Hi Jamie
I am not sure what you mean by "telescope hanging" - I assume you mean pier side i.e., pier side east or west
If so, the target has to be reachable on both sides of pier.?
After startup, you can try slewing the mount so it's slightly pier side east (telescope on eastern side, I think your preferred starting point) and then do your goto routine.?
The Gemini prefers to stay on same side of pier, so after you startup and sidereal is engaged, the telescope has already moved a little bit to pier side west
Brian ??
With my backyard view it's best if I can have the scope hang to the east to start the night. I use kstars/ekos/indi connected to skysafari to select and slew to a target. It usually seems to end up with the scope hanging west. I usually have to use the manual control in skysafari to position it close to the target, and then slew to it. I'm assuming that scope position is determined by my GeminiII system on the GM811G (couple years old). Is there a setting to prefer positioning the scope to the east??
Jamie
-- Brian?
Brian Valente portfolio
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With my backyard view it's best if I can have the scope hang to the east to start the night. I use kstars/ekos/indi connected to skysafari to select and slew to a target. It usually seems to end up with the scope hanging west. I usually have to use the manual control in skysafari to position it close to the target, and then slew to it. I'm assuming that scope position is determined by my GeminiII system on the GM811G (couple years old). Is there a setting to prefer positioning the scope to the east??
Jamie
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Re: Gemini-2 momentarily went haywire
That's not how the Gemini H bridge drive works....its PWM....both motor poles are held high (at input voltage aka 12V-18VDC) one pole pulses low at a preset freq (the pulse width is determined by the system...which is to the motor, an avg DC offset, it drives.? It Not only drives it move it does so with good torque due to the drive system PWM design.
The H bridge does have ceramic capacitors on each output and a large electro on its Vin drive power close by (There is another at pwr in).?? The H bridge It is laid out exactly to the design specs of the ICs mfgr.
Any large filter on the motor drive lines will distort the motor power factor.?? This design is basically the same or similar to that in the Gemini 1....just using newer ICs....aka a dual G bridge in SO20 package.
It works there is nothing wrong with the design
--
Brendan
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Re: New mount, old tripod
This is normal. Don't worry about it.?
--
Chip Louie Chief Daydreamer Imagination Hardware?
? ?Astropheric Weather Forecast - South Pasadena, CA?
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Re: Gemini-2 momentarily went haywire
Ceramic cores are fine if properly sized for the application but at very low frequencies the core would not be very effective plus the core would be large and heavy. ?See the ARRL RFI handbook. ? If possible first measure the noise on the DC motor circuit with an Oscilloscope, maybe one of your ham radio or techy friends has one. ?A ?.1mfd ceramic disc capacitor (dot 1 mfd) rated at anything above 50 volts at the dc connection to the motor DC terminals. ?$0.10 . ? ?I have remote controlled DC motors with various decoders not only in my Astro gear but ham radio antenna rotators and WiFi controlled antenna tuners to suppress motor noise. ? Ceramic Ferrite Cores with sufficient inductance would be too large and heavy and are more effective to suppress high frequency noise. ? ?
It would not hurt to add a large filter capacitor across the DC plug to smooth out voltage drop due to motor start surge current . ?Some people have mentioned replacing the power supply but I wonder if that is really necessary , large current surge can be ¡®smoothed¡¯ out with a properly sized electrolytic capacitor across the DC line, such a capacitor is in every power supply ever made , 1000mfd at 50 volts ?but again I like to see the circuit on an oscilloscope for a before and after picture but Non of these components would harm anything ... ceramic disc capacitors are not polarized +/- but Electrolytic capacitors are Polar sensitive, the terminals are marked positive and negative so pay attention to connect positive to positive and negative to negative. ? ?
? ?
Of course proceed at your own risk, all mentioned components are common electronic parts, The electrolytic can be installed anywhere along the DC cable or at a connector just remember positive to positive, negative to negative, thevalue is not critical but the voltage rating should be at least 3 times the power supply output for safety so 35volt or higher rating is Ok, ?The ceramic disc capacitor is very small and should be at the motor terminals. ?A 15 watt soldering iron is best for the job, not 100 watts which could destroy parts. ??
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Re: Reducing DEC Backlash with Titan 50
Dan,
Some notes on adjusting the worm on a Titan vs G11 or GM8
1. The G11 and GM8 use individual worm bearing blocks.? Each block has a bottom "nipple" that fits a specific hole.? The left hole, closest the gearbox, is a pivot point.? You simply pivot the worm into the ring gear using the pivot point, feel for free worm tightness, then tighten down the worm blocks....done. Then you adjust the gearbox until the Oldham coupler plastic center just rotates, not shifts.? Then attach the motor...done.??
2. The Titan has no pivot point.? Both mounting bolts can swivel and pivot so the worm can shift left or right.? The length of the worm enclosure block is larger than the plate on which it mounts. You must therefore rest the worm in its enclosure on top of the ring gear, and perhaps use a level, and feel the ends to see if your block is nearly centered.? ?
Fortunately, if your Titan has tucked motors, the entire drive gear assembly is bolted directly to the worm enclosure.? You can tilt or shift the week RM and not affect the drive gear train at all.??
Some owners have used automotive feeler gauges to measure the gap on either end of the worm block, to see if it is level.? You'd need two sets of feeler gauges and the gap will be thick.??
When you have the worm block assembled don't completely tighten the 14mm nuts that hold the worm block down.? You can use the upper Allen head bolts to pull the worm block up off of the worm if it has too much friction.??
It is best to have an ammeter equipped power supply to the Gemini, to tell the Gemini motor current.? Then you can determine the gear adjustments that give consistently low motor current. (If you need one, contact me separately).?
---- other related adjustments ----
As I mentioned in an earlier post, one problem area is the worm can have a lateral shift, or be pressed too tight leading to worm friction.? On the OVision worm block for the G11, they used a Belleville spring washer under the end cap screw.? Losmandy doesn't use one but I think that's a best approach. The spring size to use is for a 6200 size bearing.? You put the outer cup edge forcing into the worm bearing OD, and let the inner cup edge go against the threaded endcap.? I use two such Belleville washers inner cup to inner cup.? Then just screw in the end so until the Belleville washer(s) and worm bearing are in contact and turn another 1/8 turn.?
Finally (?) I find the worm to ring gear grease is also important.? You want the lowest friction possible because the worm has to rub nearly perpendicular to the ring gear.? This action is like the bowing of a violin string, and can lead to a vibration ("chatter").? The lube with lowest "4-ball test mark distance" of 0.6mm, and highest Timken test rating of 60 lbs is the CRC Brake and Caliper Grease.? This gave the smoothest performance to my G11T titan RA drive.? That lube has anticorrosion ingredients and the same low copper corrosion behavior as Super lube.? But it seems to stays in the metal to metal high pressure contact point of the worm to ring gear better than superlube.
?Best of luck,
Michael
Thanks to you both.? Very informative.??
At some point I will give it a shot.... you are making it sound fairly easy.? When I do it.... I'll have both the scope/imaging equipment and the counterweight's removed (actually though I guess that may only be applicable for the RA worm, and in the CWD position, I can't see anything would turn there).
It is sounding like adjusting the worm mesh on the block bolts is once again the trickiest part about it.
Thanks again.
Dan
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Re: Still some DEC issues
It's better to use the built-in PHD log uploader and paste the link
Also trimmed logs are not helpful - you can't auto load them into the PHD Log Viewer
Brian
Is there a way to trim the guide log?? Do I post it here or some other place?? Because SOME people who complain about getting a second message from editing probably don't want to get a several hundred kilobyte file that they aren't going to look at anyway.
-- Brian?
Brian Valente portfolio
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Re: Still some DEC issues
On Tue, May 11, 2021 at 05:54 AM, alan137 wrote:
Is there a way to trim the guide log?? Do I post it here or some other place?? Because SOME people who complain about getting a second message from editing probably don't want to get a several hundred kilobyte file that they aren't going to look at anyway.
Use a Zip utility to compress the log file and upload it to the Files section here:? /g/Losmandy_users/files?and then post a link to it in a message. Don't send it out as an attachment to your message, unless it's a small file. Regards, ? ? ?-Paul
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Hello folks,?
I have a new mount with an old HD tripod, the non-folding kind.? It seems that the base diameter of the mount is about 2 mm smaller than the inner diameter of the tripod mounting surface.? So what happens when I go tighten the three mounting screws is:
The first screw goes in easily and firmly bottoms out
The second screw has a small range between when it starts to get tighter and when it bottoms out.? I can see that it moves the mount by a little bit.
The third screw takes a while to bottom out and becomes really tight as it starts to ovalize the tripod head.
And at the end of the day when I try to loosen the screws again, they are almost stuck because they are all under a lot of tension now.
Can I shim up this gap with washers or strips of aluminum somewhere?
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Re: Still some DEC issues
Is there a way to trim the guide log?? Do I post it here or some other place?? Because SOME people who complain about getting a second message from editing probably don't want to get a several hundred kilobyte file that they aren't going to look at anyway.
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Re: Gemini-2 momentarily went haywire
John
Could you please re-photograph the top of the PCB again particularly U7 DSPic!?? It looks like its bee a little hot on the sticker on top.? The problem here is U7 is DSPic for DEC...the issue is DEC isn't it?
I've worked on Gemini's? that have had runaway issues and odd issues like you said.? Sometimes there sometimes touching a direction arrow causes runaway etc.? Along the food chain of ICs and problems it can be are:
A cracked solder join on the connector to PCB....unlikely with the mini
A bad H bridge U13.??? Yes this can cause the said same issues, usually one channel.
A bad DSPic.?? I'd first attempt to re-flash it to see how that went but the firmware is not available to public.?? Yes this could be the issue...or changing on spec and flashing it.
Or the ARM processor U11.? Which has firmware not publicly available.
PCB cracks....no apart from some motor connectors.? The Gemini uses good leaded solder not that crappy "no lead"....which fractures and needs a furnace to melt/re-flow.
My bet is the H Bridge U13 in one channel.?? Its not easy to replace s the PCB has 4 layers and GND/PWR planes in-between so heat soak is huge.?? You need good equipment and techniques to replace this.
I think its at the point you send it either to Losmandy of one of the repairers.
--
Brendan
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Re: Counterbalance weight calculation for rig
Glenn,
Please see attach pdf. As iterated by the comments so far, more weight higher up is better. This doc explains some of the basic calculations and reasoning. I like to make adjustments with a small weight, as moving the 21 pounders to the exact sweet spot is more tedious.
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Re: Gemini-2 momentarily went haywire
On Mon, May 10, 2021 at 01:09 PM, Bill P. wrote:
Noise is not an unusual problem in motor circuits and most often the resolution is cheap and not too difficult, in fact the solution can be made into a cable pigtail for each RA and DEC cable but I won¡¯t go further as I know any electrical engineer knows the answer. ? ?
Bill, No engineer here, but what is this simple solution? I assume you mean a ferrite core noise suppressor which is found on some data cables. I think some of these can be snapped over the outside without cutting and re-soldering the wires. My next step is to replace the Gemini 2 PC board as a whole, not solder in a new chip. My motors and cables appear to be sound, so by elemination the source would be the Gemini unit itself. Thanks, John
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Re: Losmandy G11 Gemini 1 Battery
Enol
You can take the motors off and Gemini set it up on a bench to test!?? Of course the motors are not loaded with inertia but never the less its a good way of testing and narrowing down issues.
--
Brendan
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Re: Losmandy G11 Gemini 1 Battery
I don't think It power off. The conexi¨®n with the PC continues. The mount only stop the slew and continue with the tracking. I don't remember if the mount buzzer sound, but I think don't.
Greetings, Enol.?
Chuck.....I've seen one operating on a Gemini no problems.?
Look at fig 19 "Boost" control.?? You probably saw the flyback control design versions.?? But in boost,,,,no problems running a Gemini with some overhead current available.
You can soft start it its internally protected and referenced and designed to open cct if fault. (many fleabay Copies do not do this).
You can parallel devices, but one one is sufficient.?? You can buy the appropriate inductive coil, Bournes PM2102 series.? It will cost around $20~25 USD to make (not incl PCB) design layout is paramount, use a star earth and follow design app notes, TI SNVA731,
If you want to parallel devices, look at TI app note SNVA552.? A single device is enough maybe use a DPACK and solder it to the PCB and use a large PCB PAD as heat dissipation.? The LM2588 is pretty much the same device.
I did design one of these "LM2578 Boost 12-18VDC"? PCBs in EaglePCB (a 60mm x 50mm PCB...should be able to squeeze it to a 50x50mm PCB) but haven't made it yet.?? Its single sided but would rather double side it...so usually send to PCB fab house.
As fro Enol.....as Michael said the system failing on both axes sounds like a Power supply problem...2.1 Amps may be too low as initial start peak may be quite a bit higher.?? Lowering the slew to 600X is a good idea and many users do this.? You will never see this initial current spike on a digital meter as their refresh rate is 2~3 times per second at best.
Another thing about many 12V DC power supplies is that they droop in voltage when loaded with higher current.? I was measuring a 7.5A 12V PSU the other day at 3A (with a Digital active load) and its drooped to 11.1V DC 3A out!?? Wow.... .......!? This is too low way too low.
A question for Enol........is your system shutting down when it doe this....like does the HC "LED" stop???? I'm wondering if your PCB needs Fuse F2 replacement.
Cheers
Brendan
--
Brendan
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Re: Losmandy G11 Gemini 1 Battery
Chuck.....I've seen one operating on a Gemini no problems.?
Look at fig 19 "Boost" control.?? You probably saw the flyback control design versions.?? But in boost,,,,no problems running a Gemini with some overhead current available.
You can soft start it its internally protected and referenced and designed to open cct if fault. (many fleabay Copies do not do this).
You can parallel devices, but one one is sufficient.?? You can buy the appropriate inductive coil, Bournes PM2102 series.? It will cost around $20~25 USD to make (not incl PCB) design layout is paramount, use a star earth and follow design app notes, TI SNVA731,
If you want to parallel devices, look at TI app note SNVA552.? A single device is enough maybe use a DPACK and solder it to the PCB and use a large PCB PAD as heat dissipation.? The LM2588 is pretty much the same device.
I did design one of these "LM2578 Boost 12-18VDC"? PCBs in EaglePCB (a 60mm x 50mm PCB...should be able to squeeze it to a 50x50mm PCB) but haven't made it yet.?? Its single sided but would rather double side it...so usually send to PCB fab house.
As fro Enol.....as Michael said the system failing on both axes sounds like a Power supply problem...2.1 Amps may be too low as initial start peak may be quite a bit higher.?? Lowering the slew to 600X is a good idea and many users do this.? You will never see this initial current spike on a digital meter as their refresh rate is 2~3 times per second at best.
Another thing about many 12V DC power supplies is that they droop in voltage when loaded with higher current.? I was measuring a 7.5A 12V PSU the other day at 3A (with a Digital active load) and its drooped to 11.1V DC 3A out!?? Wow.... .......!? This is too low way too low.
A question for Enol........is your system shutting down when it doe this....like does the HC "LED" stop???? I'm wondering if your PCB needs Fuse F2 replacement.
Cheers
Brendan
--
Brendan
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Re: Losmandy G11 Gemini 1 Battery
Brendan
I went to TI and used their web designer. The good : 2587 comes in to 220 package. The bad : limited to 1 amp at 18v. I'm not sure the current limit would be a problem but.....
Chuck On Monday, May 10, 2021, 03:39:51 AM PDT, Brendan Smith <brenatlilydale@...> wrote:
Enol . ?Boost converter. ?There are a lot of Chinese knockoffs on fleabay which have been known to fail. ?Best you make your own. ?The Ti data sheets and app notes are sufficient to build one but do use star ground return? ive been thinking of doing one....just to try it. ?I had the opportunity to test one. ?It was excellent. I could hear the difference in the motors. ? Cheers
--
Brendan
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Re: Reducing DEC Backlash with Titan 50
Thanks to you both.? Very informative.??
At some point I will give it a shot.... you are making it sound fairly easy.? When I do it.... I'll have both the scope/imaging equipment and the counterweight's removed (actually though I guess that may only be applicable for the RA worm, and in the CWD position, I can't see anything would turn there).
It is sounding like adjusting the worm mesh on the block bolts is once again the trickiest part about it.
Thanks again.
Dan
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Re: Gemini-2 momentarily went haywire
An issue that has never been mentioned on this Gemini forum is electrical circuit noise inhibiting the normal processing of Firmware commands. ?Barring the obvious bad cable/connector/battery/dirty encoder wheel ?DC motors are miniature spark gap radio transmitters and the attached cables are radio transmitter antennas. ?The onboard circuits contain thousands if not millions of radio receivers in the form of Diode junctions that normall act as switches but can act as analog signal rectifiers. ? Its very possible to introduce electromagnetic (EMI) noise into the attached circuits and at sufficient levels this electrical interference is rectified above 0 and/or 1 logic levels to disrupt the onboard computing processes. ?I¡¯m sure everyone is familiar with the MS Windows Blue Screen of Death , the result of a computing problem. ?
When the DC motor is energized the motor winding inductance creates a sufficient EMF noise spike ( a current opposite of the primary source is generated) ?the source of the noise, the duration of the noise spike and amplitude are the culprit. ?Easy to cure. ? ?
Its not hard to determine if EMI is on the cable and most circuit board designs are tested but this is astronomy and who would have thought about such a condition.but at 12 to 18 volts and motor start surge currant this is not a condition to be overlooked.
Noise is not an unusual problem in motor circuits and most often the resolution is cheap and not too difficult, in fact the solution can be made into a cable pigtail for each RA and DEC cable but I won¡¯t go further as I know any electrical engineer knows the answer. ? ??
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Re: Reducing DEC Backlash with Titan 50
Dan?
I have the same scope mounted.
The worms come off regardless of if the scope is mounted or not.? ?Remove the 14mm nuts first.? Then you unscrew the top mounting worm back off bolts.? Those thread into threaded holes in the bigger mounting bolts.? See the photos attached.? Then the bottom bolts unscrew from the worm block, and you can lift off the worm block.? ?With the worm off the axis can rotate 360 degrees freely.? You can lube the entire circumference of the ring gear. But be sure the scope doesn't bump into anything and the cables do not get damaged.?
Thanks, guys.
Paul:
Your write-up on adjusting the worm mesh is basically what I was doing with those bolts.... a tad of torque on the wing bolts, and I get the noise.? Back off just a little, but not totally loosened, and the sound goes away.
I would like to attempt to lubricate the worms.? My questions would be:
1.? I have a heavy scope.... C14 Edge.... do I need to remove all equipment from the mount to remove the worm gears?
2.? I think Scott has a video on greasing a worm, but it looked like it was on a G11.? Are there other sources to look at?
3.? Is it basically that I remove the worm block bolts to remove the worm housing block, and open it up?? I'm assuming the end cap needs to be removed.
4.? I think Scott was saying to use alcohol to remove old grease, and then apply new?
5.? Just re-assemble, and adjust the mesh (play with the block bolts again)?
Thanks a lot for your help.
Dan
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Jamie Amendolagine
Chip Louie
Bill P.
Michael Herman
Paul Kanevsky