Today's Message Index:
----------------------
1. 12:11 AM - Re: Twisted Wires vs. Parallel (raymondj)
2. 02:34 AM - Re: Pitts S1 Wiring Diagram (John Cleary)
3. 03:41 AM - Re: Twisted Wires vs. Parallel (Eric Tiethoff (HCCNet))
4. 04:19 AM - SD-8 Relay Questions (Andrew Butler)
5. 05:41 AM - CBA-II Battery Tester modifications/improvements? (Robert L. Nuckolls, III)
6. 08:14 AM - Re: Re: D-Sub Pins ()
7. 09:33 AM - Re: Twisted Wires vs. Parallel (Steven G Lynn)
8. 01:46 PM - Re: CBA-II Battery Tester modifications/improvements? (CamLight)
9. 06:04 PM - Re: Re: Twisted Wires vs. Parallel (S. Ramirez)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Twisted Wires vs. Parallel |
I think this paragraph from Bob N. earlier this week bears on this
discussion.
===============================================
At higher frequencies it can be shown that parallel
lines do not exactly cancel mutual magnetic effects
because of the non-zero distance between their centers.
Here it becomes valuable to twist the two conductors
such that what ever leakage exists perpendicular
to the conductors tends to be washed out by the reverse
polarity of effects longitudinally displaced 1/2 twist
away.
================================================
Raymond Julian
Kettle River, MN
"Hope for the best,
but prepare for the worst."
----- Original Message -----
From: "S. Ramirez" <simon@synchdes.com>
Sent: Sunday, December 28, 2008 9:16 PM
Subject: RE: AeroElectric-List: Twisted Wires vs. Parallel
> Dennis,
>
>
> There is no difference electrically between two wires that are kept at the
> same distance in parallel and two wires that are twisted together to stay
> parallel. The reason they are twisted together is that it is the simplest
> way to keep them in parallel while the cable (a combination of wires,
> shields, insulation, etc.) bends and distorts.
>
>
> When an RS-422 transmitter generates a signal, it has two circuits that
> drive the twisted wire pair. One circuit sources current, while the other
> circuit sinks current. When a differential twist wire pair carries two
> currents from the transmitter to the receiver, they travel from the source
> driver to the load (a termination resistor next to the receiver), then
> back
> to the current sink. Along each wire, the current generates an
> electromagnetic field defined by the right hand rule, where the direction
> of
> the field is per the direction of the hand's fingers when the thumb is
> pointing toward the direction of current flow. Since the current in one
> wire is traveling opposite the current in the other wire, the fields
> oppose
> each other and ideally cancel each other out. They also ideally cause no
> noise to be radiated.
>
>
> Perhaps the greatest benefit of RS-422 and differential signaling is
> immunity from external noise in the receiver. RS-422 receivers are built
> to
> reject "common-mode noise, which is noise that is of the same amplitude on
> both the + and - terminals of the receiver. This is where the twisted
> wire
> pair comes in. It connects to the receiver's + and - terminals and brings
> in both the real signal and common-mode noise. While the twisted-wire
> pair
> is shielded, some noise will leak in, but the electromagnetic and
> electrostatic fields will cut across wires at the same amplitude, because
> the wires are so close together. Thus, the noise's amplitude will appear
> at
> the receiver's + and - terminals equally and will be rejected by the
> receiver, since it is designed to reject common-mode noise. As an
> example,
> the AM26LV32 is a commonly used differential line 3.3V receiver. It has a
> common mode input voltage range from -0.3 to 5.5V and will reject any
> voltage that appears on both terminals in this range. The voltages on its
> terminals must have a delta of greater than 0.2V for it to change its
> outputs. You probably have to be involved in the measurement of real
> world
> signals and problems to appreciate just how good the AM26LV32 works to
> reject common-mode noise. One of the things that I haven't mentioned is
> that the termination resistor not only serves to terminate the twisted
> wire
> pair's characteristic impedance but also provides a low impedance to
> prevent
> electrostatic and electromagnetic fields from developing high voltages in
> twisted wire pairs.
>
>
> So to reiterate, there is nothing magical about twisted wire pairs other
> than they keep the wires in close proximity to each other and that's it.
> Everything else I said above is just fluff! :)
>
>
> Simon Ramirez
>
> Copyright 2008
>
>
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Dennis
> Johnson
> Sent: Sunday, December 28, 2008 12:29 PM
> To: aeroelectric-list@matronics.com
> Subject: AeroElectric-List: Twisted Wires vs. Parallel
>
>
> We often see instructions to twist the positive and negative wires
> together
> to reduce noise problems. Instructions from B&C for their voltage
> regulator
> even specified the number of twists per inch.
>
>
> But I'm wondering about the physics. From studying the 'Connection, it
> seems that paralleling the positive and negative wires tightly together
> would have the same effect as twisting them together. Is twisting the
> wires
> together recommended because it is a convenient way to keep the wires in
> close contact? Or is there something about the nature of the
> electromagnetic fields that makes twisting more effective?
>
>
> Thanks,
>
> Dennis
>
> Legacy, 220 hours, mostly twisted positive and negative wires
>
>
--------------------------------------------------------------------------------
Checked by AVG - http://www.avg.com
9:40 AM
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Pitts S1 Wiring Diagram |
Stuart,
I run a VHF, a smoke pump and a Garmin 296 plugged into a cigarette lighter
outlet for power if required. All the rest are steam gauges, and the fuel
pump is manual.
Since most my trips are short aerobatics trips, the biggest consumer is the
starter motor, and the SD-8 is more than adequate to keep the battery
charged even if I do a series of 10 to 12 minute sorties. On longer trips
the SD-8 has much longer to catch up, and it has never been an issue. This
system, apart from the 296, has been in satisfactory operation since the
early 80s.
Sorry, no photos of that area, but the next 100 hourly is due late January,
and if you still want photos then, I am more than happy to snap a few and
send them off line to you.
Cheers,
John
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Stuart
Mackereth
Sent: Monday, 29 December 2008 6:03 PM
Subject: RE: AeroElectric-List: Pitts S1 Wiring Diagram
--> <mac@incendio.co.nz>
Great, thanks John. What line up do you run - VHF, XPDR, GPS, etc?
Don't suppose you have a picture of the back for me to have a look at?
Sorry, but now you got me started ;-)
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of John
Cleary
Sent: Monday, 29 December 2008 7:40 p.m.
Subject: RE: AeroElectric-List: Pitts S1 Wiring Diagram
--> <john_rv10@yahoo.com>
Hello Stuart,
I have an S1 with an SD-8, standard slick mags and an inverted oil system.
It is tight but doable.
Cheers,
John
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Stuart
Mackereth
Sent: Monday, 29 December 2008 4:53 PM
Subject: AeroElectric-List: Pitts S1 Wiring Diagram
--> <mac@incendio.co.nz>
Hi all.. been trawling through all the posting history on this list looking
for some help with what layout and equipment set make sense in the tight
engine compartment of a Pitts S1. Sorry if any of this is repeat/old stuff,
but it's all new to me. Thanks also to Bob who has given me many hours of
enjoyment trying to get to grips with his manual, and Z figures. I started
on Z13/8 and pulled out the 2nd big alternator in favor of a single small
SD-8 one, and have gone from there.
A Pitts should be rather simple, I would have thought. This is a VFR
short-hop plane 99% of the time, doing aerobatics I had a good look at the
aerobatic wiring diagram from B&C... so I had assumed I could get by on a
SD-8 alternator as only electrical generation source. I have a Icom A200,
Narco Xpdr, Encoder and the usual engine instruments (EGT, CHT, OILT, OILP,
FUELP) so thought I could get away it. Um, ok, also a Fuel boost pump (only
during starting) and smoke pump (couple of minutes a flight)... I also would
like to run a AV80R GPS as well, if possible. Now I'm wondering about the
SD-8... and if not, well, then the SD-20. I can add up all the Amp loads on
each thing, but I'm not sure how much under/over capacity I need to run
everything? Is there a general rule of thumb?
My other question is whether there is enough space behind the engine for the
vacuum mounted SD-8 - considering I'm planning dual PMAGS, and have an
inverted OIL kit right there in the same place. A friend building an S1 that
I talk to a lot as opted for the PlanePower 60Amp unit that is belt driven
up front to free up some space, as he reckoned it was too tight. Would love
a second opinion from someone with an S1.
Most S1's flying out there are 20, 30 years old, even older, and I'm hoping
someone can help me take advantage of the new technology advances to build a
simple, clean and lightweight electrical system.
Thanks to anyone who can help.
Checked by AVG - http://www.avg.com
2:23 p.m.
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Twisted Wires vs. Parallel |
When wiring a tube amplifier it is common practice to twist the filament
lines to the tubes. Reason is that they are AC fed with a relative high
amperages (6,3 volt and 2 or 3 amp). The rest of the wiring is or signal or
DC. When the filament lines are NOT twisted they introduce humm (50 or 60
Hz) in the system. Since in an aircraftsystem there is no AC feed (except
the output of the alternator field tot the regulator) the only usance is to
keep the lines together.
--------------------------------------------------
From: "raymondj" <raymondj@frontiernet.net>
Sent: Monday, December 29, 2008 9:09 AM
Subject: Re: AeroElectric-List: Twisted Wires vs. Parallel
> <raymondj@frontiernet.net>
>
> I think this paragraph from Bob N. earlier this week bears on this
> discussion.
>
> ===============================================
> At higher frequencies it can be shown that parallel
> lines do not exactly cancel mutual magnetic effects
> because of the non-zero distance between their centers.
> Here it becomes valuable to twist the two conductors
> such that what ever leakage exists perpendicular
> to the conductors tends to be washed out by the reverse
> polarity of effects longitudinally displaced 1/2 twist
> away.
> ================================================
>
> Raymond Julian
> Kettle River, MN
>
> "Hope for the best,
> but prepare for the worst."
>
> ----- Original Message -----
> From: "S. Ramirez" <simon@synchdes.com>
> To: <aeroelectric-list@matronics.com>
> Sent: Sunday, December 28, 2008 9:16 PM
> Subject: RE: AeroElectric-List: Twisted Wires vs. Parallel
>
>
>> Dennis,
>>
>>
>>
>> There is no difference electrically between two wires that are kept at
>> the
>> same distance in parallel and two wires that are twisted together to stay
>> parallel. The reason they are twisted together is that it is the
>> simplest
>> way to keep them in parallel while the cable (a combination of wires,
>> shields, insulation, etc.) bends and distorts.
>>
>>
>>
>> When an RS-422 transmitter generates a signal, it has two circuits that
>> drive the twisted wire pair. One circuit sources current, while the
>> other
>> circuit sinks current. When a differential twist wire pair carries two
>> currents from the transmitter to the receiver, they travel from the
>> source
>> driver to the load (a termination resistor next to the receiver), then
>> back
>> to the current sink. Along each wire, the current generates an
>> electromagnetic field defined by the right hand rule, where the direction
>> of
>> the field is per the direction of the hand's fingers when the thumb is
>> pointing toward the direction of current flow. Since the current in one
>> wire is traveling opposite the current in the other wire, the fields
>> oppose
>> each other and ideally cancel each other out. They also ideally cause no
>> noise to be radiated.
>>
>>
>>
>> Perhaps the greatest benefit of RS-422 and differential signaling is
>> immunity from external noise in the receiver. RS-422 receivers are built
>> to
>> reject "common-mode noise, which is noise that is of the same amplitude
>> on
>> both the + and - terminals of the receiver. This is where the twisted
>> wire
>> pair comes in. It connects to the receiver's + and - terminals and
>> brings
>> in both the real signal and common-mode noise. While the twisted-wire
>> pair
>> is shielded, some noise will leak in, but the electromagnetic and
>> electrostatic fields will cut across wires at the same amplitude, because
>> the wires are so close together. Thus, the noise's amplitude will appear
>> at
>> the receiver's + and - terminals equally and will be rejected by the
>> receiver, since it is designed to reject common-mode noise. As an
>> example,
>> the AM26LV32 is a commonly used differential line 3.3V receiver. It has
>> a
>> common mode input voltage range from -0.3 to 5.5V and will reject any
>> voltage that appears on both terminals in this range. The voltages on
>> its
>> terminals must have a delta of greater than 0.2V for it to change its
>> outputs. You probably have to be involved in the measurement of real
>> world
>> signals and problems to appreciate just how good the AM26LV32 works to
>> reject common-mode noise. One of the things that I haven't mentioned is
>> that the termination resistor not only serves to terminate the twisted
>> wire
>> pair's characteristic impedance but also provides a low impedance to
>> prevent
>> electrostatic and electromagnetic fields from developing high voltages in
>> twisted wire pairs.
>>
>>
>>
>> So to reiterate, there is nothing magical about twisted wire pairs other
>> than they keep the wires in close proximity to each other and that's it.
>> Everything else I said above is just fluff! :)
>>
>>
>>
>> Simon Ramirez
>>
>> Copyright 2008
>>
>>
>>
>>
>>
>>
>>
>> From: owner-aeroelectric-list-server@matronics.com
>> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Dennis
>> Johnson
>> Sent: Sunday, December 28, 2008 12:29 PM
>> To: aeroelectric-list@matronics.com
>> Subject: AeroElectric-List: Twisted Wires vs. Parallel
>>
>>
>>
>> We often see instructions to twist the positive and negative wires
>> together
>> to reduce noise problems. Instructions from B&C for their voltage
>> regulator
>> even specified the number of twists per inch.
>>
>>
>>
>> But I'm wondering about the physics. From studying the 'Connection, it
>> seems that paralleling the positive and negative wires tightly together
>> would have the same effect as twisting them together. Is twisting the
>> wires
>> together recommended because it is a convenient way to keep the wires in
>> close contact? Or is there something about the nature of the
>> electromagnetic fields that makes twisting more effective?
>>
>>
>>
>> Thanks,
>>
>> Dennis
>>
>> Legacy, 220 hours, mostly twisted positive and negative wires
>>
>>
>>
>>
>
>
> --------------------------------------------------------------------------------
>
>
> Checked by AVG - http://www.avg.com
> 9:40 AM
>
>
>
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | SD-8 Relay Questions |
All,
I am in the process of making my drawings a reality and unpacked the SD-8 and its
accompanying S-704.
I have my S-704 wired up like in Z-13/8 and Z-32. From the diagrams it looks like
power is supplied to the relay coil using an external wire attached from one
end of the COIL to COM.
Am I reading the diagram correctly?
Does anyone have any pictures like those that show how S-704 DIODEs are inserted?
Also, does it matter which way round YEL/BLK leads of the OVM-14 module are connected
to the coil (the instructions that come with the SD-8 appear to show the
opposite way round to that depicted in SD-13).
Thanks for your help,
Andrew Butler,
Wiring
RV71700
Galway, Ireland.
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | CBA-II Battery Tester modifications/improvements? |
> > but from an engineering perspective, a numerical value for
> > energy delivered under the prescribed test conditions is
> > quite sufficient. The results of dynamic tests for evaluating
> > battery source impedance could be offered out as numerical
> > values.
>
>As someone involved heavily in engineering, I agree.
>But you'll find a lot of very strong opposition to devices that only
>output numerical values for later importing and graphing or for use
>in creating a table. These all take extra work to do and is
>considered a total PITA by those who don't revel in the numbers the way we do.
>
>In my opinion, the success of the CBA is in its software (and its
>price, of course). It allows for very, very easy and no-work
>testing and comparison of different cells. There are other devices
>out there that allow for exporting to Excel or other saving of data,
>but they aren't nearly as popular.
>
>As a first step, just storing the data for import into Excel is
>OK. Even for taking and creating tables with. But, it would be
>nice to see a growth path possible for the software to include
>on-screen graphing/plotting. There are many constant-current load
>circuits out there but they're not being built and used by very many
>people, I think the right software is what would make the difference.
I bought the devices when they offered a high
return on investment for answering some questions
about battery performance between brands and
battery condition for insuring performance in a
$high$ instrumentation job. Looking at all the
data files in my CBA output folder I see that I've
conducted perhaps 100 battery cap-checks on various
devices.
Even when I was doing cross brand comparisons,
graphical display of data was useful only for helping
my readers understand . . . it was of no value in
deducing the results of the tests, i.e. total energy
delivered under a particular test condition.
I guess I'm not clear as to your design and market
goals. If it's your desire to fabricate large
quantities of a product to compete with the CBA-II
then "window dressing" will be important. If you're
goal is to offer a sort of DIY work-around for
the CBA-II's shortcomings to be shared with some
cognizant individuals, then the super-graphics
features become problematic for return on investment.
<snip>
>Another option is one you alluded to earlier, a PIC. That would
>result in a very small and inexpensive unit to control the load with
>and acquire and upload the data from. Someone would have to develop
>and test the firmware though.
>
>There's still a decent amount of hardware left to work out
>though...PCB design and selection of the MOSFETs, op-amps,
>resistor/capacitors, voltage regulators, microprocessor, connectors,
>heat sink, fan, etc., for the load itself.
Yes . . . if you're looking to optimize a
product and marketing effort. I would estimate
30-40 hrs to work up a documentation package
for hardware. Firmware in the PIC would take
10-20 hrs. The PC based application could take
as long or longer than the hardware and firmware
combined. So if your goals are to compete with
the CBA-II in their sandbox, you're looking at
a development program with a market value on
the order of $10K before you manufacture and
sell a single device.
>I think you bring up a very good point. There will be two groups of
>users for this load. The ones who just need the raw data outputted
>in the simplest way possible and those who want it displayed in
>graphical form to allow for the quickest way to see what they need to see.
I'm not sure what a graph tells me that a number
in an output box doesn't tell me. In fact, the way
the early CBA-II software outputs graphics, one has
to get out a pencil and straight edge to drop the cut-off
crossing to the baseline and then visually do a
linear interpolation to arrive at a number. The
upscale version of the software give you the "box
score" and the graph . . . what does the graph tell
anyone that the box score does not?
My disappointments with the CBA-II application is that
it offers only constant-current discharge testing
which doesn't emulate very many real life situations.
After all the work has been done to achieve their
present software package, it's a relatively simple
addition to offer constant-resistance and constant-
power discharge protocols with some dynamic internal
impedance measurements thrown in for "frosting on
the cake". Of course there's still the issue of
marginal thermal performance and selection of load
devices.
No doubt West Mountain Radio has made a significant
market penetration and their product offers a lot
of bang for the buck. I own two of them! If you're
considering development of a competing product, will
the features you and I find useful convince future
buyers of battery analyzers to pay more dollars for
the offerings of the new kid on the block? More
importantly, do potential sales for the super-whizzy
product bode well for return on investment?
Bob . . .
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
Henry,
I too use them for various connection points, especially those that may
need to be separated at some point. They are indeed handy. Rather than
get into some fancy connector I butt the male/female pins together,
shrink wrap the whole mess - done. Make sure your shrink wrap is well
done so they don't pull apart. If you need to take them apart use a p
blade or other against the connector to remove the shrink wrap. Don't
touch the wire with the knife.
If you have a connection that needs to come apart regularly, just go to
RS and get two 9/15 pin connectors to join the two. You will need two
4/40 bolt/nuts to keep the DB connectors together. Use a bit of
lock-tite or epoxy on bolts to keep them from separating.
The only thing you need to obey are the amperage limits on the pins. The
rest is up to your imagination.
If you're always in a hurry like me, get your stuff from L-com. Great
prices, incredible service (get your own rep if you like) and very fast
shipping. I get most stuff within a day or two of ordering. They will
also make any custom cable you need.
http://www.l-com.com/
Glenn
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Henry
Trzeciakowski
Sent: Saturday, December 27, 2008 7:56 PM
Subject: AeroElectric-List: Re: D-Sub Pins
<hammer408@comcast.net>
Bob:
Looking thru your archives, I see that one can use D-Sub's are wiring
connections: I.E. - joining 2 wires together, rather than use butt
splices,
solder seal, etc....
So my question is:
1- Rather than soldering my Mic & Phone jack wires directly to my jack
outlets, can I solder leads, then use D-Sub pins to join to the leads to
the
amin wires?
2- Can I also use these D-Subs for splicing shielded wire: 22 awg wire?
I can see al lot of uses for these D-subs, amazing !!!
Henry
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Twisted Wires vs. Parallel |
Please how do I remove this email from receiving informative notes like
the
ones below?
thanks
Steven Lynn
Global Business Services
IBM Americas
Cell: 425-280-4404
Fax: 360-851-2211
sglynn@us.ibm.com
"raymondj"
<raymondj@frontie
rnet.net>
To
Sent by: <aeroelectric-list@matronics.com
>
owner-aeroelectri
cc
c-list-server@mat
ronics.com Subj
ect
Re: AeroElectric-List: Twisted
Wires vs. Parallel
12/29/2008 12:09
AM
Please respond to
aeroelectric-list
@matronics.com
<raymondj@frontiernet.net>
I think this paragraph from Bob N. earlier this week bears on this
discussion.
========================
========================
At higher frequencies it can be shown that parallel
lines do not exactly cancel mutual magnetic effects
because of the non-zero distance between their centers.
Here it becomes valuable to twist the two conductors
such that what ever leakage exists perpendicular
to the conductors tends to be washed out by the reverse
polarity of effects longitudinally displaced 1/2 twist
away.
========================
========================
Raymond Julian
Kettle River, MN
"Hope for the best,
but prepare for the worst."
----- Original Message -----
From: "S. Ramirez" <simon@synchdes.com>
Sent: Sunday, December 28, 2008 9:16 PM
Subject: RE: AeroElectric-List: Twisted Wires vs. Parallel
> Dennis,
>
>
> There is no difference electrically between two wires that are kept a
t
the
> same distance in parallel and two wires that are twisted together to
stay
> parallel. The reason they are twisted together is that it is the
simplest
> way to keep them in parallel while the cable (a combination of wires,
> shields, insulation, etc.) bends and distorts.
>
>
> When an RS-422 transmitter generates a signal, it has two circuits th
at
> drive the twisted wire pair. One circuit sources current, while the
other
> circuit sinks current. When a differential twist wire pair carries t
wo
> currents from the transmitter to the receiver, they travel from the
source
> driver to the load (a termination resistor next to the receiver), the
n
> back
> to the current sink. Along each wire, the current generates an
> electromagnetic field defined by the right hand rule, where the direc
tion
> of
> the field is per the direction of the hand's fingers when the thumb i
s
> pointing toward the direction of current flow. Since the current in
one
> wire is traveling opposite the current in the other wire, the fields
> oppose
> each other and ideally cancel each other out. They also ideally caus
e no
> noise to be radiated.
>
>
> Perhaps the greatest benefit of RS-422 and differential signaling is
> immunity from external noise in the receiver. RS-422 receivers are b
uilt
> to
> reject "common-mode noise, which is noise that is of the same amplitu
de
on
> both the + and - terminals of the receiver. This is where the twiste
d
> wire
> pair comes in. It connects to the receiver's + and - terminals and
brings
> in both the real signal and common-mode noise. While the twisted-wir
e
> pair
> is shielded, some noise will leak in, but the electromagnetic and
> electrostatic fields will cut across wires at the same amplitude, bec
ause
> the wires are so close together. Thus, the noise's amplitude will ap
pear
> at
> the receiver's + and - terminals equally and will be rejected by the
> receiver, since it is designed to reject common-mode noise. As an
> example,
> the AM26LV32 is a commonly used differential line 3.3V receiver. It
has
a
> common mode input voltage range from -0.3 to 5.5V and will reject any
> voltage that appears on both terminals in this range. The voltages o
n
its
> terminals must have a delta of greater than 0.2V for it to change its
> outputs. You probably have to be involved in the measurement of real
> world
> signals and problems to appreciate just how good the AM26LV32 works t
o
> reject common-mode noise. One of the things that I haven't mentioned
is
> that the termination resistor not only serves to terminate the twiste
d
> wire
> pair's characteristic impedance but also provides a low impedance to
> prevent
> electrostatic and electromagnetic fields from developing high voltage
s in
> twisted wire pairs.
>
>
> So to reiterate, there is nothing magical about twisted wire pairs ot
her
> than they keep the wires in close proximity to each other and that's
it.
> Everything else I said above is just fluff! :)
>
>
> Simon Ramirez
>
> Copyright 2008
>
>
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of De
nnis
> Johnson
> Sent: Sunday, December 28, 2008 12:29 PM
> To: aeroelectric-list@matronics.com
> Subject: AeroElectric-List: Twisted Wires vs. Parallel
>
>
> We often see instructions to twist the positive and negative wires
> together
> to reduce noise problems. Instructions from B&C for their voltage
> regulator
> even specified the number of twists per inch.
>
>
> But I'm wondering about the physics. From studying the 'Connection,
it
> seems that paralleling the positive and negative wires tightly togeth
er
> would have the same effect as twisting them together. Is twisting th
e
> wires
> together recommended because it is a convenient way to keep the wires
in
> close contact? Or is there something about the nature of the
> electromagnetic fields that makes twisting more effective?
>
>
> Thanks,
>
> Dennis
>
> Legacy, 220 hours, mostly twisted positive and negative wires
>
>
-----------------------------------------------------------------------
---------
Checked by AVG - http://www.avg.com
9:40 AM
========================
============
========================
============
========================
============
========================
============
Message 8
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: CBA-II Battery Tester modifications/improvements? |
nuckolls.bob(at)aeroelect wrote:
> I bought the devices when they offered a high
> return on investment for answering some questions
> about battery performance between brands and
> battery condition for insuring performance in a
> $high$ instrumentation job. Looking at all the
> data files in my CBA output folder I see that I've
> conducted perhaps 100 battery cap-checks on various
> devices.
>
> Even when I was doing cross brand comparisons,
> graphical display of data was useful only for helping
> my readers understand . . . it was of no value in
> deducing the results of the tests, i.e. total energy
> delivered under a particular test condition.
>
> I guess I'm not clear as to your design and market
> goals. If it's your desire to fabricate large
> quantities of a product to compete with the CBA-II
> then "window dressing" will be important. If you're
> goal is to offer a sort of DIY work-around for
> the CBA-II's shortcomings to be shared with some
> cognizant individuals, then the super-graphics
> features become problematic for return on investment.
>
You mention it three times in your post so I want to be clear, I'm not interested
in designing a product to compete with the CBA. I create high-power loads for
dischargers/cyclers/analyzers/testers. I don't want the ultra price-sensitive
"low" end of the market. But, if this project moved forward, I would offer
to lay out a PCB that others could use for building the load. If enough people
were interested, I'd have a batch of boards run and offer them at my cost.
Each person involved would contribute to the project where they can, and for me,
it's the hardware.
I'm just bringing up other thoughts about the possible feature set for a very good
DIY project. You want just raw data and feel it offers the most and that
graphics offer little, if nothing, compared to box-scored raw data. But many
users of battery analyzers disagree. I have to keep going back to the CBA and
its popularity. A lot of people don't care what the actual number is. They can
look at a graph of a test involving several cells or packs and see instantly
which lasted the longest, or had the highest voltage-under-load, for that test.
Whether the "best-performing" battery had a capacity of 10.02Ah or 10.10Ah,
they wouldn't care. Which battery that they can afford (or physically fit,
etc,) came out on "top". No need to check or compare actual numbers.
But, we should definitely have just a raw data-capture and store program. In fact,
it should be the first thing developed as it's the easiest to do. But I feel
strongly that we shouldn't design out the ability of someone to do a more
graphics-oriented package. It makes the project more desirable for more people
and that's important to help draw other designers and developers to the project.
This results in better, less expensive designs for those who want to DIY
the hardware, and easier to use and fuller-featured software. Hopefully not with
useless bloat but with great stuff like various discharge modes, IR measurement,
etc.
Never at the expense of a really good, very basic, data capture hardware design
and software program. Just as other options for an open-source project that
should encourage anyone to contribute to. Whether we'd ever use that hardware
or software or not.
nuckolls.bob(at)aeroelect wrote:
>
> Yes . . . if you're looking to optimize a
> product and marketing effort. I would estimate
> 30-40 hrs to work up a documentation package
> for hardware. Firmware in the PIC would take
> 10-20 hrs. The PC based application could take
> as long or longer than the hardware and firmware
> combined. So if your goals are to compete with
> the CBA-II in their sandbox, you're looking at
> a development program with a market value on
> the order of $10K before you manufacture and
> sell a single device.
>
No marketing effort, no product development. This is an open-source DIY project.
You mentioned the use of a PIC earlier and I was alluding to that. If that's
no longer an idea you're interested in seeing possibly be used for this DIY
project, then the Weeder modules (or other equivalent) are a quicker way to get
going. You also mentioned a friend who might possibly, maybe, be interested
in taking on the PC software development. No $10K to develop something great
that everyone could use.
As a open-source project, anyone who wants to contribute, can. Whether its integrating
existing I/O boards, creating an integrated PIC board, writing data storage
PC software or creating a full-blown graphics package (which will certainly
do the raw data storage), I think there's room for someone who wants to do
any of the above. We'd all just use the software/hardware that best matched
our needs and wants.
nuckolls.bob(at)aeroelect wrote:
>
> I'm not sure what a graph tells me that a number
> in an output box doesn't tell me. In fact, the way
> the early CBA-II software outputs graphics, one has
> to get out a pencil and straight edge to drop the cut-off
> crossing to the baseline and then visually do a
> linear interpolation to arrive at a number. The
> upscale version of the software give you the "box
> score" and the graph . . . what does the graph tell
> anyone that the box score does not?
>
> My disappointments with the CBA-II application is that
> it offers only constant-current discharge testing
> which doesn't emulate very many real life situations.
> After all the work has been done to achieve their
> present software package, it's a relatively simple
> addition to offer constant-resistance and constant-
> power discharge protocols with some dynamic internal
> impedance measurements thrown in for "frosting on
> the cake". Of course there's still the issue of
> marginal thermal performance and selection of load
> devices.
>
> No doubt West Mountain Radio has made a significant
> market penetration and their product offers a lot
> of bang for the buck. I own two of them! If you're
> considering development of a competing product, will
> the features you and I find useful convince future
> buyers of battery analyzers to pay more dollars for
> the offerings of the new kid on the block? More
> importantly, do potential sales for the super-whizzy
> product bode well for return on investment?
>
> Bob . . .
A graph doesn't tell you anything a number doesn't. But, the right graph can make
understanding various numbers, groups of numbers, and their relationships,
easier to understand. Edward Tufte's books so wonderfully illustrate that.
What's great about this project is that everyone can get exactly what they want.
One person can create a bare-bones, tiny-footprint, data uploading and storage
program. Another person can create a graphics-analysis package to show tons
of data in easy to read graphs. One person could develop hardware that integrated
existing products, another could create a custom PIC board.
I think a really important part of al of this would be to create a set of standards
for comms between the PC software and the boards, and for a data storage
format. This would allow for easy "black-box" development of both the hardware
and the software. Either could have any set of features but all would be compatible
with each other.
I agree with you on the lack of discharge profiles for the CBA. They do have a
constant-power discharge option in the Pro software now though. It would be nice
to see constant-current, constant-power, and constant-resistance "modes" in
the open-source hardware/software. Also nice would be allowing the user to
be able to create or select a "profile" for discharging. Whether it's just a
burst of current for a while every minute, or a complex profile to recreate a
"real world" usage scenario, I think it would offer a lot.
And the IR measurements feature is a great idea. There are so many "standards"
and methods for measuring IR that it would be great to see the hardware/software
eventually support a user-created IR test (timing, current, etc.).
We're starting to get into the meat of this...good stuff. :)
--------
John M.
Owner
CamLight Systems
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=221696#221696
Message 9
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Twisted Wires vs. Parallel |
Yes and yes, John. Untwisted pair cables suffer from more crosstalk and are
more susceptible to interference because during their run, they tend to be
farther apart in places than their twisted pair counterparts. Per my
earlier post, when an electromagnetic or electrostatic field crosses their
path and induces a current or voltage into them, it will be a different in
each wire because they are at different relative distances from the source
wire, which is probably running parallel but not necessarily. Then the
common-mode receiver will not be able to reject this noise as effectively as
if the noise at its two terminals were more "equal."
Also, if a differential transmitter is generating + and - currents through
the two non-twisted wires, they will not cancel each other out as
effectively as their twisted wire counterparts, because they will be farther
apart in places, and their electromagnetic fields will not be mutually
inductively coupled into each other as well along the wires' runs.
Furthermore, it is easier to maintain characteristic impedances more
accurately when the wires are twisted together and their distances apart are
more accurately maintained. By providing a termination resistor at the
receiving end of the twisted wire pair, reflections are more carefully
controlled, if not cancelled. For this reason and for the reasons cited
above, longer runs are possible with twisted wire pairs than with untwisted
wire pairs.
BTW, the same theory that applies to keeping the distances equal between
wires in twisted wire pairs also is used in printed circuit boards to
propagate signals along traces. There the traces are geometrically
controlled so that their widths and distances from each other and from other
traces, ground and power planes are maintained, as well as the separation
material, to do a much better job than wires in cables, especially in
Gigabit applications.
Simon Ramirez
Copyright 2008
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of CamLight
Sent: Monday, December 29, 2008 2:34 AM
Subject: AeroElectric-List: Re: Twisted Wires vs. Parallel
simon(at)synchdes.com wrote:
> There is no difference electrically between two wires that are kept at the
same distance in parallel and two wires that are twisted together to stay
parallel. The reason they are twisted together is that it is the simplest
way to keep them in parallel while the cable (a combination of wires,
shields, insulation, etc.) bends and distorts.
But don't pairs in untwisted pair cabling suffer from more crosstalk and
susceptibility to interference than in twisted-pair cabling? And, IIRC,
can't you do a longer run with twisted-pair than with untwisted-pair cable?
--------
John M.
Owner
CamLight Systems
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|