<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<font face="Arial">Jonathan,<br>
You can use a standard silicon diode like the 1N4000 series (1A
rating) for the polarity protection diode unless you want to clamp
the reverse voltage at less than 0.7-0.8 volts, in which case a
Schottky will provide a lower clamping voltage. Since the reverse
protection diode will clamp reverse transients, you don't need a
bidirectional TVS.<br>
Jules<br>
<br>
</font><br>
<div class="moz-cite-prefix">On 7/28/2021 3:16 PM, Jonathan wrote:<br>
</div>
<blockquote type="cite"
cite="mid:3C665254-3390-47EF-9372-4B1745A06EA2@gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">Phil,</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">This design (Integrated VLF antenna/preamp in PVC
pipe with Raspberry Pi box) was used for an MIT study and the
author of vlfrx-tools built a bunch of these antennas and boxes
for those conducting the study. This was in 2018. Since this
might have fallen under your umbrella, did you hear of it or
know who the PI might be? The DC-DC converter has an operating
frequency of 100-600 kHz, so it doesn’t really affect anything
below that. Paul really liked the performance of his design. He
even wrote a guide on how to set up the Radpberry Pi as a VLF
SDR using his vlfrx-tools software. </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Jules,</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">I really appreciate the supplied schematic. Should
I use the Schottky diode where you drew the regular diode, in
parallel like you said? I could also probably solder the MLCC
across the leads of the electrolytic and install it. Also, that
TVS is bidirectional. Should a unidirectional TVS be used so it
clips any negative spikes closer to 0V? </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">David, </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Tom mentioned the same. I’ll be working on trying
to fit an electrolytic and a ceramic capacitor. </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Khan,</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">This is good news. Email me if you have issues. </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Jonathan</div>
<div dir="ltr">KC3EEY</div>
<div dir="ltr"><br>
</div>
<div dir="ltr"><br>
</div>
<div dir="ltr"><br>
On Jul 28, 2021, at 2:27 PM, Julius Madey <<a
href="mailto:hillfox@fairpoint.net" moz-do-not-send="true">hillfox@fairpoint.net</a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<meta http-equiv="Content-Type" content="text/html;
charset=UTF-8">
Jonathan,<br>
I still think you need to get rid of the series polarity
protection diode and suggest the following schematic (with
22uf 50 volt Aluminum electrolytic)<br>
<br>
<br>
<eaeficdplljflikc.png><br>
<br>
The PTC poly fuse will open either on overload, sustained
voltage above TVS rating or reverse polarity. This will also
snub transients on the line the series diode may have
permitted. There might be some virtue in adding an MLCC cap
of ~ 0.47uf in parallel with the electrolytic for lower
overall ESR.<br>
<br>
Regards,<br>
Jules-K2KGJ<br>
<br>
<br>
<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 7/28/2021 12:41 PM, Jonathan
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:59FAEE9C-11F5-4CDF-B960-2E583E42E89C@gmail.com">
<meta http-equiv="content-type" content="text/html;
charset=UTF-8">
<div dir="ltr">Hi Tom,</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">That makes a lot of sense. I’ll try fit a
0.1uF and a 22-47uF electrolytic on the feedline loop. </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Thanks again! </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Jonathan</div>
<div dir="ltr">KC3EEY</div>
<div dir="ltr"><br>
On Jul 28, 2021, at 10:55 AM, Tom McDermott <<a
href="mailto:tom.n5eg@gmail.com" moz-do-not-send="true">tom.n5eg@gmail.com</a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div dir="ltr">
<div>Hi Jonathan - a concern is that the DC-DC
converter input stage would become unstable and
oscillate</div>
<div>with the cable inductance. If that happens then
there could be high frequency AC voltages present at
the</div>
<div>input of the converter. Would those over-voltage
the input? Possibly. Would it radiate RFI from
the cable? Likely.</div>
<div><br>
</div>
<div>Good design dictates sufficiently low source
impedance to the DC-DC converter. Almost all linear
regulators</div>
<div>require it. An electrolytic and ceramic bypass
pair right at the DC-DC input would be considered
good design by many.</div>
<div><br>
</div>
<div>-- Tom, N5EG</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Wed, Jul 28, 2021
at 7:30 AM Jonathan <<a
href="mailto:emuman100@gmail.com"
moz-do-not-send="true">emuman100@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)">John, </span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)">Thanks
for the suggestion! I think I’ll start with
the overvoltage age spike of 50V for 100ms or
less based on the datasheet spec of the DC-DC
converter. I was thinking of some sort of
fusable circuit protection now that I’ll be
using a TVS diode to mitigate stress from the
follow current. </span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)"><span></span><br>
</span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)">Tom,</span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)">The
datasheet wasn’t clear on the need for input
filtering. On the output of both the IP2415S,
I have 0.1uF ceramic capacitors. In the
datasheet, it only mentions a spec of “Input
Reflected Rated Current” with a series
inductor and shunt capacitor. I don’t really
understand exactly what this is, but it lists
“20mAp-p through a 12uH inductor and 47uF
capacitor”. Nothing else is mentioned about
input protection or filtering.</span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)">In
both situations that the DC-DC failed, the
cable length was only 4’ of cat 5. This
circuit that was proved and tested by Paul,
including the receiver and schematic I
attached, did not have such an issue, but the
only difference is that the voltage was lower
than 30V. That’s why I was thinking it was a
turn-on/off spike. I think that in a lot of
typical applications, the input voltage isn’t
that high, so spikes don’t normally present a
problem. The DC-DC that feeds the receiver
DC-DC has never failed and it was always fed
with 18V or less. </span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)"><span></span><br>
</span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)">Jules,</span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)">You
recommend the Schottky diode in parallel with
the TVS, then a series PTC, so during a spike,
the TVS will conduct and the PTC would fuse,
and during a reverse polarity condition, the
Schottky diode will conduct with limited
current due to the PTC fusing? I can see the
benefit that the series PTC in normal a normal
circuit condition would drop much less voltage
that the Schottky diode. </span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)"><span></span><br>
</span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)">All
in all, I agree with adding some capacitance
to filter voltage spikes and reduce or
eliminate them. I’ll need to be sure not to
exceed the DC-DC max load capacitance, which
is 47uF in this case. </span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)">But,
to me, the most plausible cause for the
failures are turn on/off voltage spikes, even
with a short length of cable. Adding
electrolytics is a bit difficult due to the
tight space constraint as seen in my previous
email, so I’ll try out the TVS and a PTC.
Other than voltage spikes, does anything else
come to mind? </span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)"><span></span><br>
</span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)">Thanks
guys. </span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)">Jonathan</span></p>
<p
style="font-family:UICTFontTextStyleBody;font-size:17px"><span
style="background-color:rgba(255,255,255,0)">KC3EEY</span></p>
</div>
<div><br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, Jul
27, 2021 at 9:34 AM Jonathan <<a
href="mailto:emuman100@gmail.com"
target="_blank" moz-do-not-send="true">emuman100@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="auto">
<div dir="ltr">
<div dir="ltr"><span
style="background-color:rgba(255,255,255,0)">Hi
Everyone,</span></div>
<div dir="ltr"><span
style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span
style="background-color:rgba(255,255,255,0)">Before
the meeting ended last night, I wanted
to discuss the issues I’ve experienced
with my VLF active antenna. As I
mentioned, the DC-DC converter (XP
Power IP2415S) failed after I applied
power. I turned the volume up because
I wasn’t hearing sferics, and shortly
after, I heard the squeal of the DC-DC
converter. When I pulled out the
smaller foam core partially, I heard a
squeal coming from the DC-DC converter
itself. </span></div>
<div dir="ltr"><image3.jpeg><span
style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span
style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span
style="background-color:rgba(255,255,255,0)">I
had a failure of the DC-DC converter
when I first built the VLF preamp. It
was being powered by the Raspberry Pi
box (same power circuit as my text
box). I had a power failure and when
the power was restored, the DC-DC
converter failed. In both situations,
it was being supplied with 30VDC, with
the limit is 36V. The reason for using
30V is to overcome the voltage drop
from long cable lengths.</span></div>
<div dir="ltr"><span
style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span
style="background-color:rgba(255,255,255,0)">After
both failures, there was a low
impedance across the input of the
DC-DC converter causing the supply to
be pulled down. Because the input and
output are isolated, I figured the
fault had to have been caused by a
voltage spike on the input due to
power being turned on and off. The
datasheet mentions that it can
withstand 50V spikes at 100ms, but I
can’t think of anything else that
could cause the DC-DC to fail,
especially that 30V is used to power
it and any voltage spike would ride on
top of that 30V. I contacted XP Power
about the issue. </span></div>
<div dir="ltr"><span
style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span
style="background-color:rgba(255,255,255,0)">Here
is the schematic of the power path.
The blocks are the IP2415S DC-DC
converter.</span></div>
<div dir="ltr"><image1.jpeg><span
style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span
style="background-color:rgba(255,255,255,0)">I’m
powering the DC-DC converter with 30V
from another DC-DC converter in the
test box and Raspberry Pi box
(Raspberry Pi box not shown, but same
circuit). </span>Keep in mind, the
length is still relatively short in my
testing, so cable inductance isn’t the
primary reason for the spike. Plus, at
long lengths, the voltage would be much
lower due to voltage drop across the
length, and I think this was why Paul
might not have seen this issue when he
originally tried and built this design. </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">To mitigate this problem
with the supply voltage at 30V, I
decided to use a TVS diode across the
input of the DC-DC converter. Here is
the schematic: (my apologies for the TVS
diode being backwards)</div>
<div dir="ltr"><image2.jpeg><br>
</div>
<div dir="ltr">I chose a unidirectional
TVS so there is also protection if the
voltage spikes have any negative
components. I picked a TVS with a
working voltage of 33V, a Littel Fuse
P4KE39A. According to the datasheet, it
looks like this would be adequate. TVS
diodes have a PN junction that is more
rugged, with a larger surface area for
greater current density. One thing I
overlooked with this type of circuit
protection is that once the TVS
conducts, current from the power supply
will be shunted too, known as the follow
current, and in some situations, this
may cause issues requiring a fuse. In
this case, since the spikes are probably
short duration, and since the DC-DC
converter in the text/Pi box has short
circuit protection, this should not be
an issue. </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">So the questions I have
are: do you also think it could be
voltage spikes that caused the failures,
and if so, was my choice of TVS diode
adequate. Also, one important question,
if I connect the anode of the TVS diode
to the receiver side ground, will I lose
isolation? I know that during spike
current conduction, I will. I’m sure I
can still get adequate protection with
the TVS diode anode connected to the
negative of the isolated power loop too,
but I just wanted to be sure. </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Lastly, since the
magnetometer board will undergo another
revision, I feel it may be worth it to
add some sort or adjustable regulator or
use of an external power source (not
connected to the 5V pin of the Pi
header) because even with paralleling
wires or pairs, some installations will
require very long lengths (especially
since interference-free locations are
often far away from the shack) and the
voltage may drop to where the LDO cant
regulate. Using a higher voltage at the
Pi end (like I do with the VLF preamp)
may be required for some installations.
I think this should be considered if it
already wasn’t addressed. </div>
</div>
</div>
<div dir="auto">
<div dir="ltr">
<div dir="ltr"><br>
</div>
<div dir="ltr">Jonathan</div>
<div dir="ltr">KC3EEY</div>
<div dir="ltr"><span
style="background-color:rgba(255,255,255,0)"><br>
</span></div>
<div dir="ltr"><span
style="background-color:rgba(255,255,255,0)"><br>
</span></div>
</div>
<div dir="ltr"><br>
On Jul 27, 2021, at 7:21 AM, Dr. Nathaniel
A. Frissell Ph.D. <<a
href="mailto:nathaniel.frissell@scranton.edu"
target="_blank" moz-do-not-send="true">nathaniel.frissell@scranton.edu</a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div dir="ltr"><br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<div><br>
<br>
<p class="MsoNormal">Thank you, Tom.</p>
<br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
<p class="MsoNormal">The recording
will be available later today at <a
href="https://youtu.be/AammohuygMw" target="_blank"
moz-do-not-send="true"><br>
<br>
https://youtu.be/AammohuygMw</a>
and <a
href="http://hamsci.org/telecons"
target="_blank"
moz-do-not-send="true">hamsci.org/telecons</a>.</p>
<br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
<p class="MsoNormal">73 de Nathaniel
W2NAF</p>
<br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
<div
style="border-color:rgb(225,225,225)
currentcolor
currentcolor;border-style:solid none
none;border-width:1pt medium
medium;padding:3pt 0in 0in"><br>
<br>
<p class="MsoNormal"><b>From:</b>
TangerineSDR <<a
href="mailto:tangerinesdr-bounces@lists.tapr.org"
target="_blank"
moz-do-not-send="true">tangerinesdr-bounces@lists.tapr.org</a>><br>
<br>
<b>On Behalf Of </b>Tom McDermott
via TangerineSDR<br>
<br>
<br>
<b>Sent:</b> Monday, July 26, 2021
10:02 PM<br>
<br>
<br>
<b>To:</b> TAPR TangerineSDR
Modular Software Defined Radio
<<a
href="mailto:tangerinesdr@lists.tapr.org"
target="_blank"
moz-do-not-send="true">tangerinesdr@lists.tapr.org</a>><br>
<br>
<br>
<b>Cc:</b> Tom McDermott <<a
href="mailto:tom.n5eg@gmail.com"
target="_blank"
moz-do-not-send="true">tom.n5eg@gmail.com</a>><br>
<br>
<br>
<b>Subject:</b> [TangerineSDR]
Notes from PSWS / TangerineSDR
call of 07-26-2021</p>
<br>
<br>
</div>
<br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
<div><br>
<br>
<div><br>
<br>
<div><br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
</div>
<br>
<br>
<div><br>
<br>
<p class="MsoNormal">Notes from
PSWS / TangerineSDR call of
07-26-2021</p>
<br>
<br>
</div>
<br>
<br>
<div><br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
</div>
<br>
<br>
<div><br>
<br>
<p class="MsoNormal">1. Bill is
using chart.js for
magnetometer charting. He is
setting up a database using
Django web and database
framework for Python.</p>
<br>
<br>
</div>
<br>
<br>
<div><br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
</div>
<br>
<br>
<div><br>
<br>
<p class="MsoNormal">2. Scotty
is looking at the Intel
(Altera) Arria 10 GX FPGA
10GX270 for the version 2 Data
Engine (supporting 10GE).
These FPGAs appear to be more
available than the MAX10
FPGAs. The intention is to
develop DE Ver 1 and DE Ver 2
in parallel<br>
<br>
while awaiting FPGA component
availability. The 10 GX
development boards are pretty
expensive. </p>
<br>
<br>
</div>
<br>
<br>
<div><br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
</div>
<br>
<br>
<div><br>
<br>
<p class="MsoNormal">-- Tom,
N5EG</p>
<br>
<br>
</div>
<br>
<br>
<div><br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
</div>
<br>
<br>
<div><br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
</div>
<br>
<br>
<div><br>
<br>
<p class="MsoNormal"> </p>
<br>
<br>
</div>
<br>
<br>
</div>
<br>
<br>
</div>
<br>
<br>
</div>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
-- <br>
<br>
<br>
Please follow the HamSCI Community
Participation Guidelines at <a
href="http://hamsci.org/hamsci-community-participation-guidelines"
target="_blank" moz-do-not-send="true">http://hamsci.org/hamsci-community-participation-guidelines</a>.<br>
<br>
<br>
--- <br>
<br>
<br>
You received this message because you
are subscribed to the Google Groups
"HamSCI" group.<br>
<br>
<br>
To unsubscribe from this group and stop
receiving emails from it, send an email
to <a
href="mailto:hamsci+unsubscribe@googlegroups.com"
target="_blank" moz-do-not-send="true">hamsci+unsubscribe@googlegroups.com</a>.<br>
<br>
<br>
To view this discussion on the web visit
<a
href="https://groups.google.com/d/msgid/hamsci/SA0PR03MB5547CBF733EFEB4D829E659FF2E99%40SA0PR03MB5547.namprd03.prod.outlook.com?utm_medium=email&utm_source=footer"
target="_blank" moz-do-not-send="true">https://groups.google.com/d/msgid/hamsci/SA0PR03MB5547CBF733EFEB4D829E659FF2E99%40SA0PR03MB5547.namprd03.prod.outlook.com</a>.<br>
<br>
<br>
</div>
</blockquote>
</div>
</blockquote>
</div>
</div>
</blockquote>
</div>
</div>
</blockquote>
-- <br>
Please follow the HamSCI Community Participation Guidelines
at <a
href="http://hamsci.org/hamsci-community-participation-guidelines"
moz-do-not-send="true">http://hamsci.org/hamsci-community-participation-guidelines</a>.<br>
--- <br>
You received this message because you are subscribed to the
Google Groups "HamSCI" group.<br>
To unsubscribe from this group and stop receiving emails
from it, send an email to <a
href="mailto:hamsci+unsubscribe@googlegroups.com"
moz-do-not-send="true">hamsci+unsubscribe@googlegroups.com</a>.<br>
To view this discussion on the web visit <a
href="https://groups.google.com/d/msgid/hamsci/59FAEE9C-11F5-4CDF-B960-2E583E42E89C%40gmail.com?utm_medium=email&utm_source=footer"
moz-do-not-send="true">https://groups.google.com/d/msgid/hamsci/59FAEE9C-11F5-4CDF-B960-2E583E42E89C%40gmail.com</a>.<br>
</blockquote>
<br>
</div>
</blockquote>
</blockquote>
<br>
</body>
</html>