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Topics - pterodyne

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1
AstroEQ Support / RA Motor hot even when not slewing
« on: August 19, 2018, 19:46:26 »
I have my losmandy titan astroEQ running ok. Unfortunately I am back home in south Baja California and I remembered something I forgot to fix.  I noted that my RA motor gets somewhat hot just sitting there, not tracking or slewing.

I have VREF set to 1, and very large heat sinks (NEMA 23).  The DEC motor doesn't get hot slewing or not.  I also have made the fast decay hack by shorting thew two appropriate pins on the RA axis only.  In another thread Tom suggested replacing the DRV8825 for a similar problem.  Unfortunately I am over 3000KM from the observatory now, and my remote hands person probably couldn't replace the DRV 8825.  It seems to be operating fine however as far as tracking and slewing. 

SO the real question is, should I try to address?  Is the motor in any danger (fairly expensive stepperonline motor)? driver (who cares).  Id say I probably need to remove the diode too as it is always really hot.

I can touch both the motor and the heatsink ok without burning but I don't have a ir thermometer.

Thanks.

2
Capabilities Question / PEC and VSPEC
« on: August 07, 2018, 20:48:19 »
Tom, as always thanks for your time and dedication to this project!

Something I haven't messed with yet, but plan to now that my Titan mount is astroEQ based:

Because our AstroEQ mounts have various and different worms/gears/pulleys/ratios and microstepping modes, does eqmod PEC routines work as expected?  What if anything should change about the workflow as described in the VSPEC manual?

Thanks for suggestions!

Bryan Ramsey

3
AstroEQ Support / Read failed
« on: April 05, 2018, 06:02:39 »
Strange new error now that Im trying to put in my TMC2100 drivers.  I can't configure using the latest utility, it times out.  Strangely if I run "update firmware" it seems to go through all the motions and avrdude reports complete.

Any suggestions?  I had a similar problem a while back and Tom asked me to upload a specific hex file to troubleshoot, but I never did because it magically started working again.

I have a manufactured 4.4 astroeq.

4
AstroEQ Support / TMC 2100 5V
« on: April 04, 2018, 00:24:09 »
I have some TMC2100 5v drivers from watterot (the official maker I think).  I know the config utility shows them now.  Can I slot these in and just configure the way I want?

Mainly I'm concerned that I need to disconnect some of the pins, because I think that people do that for 3d printers, and set jumpers for microstepping modes. 

Ideally Id like to use 16 for tracking and whatever I should use for gotos.  And then I think they transparently do the 256 stepping internally.

Any help anyone had before I put them in would be great.  I'm having problems with my 8825s, not sure if it's because of the latest firmware and I had these for another project. Seems worth a try,  maybe my tracking will improve

5
AstroEQ Support / latest firmware hunting at end of slews
« on: March 06, 2018, 04:29:52 »
Ive been trying to track down an issue that seemed to appear after I upgraded, but I cant say for sure because the mount was in a closet for a long time.

It seems that after a goto slew it does a sort of consistent approach procedure end to the goto (as in always approach the target from the same direction).  Not sure if that is implemented in astroeq or not. Just trying to describe the behavior.  Anyhow, It seemed that the mount used to hunt a little at the end of the slew and then settle on the target, Now it does that, except it goes WAY past the target and back and forth several times before it settles on the final spot.  Also the gotos are way off.

Stats:

CG5
purchased astroeq /drv8825 (8.11)
current limits set
.9 degree Nema 17 steppers
GT2 Pulleys 38:18 (2:1)
144:1
1/32 uStep
ustep gear changing flagged on


6
Capabilities Question / Resolution for good guiding/tracking
« on: August 16, 2017, 23:27:28 »
I've pulled out a back burner project of converting a celestron CG5 mount. I have everything working fine, but with my NEMA 17 1.8 degree stepper I get a resolution of .703 Arcsec/step. Is this sufficient for autoguiding and good tracking?  I have some .9 degree steppers but I had some problems with grinding which seemed like them being underpowered.  The 1.8 degree drive the mount around great so I'd like to keep em in place.

Ive attached my config as a PNG

Thanks for looking!

7
AstroEQ Support / Confusion on config utility
« on: September 15, 2015, 18:28:31 »
Tom, can you explain the field "RA and DEC Goto Rates (x side.)?

I understand that they are a speed in X sidereal for goto movements.  What I don't understand is how they are derived and what we can expect based on them. 

For example on my current project if I put in the following for RA:

1.8 Motor step angle
2 motor gear ratio
359 worm gear ratio
32 uStep

it auto fills in the goto rate as 16 which would be pitifully slow.    So I put in 1600 (which I don't need, but sounds fast!). 

Then if I hit update again it lowers it to 1200.

The other strange thing is,

On the DEC side if I put in:

1.8
2.5 motor
221 worm
32 uStep

It also puts in 16 as the Dec Goto Rate.  If I put in 1600, it also lowers to 1200.  BUT if I click on update again it lowers it to 1000.  Later presses of update do not lower it below 1000.  If I put in something over 1200 say, 1300, and update it will lower it to 1200 again. And after that updates will lower back to 1000.

Im really just trying to determine if I will get enough speed out of this gear/motor combination.  Anything over 800 or so is gravy.

Can you clear this up for me?? 

Thanks.

8
Mount Support / New conversion project
« on: September 15, 2015, 17:49:24 »
Previously I had been working on a Losmandy Titan conversion.  This project never finished because my original motors (nema 17) were too weak.  And after all the mount is "working" as is with the gemini II controller and it is my live mount and installed 100 miles away in the observatory.

Anyway, recently I made a trade for the mount in the attached pictures.  It has a 15" 359 tooth worm wheel on RA and a 9.7 221 tooth worm wheel on the DEC.

Im working on using my previously purchased NEMA 23 motors.

https://www.pololu.com/product/1478
They are 2.8A per phase @ 3.2V nema 23 @ 270 Oz-In

These will have to be current limited, and the torque will suffer as noted by Tom in the Losmandy Titan conversion thread.

So Tom, my question is as follows.  Im going to mechanically get the NEMA 23 motors working for fit and gear mesh etc. then I have two options (three really)

1. Use those current limited motors and hope they perform.
2. Get these motors:  https://www.pololu.com/product/1472   (Also NEMA 23 but 1A coils at a higher voltage rating of 7.4)  They are also rated at 125 OZ-in. instead of the 270 on the above. 

Tom, based on your experience do you think the 1A 7.4V motor will perform better as it is in spec of the drivers? Or do you think the current limited 2.8A 3.2V motor will work better?

3.  The last option is what I was really planning until I saw the 1A motor.  Get whatever spec NEMA 23 motor I need, and they are available way more powerful than either of the above, and use external DIR/STEP drivers but still use the Astro EQ to drive them.

Thanks!

9
Hi Tom,

Still thinking of (possibly crazy) uses for astroEQ.  One idea I had was a high ratio harmonic gear head on a .9 degree stepper (or higher if there is a bipolar one available.  All the 1000 step steppers I've seen require a custom driver (which obviously could be interfaced with astroEQ with the right changes)

there are a wealth of harmonic drives on ebay.  Recently I saw this one which had a 260:1 reduction ratio.  Mechanical parts aside, it appears as if one could use a 400 step stepper at 32 microsteps and get over 5 degrees a second at .38 arcsec per step.

I have been putting in as follows:

stepper degrees:  .9
microsteps 32
gearbox ratio 260:1
worm ratio 1:1

Is this making sense?  I didn't use your configuration program because I have to have an astroeq or arduino connected (any way to make it have a dummy board attached for this spec-ing out purpose?) but rather I put the variables into onstep.xls which I found at stellarjourney.com (a very similar project but without eqmod compatiblity).  I've in the past put in these variables into your configuration program before though and gotten similar results.

So the questions are:


1. Am I crazy?
2. Is there a way to use the config program without an astroEQ attached just to use the calculations?
3. Can the worm ratio be 1:1 or does this break something?  I'm assuming in the end your software looks at a total reduction.
4. is a way for the layman to tell how fast it will go (*sidereal) without stalling the motor or missing steps? (the onstep.xls file does provide a maximum slew rate as part of the calculation, but it is based on interrupt rate and I have no idea what that means in this context.
5. Trying to get up to 1000 steps to improve resolution requires different drivers.  Oriental motor sells 1000 step steppers and these controllers:
http://www.orientalmotor.com/products/pdfs/2012-2013/A/usa_st_crk.pdf

interfacing with a controller like this would allow for higher spec motors.  Just wondering if you would ever consider (even for hire) to swap out the driver components/firmware that would allow this type of controller? Or will this project always stay with the easystep type drivers.

Refer back to question 1 if need be.


Thanks!  just thinking outside the box. In my mind the directly drive harmonic drive would be most interesting way to go on a custom designed mount.  Minimum of machining to be done..

10
DIY AstroEQ / Losmandy Titan stepper conversion
« on: December 09, 2014, 21:41:57 »
Tom,

Ive been experimenting with the Arduino version and a pair of 8825 drivers.  I have now ordered the official version from you.  It is destined for the USA, (understood that it won't be here by xmas).

Last night, I blew one of my stepper boards while adjusting the current limiter. This is on the bench only at this point as the Titan is installed in the observatory 100 miles away.   I'm wondering if I could send you my motor/gear specs and if you could tell me if you think it will work?

Losmandy Titan
Worm wheel 270 teeth both axes
Pulleys 40T on worm gear, and 10T on the stepper for 4:1 ratio
1.8 Degree Stepper NEMA 17 1.68A/Phase bipolar (full motor specs attached.)

Ive been putting into the configuration program:
1.8
4
270

and trying to get to 500 or more for max slew speed.

Im having a bit of a hard time between the relationship between the Motor voltage and the amp draw/vs speed.  I have some micro heatsinks for the driver chips as I read that 1.5A is the max per phase on the motor drivers without additional cooling.  That said, how do I figure out if the above will work without blowing my official unit when I get it?  Could the current be below 1.5 and still meet the above specs/speed requirement?  In the case of me blowing my stepper board, I was adjusting the current limiter, but was at a high voltage of 20V for the motor.  Trying to get EQMOD to not stop the motor at the high slew speed.  (Choosing a max slew speed the motor would spin up slowly, then stop)


11
Tom, Hopefully you won't mind, I converted your Eagle schematic to a PDF for those who don't have access to Eagle.

12
DIY AstroEQ / Arduino Instructions
« on: October 31, 2014, 15:48:05 »
Thinking it might be easier to use an arduino, I looked for any information on the schematics/wiring to do so. I can't seem to find any information.  Does anyone have this info?

Id like to at least prototype and test this and using an arduino while waiting for Tom to get back to the UK during the Holidays...

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