nuckolls.bob(at)aeroelect
Guest
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 Posted: Sun Apr 16, 2023 12:38 pm Post subject: LightSpeed Ignition wiring |
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At 02:40 AM 4/14/2023, you wrote:
| Quote: | Bob,
In reference to a 3/28/23 post regarding wiring for a dual LightSpeed Ignition application,
you basically replied that the use of shielded wire (for the power supply from the battery to the two boxes) was unnecessary and contrary to a 747-load of lessons learned.
Positive and Negative Connections:
Just to make sure I understand your response, I could run an
18 awg wire or larger from the positive post of the battery to PINÂ 8
of the "Input <SNIP> |
If it were my airplane:
NO wires for any system need be connected to the
(+) or (-) terminals of the battery for any
reasons supported by the physics or practice
in aviation. To my knowledge, it has never
happened in either type certified or military
aircraft . . . arguments that support the
idea are weak at best.
Lightspeed systems draw about 3A maximum.
22AWG wire is electrically adequate to the
task of transporting electrons from the BUS
to the ignition system. 20AWG wire is often
preferred for mechanical robustness in some
installations . . . and D-SUB connectors
readily accept 20AWG wire. Anything larger
is completely unnecessary and most inconvenient.
| Quote: | | I recall from some of your earlier conversations with Klaus that the solder bridge from Pin 8 and 7 on the Input Connector was redundant and not necessary, and the same for the negative supply for Pins 15 and 14. |
At 3A max, the single D-Sub pin is quite
adequate but paralleling at the connector
body doesn't add much integrity for
current sharing. To make paralleled pins
share a potential for single pin overload,
you need to add ballasting resistance in
each of the paralleled paths. I illustrated
this here https://tinyurl.com/288uppe4
This was used successfully in boosting
the currents conducted through D-subs on
both the AQM163 target and the Hawker-Beech
4000.
But with a 3A draw, adding more pins in the
pathway is of minuscule value.
| Quote: | If this is correct, could a twisted pair be used for these two connections? Would there be any benefit of using twisted pair here rather than two separate wires?
The positive wire would use a circuit breaker and switch as shown on the Input Connector Diagram. |
No special treatments for managing electromagnetic
compatibility are necessary or useful. Wire this
critter up the same as you might for a light
bulb.
Here's the rub: Assume the manufacturer says
shielding that wire is necessary to reduce risk of
electrostatically coupled interference either to
or by other ship's systems. What then what is the philosophy
for connecting that same wire to the battery? Batteries
are NOT good noise abatement devices. If lack of
shielding presents a risk, then there is risk
that same antagonist is hazard for propagation
out onto the bus.
At the current it takes to run this system,
any NECESSARY noise abatement could be easily
accomplished inside the device thus making it
unnecessary to shield that wire. Given the apparently
noise-free, marketplace age of this product
I submit that no such noise risk exists.
No shields, no twisting, no splicing is necessary
or useful. Keep it simple. Why 3-wire cable?
| Quote: | I am also planning on using your recommendation to replace the RG 400 coax cables to the coils.
For the wiring from the magic boxes to the ignition coils, can a 2-conductor, unshielded,
twisted or un-twisted cable be used to drive the coils, rather than using the RG 400 coax cable? |
DO use shielded wire for the coil drive wiring.
Those wires do carry fast rise-time, high-voltage signals
and MIGHT pose a risk of electro-static coupling to
other wires in the airplane especially given the long
runs you're proposing. Klaus has claimed that
the superior high-frequency qualities of coaxial
cable are a benefit to performance of his system
but the physics do not support this notion. Ever
notice that you don't find shielded wires on any
cars/trucks?
That being said, there's nothing BAD about
substituting more generic shielded wire as
I've suggested but, you're still have to
wrestle with terminating your coil drive wires
onto UG88 coax connectors to mate with the
LSE coil output connectors. Using RG58 or
UG400 reduces the risk for installer-generated
difficulties for mating generic shielded wire
with the UG-88 connectors.
I think I'd opt for RG58 coax . . . given
your long wire runs, RG400 is pretty pricey
and adds no performance value to this
installation.
| Quote: | his application is for a 4-cylinder Lycoming, with the Dual LightSpeed boxes located behind the firewall, in fact behind the seats (2-seat airplane) under the baggage compartment.
The 4 coils will be on the engine or engine mount - a considerable distance (appx. 12 ft)Â from the 2 magic boxes. |
Why so far away?
| Quote: | My takeaway from your previous postings is that with the LightSpeed Ignition System, there is no need for shielded wire anywhere in the installation.
Please correct me if I have this wrong. |
WHOA! The ONLY place I've suggested shielding to
be unnecessary is the power supply feeder. If
that were my product, I would have strived to
wire all the signal wires with twisted, unshielded
pairs to trios . . . which is entirely possible
to do. But without specific knowledge of the
input circuitry of this product, I have no
basis for arguing with the manufacturer's
installation instructions as published.
| Quote: | | I am sending this to you rather than using the list to avoid any heartburn with Klaus. |
If he's got any heartburn about this, he's most
welcome to join the conversation and defend
his position with an exchange of ideas supported
with physics and demonstrable practice.
Look my friend, if you're feeling risk of alienating
the good intentions of anyone you depend on, then
you will not be disappointed by installing
the LightSpeed system EXACTLY per manufacture's
instructions.
Certainly far more systems are successfully flying
'per instructions' than 'per AeroElectric'. I
would hope this forum is about making practical
decisions that go to reduced cost, simpler
installation/maintenance without compromising
performance. LightSpeed systems obviously perform
as advertised . . . similarly, there have been
no discussions here on the list for FAILURE to
meet expectations in LightSpeed systems installed
with more attention to convenience, legacy practice
and physics for now over 20 years.
Were I tasked with integrating the LightSpeed
hardware into a TC aircraft, then serious dialog
between LightSpeed and my employer would be dealing
with these same details. I would not be able to
'sell' the as-published power wiring to the cadre'
of airplane-police I answered to.
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
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