Congratulations on a fine job of engineering! One of things I learned
early on was that good engineering is doing enough to solve the problem,
not enough to gold plate it. :)
73, Jim K9YC
On Wed,2/10/2016 12:03 PM, Don Kirk wrote:
Here is the final update on my 160 meters interference that was originating
from an injection molding machine located at a manufacturing facility 0.5
miles from my house.
Last Friday a low cost 3 phase EMI filter was installed on the input side
of the AC Servo Drive, and the interference that was peaking 10 dB above my
noise floor on 160 meters at my house disappeared, and it can longer even
be detected while sitting in the parking lot of the manufacturing facility
(about 100 feet from the machine). I was hoping the low cost filter would
reduce the interference by at least 10 dB, so the final results are
extremely pleasing (really amazing).
Filter: Delta Electronics model 30TDVST2
Cost: ($76.29 at DigiKey)
The filter was purchased and installed by the owner of the manufacturing
facility, but I did point him toward this particular model (due to current
rating, cost and size) with the understanding that I was only providing
some options and that he was totally responsible for any and all action
taken.
The AC Servo Drive manufacturer recommended an EMI filter available out of
Japan at a cost of $955. This $955 filter is the "default" filter they
specify for the AC Servo Drive we were working with but it does not take
into consideration that we were using the AC Servo Drive with a motor
smaller in size than the max rating of the drive, nor did it take into
consideration that we might be able to get away with a simpler designed
filter (less attenuation, etc). Taking the low cost filter approach is
what kept things moving forward.
P.S. I baked cookies and brownies last night and delivered them to the
manufacturing facility this afternoon to say thanks (this is my typical
approach).
73,
Don (wd8dsb)
On Tue, Dec 1, 2015 at 6:20 PM, Don Kirk <wd8dsb@gmail.com> wrote:
Here is a somewhat long update on the RFI I tracked down to a local
manufacturing facility a few weeks ago.
Went to the facility a week ago with portable HF receiver and portable
tuned shielded loop in hand, but there was so much broadband white noise
within the facility that direction finding and/or sniffing of the signal of
interest was impossible (could not hear the signal of interest through the
local broadband white noise). We (the owner and I) tried watching the
manufacturing machines from a remote location where we could hear the
interference of interest to see if we could visually match up the
interference on/off sequence with machine motions, but we were not
successful. Therefore I decided I had to take a more technical approach.
I went back home and designed a circuit that would log the on off status
of the interference every second on my PC, and also used Audacity to
continuously record receiver audio. Both of these systems were connected
to my HF transceiver in my shack and they allowed unattended logging of the
interference.
Using the above recording systems I was able to tell the owner of the
facility today that the machine cycle time average was currently running 71
seconds, and that the machine generating the noise started back up after
the Thanksgiving weekend yesterday (Monday) afternoon at approximately
12:38 pm.
The owner then looked at his historical data logging system, and
immediately told me that my data matched up with his machine #18.
This afternoon we confirmed that his machine #18 was the culprit. The
owner was at machine #18 while I was at my house listening real time to the
interference. The machine was turned turned off and also ran some cycles
which allowed us to confirm the interference patterns at my house matched
up exactly with his #18 machine.
The machine is an injection molding machine (only 6 months old, with 3
more of the same machines on order), and it has a servo AC motor. I am now
going to work with the owner to investigate the design, before we decide
how to proceed. One of the first things I want to see is if an input line
filter is part of the build, and to determine the manufacturer and model
number of the drive so I can look into the manual of the drive to see if
the machine builder followed the drive manufacturers recommendations for
RFI compliance.
Just FYI,
Don (wd8dsb)
On Fri, Oct 30, 2015 at 7:48 AM, Don Kirk <wd8dsb@gmail.com> wrote:
Thought I would share my latest RFI issue that I tracked down yesterday
to a local manufacturing facility located 0.5 miles from my QTH. Below is
a link to a website that documents the interference, and it includes a link
to a youtube video that has recordings of the interference from my shack as
well as from within the office area of the manufacturing facility.
I will now work with the facility manager to track down the actual source
of the interference. Turns out that I am actually an old customer of this
facility through my daytime job (very small world).
website link http://sites.google.com/site/rfimetro/
Stay tuned to find out the actual source.
73,
Don Kirk (wd8dsb)
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