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My NexStar 127SLT Mak Motorized Focuser 3D Printed

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#1 Ssayer

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Posted 17 September 2019 - 02:03 PM

I wanted a Motorized focuser, but the cost is more than I'd like and it isn't even in stock at JMI with no clue as to when it might be. But, this scope just jitters too much and too long for my taste. So... I drew some parts up for my 3D Printer, printed them out, and outsourced whatever parts I didn't have on hand. This is what I came up with. Focusing speed goes from 4 seconds per revolution to 15 second per revolution (the motor stalls out with anything slower). Seriously, that's plenty for me and no jitters when focusing!!! I had my wife try it out as well, and she had no trouble at all getting a good focus. Also, I can put it on or take it off of the scope in way less than a minute! Hah! File sizes are too large! Ok, I'll post only two pics. One in this post and the other in my next post...

 

BB1.jpg

 

 

 


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#2 Ssayer

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Posted 17 September 2019 - 02:04 PM

So, here's what it looks like on the scope:

 

 

BB5.jpg

 


Edited by Ssayer, 17 September 2019 - 02:04 PM.

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#3 photoracer18

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Posted 17 September 2019 - 02:53 PM

Reason the motor stalls out is you are using a pot (rheostat) that adjusts the voltage. Once the voltage gets low enough it does not have enough torque to move the gearing. What you really want is the system inside the Rigel nFocus controller (or buy one of those as I have used them all the time on JMI focusers). It uses full power pulses in which you can vary the pulse frequency and the pulse width. You can go right down to a dead stop and still get it to work.



#4 Ssayer

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Posted 17 September 2019 - 04:52 PM

Oh yeah, I get it. I was just seeing what I could make on the cheap and then seeing if I could be happy enough with it (I only outsourced $27 in parts on it as I had everything else here in all my bins). So far, I'm happy. Time will tell soon enough (weather permitting).



#5 Ssayer

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Posted 30 September 2019 - 07:55 AM

Heck, Amazon has a PWM controller WITH toggle switch for a whopping $7.69! My understanding is that I will now be able to fine tune right down to nothing. I'll have it in my hands tomorrow and give it a shot. I'll probably be printing a new control box... tongue2.gif



#6 Ssayer

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Posted 02 October 2019 - 12:33 PM

Just in case anyone that reads this cares, the PWM controller worked perfectly. I can now adjust focus speed right down to a dead stop. Heck, the PWM control board is pretty much dirt cheap!

 

20191001_203109.jpg

 

20191001_201833.jpg



#7 Ssayer

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Posted 06 October 2019 - 01:16 PM

As you can see from the previous post, the change to a PWM controller warranted changing the control box. So my  setup doesn't quite look like the original pic anymore. If you have a 3D Printer, and IF you're interested, I put the stl files up on Thingiverse: https://www.thingive...m/thing:3897861



#8 rigelsys

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Posted 07 October 2019 - 06:30 PM

PWM is the way to go.  That's why we've been going that way for 20 years with nFOCUS :-)  But what we do is make pulse width and pulse interval separately settable, so one can have a pause between pulses to see the focus has changed and perhaps lift finger off the button before it pulses again.  We also use 3AA batteries and kick the voltage up internally to 12V DC.

 

best regards, sounds like your PWM controller is a winner!




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