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[Xevious]

Hi guys!  I'm itching for a tutorial or for a little more information on how to build this... I've seen all the parts sitting on Ebay and at the local Radio Shack.  Let me know... OR let me know if you have some of those AstroEQ's for sale!!!!

[photo444]

Tom, I have spent some time last night. Please see attached Excel Sheet showing numbers in various checking procedures.  I have erased EEPROM, freshly downloaded the firmware, running the program carefully copying displayed numbers at :011 and :012 phases, and copied the table (screen). Then I was using Arduino IDE serial terminal to read the data from the Mega board.  Also checked was the reading of EEPROM using Arduino eaxample. All is captured in the Excel Sheet.  It is interesting that the only discrepancy comes with the data read by the serial terminal using :xn commands and all others are agreeing each other.

The bottom line is the behavior of the mount: A disobedient mount.

Thank you for the support.  Christmas is coming near and I will wait for your final solution!

Merry Christmas!

Paul

[TCWORLD]

Ahh, I know what that discrepancy is and it is nothing to worry about.

The bVal is rounded slightly before being sent to EQMOD to correct for some integer truncation in calculations done by EQMOD. It's something that only affects AstroEQ because of the way it is programmed.
When the config utility reads it back it puts the controller into a special mode (the :O1x command) which disables this rounding so you get the true value.

So the fact that the mount is moving by an incorrect amount suggests that something in either the step angles or gear ratios that you have used is wrong - could you double check those values.

[photo444]

Hope it is that simple.  I am going back to my counting business tonight. I will let you know.
Actually I was trying to recompose the gear ratio to fool your program but I was not successful at all.

Paul

[TCWORLD]

There's another possibility, your motors may not be able to move fast enough and are skipping steps. Try setting the go-to speed lower and see if they move the correct amount. Start with, say, 20x, then try 40x, the 80x and so on.

[photo444]

It's not gear ratio, or speed, it's a mystery.  It is better wait for your board to come out. -Paul

[TCWORLD]

I wonder if the mode pins aren't wired up in the right order. Although that would result in a power of 2 variation from the right place.

Out of curiosity, if you get CdC to move to a star, and then go to a second star, and then back to where it started (before the first slew), does it end up back at the starting point, or somewhere different?

[photo444]

I have checked the three pins with multimeter and the readings are according to the microstepping commands. And during slewing, it repeats and goes back to the same place accurately.  The trouble is that the scope is pointing wrong places.  As I said earlier, the movement is always some fraction of what it was told to move, both RA and DEC.

Do you have the source code for Arduino Mega? I think it is worth to check if you have.

[TCWORLD]

The source code for the Arduino Mega is the same as that for the Atmega162, so it is unlikely to be a firmware issue.

If it is returning to the same place it started it means the issue isn't the motors skipping steps or stalling. It suggests that the gear ratios you have used don't match your mount.

Could you remind me what your current mechanical setup is, motors, gearing, worm ratios etc.

[condorito9]

Hello Tom: you made the PCB proto shield for Arduino Mega?

[TCWORLD]

I haven't designed a proto shield layout as there are about 20 different variants of proto shield from different manufacturers. I published a schematic, so it is up to you to wire it up.

[photo444]

RA: worm=144 gear=4 Stepper (1.8deg) Microstepping=32
DEC: Worm=90 gear=6 Stepper (1.8deg) Microstepping=32

I was playing with other combinations as well, and all behave the same way. RAgear=42/15, DEC gear=4, and stepper(0.9deg), for example.

I have found OnStep on the net and it is working fine with the gear train.

Paul

[TCWORLD]

I thought you said in your other thread about gear ratios that you had the DEC axis at 300:1 and the RA axis at 336:1.

Assuming you have an RA worm of 144:1 and DEC worm of 90:1 (as in your last post), you should be using gear ratios of:

RA gear = 2.333333333 (:1)
DEC gear = 3.333333333 (:1)

If you used 4 for RA and 6 for DEC, then your axes would move the wrong amount.

[photo444]

Do you mean that the firmware is preset for the ratios (2.333333:1 and 3.33333:1)?  Can the setup program calculate for different ratios?  If it was preset for a particular ratio then I made a terrible mistake.  -Paul

[TCWORLD]

Not at all, it works for any ratios, that's what you enter on the configuration screen.

But if you have an overall gear ratio from the motor shaft of say 336:1, and the worm gear has a ratio of 144:1, then you get a motor gear ratio of (336:1)/(144:1) = 2.3333333:1.


For example, my mount has a worm gear of 144:1, and I use a 40T gear on the worm screw and a 15T gear on the motor shaft, giving me an overall gear ratio of 40:15 * 144:1 = 384:1. I enter into my config setup, worm ratio = 144:1, and motor ratio = 2.666667:1 (=40:15).