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25 Jul 2018
Glad to announce of release of INDI Library v1.7.4 on 2018-07-25. A few drivers were added in this release as we continue to improve & stabilize existing drivers.
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TOPIC: Convert JMI Motofocus to something Ekos can drive

Convert JMI Motofocus to something Ekos can drive 6 months 1 week ago #23096

Hi all,

I'm new here--my first post.

I have a JMI EV-1n focuser on my JMI NGT-18 that I'd like to convert to something that Ekos can use as an autofocuser. The Motofocus uses a handpad with a 9v battery that connects with a simple mono-headphone type coiled cable/connector to drive what has to be a DC motor. The motor unit doesn't have any ids or other identifying marks so I can't look it up.

The handpad has an "inward" button, an "outward" button and a slider switch to select normal speed or slower speed. As a part of the design, if you hold either button in for more than 2 seconds the speed goes to "full". Also as a part of the design is an easy way to decouple the motofocus motor from the focuser so switching from motofocus to manual focus is a snap. I like that idea as I'm just starting to get into astrophotography and would like to have manual focus available.

Testing with a digital volt meter I see that , as expected, the tip of the connector changes polarity if the motor is moving in or out.

The various voltages are as follows:
Buttons pressed less than 2 seconds:
     Slider switch to left is "slow" speed:
          Left button: +3v  Right Button" -3v
     Slider switch to right "very slow" speed:
          Left button:  +2.1v Right button: -2.1v

Button down more than 2 seconds:
     Left Button:  +9v  Right Button: -9v

What I really want is something I can connect to the focuser motor with the mono headphone on one end and have a USB on the other end that I can plug into the Odroid XU4 (or another device that connects to the XU4) and that the XU4 or other device can send the +/- voltages to the motor to focus in or out. There are no encoders on this setup but I believe one could be added pretty easily if needed--in fact JMI used to sell a couple of different kits that did just that.

I can live without the full speed option, in fact would prefer to so that I could drive the focuser with the same USB battery pack that runs the Odroid and the ZWO camera.

Is this even remotely possible in a software / hardware combination?

I apologize in advance if I haven't provided enough information--that's a part of still wrapping my head around the whole autofocus thing but I do know already to correct focus is critical--too many throw away images already.

Thanks,
Jeff Ross
Townsend, MT

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Convert JMI Motofocus to something Ekos can drive 6 months 1 week ago #23120

As an update, it occurs to me that this sort of thing, whether it's just a cable or a hardware box, should be usable to convert a lot of manual electronic focusers to computer control.

My 8" Meade LX-200 Classic Microfocuser has a "stereo" cable connector but I'll bet if I test the hand controller I'll see that the voltages change polarity depending on moving "in" or "out". I'll do that this weekend and report back.

Again, sorry if this has been covered a zillion times--I didn't turn up any answers after many google searches.

Jeff

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Convert JMI Motofocus to something Ekos can drive 6 months 1 week ago #23142

As a final follow up, it looks like either Shoestring Astronomy's FCUSB or Hitech Astro's DCFocus Basic Controller will work with both the JMI Motofocus and the Meade #1209 on my LX200 Classic.

I'm leaning toward the FCUSB because of the single USB connector to the XU4 and because I'm in the US.

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Convert JMI Motofocus to something Ekos can drive 6 months 6 days ago #23152

I have the Shoestring FCUSB and use it to drive a JMI autofocuser on my Explore Scientific 102ED APO. Works fine, but you need to play around with pulse length (500 ms in my case) and tolerance % (start at 10% and adjust up or down, depending on what your system needs). I also built my own DIY autofocuser using a generic low speed DC motor, which works as expected through Ekos using FCUSB, but I still have to test it in the field.
The following user(s) said Thank You: JeffRoss_MT

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Convert JMI Motofocus to something Ekos can drive 6 months 6 days ago #23162

If you can drive your stepper directly, you can use stepper motor controller and a driver. As an example see Astroberry DIY
The following user(s) said Thank You: JeffRoss_MT

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Convert JMI Motofocus to something Ekos can drive 6 months 6 days ago #23197

I'm pretty sure the FCUSB is where I'll end up, for now at least. Thanks!

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Convert JMI Motofocus to something Ekos can drive 6 months 6 days ago #23198

The JMI Mototfocus is not a stepper motor so that won't work thistime--interesting project, though! Thanks!

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