
A fortune? I don't think there is that large a market for any ham
product. Who has made a "fortune" selling anything to hams?
Gents, can you please **** off.
Vote Steve!
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