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Meade AutoStar Replacement

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#1 AtechLabs

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Posted 14 February 2024 - 06:32 PM

Hello Everyone!

 

I recently bought a used Meade DSX-90 telescope for $40, which seemed like a pretty good deal. It has the computerized mount, but it did not come with the AutoStar controller. It seems like there are lots of options when buying a new controller, and I am not sure which ones are compatible with my telescope. This website seems like a good guide, but it never mentions the DSX series. 

Can anyone shed some light on which models are compatible? Do I absolutely need the AutoStar handset to use the mount? I have seen some mentions of computer software, but it isn't clear to me if that works with the handset or as a replacement for it?

 

Thank you very much!


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#2 Skywatchr

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Posted 14 February 2024 - 08:00 PM

Hello Everyone!

 

I recently bought a used Meade DSX-90 telescope for $40, which seemed like a pretty good deal. It has the computerized mount, but it did not come with the AutoStar controller. It seems like there are lots of options when buying a new controller, and I am not sure which ones are compatible with my telescope. This website seems like a good guide, but it never mentions the DSX series. 

Can anyone shed some light on which models are compatible? Do I absolutely need the AutoStar handset to use the mount? I have seen some mentions of computer software, but it isn't clear to me if that works with the handset or as a replacement for it?

 

Thank you very much!

You can use the Autostar #495 #497 Or the Audiostar.  But no other "Autostar" type will work.

 

Here is the user manual for your scope;

 

https://www.meade.co...01DSXmanual.pdf

 

Here is the Autostar #497 user manual (will be the same for the #495 too)

 

https://www.meade.co...r497english.pdf


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#3 AtechLabs

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Posted 14 February 2024 - 08:05 PM

Thank you, Skywatchr! Do you know if I need the AutoStar handset to use the mount? I have seen some mentions of computer software, but it isn't clear to me if that works with the handset or as a replacement for it?


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#4 OzAndrewJ

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Posted 14 February 2024 - 08:55 PM

Gday AtechLabs

For the 497/Audiostars, 98% ot the brains are in the handset

so you must have that fitted in order to run the mount.

There are ways to run the motors directly, but its all that it will do

ie run motor at speed "X".

In your case, you need an handset.

Andrew Johansen Melbourne Australia


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#5 Skywatchr

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Posted 15 February 2024 - 08:17 AM

Thank you, Skywatchr! Do you know if I need the AutoStar handset to use the mount? I have seen some mentions of computer software, but it isn't clear to me if that works with the handset or as a replacement for it?

Yes as OzAndrewJ says.  There are 2 ports on these particular handboxes. 

One, the larger of the two, is to connect it to the HBX port on the scope base. 

The other smaller one is the serial port that you use for two purposes.  * With the proper USB to Serial cable *

The first purpose is to be able to connect it to a computer to control the scope with. 

The other use is to update the firmware that is in the Autostar itself IF an update is needed.

Note a #495 can be updated to a #497 firmware.  But it has to be done properly.

 

When you get a compatible handbox (one of the 3 mentioned), report back and OzAndrewJ will guide you in case an update is warranted. He will need to know what the current firmware is in it before proceeding.  It is easy, but do not use the Meade ASU (Autostar Updater).  There is a better way and he will explain it with screenshots and all for using StarPatch updater instead.

 

The Audiostar probably won't need any updates.

 

Note:  Do NOT plug the USB to serial cable into the AUX port on the scope base.  Bad things will happen if you do.


Edited by Skywatchr, 15 February 2024 - 08:19 AM.

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#6 AtechLabs

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Posted 15 February 2024 - 02:36 PM

Many thanks to you both! If I find a new handbox at a reasonable price, I'll post an update with the relevant details. 


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#7 AtechLabs

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Posted 15 February 2024 - 05:57 PM

There are ways to run the motors directly, but its all that it will do

ie run motor at speed "X".

OzAndrewJ - Would you be able to elaborate on this? Is it simply a matter of sending a PWM signal to the drivers? Is there a detailed overview of how to communicate with the drivers?


Edited by AtechLabs, 15 February 2024 - 05:58 PM.


#8 OzAndrewJ

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Posted 15 February 2024 - 06:10 PM

Gday AtechLabs

The best place to start is the roboscope group

https://groups.io/g/RoboScope

There are full worked examples of the code and how some people have used it.

One user even mapped the EQMod control system to talk to Meade motor cards

 

There is also an excellent thread on the LX200 site

https://groups.io/g/...PS/message/4599

where a user made up an arduino based controller for his 497 then 16"LX200 :-)

It is only designed to track satellites using visual feedback ( ie he needed limited control )

but its not "trivial" to get it all going

 

In simple terms

Meade use a bitbanged form of I2C ( more like clocked serial with Ack )

to talk to the motor cards.

These commands vary slightly between 497 based units and ASII based units

but the commands are very simple, but are constrained by certain limits

Again, its up to you to do everything re keeping position data etc

and thats the hard bit

 

Andrew Johansen Melbourne Australia


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#9 AtechLabs

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Posted 15 April 2024 - 04:15 PM

Hello again! I've managed to get my hands on a #495 or #497, but I can't figure out how to tell the difference, or what the firmware version is. Are there any key differentiating features between the two models? Where in the menus can I find the firmware version?


Edited by AtechLabs, 15 April 2024 - 04:15 PM.

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#10 OzAndrewJ

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Posted 15 April 2024 - 04:36 PM

Gday AtechLabs

The 495/497 are the same thing "physically/functionally"

( with the caveat they may have different LCD screens,

as the very early models had 24 pin LCDs and the later ones had 14 pin )

All you do to make a 495 into a 497 is load the later firmwares.

To know what you have now, you can use my app and serial commands to get the version

or you can just start the handdset and go to the "Statistics" menu

The version is one scrollable item in that screen

Andrew Johansen Melbourne Australia


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#11 AtechLabs

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Posted 19 April 2024 - 09:02 PM

Looks like I have Version 33En. 


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#12 OzAndrewJ

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Posted 19 April 2024 - 09:41 PM

Gday Atechlabs

OK, not the earliest but still very old, and definitely a 497.

Just load the latest 43Eg patch ( deselect the first three options tied to StarGPS )

do a handset reset and reload your data, do a drive train and all should be well

 

Andrew Johansen Melbourne Australia


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#13 AtechLabs

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Posted 22 April 2024 - 10:27 PM

Hello Andrew, 

 

Thank you for the time you have taken on this and all the other similar posts. I imagine it must be frustrating to repeat the same advice over and over, but it really is very helpful.

1) Everything was, briefly working nicely after the update. Unfortunately, I was messing about with some power for the mount and accidently reversed polarity for a moment. I was greeted with a pop and the smell of freshly toasted FR4. It looks like I popped a trace, which a forum search seems to confirm is a common failure mode for this kind of accident. Is that correct?

2) My Autostar handset, which was foolishly connected at the time, seems to have survived. I connected it to an ETX mount and it happily slewed to the appropriate stars. Is it likely that there is unseen damage to the handset? I am fairly comfortable soldering, so I am considering just jumping over the burned trace. My main concern is doing (further?) damage to the handset. Is that likely?

I also have a few other, probably very stupid, questions. 

3) I have acquired an ETX-90 which has a very bad primary mirror. Is it possible to swap the OTA of the ETX with the DSX?

4) Is it possible to switch the primary mirrors?

5) Could I take a DS mount from a different DS-Series telescope to replace my burned out mount? Are all DS mounts interchangeable?

6) Any other suggestions for what to do in this situation?



#14 OzAndrewJ

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Posted 22 April 2024 - 11:14 PM

Gday Atechlabs

It looks like I popped a trace, which a forum search seems to confirm is a common failure mode for this kind of accident. Is that correct?

For mounts like the LX90 or ETX-90to125 that have a std input panel, yes,

a trace dies and can normally be jumpered.

I am not sure of the layout of the DS mount board

so if you have a piccy, we can quickly see whats going on.

The circuitry of the Aux and Hbx ports wiring is common

but the layout ,may be different.

 

Most of the time, the handbox isnt affected, so maybe buy a lottery ticket.

Re future damage to the Hbx, unless you really cross over or short traces

when repairing, it shouldnt matter.

After jumping the damaged, a simple continuity test of the mounts RJ port contacts

will show if any are shorted internally.

If not, it shouldnt hurt the hbx.

Re 3) No idea

Re 4) I doubt it

Re 5) AFAIK, the DS "mount" is common to all the tubes it lists

          Just using a named version in the selection allows setting the focal length

          and upper/lower slew limits

          All the critical info like ratios etc is common

Re 6) If the Hbx is stil OK, buy a lottery ticket

Several people i know have put their own reverse polarity protection

systems in place and there are a variety of options these days

The best/simplest is an external one based on a reverse biased PCh mosfet

as it gives protection without a large voltage drop ( like a series diode )

or a fuse blow each time, ( like a parallel diode )

There are now cheap kit versions of this sort of device

and i wonder why manufacturers arent building it into the cards.

 

ref

https://kc9on.com/pr...ity-protection/

https://sites.create...oke_Stopper.pdf

for some of the many kits out there now

 

Andrew Johansen Melbourne Australia


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#15 AtechLabs

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Posted 23 April 2024 - 09:28 PM

Let's see if I can manage to attach these images. 

I think this is the area where the ground plane blew out and took the trace below with it. It looks to me like the top and very bottom are still okay. My fear is that the highlighted IC might have also been affected, as there is (maybe) a tiny pinhole on the right side a little more than halfway up. Hard to make out in the photo, and unfortunately I cannot make out the IC code.  
DS
DS highlighted

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#16 OzAndrewJ

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Posted 23 April 2024 - 10:51 PM

Gday Atechlabs

According to the circuit diag, U2 is a std 5V regulator

I cant see the damaged trace clearly but it looks like it may

only have been a thin ground connect.

Can you clean away the burnt bits with isopropyl alcohol or similar

so we can see the damage.

Maybe someone with an undamaged one can get a piccy of the same spot???

Andrew Johansen Melbourne Australia


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#17 AtechLabs

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Posted 24 April 2024 - 06:37 AM

I already used some isopropyl alcohol on a cotton swab to clean it up the best I could. I think the next thing to do is dig out the multimeter and see what it says. 


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#18 AtechLabs

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Posted 24 April 2024 - 10:28 AM

Interesting results!

A little poking around with the multimeter seems to confirm that U2 is supposed to be a 5v regulator and the ground plane is disconnected from all the other ground planes on the board. Or, more accurately, they seem to be disconnected from it. It seems that all the other ground planes are connected through that tiny bridge.

I've soldered the planes together and the multimeter confirms they are connected. The 5v regulator's output went from ~5.6v when the planes were separate to ~4.2v after bridging. Connecting the handbox and powering on looks fine at first. Slewing with the buttons works nicely and everything looks good. But calibrating the motors gives a "Motor unit fault" which locks the handbox into a testing-failed loop that can only be broken by a power cycle. I've tried with batteries and a power supply, same result for both. This happens both when assembled and disassembled. 

Any thoughts? 


Edited by AtechLabs, 24 April 2024 - 12:04 PM.


#19 Skywatchr

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Posted 24 April 2024 - 12:52 PM

 

Let's see if I can manage to attach these images. 

I think this is the area where the ground plane blew out and took the trace below with it. It looks to me like the top and very bottom are still okay. My fear is that the highlighted IC might have also been affected, as there is (maybe) a tiny pinhole on the right side a little more than halfway up. Hard to make out in the photo, and unfortunately I cannot make out the IC code.  

 

Check the solder joint at U1 to the ground trace.  It is hard to tell from the photo, but from way over here grin.gif  it appears to be a cracked solder joint on that lead of the chip.

 

The motor fault may be something that happened when the trace blew.  It's hard to tell but that usually indicates there is no feedback from the motor encoder(s). 


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#20 OzAndrewJ

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Posted 24 April 2024 - 04:15 PM

Gday atechlabs

Skywatch got it right in that a "Motor UNIT fault" during operation

happens if there is NO feedback at all from the motor encoder.

What should also happen no matter what speed the handset is set to,

the relevant motor wil ramp up to full speed as it tries to detect feedback.

If you look at the schematic, you will see there is a series of parallel resistors

and these are used to control the current going into the encoder LED

such that it gets the best feedback. Follow the traces from there to the LED or receiver

Next test is use a webcam / camera feed to look at the led

They use IR light so will glow in a camera sensor if working.

Andrew Johansen Melbourne Australia


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#21 AtechLabs

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Posted 25 April 2024 - 06:59 AM

I should probably have mentioned that, upon calibrating, nothing moves or tries to move. Only the four manual slew buttons seem to have any effect on the motors. The encoders are emitting light


Edited by AtechLabs, 25 April 2024 - 07:01 AM.


#22 DAVIDG

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Posted 25 April 2024 - 01:38 PM

 The regulator should have an output of a solid +5 volts so something is wrong if it is  +4.2. It could be oscillating and that type of noise makes microcontrollers have problems. I had a similar situation with  DS2000 that was given to me and the regulator had issues. I replaced it with a common LM7805 which is good  for a couple of amps vs  about 300ma for the ones used on the board now.   I didn't try to remove the original regulator but cut the trace feeding the input voltage and soldered the input leg of the LM7805 to that  trace and  used jumpers to a ground point  and were the +5 used needed. That fixed my problem. 

 

            - Dave 

 

meade DS2000 circuit board.jpg

 

 

 


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#23 OzAndrewJ

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Posted 25 April 2024 - 04:59 PM

Gday atechlabs

upon calibrating, nothing moves or tries to move. Only the four manual slew buttons seem to have any effect on the motors.

That is very weird

Commands are sent to the motor cards using a single clock and data line

so you either get all commands being transmitted or no commands.

As such the command to calibrate is no different to the command to move

If one works, the other should.

Just for info, if you start the mount and put the hbx into alternate mode

scroll to the alt/az screen

When you slew in either axis, is there any change???

Andrew Johansen Melbourne Australia



#24 AtechLabs

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Posted 25 April 2024 - 08:50 PM

Just for info, if you start the mount and put the hbx into alternate mode

I'm unsure if this is what you meant by alternate mode, so please correct me if I am wrong. By default the handbox is in Alt-Az mode on startup. If I switch to polar mode (Setup>Telescope>Mount>Polar), the base motor spins up to full speed and continues until about 15 seconds later it stops and the handbox displays the motor fault message. Interestingly, the base encoder (the top one is still assembled) has stopped emitting light. Is it a standard part? Can I get a replacement without a second mount or is this mount toast?


Edited by AtechLabs, 25 April 2024 - 08:50 PM.


#25 AtechLabs

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Posted 25 April 2024 - 09:01 PM

 The regulator should have an output of a solid +5 volts so something is wrong if it is  +4.2. 

That's what I suspected, thank you for confirming. I'll swap out the regulator and see if we get anything more sensible out of it's behavior. 


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