View Full Version here: : GS-280 hand controller - possibly replace with PC and software?
11-01-2012, 04:02 PM
G'day. Over Christmas I got an old EQ mount up and running. It's about an EQ3 I think, but no labels on it. It has a simple RA motor and this GS-280 hand controller that just has forward and backward direction buttons, and you can toggle through 1x, 2x, and 4x sidereal rates. The connection to the motor is a lot like a PS2 type keyboard connection.
I'm wondering if there's some software that can emulate the controller, and if I can get a USB cable with PS2 jack on the other end and plug it into the controller? Maybe a bit of DIY, but not sure where to start? Any ideas?
11-01-2012, 04:38 PM
Congrats on reviving the old mount.
The PS2 connector is just a generic 6-pin mini DIN connector so it doesn't imply that any standard signalling scheme has been used. The chances that they've used something signal compatible with USB (a high speed serial protocol) are vanishingly small. If you're handy with an oscilloscope you might be able to figure out what is going on, but you'll probably need some fancy hardware to emulate the controller.
11-01-2012, 04:50 PM
Ah, gotchya. Bit beyond my capabilities to reverse engineer the signals etc. The hand controller does work, just the rate button is a bit sticky. Sounds like it'll be simpler to just stick with it. It's only for unguided widefields anyway, and I was using the 4x rate to help with CCD drift align method.
13-01-2012, 11:55 AM
These simple controllers have small stepper motors driven by very simple electronics that roughly simulate sidereal speed with two or three optional speeds from a pulse generator.
While it is often possible to use the motor drive hardware to move the motors and add additional hardware to cause micro stepping and then a computer control similar to the EQMOD it is hardly practical. See also the Bartells system. For the cost of parts and design work it would be far cheaper to ditch the EQ3 and replace it with a EQ5/HEQ5 or a HEQ5 Pro with Synscan.
If you just want to display a position on a planetarium program you can add encoders with an Argo Navis. But again that is almost as expensive as a new goto mount.
13-01-2012, 12:30 PM
Thanks Barry. Pretty much came to that conclusion. Think I'll just keep it and put up with it as is.
19-02-2012, 05:00 PM
I am actually working on this very thing..
originally it was just a side project, but it has taken on more urgency since my GS-280 controller seems to have failed completely sometime.
A few things: (some might be obvious, no offence meant if they are!)
12v into the stepper motor casing. From there it is not actually connected directly to the stepper, but goes out the mini-DIN (PS2 type) cable into the GS-280 controller. The rest of the wires are used for the handset to drive the stepper, using a ULN2003 chip (controlled by a microcontroller) to drive the stepper - this uses the majority of the rest of the wires in the PS2 cable. None of this really matters of course.
Creating a PC interface to the controller should not be especially difficult, however is of limited use.
The only thing you can control is forwards and reverse speed, so the only reason i can see to do this is for extended length drift alignment using a relativly wide field of view - ie, DSLR + standard lense, using the "V" alignment method. That was one of my reasons for wanting to do this. The hardware required could all be picked up at Jaycar for quite cheaply - Arduino (or compatible), ULN2003 chip, and however many extras you want to add (sockets, perfboard, USB bulkhead mounts, buttons, etc)
I have actually added a second stepper to my EQ3, so i am working on something that can be driven with LX200 commands - I recently found a similar package, Astroduino, which has done a lot of the hard work, which allows LX200 commands to be used to drive an ST4 style autoguided system.
One unfortunate thing i have found with me EQ3 is it seems to have a quite severe amount of noise in the gears - even after a teardown, clean and regrease. I recently ttried using some rogue and an electric drill to "smooth" them down a bit, but it was when i tried to test this i found that my GS-280 controller seemed to have failed.
29-03-2012, 01:31 PM
The main thing i had problems working out was the delay timing for each step. 34720 microseconds seems to be pretty spot on, going on 200 seconds per rotation of the motor. The motor does not like pulses lower than 6000 microseconds.
The GS-280 pulses are 8.3milliseconds long, however there is about a 50% idle time for some reason. So the controller pulses each pin on/off 6 times in 50ms, and then is idle for another 50ms. The value i worked out gives constant pulses. I doubt it will make a noticable difference though.
I used an Arduino Deumilanove, and a ULN2003 darlington array as a driver chip to switch the 12v. Its quite easy to construct. Jaycar sells all of the parts. The most expensive is the Arduino microcontroller - There are cheaper ways to do it, i am sure.
I have implemented a basic serial command set that allows modification of the delay, plus a simple rate change/rate reset and direction change. I interface to this with a simple python script to send the commands at the appropriate times. This allows me to perform drift aligns with an exposure length of my choosing, all fired off from the comfort of the big screen computer i can then use to examine the images to determine what sort of alignment is required. I only need to go outside to make the adjustments if required - No more crouching over a handset!
29-03-2012, 02:13 PM
That's awesome! All this Arduino stuff is way over my head. How much do you reckon it's costing you to put this together in terms of parts? Got any photos?
04-04-2012, 09:54 AM
The main cost is the Arduino itself - $40 or so from Jaycar for an Australian designed clone. The Arduino is overkill, but its handy and flexible and perfect if you dont know what it is.
The driver IC's are $4 or so each. Everything else is relatively cheap bits of hardware - The panel-mount USB socket is probably the most expensive thing after the Arduino!
In the images shown, i have it set up with the connectors and IC's etc, to drive three motors, so to drive just the factory motor would have substantially less wires, etc needed. I have also eliminated the need for the power cable to the motor housing.
Adding a hand controller to this configuration would be trivial as well - essentially just the cost of the buttons of your choice and some wires, resistors and a case.
04-04-2012, 10:10 AM
Hmm. New EQ2 drive motor and controller is $149 from Bintel. Will all the equip costs, time to learn and put it all together, I'm wondering if I'd just be better off either putting up with it as is, or getting new motor and controller new. The whole mount with motor and controller I bought used for less than that!
04-04-2012, 10:23 AM
This is really interesting. I had a look at AstroDuino this morning on Sourceforge, but the links to the code throw a 403 error???
I've been looking for a method to interface with an Arduino to send pulses, RA and DEC, to the hand controller of my mount, so that I can guide using CdC or Xephem - but I'm not sure that that is an effective/rational/sensible approach to the guiding problem.
Still very much a learner with the Arduino and little idea on how to create a serial interface between my Linux laptop and the Arduino board.
At the moment I use two Arduino boards, one for camera control and dithering via the hand controller and the other for DSLR cooling temperature control. I plan on using the cooling board to implement guiding.
04-04-2012, 02:02 PM
The EQ2 drive motor and controller may be slightly different - in tooth count for the gear, or rotation speed.
I didnt notice that you actually had a problem with your current hand controller - it may actually be possible to de-stickify the button as well.
This system really is quite simple to put together. The hardest part would be making up the attachments for the mini-din connectors/cables!
04-04-2012, 02:33 PM
I downloaded Astroduino and had a look a few weeks ago - Its quite a comprehensive bit of software. It contains libraries for encoders for positioning feedback and a serial parser for LX200 -> ST4 style pulses.
The author has modified his telescope hand controller to accept ST4 pulsed autoguiding, and uses the Astroduino to convert LX200 serial commands into pulses for guiding.
I have had to come at the issue from a different direction - my mount does not move at all without the arduino sensing pulses at the appropriate rate directly to the motor. I do have a second stepper i have attached to the EQ3 that i'd like to see if i can use for autoguiding with LX200 commands
04-04-2012, 03:09 PM
Sorry, I don't mean to hijack the thread. But you have me thinking the right order of things.
I guess the difference is, that I want to pulse the hand controller - simple enough through an optocoupler.
I think it would work this way. The Linux box running CdC set to a generic encoder setup will receive position information from the mounts shaft encoders, which is translated to serial output and fed the Arduino which schedules the hand controller and activates the motor, and so on...
The difficulty for me is the serial interface with the Arduino. Is it just a matter of knowing the pin out for the serial connector and hooking the output to the Arduino pins as INPUT? I think it would need 2x RA and 2x DEC outputs - one for each button. I guess so:question:
vBulletin® v3.8.7, Copyright ©2000-2013, vBulletin Solutions, Inc.