I Forgot To Add -- Polar Express Module Creation And System Definition

Moderator: BlueStrat

Mike McCarthy
Site Admin
Posts: 145
Joined: Thu Apr 16, 2015 8:07 pm

I Forgot To Add -- Polar Express Module Creation And System Definition

Postby Mike McCarthy » Thu Aug 27, 2015 6:13 am


To: rickbernstein@fehuproductions.com


I forgot to add th mat twice I've said that there needs to be a backup manual way of running the show. Each time you have finessed the issue, once going so far as to say that sometimes you just have to trust the Gods of Theater because we are not going to have a backup manual capability, it being too dangerous to have volunteers plugging and unplugging power extension cords on the hill during bad weather.

That's an interesting viewpoint -- that there will be no manual reversion for a show that you told me is costing $600,000 to produce. I would think that a situation like this would call for a show insurance policy so that instead of trying to run manually the museum would simply cancel the event and put in a claim for the lost gross revenue, which presumably would be $700,000 siince you tolkd me that the show is expected to net $100,000.

If I were an insurance adjuster and I heard that the show electronics were known by an expert wittness to have been inadequate to the task at hand, and that tthis expert witness had warned the project manager about this in advance of even construction of the first FRU, I might challenge the validity of the claim, so this is perhaps another reason for my being concerned about the Seven FRUs Only approach -- that the museum might think it was insured when in fact a claim stood little chance of ever being paid.

I know nothing about show insurance but I assume that any such policy would call for your show subcontractors to be paid regardless of whether the show had been cancelled by in the way I just described. Indeed, this would be the point of the insurance -- to ensure that the subs get paid without having to dip into museum funds in the event of a cancellation.


-------- Forwarded Message --------r
Subject: Polar Express Module Creation And System Definition
Date: Thu, 30 Jul 2015 16:39:28 -0600
From: Mike McCarthy <mike@impactphotoart.com>
To: Rick Bernstein <rick@crrm.org>


After giving the matter much thought I've decided that I cannot in good
conscience agree to build any hardware for the Polar Express project.
My expertise lies in component selection, overall system design,
hardware/software tradeoffs, and firmware and software programming. I
thoroughly understand digital electronics at the register ransfer level,
and I understand analog stuff at the level of ADCs (analog to digital
converters) and the like, but when it comes to the flow of electrons
across pin/substrate junctions, or the soldering of wires, we are well
outside my area of expertise and I have no desire to test my ability to
learn this stuff. If hardware is going to fail in service I don't want
there to be a hint of a chance that it was because of a construction
error I made while building modules or FRUs (field replaceable units).

Also, I have spent some of my own money to try to make atil least one of
my two portable computers useable for the Parallax IDE (interactive
development environment) in order to create the software for the FRUs
and any test rigs. If my efforts continue to be unsuccessful it will be
necessary for the museum to purchase a Surface 3 with physical keyboard
for my exclusive use through the end of Polar Express. My wife and I
are way over budget this month and next and simply cannot afford to
carry the museum on something as expensive as a $600 (or whatever) computer.


Now ... Last night you, Jack and I spoke of three phases to this
project, which I discuss below. We also spoke not only of modules to be
built as FRUs but also of module test rigs to enable newly built
modules, and modules that are believed to have failed on the hill, to be
checked out on a test bench using a known good module test rig.

Today you want nothing to do with anything beyond the bare bones seven
FRUs required to light the wolves, the hobo, the elves and the signs,
with no overtones of Phase I spare FRUs, Phase I module test rigs, and
no traces of Phases II and III. This is fine -- I will program anything
you ask for. However, I feel the need to explain in this email the
differences between the seven modules you have asked for and the Phases
I, II and III that we had agreed to yesterday evening.


I"m qualified to speak to these differences because of a) the Omnitech
Robotics CANbus-based remotely operated mine clearing bulldozer project
I worked on in 2003 for which I did all the outboard firmware and
software, and because b) in 1987 I was sworn as an expert special
investigator by the City of Philadelphia regarding the Building Control
System for the then-new Philadelphia Jail (CANbus did not exist at the
time), and because c) a judge swore me as an expert witness during an
investigation of the Building Control System for the Annandale Youth
Correctional facility in New Jersey (CANbus did not exist at the time).
I have never testified in court because it was never necessary --
contractors realized that it was in their best interests not to
challenge my findings and instead to modify and then complete their
projects per my professional opinions and directives.

It is my professional opinion that below is what is likely to happen if
we simply build only the seven FRUs you want built by the time of my
departure from the museum for Southern California on Sunday, August 30,
2015. We'll take the Wolves FRU as representative of all seven FRUs ...

If the Seven FRUs Only Wolf FRU fails in service it will affect the
entire Wolf lighting system on both sides of the track. Because of the
noisy RF environment, failures of this FRU will take several forms
including a) uncommanded operation of the Wolf FRU, b) commanded
operation of the Wolf FRU that never happens, and c) unintended
operation of some FRU other than the Wolf FRU. These failures are
likely to be transient in nature and not repeatable for trouble shooting
purposes. Worse still, it will be impossible to determine whether the
Wolf FRU failed because of RFI (radio frequency interference) or because
of a transient defect in the FRU hardware itself. A laborious set of
pin functionality tests will be required to assess board health. If the
FRU is left in service, the only way to recover from a Wolf FRU failure
witll be to cycle power on the Wolf FRU in order to bring it to a clean
state. All this because module testing stations are not part of the
definition of the Seven FRUs Alone project you imposed today

My definition of Phase I would have created three spare FRUs for a total
of ten, and it would have created at least one and maybe two FRU
checkout testbeds so that a rapid distinction could be made between FRU
hardware failure and FRU transient response to RFI, allowing for field
replacement of FRUs with known good FRUs along with depot checkout and
repiar of suspected failed FRUs.

Phase II would have added a failsoft capability to the lighting design.
Instead of the single Wolf FRU taking out the entire Wolf lighting
display, the lights on each side would be driven partly by Wolf FRU A
and partly by Wolf FRU B. As a result, a failure of either the A or the
B module would take out half the Wolf lights on both sides of the train.
Recovery could be affected either by rebooting the failed A or B
module, or by swapping a known good FRU in place of the failed A or B
module, but it would be highly improbable that at any time there would
be no Wolf lights at all.

Finally, Phase III would have used so-called distance coding of Wolf
Phase II light FRU addresses in conjunction with code that detected and
retried erroneous transmissions to achivee a higher level of reliability
of communication in the face of unavoidable RFI. It would not have been
as good as CANbus, but it would have been better than nothing.

I'm telling you all this because if, for some reason, the show were to
fail due to RFI or module defect problems, I would want it clearly
understood that you were warned beforehand, in the form of this
professional opinion, about the risks and the difficulties of trouble
shooting in a Seven FRUs Only project environment.


Return to “I Forgot To Add -- Fwd: Polar Express Module Creation And System Definition”

Who is online

Users browsing this forum: No registered users and 1 guest