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Author Topic: Confusion on config utility  (Read 2044 times)

pterodyne

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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.
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TCWORLD

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Re: Confusion on config utility
« Reply #1 on: September 16, 2015, 01:29:06 »

Hi,

16 is the minimum allowed which is why it defaults to that.

1200 is the maximum which is why it limits it to that. If you press update a second time it can sometimes recalculate a different number which is rounded based on what speeds EQMOD can send.

Due to the Synta protocol of which I have no control, there is a limited number of speeds which can be sent, and they are distributed non-linearly (there is more choice at lower speeds than higher speeds). The actual calculation is not that complex, but it is also not easy to explain! Essentially there is a 1/x in the equation where the lower the result the faster the speed, but due to integer truncation as the number gets smaller there are fewer discrete values.

I have tried to correct the utility so that the first update rounds to the correct value, but sometimes it doesn't. In the end it doesn't really matter as the values are refreshed before uploading (to ensure that the double update issue doesn't cause incorrect values to be uploaded).

One thing to not is that just because the config utility allows numbers that high doesn't mean your motors can go that fast. It is impossible for me to know if they will!
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Tom Carpenter (AstroEQ)

pterodyne

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Re: Confusion on config utility
« Reply #2 on: September 16, 2015, 04:53:54 »

Thanks, that clears it up.  Understood about the reported speed not being possible.
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