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SARCNET
Published by Julie & Joe in News · 24 August 2019
Welcome to the SARCNET Forum. Forums are a great way to get the latest information from us and let all our readers know what you think. We changed from using phpBB to WebSite X5 on 24/8/2019. We hope you like the new format and we look forward to reading your posts.

This Forum is just for general comments like:
  • What you like or dislike about our site.
  • Something you would like to see or prefer not to see.
  • Ideas and suggestions.
  • Corrections and broken links.
  • Requests for new Forums on a different subject.
  • Requests for more information, links or new projects.

Because this is a child-aware site, with strict content and privacy policies, we will 100% review all posts before they are published. We may contact you with questions like: Do you have parental permission to publish those photos or do you mind if we rephrase your comments about X without using words like Y and Z.  

Kind regards, Julie VK3FOWL and Joe VK3YSP.


14
reviews

Denis Brown
27 Aug 2019
Hello Julie and Joe

Maybe I am an "early adopter" of your new forum format hi hi. Is the technical (phpBB) forum still available for the exchange of technical questions, construction notes, etc which are then visible to all other forum registrants? I wanted to comment that in my build of the Mk1 rotator I am going to include an LM7809 style voltage regulator fed from the 12 volt motor power source, feeding into the Pro Micro's RAW pin. The idea here is that in the event that 12 volts is applied and the USB power disappears - flat laptop battery, disconnected USB cable, etc - there is no concern about the driver board feeding back into the Arduino's I/O pins. In the absence of a controlling PC, the Arduino would enter a pause state so no danger of the motors being activated and creating havoc.

73
Denis VK6AKR
Julie & Joe
27 Aug 2019
Hi Denis,
That makes three of us. The new format is different and takes a bit of getting used to. There is a forum called “SARCNET Mini Satellite-Antenna Rotator Mk1” in the satellites category. We have copied all your phpBB posts there. The regulator sounds like a good idea. We will comment on it there too.
Kind regards,
Julie and Joe.
20 Oct 2019
Hi Joe and Julie, just letting you know I have advertised your attendance and work at this year's SPARC Rosebud RadioFest. Thanks for your terrific support, looking forward to catching up with you both on November 17th. Cheers, Mark VK3PDG.
Julie & Joe
20 Oct 2019
Hi Mark,
The Rosebud RadioFest is in our opinion one of the best organised Amateur Radio events in the country. Congratulations to you and the SPARC team for doing all the hard work. We will be delighted to attend.
Kind regards,
Julie and Joe.
John Pigott
26 Apr 2021
Any idea when the Mk2 rotator will be upgraded to hamlib 4.1 (already released) ?
Also any recommendation for a low cost handheld that will work with ut ?
Julie and Joe
26 Apr 2021
Hi John,
The process for the update to HAMLIB 4.x will be straightforward for the user: Download a sarctrac file from our website; copy it to the root folder of the SARCTRAC USB Disk; insert into SARCTRAC and power up with an Internet connection; wait (~10 minutes) for the beep then check the version number. We have tested our field-update scripts on version 3.3 and they works OK. However, HAMLIB 4.x was released while we were busy in production and we haven’t started putting together the update scripts and the new radiocap.txt file for it. Unfortunately, HAMLIB must be downloaded, compiled from source, and configured on your SARCTRAC platform. The new radiocap.txt file is created here with a script we wrote to interrogate HAMLIB for all available rigs and to sort them into categories. We will have to create/modify and thoroughly test all these scripts to do this. Probably, there will be some changes to HAMLIB, which we will also have to accommodate. It is an engineering task, which we will do carefully and which will take us some time. We will be busy with shipping for a while, then we have some other school tasks, so it may take us a few months to complete. We are already thinking of SARCTRAC Mk3 for next year. It might be part of that. We will then let everyone know when it is ready.
73, Julie and Joe
Amey Pandit
22 Aug 2021
Hello Julie and Joe

Thank you for the wonderful project. I finally got the 0.6rpm motors and now building the rotator. Construction is complete and now I am working on calibration. I am facing a small issue with it. I followed all calibration the steps mentioned on the Rotator MK1b design page. After I complete the calibration when I enter m command, I see that my elevation angle is okay. It is in line with the elevation of sensor. But the Azimuth is not correct. The values does not correspond to actual value of azimuth that sensor is pointing to. When I point it towards North, I see 0 deg but then value jumps randomly. Also when I change to N-E or N-W the sensor value does not change. Kindly let me know if such observations are seen by other users or is there any fault with sensor. I tried to do the caibration multiple times, even in open areas.

Thanks in advance

73s
Amey
(VU2YQ)
Julie and Joe
22 Aug 2021
Hi Amey,
Thank you for your kind words and good job on completing the project! Since EL is working, the problem you have could be associated with a defective sensor axis. The best way to check this is to hold the sensor in your hand and use the 'd' command to display the raw sensor data, as shown here: https://www.sarcnet.org/rotator-mk1.html#SetToWork1. The data displayed is the value from the 3 magnetic axes (mx, my, mz) and the 3 gravitational axes (gx, gy and gz). Note the axis transformations here: https://www.sarcnet.org/rotator-mk1.html#SensorOrientation. When you point each sensor axis along and opposite the magnetic field, in your area, the corresponding m values should swing from a large +ve number to a large -ve number. When you point each sensor axis vertically up or down the the corresponding g values should swing from a large +ve number to a large -ve number. Check the maximum +ve and minimum -ve values have approximately the same magnitude +/- 10%. If everything is OK here, we can proceed to the next test. We have seen one or two defective sensors like this.
73, Julie and Joe.
Amey Pandit
25 Aug 2021
Hello Julie and Joe

I tried the step mentioned in your comment earlier. I do not see any change in values of magnetic axes for e.g.
-8,-4,0,5460,-6690,-6048
-8,-4,0,5603,-6980,-5925
-8,-4,0,5768,-7267,-5780

The magnetic sensor values doesn't change irrespective of sensor orientation. Whereas, the g axes values change from large +ve to -ve values as I point it vertically upward or downward.

Does this mean the sensor has some issue w.r.t magnetic axes?

Thanks
Amey
Julie and Joe
25 Aug 2021
Hi Amey,
Please check you have a LSM303DLHC sensor and it is configured correctly in rotator6.ino like this:
const int SensorType = LSM303DLHC; //Please uncomment this line to use the LSM303DLHC sensor.
However, configuring the wrong sensor would normally displays 0's for each value.
Unchanging values could also indicate that the sensor is in the presence of a strong magnetic field, but the values are low, so it is not that.
A very long, or shielded, I2C cable could cause read errors, but that is unlikely.
Try holding a magnet near the sensor: If the values do change a little bit it is not a read error.
It could be as we feared: A defective magnetometer. We had, maybe, 1 in 200 fail like this, but then it was only one axis, not all three.
Good luck and keep in touch.
73, Julie and Joe
Amey Pandit
26 Aug 2021
Hello Julie and Joe

Thanks for the support all through the debugging session :)
Yes. Firmware is okay w.r.t Sensor type. When I hold a strong magnet close by, the magnetic axes values changes. So I guess that indicates a defective sensor. I have ordered a new one. I shall let you know once test with new one

73s
Amey
Amey Pandit
28 Aug 2021
Hello Julie and Joe

Today I received my replacement sensor. I first did the test (which you mentioned earlier) on the sensor and yes it is working. So I went ahead with the calibration and now AZ and EL values are working fine. Also when I give the command the rotator is pointing correctly. I shall do further testing with GPredict and also share pics of the setup via email

Thank you very much

73s
Amey
Julie and Joe
28 Aug 2021
Hi Amey,
That is great news! You were unlucky, though. Getting a bad sensor is rare. Yes, we would like to see pictures of your project. Well done.
73, Julie and Joe.
Julie and Joe
01 Sep 2021
Hi again Amey.
We would like to provide this update: We recently purchased on eBay from China, Qty 120, GY-511, 3D sensor modules with the LSM303DLHC MEMS sensor on it. When we found one failure we decided to test the whole batch. The results were very disappointing to say the least. Over 10% of the devices were defective in some way! 7 units had weak magnetometer outputs, like yours. 3 units had the mz output stuck. 2 units displayed exactly the same data for the magnetometer as the accelerometer (which is really bizarre). In the future we will be buying 10% extra and testing 100%.
73, Julie and Joe.
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