SatNOGS rotator Version 3

Basic potentiometers work quite well in this application. You can buy slightly more expensive 3 turn or 10 turn precision potentiometers

If the potentiometer goes faulty you can detect that, and stop and give an error. Many commercial units do that, basically if they should be moving, and there is no change in feedback, they stop. The same is true for any feedback system.

There are some fairly low cost digital precision units for pedal sensors for car accelerator pedals, and others based on just a digital hall chip near a magnet. For digital it would work out as 20 to 50 Euro for a set. The more you gear them down afterwards the more precision they gain, but they would need to be multi-turn.

Absolute position feedback: Youre right. Although “rather” expensive (5-10) Euro per good multiturn potentionmeter it looks like the best way. I found them cheaply in one store (http://www.reichelt.de/Mehrgang-Potis/534-1-0K/3/index.html?&ACTION=3&LA=2&ARTICLE=2540&GROUPID=3138&artnr=534-1%2C0K) however on digikey, rs, farnell, they start at 12 Euro, and for some weird reason the 10 turns are cheaper than the 3 turn ones. I am looking into the eletrical design, to adjust the measured signal with an opamp so you can basically use any potentiometer and easily adjust to reach best precision with arduino. Anyone wants to to take on the mechanical design for this?

Rigid is something that the tracking box regards, portability is something that regards the Tripod. I think we can observe them as two different systems. For a permanent setup I would directly attach the mast somewhere and not the tripod, then the setup can become rigid.

The conclusion I came to is for a rigid setup we must use solid booms and masts. I would say that a 40mm galvanized aluminium diameter would be a reasonable decision for starters for the mast and it doesnt push the price very much. If you want to be lightweight you may still use a PVC pipe on the trackingbox.

Normally they just connect one side of the pot to 5V, the other to ground, and connect the wiper to an analogue input. For a 3 turn or 5 turn an op amp might help but normally they do not use this. We do not need very high accuracy as the beam width of the dish is so wide. Most a/d converters have at least 256 levels. Some of the fancier systems can use look up tables as the pot may not be linear.

With a wide beam width dish it should be good enough.

Yes, thats what I am looking into at the moment. Basically most 1 turn potentiometers fall out, and for some weird reason I find 10 turn potentiometers are more available for me and cheaper than 3 turn ones.

If someone is into doing mechanical stuff for the potentiometer drop me a message, I really dont know FreeCad or else.

Adding to the discussion stepper vs dc motor:
Of course with stepper you have worst EMI noise, but through commutation you also have the issue with dc motors. I find the key difference is that dc motor forces you to have a closed loop, while when sticking with steppers you can do both. I think there is some potential we can still use with dc motors (1/16 step mode) which should bring improvements in speed, ringing effect and torque.
I am really curious about your results of dc motors vs steppers, looking forward to that!

Doesn’t related to mechanics, but general suggestion to stick to single sizes for bolts. Just ordered bunch of hardware from aliexpress…It wasn’t easy as it might seem. Just see how many standards are used in v2 guide. See “relevant parts” section.

Hello, we try to fix this in the third version but sometimes is difficult to avoid all those different lengths.

Hello, this is my first post in this community. Exist documentation for rotator ver.3? Im printed 3d parts yet worm gear (involved part for 3D printers :slight_smile: ) and axis gear all in ver. 3 and I do not know yet how passed in other parts. Would help me either snapshot fully assembled rotator box ver. 3 or drawing assembly. More thanks. Dalibor OK2JKD

Sneak peek! More designs and info soon :smile:

mmm…I see…new version worm gear in git repo…previous will need sharpen :smile:

thanks of photo, Dalibor Ok2JKD

More sneak peek!

Things are looking great overall. @azisi & @manthos are working non-stop on fine-tuning the design.

That looks new and fancy :smile: Keep up :slight_smile:

1 Like

Moar SatNOGS rotator v3 sneak peek.

:smile:

very good boys :), wholly different construction than with “ABB” box. It is not the E tube loose in beering?

Indeed, as it is missing the adapters :slight_smile: (like the Az has). It was in disassembly phase to pack for Hamvention 2015!

Have you considered using the T-Slotted Profile tube which is used for the frame instead of the PVC used as the cross piece? Then the drive gears can be modified to snugly fit the T-Slotted form. Small round adaptors for the bearings may allow for smaller bearings. I wish I had thought of this when I spoke with you at the Dayton Hamvention, but sometimes the mind works slowly. :slight_smile: The metal shaft may also be more rigid and give more strength to the cross member.
Ed N3OB

This is a very good idea and is very easy to try it, the only concern is you ll have some interference with helical and cross yagi antennas unless they are frond mounted, because of the conductivity of the aluminum.

Hi all!

Is there a draft BOM for v3 yet ??? What about draft assembly instructions? … we’re looking to build v3 for field day. Found the “Master branch” so we’re good on the 3d printed parts … consider us BETA TESTERS! Thanks.

–> Rob, KA2PBT
http://wc2fd.com … the “green shirts”

1 Like

me too. I would much rather test the v3 alpha designs than start from scratch on v2. We need imperial measurements here in imperialist united states though (for our imperialist PVC).