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Issue 15
October 11, 2011
Eric Holland
Design Engineer
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TABLE OF CONTENTS
4
Eric Holland
SENIOR ELECTRONICS DESIGN ENGINEER, HACKER, AND BLOGGER
Interview with Eric Holland, Avery Weigh-Tronix
9
Touchstone Semiconductor
TS1001 Coolest Opamp Design
Contest
BY
ERIC HOLLAND
Holland describes the details of his contest-winning Opamp design.
10
Featured Products
11
Control Synthesis Output with
Combinatorial Logic in Procedural
Code
BY
RAY SALEMI
An explanation of various coding styles and their effects on synthesis results.
16
All Storage Not Engineered Equally
BY
GARY DROSSEL
WITH WESTERN DIGITAL
A careful look into the technology of various storage products to compare the
quality of their operations.
21
RTZ - Return to Zero Comic
3
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INTERVIEW
Eric Holland
really well. This high mix of products
makes keeping them updated with
the latest and greatest electronic
components challenging, and
needless to say, we fight End-of-Life
and Last-Time-Buy issues daily.
Senior Electronics
Design Engineer
Getting data out of the box is another
interesting challenge. Just providing
a product that has the most elegant
A-to-D section and weighs better
than anything else on the market is
not good enough. We need to have
means of getting the weight, time,
and other entered information out
of the box and to the customer’s
PLC or central computer server.
We are moving to many Ethernet
based field bus standards like
EthernetIP and ProfiNet, but also
use USB, RS232, and RS422/485 as
a communication medium.
What are you working on?
I design embedded electronics for
the weighing industry when I am not
working on my latest electronics-
related blog post. These scales
range from small postal scales to
larger tank weighers, all the way up
to huge truck and rail scales. It is a
fun industry, because I get to work
on precision test and measurement
equipment. Unlike voltmeters and
oscilloscopes, these scales do not
just need to function in a pristine
lab environment; these scales have
to weigh accurately when mounted
outside in a desert heat or buried in
a pile of snow on the frozen tundra.
Most of the products I work on
could be used in the food industry
as well, so we need to seal up my
electronics in a stainless steel water
tight box.
means we can make use of 20 or
24-bit Delta Sigma analog to digital
converters that Texas Instruments,
Analog Devices, Linear Technology,
and many other semiconductor
manufacturers provide.
What are some challenges
in the weigh scale market
today?
Time. Most industrial weigh scale
companies have product lines that
I would call high mix, low volume.
I design and maintain hundreds of
different embedded scale products,
but if we sell 10 thousand of one
particular model, we are doing
The other challenge I’ve noticed
that isn’t so obvious is the green/low
power movement. Now it isn’t our
customers that are asking for Low
Power Scales, because 99 percent
of our products just plug into an AC
Eric Holland - Designer of Embedded Electronics for the Weighing Industry
Weigh Scale electronics are
really not much different than DC
voltmeters. A Fluke 87 Multimeter
has a DC voltage measurement
accuracy of +/- 0.1mV. Our weigh
scales need to measure down to
+/- 50nV accurately over a -20 to
+60 Degrees celsius range in order
to meet our certified weighing
specifications. Weigh scales, like
multimeters, have the benefit of
only having to make measurements
100 times per second or less. This
4
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INTERVIEW
if you wired them up to a battery
pack they would only light up when
hooked up a certain way.
What are your favorite
software tools that you use?
We use Altium at work, and even
though it has its quirks I think it is
one of the best PCB CAD tools
on the market. I’ve used Orcad
and Mentor’s PADs as well but I
think Altium is still better. Linear
Tech’s LTSPICE is my go-to SPICE
simulation tool. My favorite website
is http://www.oemstrade.com; it
enables me to search for parts at 33
different distributors with one button
click. I use it to find parts or just
simply validate P/N’s before I load
them on an AVL.
outlet. What is challenging about
the low power movement is the fact
that many of the precision analog
components we rely on (opamps,
comparators, and analog-to-digital
convertors) are moving to lower and
lower supply voltages. This trend
is not just because of the green
movement, smaller silicon feature
geometries are also pushing this
trend as well. Weigh scale loadcells
are ratiometric, so the voltage
signal you get out of them is directly
proportional to the supply voltage
you feed them. Historically, 15V and
10V excitation voltage levels were
common, but due to the shrinking
supply voltages on our analog parts,
we’ve had to either get a bit creative
and add cost to our designs or
move to lower 5V and 3.3V loadcell
excitation voltages. Now, on bench
or even floor scales this isn’t that
big of a deal, but on truck and rail
scales that have 1,000 feet or more
of cabling between the loadcells
and the analog-to-digital converter,
+3.3V excitation is a problem.
From Radio Shack,
The Forrest
Mims Engineer’s Mini-Notebooks
and a 50-in-One electronics kit
was probably my first taste at real
electronics. I was also very lucky to
go to a high school that had a couple
of electronics electives. We wired
up a three-way switch and etched
our own PCBs to make an AC-
DC power supply with a LM317. I
actually still have this PSU and use it
to power all my guitar effects stomp
boxes.
What is the hardest/trickiest
bug you have ever ixed?
Almost five years ago I was hired
as a contract engineer to help a
local medical company redesign
and update its 100 Watt, 900
MHz, microwave generator. The
microwave generator consisted
of a microcontroller PLL-based
frequency synthesizer and a RF
power amplifier.
Probably the biggest influence I
had was in high school. I took a
several BASIC, Visual BASIC, and
C/C++ courses, and the regular
teacher was on medical leave, so a
local engineer came in and taught
the C/C++ course. You could
tell he loved being an electrical
engineer and he encouraged me to
go to college and get an electrical
engineering degree.
How did you get into
electronics?
My younger brother and I loved
LEGOs and we built some pretty
elaborate castles. We would always
make them without roofs, so you
could move the minifigs from room
to room. We also had all kinds
of secret passageways and trap
doors built into the castles as well.
I remember going to Radio Shack
and buying a pack of LEDs and
stringing them all together and
using them as torches that lit up our
castles. I also remember wiring up
a 555 timer to blink a couple LEDs
for my LEGO fireplace. I had no
idea how LEDs worked but I knew
The 50 dB Power Amplifier consisted
of three RF amplification stages and
was in need of a complete redesign
as it was based around several
parts that are now obsolete. My
problems started in the lab after
my first Power Amplifier prototypes
showed up. The output stage of my
amplifier was continuing to “burst
into flames.” These made exploding
tantalum capacitors look like child’s
play in comparison. Every time the
output stage blew up it would take
a chunk of the Arlon PCB with it.
Embarrassingly, this happened
often enough with this project that
I got quite good at repairing the
burnt traces with copper tape,
What are your favorite
hardware tools that you use?
I am in love with my Agilent Infiniium
4-Channel 1 GHz MSO. The mega
zoom feature is awesome. I can
zoom out to 1 sec per division, see
the I2C or SPI lines toggling, press
the stop button and zoom right
into each byte being transmitted.
No need for fancy triggering when
you can zoom in so far. I am also a
huge fan of Metcal soldering irons;
they are what I learned on when I
was a technician soldering SMT
components and I haven’t found
anything I like better.
5
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