| |
CX2SA > SATDIG 08.08.13 21:12l 841 Lines 33081 Bytes #999 (0) @ WW
BID : AMSATBB8257
Read: GUEST
Subj: AMSAT-BB-digest V8 257
Path: IZ3LSV<IQ5KG<IK1NHL<CX2SA
Sent: 130808/1910Z @:CX2SA.SAL.URY.SA #:9497 [Salto] FBB7.00e $:AMSATBB8257
From: CX2SA@CX2SA.SAL.URY.SA
To : SATDIG@WW
Today's Topics:
1. Re: Non-mechanical Azimuth/Elevation Feedback Advice (Zach Leffke)
2. Re: Satellites List (Clint Bradford)
3. Second call for papers for 2013 AMSAT Annual Meeting and
Space Symposium (Daniel Schultz)
4. Re: Non-mechanical Azimuth/Elevation Feedback Advice
(Ing. Pavel Milanes Costa)
5. Re: Satellites List (nx9b@xxxxxxx.xxxx
6. Re: Non-mechanical Azimuth/Elevation Feedback Advice (Greg D)
7. Re: Non-mechanical Azimuth/Elevation Feedback Advice
(Gary "Joe" Mayfield)
8. ARRL Article on AO7 (k4feg)
9. D STAR Amsat users net (damon runion)
----------------------------------------------------------------------
Message: 1
Date: Wed, 7 Aug 2013 15:11:02 -0400
From: "Zach Leffke" <zleffke@xx.xxx>
To: "'Lizeth Norman'" <normanlizeth@xxxxx.xxx>
Cc: 'AMSAT BB' <amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] Re: Non-mechanical Azimuth/Elevation Feedback
Advice
Message-ID: <001b01ce93a1$dc2c94d0$9485be70$@xx.xxx>
Content-Type: text/plain; charset="us-ascii"
Hi Norm,
This looks like a fantastic starting point for me and might
have just what I need. I notice K3NG's page discusses support for a digital
compass (for az) as well as an accelerometer (for el). I haven't had the
time yet to thoroughly look through this, but at first glance it looks
nearly perfect. As you said, with some hw tweaks, it should work for my
system.
Thanks!
-Zach, KJ4QLP
From: Lizeth Norman [mailto:normanlizeth@xxxxx.xxxx
Sent: Wednesday, August 07, 2013 11:14 AM
To: Zach Leffke
Cc: AMSAT BB
Subject: Re: [amsat-bb] Non-mechanical Azimuth/Elevation Feedback Advice
Zack,
Check out K3NG's Arduino rotator control project. It incorporates the proper
sensors and should, with the proper interface hardware, drive your hardware.
I'm in the process of a build myself.
Norm n3ykf
On Wed, Aug 7, 2013 at 9:58 AM, Zach Leffke <zleffke@xx.xxx
<mailto:zleffke@xx.xxx> > wrote:
Hello Everyone,
I recently came into possession of a Pelco PT170-24P
tracking pan tilt pedestal designed to support large security cameras. My
intent with this new acquisition is to repurpose it as a "low cost" (got it
on Ebay for ~$75 + S&H) alternative for an antenna tracking pedestal for
amateur satellites. It uses 24VAC induction motors to move the azimuth and
elevation assemblies, pretty much just like the G5500s that I'm sure so many
of us are familiar with. It definitely cannot support the same amount of
weight as the G5500, but I'm looking to construct a small, portable
satellite ground station node and this thing is plenty beefy enough to
handle a couple of Arrow style antennas. Here is the problem, it provides
absolutely no feedback.
My question to the group is does anyone know of a non-mechanical method for
getting relatively accurate feedback for azimuth and elevation. I'm looking
for an all electronic means that I can mount somewhere outside of the actual
pedestal assembly (like perhaps on the cross-boom) that will be able to
provide measurement of the az/el (or pan/tilt, or yaw/pitch, whatever you
want to call it) position. I'm using an arduino microcontroller for the
tracking controller. Originally I intended to find a way to mount
potentiometers in inside the unit and simply use the ADCs on the arduino to
read the position feedback voltage from the pots, however, there is barely
enough space to mount an elevation feedback pot inside the unit, and there
is virtually no space for an azimuth feedback pot. Hence I'm looking for a
non-mechanical method.
My first thoughts for the elevation feedback was to use the old
potentiometer plus nice heavy weight method mounted out on the boom. This
idea doesn't appeal to me very much as other factors can now affect the
position feedback (such as high winds). I then thought of something along
the lines of an accelerometer. I also tossed around the idea of a 2-axis
gyro for both Az/El. My issue is I have limited experience working with
these types of sensors, and was hoping to get advice from everyone in this
group. I know for example that the gyro will provide rate of motion around
an axis and thus I have to integrate over time to get the actual position.
This becomes cumbersome because now I have to keep track of time in the
Arduino while executing movement commands (certainly do-able, just more
complicated than reading an ADC voltage). Additionally, I believe these
devices suffer from drift and require frequent calibration (although there
may be a scheme of starting from a known position, say at one of the limit
switch contact points, for each pass that might work). I also toyed with
the idea of an electric compass for azimuth feedback, but I'm worried about
distortion of the magnetic field near the pedestal due to the AC induction
motors or when the antennas are radiating. In theory the motors are housed
inside the metal pedestal enclosure and thus are shielded from the outside
world, but I can just see it now, nice steady feedback when the pedestal is
stopped and as soon as I execute a motion command the azimuth feedback
starts dancing all over the place. Since the motion stop command is based
on achieving the target position, system instability is sure to occur. Even
if I solve the AC motor EMI problem, I still worry that when transmitting
the fields could potentially be distorted if near the antenna (remember my
goal is a compact design) and taint the position feedback.
Any ideas from the group would be greatly appreciated. I'm looking for a
"sparkfun" type solution here and if anyone has experience working with
accelerometers, gyros, electric compasses, etc. I would love your advice on
which might be the way to go for the position feedback. If you think I've
hit on a good idea above and should go with it please let me know. Again
I'm using an Arduino, so analog voltage feedback, I2C, SPI, and UART serial
are all on the table for communicating with the sensors to get the feedback
info.
Thanks in advance!
Sincerely,
Zach, KJ4QLP
_______________________________________________
Sent via AMSAT-BB@xxxxx.xxx <mailto:AMSAT-BB@xxxxx.xxx> . Opinions expressed
are those of the author.
Not an AMSAT-NA member? Join now to support the amateur satellite program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
------------------------------
Message: 2
Date: Wed, 7 Aug 2013 13:35:03 -0700 (GMT-07:00)
From: Clint Bradford <clintbrad4d@xxxxxxxxx.xxx>
To: amsat-bb@xxxxx.xxxx amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Re: Satellites List
Message-ID:
<13404444.1375907704098.JavaMail.root@xxxxxxxxxxxxxx.xxx.xx.xxxxxxxxx.xxx>
Content-Type: text/plain; charset=UTF-8
This compilation reflects an awful lot of work - and you are to be
complimented for creating it. But it troubles me:
When I was new to the amateur satellites seven or eight years ago, it
was this kind of list that frustrated me, because it is, for the most part,
absolutely worthless to anyone wanting to work the currently available
amateur satellites.
Your work is a reflection of history. And is important. But I wish it had
a preface of some sort, telling viewers that is is a historical document,
and to point readers who are looking for CURRENT satellite information to
appropriate sources of information.
It was after programming MANY satellites I found during Internet searches
that I later found out were LONG DEAD that I created my meager Web site,
catering to those who wanted to work the FM birds "this week" with minimal
equipment.
Again - your compilation is a valuable, historical document. Thank you
for your work.
Clint Bradford, K6LCS
http://www.work-sat.com
909-241-7666 - cell
----------------------------------
Clint Bradford, K6LCS
http://www.clintbradford.com
------------------------------
Message: 3
Date: Wed, 07 Aug 2013 17:51:27 -0400
From: "Daniel Schultz" <n8fgv@xxx.xxx>
To: <amsat-bb@xxxxx.xxx>, amsat-fox <amsat-fox@xxxx.xxx.xxx>
Cc: sarex@xxxxx.xxxx amsat-dc@xxxxx.xxx
Subject: [amsat-bb] Second call for papers for 2013 AMSAT Annual
Meeting and Space Symposium
Message-ID: <393RHgVYb1552S06.1375912287@xxxxx.xxx.xxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
This is the second call for papers for the 2013 AMSAT Annual Meeting and Space
Symposium to be held on the weekend of November 1 - 3, 2013, at the Marriott
Hobby Airport Hotel, Houston, Texas. Proposals for papers, symposium
presentations and poster presentations are invited on any topic of interest to
the amateur satellite community. We request a tentative title of your
presentation as soon as possible, with final copy to be submitted by October 1
for inclusion in the printed proceedings. Abstracts and papers should be sent
to Dan Schultz at n8fgv@xxxxx.xxx
Dan Schultz N8FGV
------------------------------
Message: 4
Date: Wed, 07 Aug 2013 19:01:23 -0400
From: "Ing. Pavel Milanes Costa" <co7wt@xxxxxx.xx.xx>
To: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Re: Non-mechanical Azimuth/Elevation Feedback
Advice
Message-ID: <5202D1C3.4030209@xxxxxx.xx.xx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Yes, me to...
I do have a old Japanese tracking camera mounting also with 24 AC motors
here... 360 degrees azimuth with stop switch on 0 and 360 degrees and
about 0 to 120 degrees of elevation (0 ~ horizon, 90 ~cenit)
Pretty good construction, a ham here in Havana have one the uses to move
2 phased yaguis of 5 elements for 2m... the brake system is primitive
but works fine...
Pointing is by eye and as in your case no means of feedback... recently
after completing some TODO-IN-THE-FUTURE projects with Jal/JalLib (Just
Another Language and libs for PIC devices) and pics I get hands on this
project
A couple o months or so (maybe more) there was a thread on the list
about this...
I find the arduino project from K3NG, but no arduino here, only
Microchip PIC (PIC18F4520) so I have to re-invent the wheel...
I was thinking on gray encoding the position with 7 bits, but this is A
LOT of cables to run..
Then I see on the specs of the arduino a feedback mechanism of pulse
counting... and find on the internet a project from a polish? ham that
uses this mechanism wit a ATMEGA MCU but with a trick... (I have the
link on my work place... link will be tomorrow)
I explain, he uses several magnets glued on the edge of an intermediate
gear in the reduction mechanism... then get a magnetic switch (or a hal
sensing device if you like) close to the edge where the magnets are...
This mechanism do about 500+ pulses for each 360 degrees... pretty neat
an simple... with only 2 cables...
The only thing is you have to reset the mechanical position of the
antennas at each power-on to reset the internal count in the
pic/arduino/atmega MCU...
I'm on the ideas-on-the-boad part of this project for making it 450
degrees instead of only 360 and how to deal in software with the 0 to 90
degrees restriction on the elevation part...
Just another idea to the brain storm...
73 de CO7WT.
PS: control will be serial emulating a RS232B protocol from Yaesu...
El 07/08/13 09:58, Zach Leffke escribi?:
> Hello Everyone,
>
> I recently came into possession of a Pelco PT170-24P
> tracking pan tilt pedestal designed to support large security cameras. My
> intent with this new acquisition is to repurpose it as a "low cost" (got it
> on Ebay for ~$75 + S&H) alternative for an antenna tracking pedestal for
> amateur satellites. It uses 24VAC induction motors to move the azimuth and
> elevation assemblies, pretty much just like the G5500s that I'm sure so many
> of us are familiar with. It definitely cannot support the same amount of
> weight as the G5500, but I'm looking to construct a small, portable
> satellite ground station node and this thing is plenty beefy enough to
> handle a couple of Arrow style antennas. Here is the problem, it provides
> absolutely no feedback.
>
>
>
> My question to the group is does anyone know of a non-mechanical method for
> getting relatively accurate feedback for azimuth and elevation. I'm looking
> for an all electronic means that I can mount somewhere outside of the actual
> pedestal assembly (like perhaps on the cross-boom) that will be able to
> provide measurement of the az/el (or pan/tilt, or yaw/pitch, whatever you
> want to call it) position. I'm using an arduino microcontroller for the
> tracking controller. Originally I intended to find a way to mount
> potentiometers in inside the unit and simply use the ADCs on the arduino to
> read the position feedback voltage from the pots, however, there is barely
> enough space to mount an elevation feedback pot inside the unit, and there
> is virtually no space for an azimuth feedback pot. Hence I'm looking for a
> non-mechanical method.
>
>
>
> My first thoughts for the elevation feedback was to use the old
> potentiometer plus nice heavy weight method mounted out on the boom. This
> idea doesn't appeal to me very much as other factors can now affect the
> position feedback (such as high winds). I then thought of something along
> the lines of an accelerometer. I also tossed around the idea of a 2-axis
> gyro for both Az/El. My issue is I have limited experience working with
> these types of sensors, and was hoping to get advice from everyone in this
> group. I know for example that the gyro will provide rate of motion around
> an axis and thus I have to integrate over time to get the actual position.
> This becomes cumbersome because now I have to keep track of time in the
> Arduino while executing movement commands (certainly do-able, just more
> complicated than reading an ADC voltage). Additionally, I believe these
> devices suffer from drift and require frequent calibration (although there
> may be a scheme of starting from a known position, say at one of the limit
> switch contact points, for each pass that might work). I also toyed with
> the idea of an electric compass for azimuth feedback, but I'm worried about
> distortion of the magnetic field near the pedestal due to the AC induction
> motors or when the antennas are radiating. In theory the motors are housed
> inside the metal pedestal enclosure and thus are shielded from the outside
> world, but I can just see it now, nice steady feedback when the pedestal is
> stopped and as soon as I execute a motion command the azimuth feedback
> starts dancing all over the place. Since the motion stop command is based
> on achieving the target position, system instability is sure to occur. Even
> if I solve the AC motor EMI problem, I still worry that when transmitting
> the fields could potentially be distorted if near the antenna (remember my
> goal is a compact design) and taint the position feedback.
>
>
>
> Any ideas from the group would be greatly appreciated. I'm looking for a
> "sparkfun" type solution here and if anyone has experience working with
> accelerometers, gyros, electric compasses, etc. I would love your advice on
> which might be the way to go for the position feedback. If you think I've
> hit on a good idea above and should go with it please let me know. Again
> I'm using an Arduino, so analog voltage feedback, I2C, SPI, and UART serial
> are all on the table for communicating with the sensors to get the feedback
> info.
>
>
>
> Thanks in advance!
>
>
>
> Sincerely,
>
> Zach, KJ4QLP
>
>
>
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>
------------------------------
Message: 5
Date: Thu, 8 Aug 2013 00:43:18 +0000 (UTC)
From: nx9b@xxxxxxx.xxx
To: AMSAT-BB@xxxxx.xxx
Subject: [amsat-bb] Re: Satellites List
Message-ID:
<567999681.391889.1375922598925.JavaMail.root@xxxxxxx.xxxxxxxxxxx.xx.xxxx.xxxx
xxx.xxx>
Content-Type: text/plain; charset=utf-8
Clint, K6LCS, I would normally not ever reply to anyone else's responses to
BB postings but I could not let this one go.
I believe that you owe Mineo a very sincere apology for your scathing
response to his satellites list.
I'm sure that you feel that your information is better for the newer
satellite operators, and while that may be true, I found Mineo's posting
very informative.
Not only that, the one thing that you were criticizing the list for is
there, but you apparently didn't see it for yourself.
If you look at the very last column it clearly states Active with an * by
each one that has that status.
Both the .xls & .html versions have this column, so what information that
you thought would be the most helpful IS on the list.
I'm sorry if you are offended by someone 'calling you out' on the BB, but
this is one time I just couldn't sit idly by.
If you feel the need to respond, you can do it here on the BB or personally
at 'my call'@xxxxxxx.xxx
Sincerely,
Jeff Lamb, NX9B, EM66sj61pe
73!
------------------------------
Message: 6
Date: Wed, 07 Aug 2013 20:11:18 -0700
From: Greg D <ko6th.greg@xxxxx.xxx>
To: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Re: Non-mechanical Azimuth/Elevation Feedback
Advice
Message-ID: <52030C56.3060002@xxxxx.xxx>
Content-Type: text/plain; charset=iso-8859-1; format=flowed
Yes, indeed the fine art of pulse counting works very well. My rotor
controller does the same with the "clicker" kind of rotors, where the
contacts were intended to drive a solenoid ratchet switch mechanism for
positioning. Instead of the Arduino, I used a Basic Stamp (this is
pre-Arduino heritage), but the pulses are 6-10 degrees apart. 500 per
360 degrees would be too fast for this little squirrel.
Good luck with your projects.
Greg KO6TH
Ing. Pavel Milanes Costa wrote:
> Yes, me to...
>
> I do have a old Japanese tracking camera mounting also with 24 AC
> motors here... 360 degrees azimuth with stop switch on 0 and 360
> degrees and about 0 to 120 degrees of elevation (0 ~ horizon, 90 ~cenit)
>
> Pretty good construction, a ham here in Havana have one the uses to
> move 2 phased yaguis of 5 elements for 2m... the brake system is
> primitive but works fine...
>
> Pointing is by eye and as in your case no means of feedback...
> recently after completing some TODO-IN-THE-FUTURE projects with
> Jal/JalLib (Just Another Language and libs for PIC devices) and pics I
> get hands on this project
>
> A couple o months or so (maybe more) there was a thread on the list
> about this...
>
> I find the arduino project from K3NG, but no arduino here, only
> Microchip PIC (PIC18F4520) so I have to re-invent the wheel...
>
> I was thinking on gray encoding the position with 7 bits, but this is
> A LOT of cables to run..
>
> Then I see on the specs of the arduino a feedback mechanism of pulse
> counting... and find on the internet a project from a polish? ham
> that uses this mechanism wit a ATMEGA MCU but with a trick... (I have
> the link on my work place... link will be tomorrow)
>
> I explain, he uses several magnets glued on the edge of an
> intermediate gear in the reduction mechanism... then get a magnetic
> switch (or a hal sensing device if you like) close to the edge where
> the magnets are...
>
> This mechanism do about 500+ pulses for each 360 degrees... pretty
> neat an simple... with only 2 cables...
>
> The only thing is you have to reset the mechanical position of the
> antennas at each power-on to reset the internal count in the
> pic/arduino/atmega MCU...
>
> I'm on the ideas-on-the-boad part of this project for making it 450
> degrees instead of only 360 and how to deal in software with the 0 to
> 90 degrees restriction on the elevation part...
>
> Just another idea to the brain storm...
>
> 73 de CO7WT.
>
> PS: control will be serial emulating a RS232B protocol from Yaesu...
>
> El 07/08/13 09:58, Zach Leffke escribi?:
>> Hello Everyone,
>>
>> I recently came into possession of a Pelco PT170-24P
>> tracking pan tilt pedestal designed to support large security
>> cameras. My
>> intent with this new acquisition is to repurpose it as a "low cost"
>> (got it
>> on Ebay for ~$75 + S&H) alternative for an antenna tracking pedestal for
>> amateur satellites. It uses 24VAC induction motors to move the
>> azimuth and
>> elevation assemblies, pretty much just like the G5500s that I'm sure
>> so many
>> of us are familiar with. It definitely cannot support the same
>> amount of
>> weight as the G5500, but I'm looking to construct a small, portable
>> satellite ground station node and this thing is plenty beefy enough to
>> handle a couple of Arrow style antennas. Here is the problem, it
>> provides
>> absolutely no feedback.
>>
>>
>>
>> My question to the group is does anyone know of a non-mechanical
>> method for
>> getting relatively accurate feedback for azimuth and elevation. I'm
>> looking
>> for an all electronic means that I can mount somewhere outside of the
>> actual
>> pedestal assembly (like perhaps on the cross-boom) that will be able to
>> provide measurement of the az/el (or pan/tilt, or yaw/pitch, whatever
>> you
>> want to call it) position. I'm using an arduino microcontroller for the
>> tracking controller. Originally I intended to find a way to mount
>> potentiometers in inside the unit and simply use the ADCs on the
>> arduino to
>> read the position feedback voltage from the pots, however, there is
>> barely
>> enough space to mount an elevation feedback pot inside the unit, and
>> there
>> is virtually no space for an azimuth feedback pot. Hence I'm looking
>> for a
>> non-mechanical method.
>>
>>
>>
>> My first thoughts for the elevation feedback was to use the old
>> potentiometer plus nice heavy weight method mounted out on the boom.
>> This
>> idea doesn't appeal to me very much as other factors can now affect the
>> position feedback (such as high winds). I then thought of something
>> along
>> the lines of an accelerometer. I also tossed around the idea of a
>> 2-axis
>> gyro for both Az/El. My issue is I have limited experience working with
>> these types of sensors, and was hoping to get advice from everyone in
>> this
>> group. I know for example that the gyro will provide rate of motion
>> around
>> an axis and thus I have to integrate over time to get the actual
>> position.
>> This becomes cumbersome because now I have to keep track of time in the
>> Arduino while executing movement commands (certainly do-able, just more
>> complicated than reading an ADC voltage). Additionally, I believe these
>> devices suffer from drift and require frequent calibration (although
>> there
>> may be a scheme of starting from a known position, say at one of the
>> limit
>> switch contact points, for each pass that might work). I also toyed
>> with
>> the idea of an electric compass for azimuth feedback, but I'm worried
>> about
>> distortion of the magnetic field near the pedestal due to the AC
>> induction
>> motors or when the antennas are radiating. In theory the motors are
>> housed
>> inside the metal pedestal enclosure and thus are shielded from the
>> outside
>> world, but I can just see it now, nice steady feedback when the
>> pedestal is
>> stopped and as soon as I execute a motion command the azimuth feedback
>> starts dancing all over the place. Since the motion stop command is
>> based
>> on achieving the target position, system instability is sure to
>> occur. Even
>> if I solve the AC motor EMI problem, I still worry that when
>> transmitting
>> the fields could potentially be distorted if near the antenna
>> (remember my
>> goal is a compact design) and taint the position feedback.
>>
>>
>>
>> Any ideas from the group would be greatly appreciated. I'm looking
>> for a
>> "sparkfun" type solution here and if anyone has experience working with
>> accelerometers, gyros, electric compasses, etc. I would love your
>> advice on
>> which might be the way to go for the position feedback. If you think
>> I've
>> hit on a good idea above and should go with it please let me know.
>> Again
>> I'm using an Arduino, so analog voltage feedback, I2C, SPI, and UART
>> serial
>> are all on the table for communicating with the sensors to get the
>> feedback
>> info.
>>
>>
>>
>> Thanks in advance!
>>
>>
>>
>> Sincerely,
>>
>> Zach, KJ4QLP
>>
>>
>>
>> _______________________________________________
>> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
>> Not an AMSAT-NA member? Join now to support the amateur satellite
>> program!
>> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>>
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite
> program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
------------------------------
Message: 7
Date: Wed, 7 Aug 2013 23:15:01 -0500
From: "Gary \"Joe\" Mayfield" <gary_mayfield@xxxxxxx.xxx>
To: "'Zach Leffke'" <zleffke@xx.xxx>, "'AMSAT BB'"
<amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] Re: Non-mechanical Azimuth/Elevation Feedback
Advice
Message-ID: <BAY173-DS402D2B5ABE3D32610F2DE8A5F0@xxx.xxx>
Content-Type: text/plain; charset="us-ascii"
Maybe someone can dig the archives better than me, but I remember there was
an elegant solution years ago.
Part of a thread can be found here:
http://www.amsat.org/amsat/archive/amsat-bb/200101/msg00697.html
73,
Joe kk0sd
-----Original Message-----
From: amsat-bb-bounces@xxxxx.xxx [mailto:amsat-bb-bounces@xxxxx.xxxx On
Behalf Of Zach Leffke
Sent: Wednesday, August 07, 2013 8:58 AM
To: 'AMSAT BB'
Subject: [amsat-bb] Non-mechanical Azimuth/Elevation Feedback Advice
Hello Everyone,
I recently came into possession of a Pelco PT170-24P
tracking pan tilt pedestal designed to support large security cameras. My
intent with this new acquisition is to repurpose it as a "low cost" (got it
on Ebay for ~$75 + S&H) alternative for an antenna tracking pedestal for
amateur satellites. It uses 24VAC induction motors to move the azimuth and
elevation assemblies, pretty much just like the G5500s that I'm sure so many
of us are familiar with. It definitely cannot support the same amount of
weight as the G5500, but I'm looking to construct a small, portable
satellite ground station node and this thing is plenty beefy enough to
handle a couple of Arrow style antennas. Here is the problem, it provides
absolutely no feedback.
My question to the group is does anyone know of a non-mechanical method for
getting relatively accurate feedback for azimuth and elevation. I'm looking
for an all electronic means that I can mount somewhere outside of the actual
pedestal assembly (like perhaps on the cross-boom) that will be able to
provide measurement of the az/el (or pan/tilt, or yaw/pitch, whatever you
want to call it) position. I'm using an arduino microcontroller for the
tracking controller. Originally I intended to find a way to mount
potentiometers in inside the unit and simply use the ADCs on the arduino to
read the position feedback voltage from the pots, however, there is barely
enough space to mount an elevation feedback pot inside the unit, and there
is virtually no space for an azimuth feedback pot. Hence I'm looking for a
non-mechanical method.
My first thoughts for the elevation feedback was to use the old
potentiometer plus nice heavy weight method mounted out on the boom. This
idea doesn't appeal to me very much as other factors can now affect the
position feedback (such as high winds). I then thought of something along
the lines of an accelerometer. I also tossed around the idea of a 2-axis
gyro for both Az/El. My issue is I have limited experience working with
these types of sensors, and was hoping to get advice from everyone in this
group. I know for example that the gyro will provide rate of motion around
an axis and thus I have to integrate over time to get the actual position.
This becomes cumbersome because now I have to keep track of time in the
Arduino while executing movement commands (certainly do-able, just more
complicated than reading an ADC voltage). Additionally, I believe these
devices suffer from drift and require frequent calibration (although there
may be a scheme of starting from a known position, say at one of the limit
switch contact points, for each pass that might work). I also toyed with
the idea of an electric compass for azimuth feedback, but I'm worried about
distortion of the magnetic field near the pedestal due to the AC induction
motors or when the antennas are radiating. In theory the motors are housed
inside the metal pedestal enclosure and thus are shielded from the outside
world, but I can just see it now, nice steady feedback when the pedestal is
stopped and as soon as I execute a motion command the azimuth feedback
starts dancing all over the place. Since the motion stop command is based
on achieving the target position, system instability is sure to occur. Even
if I solve the AC motor EMI problem, I still worry that when transmitting
the fields could potentially be distorted if near the antenna (remember my
goal is a compact design) and taint the position feedback.
Any ideas from the group would be greatly appreciated. I'm looking for a
"sparkfun" type solution here and if anyone has experience working with
accelerometers, gyros, electric compasses, etc. I would love your advice on
which might be the way to go for the position feedback. If you think I've
hit on a good idea above and should go with it please let me know. Again
I'm using an Arduino, so analog voltage feedback, I2C, SPI, and UART serial
are all on the table for communicating with the sensors to get the feedback
info.
Thanks in advance!
Sincerely,
Zach, KJ4QLP
_______________________________________________
Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
Not an AMSAT-NA member? Join now to support the amateur satellite program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
------------------------------
Message: 8
Date: Thu, 08 Aug 2013 01:18:20 -0500
From: k4feg <k4feg@xxxxx.xxx>
To: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] ARRL Article on AO7
Message-ID: <5203382C.7080204@xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hello Satellite Lovers!!
Well it is nice to see that I have risen to the level of being "quoted"
by the ARRL, they got most of the stuff essentially correct but did not
get it completely right:
/*What we know for certain about AO7:*/
1) there are ZERO batteries working!
2) it only works when it has enough solar power generated to make it
operational.
3) it was only in Eclipse for periods of a maximum of 15 minutes during
each orbit and only during the period I refer to as the "Eclipse Cycle"
which occurs at the same approximate time each year for about 9 weeks.
My additional conversations with Jan A. King, W3GEY, have provided me
with additional information about the design and I have found it most
intriguing. I have considered writing a more detailed paper centered
around my conversations with Jan, and my personal observations of the
operations.
/
//I just am not sure if anyone is particularly interested in such a
detailed account of AO7's current state of operation./
Many of you have read my running accounts of AO7 operations this year
since the Eclipse Cycle began and subsequently ended. Many of you have
provided excellent insight as to why the Doppler shift varies as much as
it does after these Eclipse Periods and also the theories as to why the
distortion levels occur on some satellite passes and not others.
Thank you all that have contributed to the debate and the study.
I Hope I have not bored everyone with my posts about AO7, simply the
most successful satellite ever launched!
/*73 ALL FRM*//*
*//*STARCOM DIV GGG*//*
*//*K4FEG*//*
*//*GGHQ: Em55aj84ta*//**/
/...no grid left behind.../
------------------------------
Message: 9
Date: Thu, 8 Aug 2013 08:47:13 -0500
From: damon runion <damonwa4hfn@xxxxx.xxx>
To: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] D STAR Amsat users net
Message-ID:
<CACNBj2o_Q275__GXxPu8Wz7mHD9j5VEp6XyvF574WBvnpVfQRg@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
If all works tonight and our local repeater will stay connected, I
will call the net at 0100 utc on REF60B. I have a helper tonight that
will not only be on RF, but will be on line with a DV Dongle, to help
monitor.
Frank K4FEG will run the DRATSAMSAT side.
Thank you
WA4HFN em55 Damon
------------------------------
_______________________________________________
Sent via amsat-bb@xxxxx.xxx. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
http://amsat.org/mailman/listinfo/amsat-bb
End of AMSAT-BB Digest, Vol 8, Issue 257
****************************************
Read previous mail | Read next mail
| |
