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CX2SA > SATDIG 09.08.13 14:59l 916 Lines 34913 Bytes #999 (0) @ WW
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From: CX2SA@CX2SA.SAL.URY.SA
To : SATDIG@WW
Today's Topics:
1. Re: Non-mechanical Azimuth/Elevation Feedback Advice (Zach
Leffke) (Burns Fisher)
2. Re: Satellites List (Clint Bradford)
3. slightly off-topic - TerraTec dongle - SDR Sharp (Philip Jenkins)
4. Re: slightly off-topic - TerraTec dongle - SDR Sharp
(Stefan Wagener)
5. Re: Non-mechanical Azimuth/Elevation Feedback Advice
(Ing. Pavel Milanes Costa)
6. Re: Non-mechanical Azimuth/Elevation Feedback Advice (Zach Leffke)
7. Fw: Delfi C3 Close Approach Notification (Peter Portanova)
8. Re^2: Satellites List (Mineo Wakita)
9. Re: Satellites List (Clint Bradford)
10. Re: V/U Linear Transponder (Tanan Rangseeprom HS1JAN)
11. Re: Non-mechanical Azimuth/Elevation Feedback Advice
(William Herzberg)
12. magnetic reed switches for indication (Robert C. Campbell)
13. Re: magnetic reed switches f(not really needed) (Robert Bruninga)
14. Non-mechanical feedback follow up (Zach Leffke)
----------------------------------------------------------------------
Message: 1
Date: Thu, 8 Aug 2013 15:27:43 -0400
From: Burns Fisher <burns@xxxxxx.xx>
To: AMSAT BB <amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] Re: Non-mechanical Azimuth/Elevation Feedback
Advice (Zach Leffke)
Message-ID:
<CABX7KxWPMuiJ675AakU1XaRhWNiXGDcoJM585o_Lg8eXzbrSYA@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
I'm also thinking about an el cheapo rotator based on a pan/tilt base. (In
fact search el cheapo rotator for an article about doing the same thing
manually). The pan/tilt that I was going to start with does have a
"center" command as well as 4 memories where you can remember previous
positions. It is based on steppers, not A/C, though.
Anyway, I was thinking about programming 4 strategic positions into the
memories and using them with "center" to get close to where I want to be,
and then send step commands to get more exact. Requires some programming
of course, but that's what Arduinos are for!
I *like* the MEMS compass idea. Pretty cool!
Burns Fisher, W2BFJ
------------------------------
Message: 2
Date: Thu, 8 Aug 2013 12:33:09 -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:
<1423852.1375990389546.JavaMail.root@xxxxxxxxxxxxxxxx.xxx.xx.xxxxxxxxx.xxx>
Content-Type: text/plain; charset=UTF-8
>> ... I believe that you owe Mineo a very sincere apology ...
Then my writing was poor. And for that I do, indeed, apologize for. I actually
thought so much of that document that I added a link to it on my references
page of my Web site.
I was just trying to relate back when I first started to have an interest in
a specific aspect of the hobby, and started wandering the 'Net, and getting
conflicting info and - worse - outdated info to try to sift through.
As I wrote, that is a valuable, historical document.
YES, I apologize - it was not meant to demean the historical value of the
work.
Clint Bradford
909-241-7666 - cell
----------------------------------
Clint Bradford, K6LCS
http://www.clintbradford.com
------------------------------
Message: 3
Date: Thu, 8 Aug 2013 15:58:32 -0400
From: Philip Jenkins <n4hf.philip@xxxxx.xxx>
To: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] slightly off-topic - TerraTec dongle - SDR Sharp
Message-ID:
<CAGdEbNYiFHPm4pmVNrTd-=yE1Qe1PQWRZStU_iea=EBwdoQhwg@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
I've seen references to this floating by on the BB, and I know some of you
are experimenting with it, so I offered to post this for a local ham (who
is not on this BB) who is having trouble installing this dongle. I don't
have one myself - just posting for him - so please contact him directly.
Thanks
Philip N4HF
-----------------------------------------------------
Harry, KD4OQQ, hlrice@xxx.xxxx says that his is a TerraTec Plus, which he
can't find listed on the SDRSharp website. He has watched several YouTube
videos about installing, and read the documentation, but with no success.
He says that none of the LEDs are lighting, no matter what he does.
He's wondering if the dongle itself is bad, so please contact him and help
him with the troubleshooting.
------------------------------
Message: 4
Date: Thu, 8 Aug 2013 16:56:00 -0500
From: Stefan Wagener <wageners@xxxxx.xxx>
To: Philip Jenkins <n4hf.philip@xxxxx.xxx>
Cc: AMSAT BB <amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] Re: slightly off-topic - TerraTec dongle - SDR
Sharp
Message-ID:
<CAKu8kHBjGa1aWKzKjvNk2EzgnR20XjZepht2S7E5X0Hrdfos4g@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
Have him go to:
http://www.rtl-sdr.com/rtl-sdr-quick-start-guide/
I have used several of those.
Stefan, VE4NSA
On Thu, Aug 8, 2013 at 2:58 PM, Philip Jenkins <n4hf.philip@xxxxx.xxx>wrote:
> I've seen references to this floating by on the BB, and I know some of you
> are experimenting with it, so I offered to post this for a local ham (who
> is not on this BB) who is having trouble installing this dongle. I don't
> have one myself - just posting for him - so please contact him directly.
>
>
> Thanks
>
> Philip N4HF
> -----------------------------------------------------
>
> Harry, KD4OQQ, hlrice@xxx.xxxx says that his is a TerraTec Plus, which he
> can't find listed on the SDRSharp website. He has watched several YouTube
> videos about installing, and read the documentation, but with no success.
> He says that none of the LEDs are lighting, no matter what he does.
>
> He's wondering if the dongle itself is bad, so please contact him and help
> him with the troubleshooting.
> _______________________________________________
> 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, 08 Aug 2013 18:58:12 -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: <52042284.4020705@xxxxxx.xx.xx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
This is the link to the system I described in the earlier email
http://www.cbk.waw.pl/~mstolars/projekty/rotor/index_en.html
73
El 07/08/13 19:01, Ing. Pavel Milanes Costa escribi?:
> 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: 6
Date: Thu, 8 Aug 2013 19:04:27 -0400
From: "Zach Leffke" <zleffke@xx.xxx>
To: "'AMSAT BB'" <amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] Re: Non-mechanical Azimuth/Elevation Feedback
Advice
Message-ID: <000001ce948b$a2aaa360$e7ffea20$@xx.xxx>
Content-Type: text/plain; charset="us-ascii"
All,
Thanks to everyone that has responded both on and off list.
For my first attempt at finding a non-mechanical solution I plan to use the
MEMS accelerometer (for El) and magnetometer (for Az) solution. When still
exploring the Potentiometer solution, because of space requirements and
other factors I was pricing out multi turn potentiometers. For the gearing
ratios I needed, I required about a 5 turn potentiometer, which at least
according to digikey and the quick search I did, priced to about $20.00
apiece. The MEMS Magnetometer (HMC5883L) and Accelerometer (MMA8452Q) each
price out to less than $20.00 each on sparkfun, so I'll actually be saving a
few bucks.
That's the plan, at least for the first iteration. We'll see how it goes!
Thanks again to everyone!
Go Team AMSAT!
-Zach, KJ4QLP
------------------------------
Message: 7
Date: Thu, 08 Aug 2013 19:08:58 -0400
From: "Peter Portanova" <wb2oqq@xxxxxxx.xxx>
To: <AMSAT-BB@xxxxx.xxx>
Subject: [amsat-bb] Fw: Delfi C3 Close Approach Notification
Message-ID: <C70ED9D0DC30421ABCB192039188F785@xxxxxxx>
Content-Type: text/plain; charset="Windows-1252"
Subject: Delfi C3 Close Approach Notification
Sir/Ma'am,
The United States Joint Space Operations Center (JSpOC) has identified a
predicted conjunction between Delfi C3 (SCC# 32789) and SCC# 31066.
Primary Object: Delfi C3 (SCC# 32789)
Secondary Object: SCC# 31066
Time of Closest Approach: 11 AUG 2013 1:43 UTC
Overall miss distance: 190 meters
Radial (dU) miss distance: 183 meters
In-Track (dV) miss distance: -4 meters
Cross-track (dW) miss distance: -52 meters
Primary Radial Error (U): 14 meters
Primary In-track Error (V): 918 meters
Primary Cross-track Error (W): 12 meters
Secondary Radial Error (U): 57 meters
Secondary In-track Error (V): 2607 meters
Secondary Cross-track Error (W): 41 meters
Very Respectfully,
JSpOC Orbital Protection Team
Joint Space Operations Center
Vandenberg Air Force Base, California USA
NO WARRANTIES: The United States provides the enclosed Space Situational
Awareness (SSA) services or information "as is" and makes no warranty,
either express or implied, as to the condition or suitability of the
information and services, nor its fitness for a particular purpose.
IMMUNITY: The United States, any agencies and instrumentalities thereof, and
any individuals, firms, corporations, and other persons acting for the
United States, shall be immune from any suit in any court for any cause of
action arising from the provision or receipt of SSA services or information,
whether or not provided in accordance with 10 USC 2274, or any related
action or omission.
------------------------------
Message: 8
Date: Fri, 9 Aug 2013 12:49:35 +0900
From: "Mineo Wakita" <ei7m-wkt@xxxxxxxxx.xx.xx>
To: <amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] Re^2: Satellites List
Message-ID: <516B5D174FC84C7198535CAFB6031149@xxxxxxxxxxxxxx>
Content-Type: text/plain; format=flowed; charset="iso-2022-jp";
reply-type=original
Hello Clint/K6LCS, Jeff/NX9B, and all.
Please tell me if you notice the mistakes or errors in my list.
I have summarized in my web site for the latest Satellites information.
These are the result of the communication with the radio amateurs
around the world via Satellites. Please refer to them.
Thank you all.
---------------------------------------------
Name: Mineo Wakita / JE9PEL, JAMSAT member
Mail: ei7m-wkt@xxxxxxxxx.xx.xx
URL : http://www.ne.jp/asahi/hamradio/je9pel/
QTH : Yokohama Japan, GL: pm95tj
Date: 9 Aug 2013
---------------------------------------------
------------------------------
Message: 9
Date: Thu, 8 Aug 2013 22:50:51 -0700
From: Clint Bradford <clintbrad4d@xxxxxxxxx.xxx>
To: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Re: Satellites List
Message-ID: <1500D509-8BCE-4231-8FA7-7D58CEC5FEBD@xxxxxxxxx.xxx>
Content-Type: text/plain; charset=us-ascii
>> ... I have summarized in my web site for the latest Satellites
information ...
And as I have publicly stated here and privately written to you, I am in awe
of the historical
value of this document.
I started working on a "Top 250 Questions Asked of ISS Astronauts" - Q&A
from the ARISS
contacts ... thinking that that would be valuable for students (of all ages)
as a reference
work ...
Clint K6LCS
------------------------------
Message: 10
Date: Fri, 9 Aug 2013 12:02:34 +0700
From: "Tanan Rangseeprom HS1JAN" <hs1jan@xxxxxx.xxx>
To: <g0mrf@xxx.xxx>
Cc: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Re: V/U Linear Transponder
Message-ID: <E6DE20F241ED42C798D7237DA2FABEB1@xxxxxx>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
Dear David G0MRF
Thanks you very much for file present of FUNCUBE satellites. I 'm sorry for
reply to you late. I have work out of country. on august 4, 2013 have RAST
meeting. I have present for JAISAT-1 project. please you seen at web site
http://www.qsl.net/rast/ I would like answer the question.of you as
follows.
1.Thailand has regular to forbid for transmitt UHF band but can receive the
signal for amateur radio satellites only. we need to used VHF band same like
transponder FO-29 AO-51 SO-50 and other satellites. for interference from
China Thailand and other countries on VHF is normal.
2.Ok, please advice me for circuit diagram of V/U liner transponder.
3.We have to basic design FM repeater use to modify HX1 / RX2A RADIOMETRIX
VHF / UHF transmitter module we have change x-tal to 145.90 MHz used x-tal
13.59 MHz and used MC3361 with x-tal IF 10.245 MHz and CML IC FX465 CTCSS
Encode/Decode build test it to be via balloon successful.
On this time we and technical team of TAMSAT group need help very urgent. we
need advice of circuit diagram or datasheet IC for build V/U Liner
transponder for payload 1U cubesat of JAISAT-1 satellite project.
best regards
Tanan Rangseeprom HS1JAN
Project Manager of JAISAT-1
member of RAST
----- Original Message -----
From: <g0mrf@xxx.xxx>
To: <hs1jan@xxxxxx.xxx>
Sent: Monday, July 29, 2013 5:24 PM
Subject: Re: [amsat-bb] V/U Linear Transponder
Dear Tanan.
Thanks for the mail via AMSAT.org
My name is David Bowman G0MRF and I'm a member of the team building
FUNcube, due for launch this November.
I can help with transponder design, but there are some points which you
need to consider.
1) The use of V band for the uplink will be a poor choice for your
location. The interference from China and other countries on 145MHz
will mean the transponder will not be usable. Using U band for the
uplink is a much better choice.
2) The 100kHz bandwidth is too much for the typical power available
from a CubeSat. If you get your RF team to do a link budget analysis,
you will see the cubesat power budget will not support 100kHz of
bandwidth. Ususally 30kHz is as much as you can do with a 1U cube.
3) You may want to consider a FM 'repeater' as there is now only 1 in
orbit, while there are several linear transponder satellites ready to
be launched.
The FM design will allow you to run a very efficient power amplifier
(70%) and power can be saved over oceans and areas of low population by
using a 67Hz access tone (CML FX465)
I can assist with design but would need to know if you are planning a
1U 2U or 3U design.
William PE???? is good, but will probably just offer to sell you a
transponder.
Regards
David G0MRF
some old info is available at www.g0mrf.com/transponder.htm
The attached powerpoint has some pictures of the UV transponder and
other boards in FUNcube from AMSAT-UK
-----Original Message-----
From: Tanan Rangseeprom HS1JAN <hs1jan@xxxxxx.xxx>
To: amsat-bb <amsat-bb@xxxxx.xxx>
Sent: Sun, 28 Jul 2013 17:48
Subject: [amsat-bb] V/U Linear Transponder
Dear Sir;
My name Mr.Tanan Rangseeprom my callsign HS1JAN. I need help and advice
from you
for circuit diagram of V/U Liner transponder .I and team want to build
it for
payload of JAISAT-1 amateur radio satellites of Thailand. JAISAT means
is HEART
in thai language. JAISAT is Joint Academies Intelligent Satellites for
Amateur
Radio of Thailand. this is project research and developmentean consists
of RAST
and Amateur Radio University inThailand both instructor and students.
JAISAT-1 have payload liner transponder V/U uplink at 145.800 - 145.90
MHz and
Downlink at 435.10 - 435.20 MHz on CW/SSB to fit in CUBESAT design. but
this
time I and technical team have no knowledge of the circuit diagram of
liner
transponder V/U. So you can help and advice me for Electronic Circuit
Diagram of
liner transponder V/U.
Best Regards
Tanan Rangseeprom HS1JAN / XU7ADN
Project Manager of JAISAT-1
member of RAST
email : hs1jan@xxxxxx.xxx
_______________________________________________
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: 11
Date: Fri, 9 Aug 2013 00:20:48 -0700 (PDT)
From: William Herzberg <wthypsi@xxxxx.xxx>
To: "amsat-bb@xxxxx.xxxx <amsat-bb@xxxxx.xxx>, "Ing. Pavel Milanes
Costa" <co7wt@xxxxxx.xx.xx>
Subject: [amsat-bb] Re: Non-mechanical Azimuth/Elevation Feedback
Advice
Message-ID:
<1376032848.37539.YahooMailAndroidMobile@xxxxxxxxx.xxxx.xxx.xxxxx.xxx>
Content-Type: text/plain; charset=iso-8859-1
Sent from Yahoo! Mail on Android
------------------------------
Message: 12
Date: Fri, 9 Aug 2013 06:00:43 -0400
From: "Robert C. Campbell" <kb3pmr@xxxxx.xxx>
To: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] magnetic reed switches for indication
Message-ID:
<CAKdmorUwptTWJ3zOSbbk9wvdva4Uk7yWJLYaKveHcekOfYwbPw@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
I am using reed switches for both my AZ and EL visual feed back on my
newest build. I have had to slow the motors down with a PWM so that the
reeds don't skip a count. Both AZ and EL are still within the speed of
keeping up with ISS. You can determine the ratio of motor turns to one
revolution of the AZ full 360 or 90/180 for the EL and use that ratio to
determine the position in degrees. Repeat-ability seems very good. If you
are going visual/manual positioning you can check on utube or
instructables.com and find a easy build for a modified $ 2.00 Dollar
General calculator that then becomes a pulse counter by simply connecting
the enter button to your reed and entering the ratio and pressing the plus
sign. Then each rotation the calculator will tell you the degrees the
antenna is looking at. Yes, it does need reset after each pass, and yes, if
you run by the bird and go back the calculator will give you some extra
counts since it is counting reed switch contacts not true degrees of
indication. Purchase 5 of them, one for practice, 2 for EL and 2 for AL
then if you start from the same standard position each time one can add and
one can subtract. This should work fine assuming that the driver maintains
mental focus. It is a small fun project and cheaper then happy hour at the
local pub. The Pulse Width Modulator works good with this because you can
adjust the speed of the motors to keep up with the bird. This of course
assumes you are working with direct current motors.
Bob
------------------------------
Message: 13
Date: Fri, 9 Aug 2013 07:45:06 -0400
From: Robert Bruninga <bruninga@xxxx.xxx>
To: "Robert C. Campbell" <kb3pmr@xxxxx.xxx>
Cc: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Re: magnetic reed switches f(not really needed)
Message-ID:
<CALdCfN+-89VjxVp_957C0+Trx=KWYub9E1sdD4-oB3vb5SVLfQ@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
These motors run at a nearly constant rate. ALl you have to do to
know position is to keep track of the time they are on. It remains
calibated because at the end of every pass (it ends at zero elevation)
so you konw you are at 0 (include say a 10% overshoot after the pass
to be sure it is at 0).
Same for Azimuth. Each time you find yourself within 45 degrees of
the mechanical stop at south (or north), after the pass, send the
rotator to the stop with again, 10% overshoot, this re-establishes
that reference.
So, no feedback needed (for the beamwidths of VHF and UHF anyway).
Oh, and you dont need elevation at all really for all LEO satellites.
See http://aprs.org/rotator1.html
Bob, WB4APR
On Fri, Aug 9, 2013 at 6:00 AM, Robert C. Campbell <kb3pmr@xxxxx.xxx> wrote:
> I am using reed switches for both my AZ and EL visual feed back on my
> newest build. I have had to slow the motors down with a PWM so that the
> reeds don't skip a count. Both AZ and EL are still within the speed of
> keeping up with ISS. You can determine the ratio of motor turns to one
> revolution of the AZ full 360 or 90/180 for the EL and use that ratio to
> determine the position in degrees. Repeat-ability seems very good. If you
> are going visual/manual positioning you can check on utube or
> instructables.com and find a easy build for a modified $ 2.00 Dollar
> General calculator that then becomes a pulse counter by simply connecting
> the enter button to your reed and entering the ratio and pressing the plus
> sign. Then each rotation the calculator will tell you the degrees the
> antenna is looking at. Yes, it does need reset after each pass, and yes, if
> you run by the bird and go back the calculator will give you some extra
> counts since it is counting reed switch contacts not true degrees of
> indication. Purchase 5 of them, one for practice, 2 for EL and 2 for AL
> then if you start from the same standard position each time one can add and
> one can subtract. This should work fine assuming that the driver maintains
> mental focus. It is a small fun project and cheaper then happy hour at the
> local pub. The Pulse Width Modulator works good with this because you can
> adjust the speed of the motors to keep up with the bird. This of course
> assumes you are working with direct current motors.
>
> Bob
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
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------------------------------
Message: 14
Date: Fri, 9 Aug 2013 08:56:32 -0400
From: "Zach Leffke" <zleffke@xx.xxx>
To: "'AMSAT BB'" <amsat-bb@xxxxx.xxx>
Subject: [amsat-bb] Non-mechanical feedback follow up
Message-ID: <007701ce94ff$df9af990$9ed0ecb0$@xx.xxx>
Content-Type: text/plain; charset="us-ascii"
Hello again everyone,
I have received a couple of emails off list asking about
details of how I'm planning to use the magnetometer for the azimuth
feedback. Instead of individually replying I'm placing my response here so
everyone gets the same info (skip to the end of this long winded email for
the details). Before I get into that I want to address Bob's (WB4APR) note
about the constant rate of these motors. Basically, I like the idea because
of its simplicity. That's something I hadn't considered, but will look
into. My logic there is run my system through a few dozen trials to really
lock down the turn rate baseline. Then all I have to do is keep track of
the amount of time and in which direction I'm telling the motors to turn,
and voila I should know the azimuth/elevation. As Bob mentioned with the
beamwidth of these antennas that should get me close enough.
If I were only planning to use the system for tracking LEO birds at VHF/UHF
frequencies, I would probably just go with that. However, I was slightly
understating my goals when I initially brought up this issue. In addition
to LEO birds, I plan to also use this system for UAV tracking and High
Altitude Balloon Tracking. I am an EE graduate student at Virginia Tech and
each semester I help out with an Undergraduate Lab with Aerospace and EE
students that design and fly a high altitude balloon (generally with APRS
tracking and some kind of camera/sensor suite payload). One of the
professor in charge's (Dr. Dennis Sweeney, WA4LPR, some folks might know him
for his filter design work among many other things) goals is to up the data
rate in order to attempt a high speed real time data link. So in my own
time I want to use this tracking pedestal for LEO tracking (and for my
Master's Thesis prototype), but for this HAB project, the elevation can get
quite high depending on the geometry of our chase scenario, and beamwidths
can get quite small depending on the frequency we finally choose. In the
end it might not matter much, but when we get to that point I want to at
least have the OPTION for tight control over the pointing. This whole thing
will likely get vehicle mounted in the bed of my pickup, and though I
haven't completely thought out the details yet, My gut is telling me the use
of a magnetometer for azimuth feedback could have a slight advantage because
as the vehicle is moving the system could automatically compensate for the
turning of the vehicle, where as a potentiometer type solution would not.
With position updates from the HAB and a local GPS in the chase vehicle,
calculation of Az/El to the target is pretty straight forward. Combine that
with magnetometer feedback about the antennas' azimuth and elevation
feedback from an accelerometer (which should also be somewhat "self
compensating", say if the vehicle were moving up or down a hill), and I
should be able to come up with a fairly sexy tracking pedestal that
automatically compensates for the vehicle's motion to keep the antennas "on
target."
All that being said, here is my plan for the magnetometer implementation:
I don't really have the details locked down yet, but I can give the overall
plans. First I plan to use the HMC5883L from sparkfun. This device is
$14.95 + Shipping and handling. It is a 3 axis magnetometer. When dealing
with magnetometers it is important to understand whether or not your device
is tilt compensated. This particular device is NOT tilt compensated. What
that means is that it must be kept oriented parallel with the Earth (within
say maybe + or - ten degrees or so). Assuming it remains oriented properly,
the device will output (over I2C) the magnetic field strength in the X, Y,
and Z directions. The Z direction is essentially pointed straight up at
zenith (and should remain near zero since it is orthogonal to the earth's
magnetic field). Also assuming no other strong magnetic fields exist near
the sensor, it will detect Earth's magnetic field (the sensor just returns
the highest magnetic field for a particular direction, so if other magnetic
fields exist near the sensor, it can ruin the readings). In order to get
the bearing, or azimuth, information one simply has to use the atan2
function with the Y and X axes, here is the code snippet from some examples
online: heading = atan2(scaled.YAxis, scaled.XAxis). The rest is just
calibration and making sure the heading makes sense (i.e. if the heading is
a negative number add 360 to get a 0 - 360 output). One issue too is that
most satellite tracking programs return the TRUE heading or azimuth
(reference to the North Pole) to the spacecraft. This magnetometer with
produce a MAGNETIC azimuth (referenced to the magnetic pole). Thus one must
compensate for the magnetic declination of the area of operation. The
declination can be found online for each person's individual location and
can be hard coded into the code to adjust the magnetic readout to a true
readout.
Since this device is not tilt compensated I plan to mount it on my azimuth
base on a short boom that sticks straight out in front of the antenna
assembly. It will be center mounted on a non-conductive extension (maybe
two or three feet in front of the azimuth assembly). My logic here is to
try to get the sensor as far away from the AC induction motors and other
metals as I can. The AC motors will produce a strong magnetic field and if
the sensor is near them, it will distort the readings.
Thanks again to everyone that provided feedback for me. Below are a few
links that should help out those who want more details. Keep in mind too
that there is a plethora of information out there on these devices
(tutorials and example code) and with the links below and some skillful
Googling, anyone can found out everything they need to make one of these
work.
Sparkfun Link: https://www.sparkfun.com/products/10530
Bildr Tutorial: http://bildr.org/2012/02/hmc5883l_arduino/
K3NG's Arduino rotator control project:
http://blog.radioartisan.com/yaesu-rotator-computer-serial-interface/
(Thanks to Lizeth, N3YKF for pointing me in this direction)
---------------
-Zach, KJ4QLP
------------------------------
_______________________________________________
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 258
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