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AstroEQ for EQ mounts


Oily

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Hi All,

I'm intending to purchase the AstroEQ for my Bresser EXOS2 mount, from Tom and I've already contacted him regarding purchase/availability etc.. The only thing is I already have the stepper motors (Vixen MT-1WT clones), but these use an 8 pin DIN socket instead of the standard st4 socket on the Skywatcher drives. (It appears that only four pins are actively connected when used with the Duo Controller supplied by Bresser.)

Has anybody successfully used these motors with the AtroEQ and, if so, what is the wiring sequence from the AstroEQ to the motor?

Thanks in advance for any info.

Brian

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Hmm.. finally I got tested astroeq outdoors, and it works fine (Thanks Tom), but... I have one big problem. Ra- axis works fine, and it stop when it should. But, Dec-axis still goes and goes?  Even if I pick one star near of the pole star, I feel that collapse of telescope and a mount would be possible, if I don´t stopped it. Do I have some wrong settings an Eqmod or AstroEq? I use this http://www.astroeq.co.uk/tutorials.php?link=/doku/doku.php?id=custommotors set up (nema 14 motors). And I use these settings in AstroEq:  Motor Step Angle: 1.8 / Motor Gear Ratio: 2.666666667 / Worm Gear Ratio: 144 and 1/16th Microstepping = Enabled. Do I have missed somethin important or what is wrong? Maybe I have some wrong settings on Eqmod? Thanks in advance!

-Esa-

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Hello everybody!

I would like to share my experience with AstroEQ and especially to thank Tom for his contribution to DIY astronomy.

A couple of months ago I've decided to equip my CG4 with  AstroEQ using Arduino Mega as I had one laying around. Bought cheap A4988 and NEMA 17 motors of Ebay and MXL gears from beltingonline( by the way they've got ready kits - which are cheaper than choosing separately pulleys and belts). Took me about 2 hours to breadboard the schematics and upload the sketch and - Miracle! Everything worked from the first time! Had a little trouble running it under Linux mint (INDI EQmod and Kstars) as every time I plug USB or sd card -have to change the link to the serial port :(. I'm still trying to sort this out. Under Windows - no problems whatsoever. Managed to do pulse guiding with 114mm  Konusmotor 500 as guiding scope and Logitech 4000Pro(found it 2 weeks ago at Picks Cottage Car boot sale for 50p :)- luckily it has sony chip inside!!!  ) .I've let it go for an hour the worst correction was 3 pixels at RA( 6 pix peak to peak) - have to make some calculations to see what is the error in arcsec - anyway its impressive! Last week decided to change design from bread board - couple of fails as I've tried to change the pin mapping( The serial communication appears on RX0/TX0) so had to settle for the default pin mapping.In all redesigning and fitting in appropriate case I've managed to disconnect the motors before removing the Vmot :( :both drivers expired. Now I am choosing drv8825 - I saw couple different designs on Internet and particularly one that is branded "Design by Kliment". It has big ground pad and chip on the bottom. It supose to be direct replacement for A4988 but it has internal logic power and the pin is used for output Fault... If anyone had experience with one of theese any feedback will be appreciated.

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@velinoff

These are the ones I recommend, and use in AstroEQ:

http://proto-pic.co.uk/drv8825-stepper-motor-driver-carrier-high-current/

Though, unless you have already, make sure you double check all of your connections, especially around the motor driver boards, it is very easy to make small solder bridges on Veroboard.

The 'ready made kits' at beltingonline are actually for the HEQ5 - I know they label them as EQ5, but they got it wrong.

@Esa

That one is new. Could you try reprogramming the firmware and your configuration, it seems something may have got wrong with programming. If that doesn't work, let me know via PM and I'll see what I can work out from this end.

@Brian

Not sure about the wiring of those motors. Do you have a multimeter? If so, you can find out the connections by measuring the resistance between pins. You should be able to find two pairs of pins which have a low (10-100 ohm) resistance between them. These are the two coils. The rest should have no connection.

@Sebastien

Not sure about that. Do you have more information on the motors?

----------------------

Good news anyway, I'm back from my holiday and have ordered another batch of PCBs. It will probably take ~10days for them to arrive after which I will get in touch with those who have enquired. There will be around 10 left of the batch after those who have got in touch have theirs. In a month I will be moving to America for two years to work on a project over there, so not sure I will be making any more for a while after this batch is gone, so if you want one, now is the time. (I'll still be on the forum etc. so around if anyone needs support).

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In a month I will be moving to America for two years to work on a project over there, so not sure I will be making any more for a while after this batch is gone, so if you want one, now is the time.

A hearty congratulations Tom, I wish I was young again and had the brains to go with it. All the very best for the future. :)

For a standard EQ5 mount with standard SkyWatcher motors, this is what I put together (see post 787)

I've now installed belt drives on the EQ5 using the SW motors you sent me.

Beltingonline were very helpful.

Just had to move the motors out to get 31.5mm centers in order to use standard parts.

2x MXL # 4580 belts

2x MXL # 5173 pulleys bored to 6mm

2x MXL # 5173 pulleys bored to 5mm

a small spacer was required to move the motors slightly outwards, all the while using the OEM brackets and bolts.

Belt width 6.365mm, belt length 109.73mm, this is a standard size and thus the cheapest.

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Hi Tom,

On a personal note I can only congratulate you and wish you the best of luck on your journey to the US. On a national note it's just a shame that we in the UK, can't offer our young people the chance to expand their undoubted talents here in the UK. We have some of the best brains in the world and yet the opportunities available to them seem to come from overseas.

Anyway, Tom, enjoy the next 2 years and come back home and make a million here.

All the best Tom,

Brian

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Slewing problem solved

I deleted all eqmod files manually. Uninstalled cartes du ciel and eqmod drivers. Then I cleanup registry and installed ccd and eqmod drivers again. I think that there were something wrong in my old settings. Daylight testing is now very positive. Now I only need do night time testing.

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Hmm, those motors have a very high current rating - 1.7A per phase. AstroEQ is only capable of providing 1.2A per phase. It is however possible to run the motors at a lower current than their rating at the expense of some torque, given how large the rated torque of that motor is, I don't see that this would be a noticeable loss.

You could theoretically got up to 1.5A per phase which is quite close to the rating of those motors, but you may notice excessive heating in the reverse polarity protection diode on the input. This could be bypassed as long as you ensure never to connect a supply of the wrong polarity.

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I have a couple of the Zapp Automation stepper motors.  The motor output shafts are completely round and I've been wondering if I should grind a flat onto them to give the pulley retaining screw something to lock against.  Has anyone else found it necessary to do that?  (I know the Skywatcher motor output shafts already have a flat on.)

James

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It's worth doing. Sometimes the motors have them, the last time I bought from ZA they did have flats in the shaft, but clearly not this time.

I have done this in the past for something else and it definitely helps. You can do it with a hacksaw if you are careful, just make a couple of parallel cuts next to each other to open out a slot large enough for the grub. Alternatively a needle file would work. I'd try and go in about a mm at the deepest to give the grub screws good purchase. 

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Thanks, Tom.  I shall take my RA motor mount assembly apart again and do that.  I have to drill some mounting holes for the RJ11 socket anyhow, and I can take a few photos of the mounting bracket whilst I'm at it.

James

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I'll do a proper write-up of this when I'm finished, but just for interest here's a picture of the assembled RA motor unit and mount for my EQ3-2 conversion:

ra-motor-03.jpg

Because there is only a single mounting hole in the mount for each motor and I don't wish to drill any more I've had to take some care with the motor mounts.  Using the U channel for this one means the left-hand side in the above photo will be flush against the side of the mount, but the upper edge will also butt up against the back of the RA gear housing, meaning that even though it's only held in place with a single screw there's no opportunity for the motor mount to twist.

All I need to do now is to solder the wires to the RJ11 socket, fix that in place and shrink the shrink-wrap.  Then it can go onto the mount.

I shall skip doing that this evening though as I'm too tired for fiddly soldering jobs now and I need to think clearly to make sure I get all the wires soldered in the correct order.  The wires at the motor end are black-green-red-blue, where black and green are one motor and red and blue the other.  I have a feeling I need one motor on the outside pair and one on the inside (eg. black-red-blue-green), but I must check that before I start soldering.

James

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Hi Tom,

I didn't have a multimeter, but I do now. I've checked all pins on the 8 pin DIN motor sockets and found 2 pairs on each motor that have an impedance of 21.7 ohms between them. On one of the motors there are only 4 wires connected but the other one has 6 wires connected but 2 of them share a common pin.

I assume then that I connect the 4 wires from each AstroEQ motor outlet to each pair on the motor as per the AstroEQ instructions.

Any idea when you might have them ready?

Cheers

Brian

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21.7Ohm sounds about right. For the 4 wire motor connect as the instructions.

For the 6 wire motor, I presume you are measuring something like this:

6-pin.png

If so, you can simply ignore the two wires that have the higher resistance. This is something which I've seen on the HEQ5 motors where the RA has a high resistance set of coils which the skywatcher controller switches to to save power while tracking (all be it very badly!).

For those desperately awaiting news of when the next batch of AstroEQ controllers will be available, I got an e-mail yesterday evening saying the PCBs have been posted out to me (should arrive Monday/Tuesday). I'll be sending out PMs/e-mails to those who have asked about them this evening.

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  • 2 weeks later...

Hi folks I'm looking forward to a some holiday coming up and I thought I'd like to get my Astro EQ project completed ready for the winter.  I have the motors on the mount all working and communicating through the computer and Tom's box of wizardry.  I know I have to go back and recount the teeth on my RA but I was wondering what is the best routine to test everything out - to do the initial synchronising to confirm correct pointing etc.  At the moment my setup communicates to and takes goto commands from CDC and Stellarium but I don't think it moves correctly in RA.  For example If I start with the scope pointing at Polaris and select a target in the west the scope ends up driving East in RA.  In fact the RA always appears to drive in that direction.  I was looking to do a test by maybe just driving the scope by manually inputting RA and DEC coordinates into the EQ MOD interface.  Hope that makes sense, I could post a video if that would help.  As always grateful for any thoughts or help.

Jim

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I believe it's slightly random which way the scope drives depending on how you have your motors wired.  My recollection is that there's a configuration option that allows you to reverse the directions the motors are driven in to sort that out.

I've not got as far as testing mine yet, despite having it all built now:

astro-eq-06.jpg

James

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Hi Jim,

This is a fairly normal occurrence. If the motors are wired up slightly differently, or the gear box has a different number of gears, the mount will go the wrong way, no real way of knowing until you test it and find it slews the wrong way. 

To correct this, run the configuration utility again, this time selecting the opposite setting of the button labelled "Reverse axis Direction" for the RA axis. If you notice the Declination is backwards, select to reverse that one as well.

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James your motors look similar to mine, like your brackets, neat work there.

Thank you :)

The mount is basically an EQ3-2 by any other name.  The brackets were not hard to make up at all.  The DEC bracket is a piece of 50mm aluminium angle that I happened to have lying around, and the RA bracket is a piece of 25mm x 50mm aluminium channel I bought from ebay.  It's entirely possible I could have made something neater, but I wanted to avoid drilling additional holes in the mount and with these two the brackets are locked in position against parts of the mount body despite only being held on by a single screw each.

The hardest part was actually working out where the centre of the motor should be and then marking out the holes for the four motor mounting screws.  I ended up having two goes at the DEC mounting bracket.  The first would probably have worked, but I really wasn't happy with it.

James

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