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» Altitude control using Argo & PIC micro
Mon Oct 15, 2012 8:34 am by vinculum

» 13th October 2012
Sat Oct 13, 2012 8:35 am by sabrewulf


Altitude control using Argo & PIC micro

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Altitude control using Argo & PIC micro

Post  sabrewulf on Sat Oct 13, 2012 12:55 am

Hi all,

A bit of history first, last year I bought an Orion 14" Go-to Truss Dob. Optics are great but it has suffered from Azimuth drive problems. After back and forth with Orion and local servicing with no complete fix I decided to remove all the controls and turn the scope back into a basic push-to scope with an Argo Navis.

After installing the Argo the scope works flawlessly. The only issue I was having was aligning the scope due to the Altitude axis being quite stiff. Fortunately I still had the altitude motor connected and could move the scope in altitude with a small control that used a variable voltage supply and a toggle switch.

"I can do better than this!" I said to myself. So I contacted Gary at Wildcard and he pointed me to the serial port and SkyComm protocol. I then went and bought some PIC microcontroller SBC's and other bits (LCD's, keypads, a DSO) and a few days of coding later (I've coded PIC controllers before) I have a demonstrable version of a single axis scope controller.

The system connects to the Argo via RS232 @ 19200 baud. The system polls the Argo for guide data and drives the axis motor using a software generated PWM signal. Direction is provided by toggling the output via two relays (SPDT). The system drives the motor at varying speeds based on how much the scope needs to move. The system then "tracks" the object by moving the scope when the object drifts by a small amount. Selecting a new object on the Argo will cause the system to drive the Altitude to the new object. I still have to push the scope in azimuth but I can live with that.

I've made it so that you can operate the scope without the Argo connected and if there is any hiccup in data the system returns to a "manual mode" that stops automatic tracking to prevent the scope from driving wild.

I've made a very dodgy video and uploaded it to YouTube and you can check out to see a demonstration of the project. Sorry for my poor video skills Wink

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Please feel free to offer opinions or ask questions.

Cheers,
Simon
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sabrewulf

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Re: Altitude control using Argo & PIC micro

Post  sabrewulf on Sun Oct 14, 2012 12:48 am

It's now in a box and ready for some real field testing (as opposed to lounge room testing Wink )

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Modified Orion 14" Truss Dob + ArgoNavis
Celestron CPC925 GPS XLT (Coffee Grinfer #1)

Nagler 9mm, 13mm Type VI
Ba'ader Hyperion (3.5, 5, 8, 13, 17, 21, 24)

Sky Harbinger, AltAzAlign, SkySafari Pro + SkyWire
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Re: Altitude control using Argo & PIC micro

Post  vinculum on Mon Oct 15, 2012 8:34 am

That setup looks absolutely awesome Simon, great synergy with scope, argo & iPad! I'll like to try out the Skyfi on my EQ6 when we get a chance Wink

Youtube video is very dodgy & explains the config well gave thumbs up Smile
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