Design help / ideas current sensor...


Phil Allison

mkr5000 wrote:
This group always has some rude motherfucker show up in the midst of someone\'s post
and then take it to a level where they can vent and be hostile about the fact that they were
the kid that was picked on in grade school.

Yes, and I was the guy who stole Phil\'s briefcase and threw the dodgeball at his fucking
head while everybody laughed. \"Phil\" (man that alone sucks), is a lifelong dork who wants
his revenge. If we were face to face, even at my age -- the goofy prick would run in fear
because I\'d kick his ass and humiliate him. Something that he knows all too well.

Kiss my ass you fucking nerd.

** The POS troll just removed all doubt.
How nice of him.

...... Phil

Rich S

On Tuesday, January 4, 2022 at 3:44:24 PM UTC, mkr5000 wrote:
I\'m going to just come right out and ask for some assistance on this. There are still \"areas\" in electronics I have never had any experience \"tinkering\" with in all my years as an \"advanced\" hobbyist. You guys are walking encyclopedias on so much. This is something I\'ve never messed with --

I\'ve been wanting to somehow get a relay contact or a simple opto npn output to react to the output of an amateur radio xmtr when it\'s on the air. Simple enough and would be easy to get in there and look for the PTT contacts and diy something but I don\'t want to do that. Most (if not all) of these xcvrs don\'t have a self contained relay to perform the function either.

So --
My immediate first thought was to sense the RF with a FSM and I may still breadboard something but I\'m guessing as well shielded most of these new radios are, it\'s the actual antenna rf that would probably be the best source and I had better be pretty darn close to it. (100 watts or so output). Plan on experimenting with it -- don\'t have the parts yet.

But then it also occured to me that I may be able to make something that would just sense the current being drawn from the power supply and have looked into some of these split coil sensors etc (and asc712?). After all, in receive mode current draw from the supply would be next to nothing and transmit for 100 watts would go up to .83 amps or so. Pat myself on the back anyway for the creative thinking I guess :) But -- like I say, I
have never toyed with these sensors or instrumentation amplifiers etc. I see some off the shelf split coil ones (or maybe something diy?) and it looks like an AD623 is a good choice for amplifying millivolt signals? Anyway -- I just wondered what advice or ideas you guys may have and if it\'s possible, what the simplest lowest parts count approach would be?

Another thing I though of this morning and another thing I never messed with much are magnetic reed switches. I kinda doubt this can be
done but wonder if they make them sensitive enough to somehow react to that current draw from the supply with the right type of coil. By the way, the power supply of course has the AC mains wire but also the DC output on another cable. (Most ham xcvrs don\'t have their own power supply anymore). Long post I know but hopefully can get some input. Maybe .83 amps is too negligible?


Hi Mkr
the thing that stood out to me is you want to sense
\" the output of an amateur radio xmtr when it\'s on the air.\"
and that means knowing that normal RF signal output
is being fed to the antenna. Anything else, is just an
indirect indication. Say, there was a short or other problem
that mimicked the appearance of normal operation, an
indirect sensing method would be fooled.

I seem to recall many years ago, a hobbyist magazine
project about stealing a little signal that leaked out
from imperfect shield of the coax cable. The pickup
was a wire wrapped around the outside of the coax.
One end, fed into diode+sensitive transistor stage, and on
to panel meter.

Unless you\'re using super-high shielded coax, I think it
might work.... cheers, RS

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