Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

DIY ET-8 GOTO Mount

astrophotography eq mount
This topic has been archived. This means that you cannot reply to this topic.
285 replies to this topic

#126 hjd1964

hjd1964

    Ranger 4

  • *****
  • Posts: 368
  • Joined: 24 May 2012

Posted 06 March 2015 - 05:58 AM

Hi,

 

I'm having a bit of rouble getting smooth steeper rotation....I get a cyclic sound when tracking and a small clunk when it reaches a full step position. Have tried both 16 and 32 microsteps at varying voltages up to 24 volts - the clunk is worse at higher voltages.

 

I can get smoother rotation at 12 volts and a high amperage setting, but then the motors get warm.... I have also found that the tepper driver chips ae getting very hot - should I put some heatsings on them?

 

Any ideas for smooth rotation?

 

cheers

Gary

 

I've observed, I think, the same behavior you describe while setting up steppers.  The cyclic sound you refer to is probably the PWM and is normal, in-fact for most motors I've tuned it's a good sign that you're in the ball-park for smooth micro-stepping.  I sometimes feel some additional vibration near the full step position too.  I've also seen thin lead wire degrade stepping, make movement more erratic, and make this vibration worse.

 

The DRV8825 and A4988 based drivers I've used recommend adding heat-sinks to reach their full current rating.

 

Going from 12 to 24V should make things better not worse.  Lead losses are less, current through the drivers is less, overall equal or better results for motors I've tested.

 

More info. might help, what motors are you using (design V and A, size)?


Edited by hjd1964, 06 March 2015 - 06:03 AM.


#127 Gary.McK

Gary.McK

    Viking 1

  • -----
  • Posts: 608
  • Joined: 29 Jan 2009

Posted 06 March 2015 - 07:20 AM

Hi,

 

I'm using Nema 17  as follows

2amps/phase

Phase resistance 1.4 ohms

rated voltage/phase 2.8

Phase Inductance 3mh

 

The smoothest running is at 12 volts drawing an amp - this is actually quite smooth. I have put small heatsinks on the drivers.

If I increase the voltage to 24, the tracking becomes much less smooth, no matter how I adjust the current - the thunk becomes very noticeable, whereas at 12 volts it is barely perceptible.

 

At 12 volts/1 amp the heat sinks become quite hot

 

I have set things up for a Losmandy G11 like yourself - 32 microsteps.

 

I don't quite understand the section on microstepping - Micro-step driver mode control

I have:

#define HA_MODE 5

#define HA_MODE_GOTO 1

#define HA_STEP_GOTO 4

 

and corresponding settings for dec...

 

Don't know if this makes a difference?

 

Slewing seems reasonable (motors just on the bench).

 

Any ideas?

 

cheers

Gary

 

 

 

 

Hi,

 

I'm having a bit of rouble getting smooth steeper rotation....I get a cyclic sound when tracking and a small clunk when it reaches a full step position. Have tried both 16 and 32 microsteps at varying voltages up to 24 volts - the clunk is worse at higher voltages.

 

I can get smoother rotation at 12 volts and a high amperage setting, but then the motors get warm.... I have also found that the tepper driver chips ae getting very hot - should I put some heatsings on them?

 

Any ideas for smooth rotation?

 

cheers

Gary

 

I've observed, I think, the same behavior you describe while setting up steppers.  The cyclic sound you refer to is probably the PWM and is normal, in-fact for most motors I've tuned it's a good sign that you're in the ball-park for smooth micro-stepping.  I sometimes feel some additional vibration near the full step position too.  I've also seen thin lead wire degrade stepping, make movement more erratic, and make this vibration worse.

 

The DRV8825 and A4988 based drivers I've used recommend adding heat-sinks to reach their full current rating.

 

Going from 12 to 24V should make things better not worse.  Lead losses are less, current through the drivers is less, overall equal or better results for motors I've tested.

 

More info. might help, what motors are you using (design V and A, size)?

 



#128 hjd1964

hjd1964

    Ranger 4

  • *****
  • Posts: 368
  • Joined: 24 May 2012

Posted 06 March 2015 - 10:10 AM

Gary,

 

Assuming a DRV8825, etc. and you tuned the driver pot for the motor at each voltage tried?

 

Most of my setups have run at about 2-4x the design voltage, your motors have a design voltage of 2.8V (V=IR, 2.8V=1.4Ω*2A) so 24V operation is over 8x and outside of my personal experience.  Remember that the 2A figure for your motor is at 2.8V, and to a certain extent power/torque go hand in hand.  Power is P=I^2*R and 1.4A^2*2Ω = about 3.9 watts.  My motor is rated 0.8A^2*8Ω = 5.2 watts.

 

I would tune for smooth micro-stepping and try using it at 12V, since the motor design voltage is so low.  The higher voltage just helps with getting to higher speeds, but with an inductance that low and no need to reach more than a few rps it shouldn't matter.  I tried my G11 setup at 12V for a bit and the drivers got a little hot (not burning though, without heat-sinks) so I'm guessing that you're pushing similar if not more power into the motors.  What comes out as torque I don't know - similar but perhaps a bit less at low speed and a bit more at goto speeds possibly.

 

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

 

If using Steve's board, or Mode0,1,2 on DRV8825's (or similar) and wired in as instructed in Config.h...

 

#define HA_MODE 5

#define HA_MODE_GOTO 1

#define HA_STEP_GOTO 4

 

The HA_MODE value programs the driver's micro-stepping mode used during sidereal tracking.  The value 5 sets 32x mode (again other drivers and/or wiring might need different values.) The values are interpreted as binary numbers... a 5 is 101 in binary and the ones turn on the micro-step mode control lines of the '8825... Mode0 on, Mode1 off, Mode2 on... which gives 32x mode.

 

The HA_MODE_GOTO value works as above but is used during goto's only.  The value 1 sets 2x mode.

 

HA_STEP_GOTO is the number of HA_MODE micro-steps in a HA_MODE_GOTO micro-step (32/2) and should be 16 in this case not 4.

 

The main reason for all of this is to overcome limitations of the Mega2560 and Teensy3.1's speed.  The Mega2560 is normal limited to 32us per step and the Teensy3.1 to 16us.  These are rates set with MaxRate in Config.h

 

I say "normally limited" because turning on HA/DEC_MODE_GOTO results in additional code being inserted into the ISR's that service the motors so they can't run quite as fast.  This isn't a big deal because if you turn it on it's to drop the micro-step mode down to a lower setting and the final speed the ISR(s) have to run at is HA/DEC_STEP_GOTO times slower than the MaxRate would have had it.  So in the above example if MaxRate is set to 16 (which for my G11 would be 5 deg/sec. speed) the ISR's are firing every 256us (HA_MODE_GOTO was supposed to be 16, 256=16*16) which is far below the limit.  Personally I'd try 8x micro-stepping mode during gotos (help keep resonance down) and that would result in a 64us ISR rate which would be fine too, if the motors can get you there.



#129 orlyandico

orlyandico

    Cosmos

  • *****
  • Posts: 9,893
  • Joined: 10 Aug 2009

Posted 06 March 2015 - 10:27 AM

Shouldn't we be running full step during GoTo? that way maximum torque and speed.



#130 hjd1964

hjd1964

    Ranger 4

  • *****
  • Posts: 368
  • Joined: 24 May 2012

Posted 06 March 2015 - 10:29 AM

And BTW, here's a link to a video of Steve's driver board Rev. B spinning a couple of motors.  These motors are destined for my Tak EM10 mount and will be attached to a different controller but I was doing some testing first:

https://plus.google....=CJaP99fTydqzFg



#131 hjd1964

hjd1964

    Ranger 4

  • *****
  • Posts: 368
  • Joined: 24 May 2012

Posted 06 March 2015 - 10:36 AM

Shouldn't we be running full step during GoTo? that way maximum torque and speed.

I've heard that too, but my personal experience has been that everything works better when micro-stepping.  [And possibly this is because most of my experience is with configurations that don't get the motors running fast enough for full-step advantages.]  It's easy to experiment and I always try a couple of step mode settings, tune the acceleration for resonance suppression, and even adjust the final MaxRate speed a little +/- to avoid resonance.


Edited by hjd1964, 06 March 2015 - 10:49 AM.


#132 pbunn

pbunn

    Vanguard

  • *****
  • Posts: 2,000
  • Joined: 29 Sep 2010

Posted 06 March 2015 - 10:46 AM

I am going to pick up a Bluetooth Android tablet at Office Depot at lunch. On sale fro $99 to $79. I think I will need it to do the mount alignment.

 

Pat



#133 ssagerian

ssagerian

    Maker Uranographer

  • *****
  • Posts: 658
  • Joined: 30 Nov 2013

Posted 06 March 2015 - 10:48 AM

Yup, that is what I told my wife...worked like a champ..



#134 pbunn

pbunn

    Vanguard

  • *****
  • Posts: 2,000
  • Joined: 29 Sep 2010

Posted 06 March 2015 - 10:50 AM

I still haven't figured out what to tell my wife about the MyT that will arrive in about a month. Any suggestions?

 

Pat



#135 ssagerian

ssagerian

    Maker Uranographer

  • *****
  • Posts: 658
  • Joined: 30 Nov 2013

Posted 06 March 2015 - 11:01 AM

In those situations its always best to to counter balance the cost with something  of similar or greater cost for her. You are a dead man...



#136 pbunn

pbunn

    Vanguard

  • *****
  • Posts: 2,000
  • Joined: 29 Sep 2010

Posted 06 March 2015 - 11:21 AM

Yep - I can't afford that - If she finds out how much it costs - I am definitely a dead man!

 

I will tell her that I sold My G11, the ZEQ25 and some other stuff - BUT  - if she finds out how much the stuff that I sold cost - I am still a dead man.

 

 

 

Pat



#137 Gary.McK

Gary.McK

    Viking 1

  • -----
  • Posts: 608
  • Joined: 29 Jan 2009

Posted 06 March 2015 - 04:06 PM

Thanks Howard

 

you've cleared up a few things for me. The motors I have are very torquey, and run fine at 12 volts which just coincidentally is around the 8.2 volts that the driver chips require to work, plus the 2.8 volts that the motors are rated at.....

 

I was using a variable power supply power supply so it was easy to tune the motors with the pots and watch both voltage and current on the power supplies meters.

 

The heat sinks get quite hot at 1 amp, so I will get some bigger ones today. I would not have expected that hey would get this hot at the current levels I'm using give the rating of the driver chips.... I bought these motors:

 

http://www.omc-stepp...004s-p-122.html

 

They were rated for 12-24 volts and have really good torque, but I guess specs aren't always the full story!!

 

cheers

Gary

 

 

 

 

Gary,

 

Assuming a DRV8825, etc. and you tuned the driver pot for the motor at each voltage tried?

 

Most of my setups have run at about 2-4x the design voltage, your motors have a design voltage of 2.8V (V=IR, 2.8V=1.4Ω*2A) so 24V operation is over 8x and outside of my personal experience.  Remember that the 2A figure for your motor is at 2.8V, and to a certain extent power/torque go hand in hand.  Power is P=I^2*R and 1.4A^2*2Ω = about 3.9 watts.  My motor is rated 0.8A^2*8Ω = 5.2 watts.

 

I would tune for smooth micro-stepping and try using it at 12V, since the motor design voltage is so low.  The higher voltage just helps with getting to higher speeds, but with an inductance that low and no need to reach more than a few rps it shouldn't matter.  I tried my G11 setup at 12V for a bit and the drivers got a little hot (not burning though, without heat-sinks) so I'm guessing that you're pushing similar if not more power into the motors.  What comes out as torque I don't know - similar but perhaps a bit less at low speed and a bit more at goto speeds possibly.

 

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

 

If using Steve's board, or Mode0,1,2 on DRV8825's (or similar) and wired in as instructed in Config.h...

 

#define HA_MODE 5

#define HA_MODE_GOTO 1

#define HA_STEP_GOTO 4

 

The HA_MODE value programs the driver's micro-stepping mode used during sidereal tracking.  The value 5 sets 32x mode (again other drivers and/or wiring might need different values.) The values are interpreted as binary numbers... a 5 is 101 in binary and the ones turn on the micro-step mode control lines of the '8825... Mode0 on, Mode1 off, Mode2 on... which gives 32x mode.

 

The HA_MODE_GOTO value works as above but is used during goto's only.  The value 1 sets 2x mode.

 

HA_STEP_GOTO is the number of HA_MODE micro-steps in a HA_MODE_GOTO micro-step (32/2) and should be 16 in this case not 4.

 

The main reason for all of this is to overcome limitations of the Mega2560 and Teensy3.1's speed.  The Mega2560 is normal limited to 32us per step and the Teensy3.1 to 16us.  These are rates set with MaxRate in Config.h

 

I say "normally limited" because turning on HA/DEC_MODE_GOTO results in additional code being inserted into the ISR's that service the motors so they can't run quite as fast.  This isn't a big deal because if you turn it on it's to drop the micro-step mode down to a lower setting and the final speed the ISR(s) have to run at is HA/DEC_STEP_GOTO times slower than the MaxRate would have had it.  So in the above example if MaxRate is set to 16 (which for my G11 would be 5 deg/sec. speed) the ISR's are firing every 256us (HA_MODE_GOTO was supposed to be 16, 256=16*16) which is far below the limit.  Personally I'd try 8x micro-stepping mode during gotos (help keep resonance down) and that would result in a 64us ISR rate which would be fine too, if the motors can get you there.



#138 pbunn

pbunn

    Vanguard

  • *****
  • Posts: 2,000
  • Joined: 29 Sep 2010

Posted 06 March 2015 - 05:01 PM

I got the tablet and after screwing around a while, I got the OnStep app to pair up with the board. I have some steppers but they are not mounted on a mount (My GM8 is at Losmandy for a tune up). Is there a drawing on the board as to the stepper motor wiring. I assume that the two pole green terminal block is for the motors only and the rest of the board runs off the Arduino board via the USB or the DC connector. The trimpots are for the max current available for the steppers. Is clockwise max current?

 

The GM 8 has steppers but I doubt that they can slew as they are geared down like the Losmandy G11 steppers. I'd love to find some steppers that would work on the GM 8 with no gearbox.

 

 

Pat



#139 hjd1964

hjd1964

    Ranger 4

  • *****
  • Posts: 368
  • Joined: 24 May 2012

Posted 06 March 2015 - 06:10 PM

I got the tablet and after screwing around a while, I got the OnStep app to pair up with the board. I have some steppers but they are not mounted on a mount (My GM8 is at Losmandy for a tune up). Is there a drawing on the board as to the stepper motor wiring. I assume that the two pole green terminal block is for the motors only and the rest of the board runs off the Arduino board via the USB or the DC connector. The trimpots are for the max current available for the steppers. Is clockwise max current?

 

The GM 8 has steppers but I doubt that they can slew as they are geared down like the Losmandy G11 steppers. I'd love to find some steppers that would work on the GM 8 with no gearbox.

 

 

Pat

 

Pat,

 

The green two-pole connector is motor power in...  + is to the right.

 

The two big green four-pole connectors are for the steppers.  The four terminals of each are for the two motor phases A+,A-,B+,B-. 

 

Get out a multi-meter and check the stepper leads - on a bipolar motor you'll find two coils isolated from each other.  Hook one coil up to A+/A- and the other to B+/B-.  A unipolar motor has six wires three per phase with a "center-tap", resistance measurement can tell which two are the equivalent to bipolar.  Alternatively you can choose half-coil bipolar and wire each with the center-tap ignoring the other lead, this trades low-speed torque for high-speed torque (smaller coil = lower inductance.)

 

The trim-pot is as you described it in my experience, clockwise increases current.

 

Direct driving the worm of a GM8 is probably not practical with the motors we're using, you need a bit more reduction.  The G11 can get away with this because it has a 360 tooth worm wheel.  Your mount has a 180 tooth wheel and torque would need to be doubled and step size at 32x mode would still be a bit large also.  So think about a minimum 2:1 to 4:1 reduction [of a 400 NEMA17 step motor], diy with timing belt/spur gears, get a NEMA17 with gearbox, try the cheap MPJA NEMA11 18:1 motors that I'm experimenting with (video a few posts back), or get a tin-can hurst (or other) like I used on my first setup on the G11.  If going with the tin-can steppers of a reasonable gear ratio expect 0.5 to 1 deg./sec max.  I'll let everyone know how the NEMA11 motors work out for my EM10 mount.


Edited by hjd1964, 07 March 2015 - 06:45 AM.


#140 hjd1964

hjd1964

    Ranger 4

  • *****
  • Posts: 368
  • Joined: 24 May 2012

Posted 06 March 2015 - 08:13 PM

 

Thanks Howard

 

you've cleared up a few things for me. The motors I have are very torquey, and run fine at 12 volts which just coincidentally is around the 8.2 volts that the driver chips require to work, plus the 2.8 volts that the motors are rated at.....

 

I was using a variable power supply power supply so it was easy to tune the motors with the pots and watch both voltage and current on the power supplies meters.

 

The heat sinks get quite hot at 1 amp, so I will get some bigger ones today. I would not have expected that hey would get this hot at the current levels I'm using give the rating of the driver chips.... I bought these motors:

 

http://www.omc-stepp...004s-p-122.html

 

They were rated for 12-24 volts and have really good torque, but I guess specs aren't always the full story!!

 

cheers

Gary

 

I wouldn't say that the 8.2/2.8V thing is anything other than coincidence.  Most of the 12V should be getting to the motors, I believe the drivers chop/cut the power (on/off quickly) to keep the motors from overheating (and more.)

 

Perhaps someone who understands this stuff better than I can chime in, but I'll take a stab at an explanation for the 1A supply reading:

the motor should only need a fraction (about 1/3?) of it's rated current since it's running at 12V not 3.8 (this could be expressed as a power/watts relationship also)... so about 1/3 of 2A = 0.66A + some losses as heat at the DRV8825... and you have a bit less than 1A at 12V.  There are two coils in that motor but both aren't run at 100%, does this factor in as 2 x RMS(0.707, per phase) when micro-stepping so 0.66*1.4=.93A + resistive losses at the DRV8825, etc = 1A?  This concept is approximately correct I expect.


Edited by hjd1964, 06 March 2015 - 08:14 PM.


#141 pbunn

pbunn

    Vanguard

  • *****
  • Posts: 2,000
  • Joined: 29 Sep 2010

Posted 07 March 2015 - 09:11 AM

Has anyone looked at the NEMA 17 5.1:1 steppers with a planetary gearhead that are commonly available at about $35 each. They are used in 3 D printers. Is the 5.1:1 ratio too high?

 

Pat



#142 orlyandico

orlyandico

    Cosmos

  • *****
  • Posts: 9,893
  • Joined: 10 Aug 2009

Posted 07 March 2015 - 10:25 AM

Those are OK,  I used those in my first attempt to goto my AP600. The problem is that it's hard to mount them.  The planetary gearhead is small diameter so the mounting holes are close together. It was also disturbingly easy to strip the mounting holes... 

 

That was just my experience. 

 

The $10 MPJA motors that Howard linked to are the best. I bought the larger versions for $50+ each on ebay.  These are Japanese Vexta motors,  very high quality. The Takahashi NJP uses these motors (Vexta PK243).



#143 pbunn

pbunn

    Vanguard

  • *****
  • Posts: 2,000
  • Joined: 29 Sep 2010

Posted 07 March 2015 - 11:37 AM

The VEXTA 243 would be a nice motor  but I need a gearbox or I'll have to belt drive it and all that mounting will be a pain. I am lazy!

 

 

Pat



#144 orlyandico

orlyandico

    Cosmos

  • *****
  • Posts: 9,893
  • Joined: 10 Aug 2009

Posted 07 March 2015 - 11:52 AM

The $10 MPJA motors have 18:1 spur gearboxes.



#145 Geo.

Geo.

    Vendor - Nexstar Parts

  • *****
  • Vendors
  • Posts: 5,711
  • Joined: 01 Oct 2008

Posted 07 March 2015 - 03:25 PM

The problem with the GM-8 and the G11 is that the side mounted drives interfere with full motion. I've got some Meade LX90 drives that have some potential. just a sketch:

 

Attached Thumbnails

  • IMG_3206 crop.jpg


#146 Gary.McK

Gary.McK

    Viking 1

  • -----
  • Posts: 608
  • Joined: 29 Jan 2009

Posted 07 March 2015 - 10:23 PM

Hi Howard,

 

thanks for the explanation - as a person with a biological background rather than an electronics one I'll take your word for it !!

 

It seems to be working fine, but the slewing speed is a little slow about 1/2 rev per second so I will need to play with settings to speed things up a bit to get to the 2 deg second target I'd like.

 

It would be nice if the ascom driver could handle the initialization - rather than needing your chart program or an android ap (I have a Windows phone!).... My old laptop is filled t the limit with Pinpoint, The Sky 6, Skytools 3, and Astroart.... It would be nice to avoid having to try to fit an extra charting program on to initialize the drive..... I have been using a borrowed android tablet to play....... but this must go back soon.

 

I'm also very appreciative of Steve for doing the boards, and you for doing the development work on the software.... Much applause from a non techie person here....

 

cheers

Gary

 

 

 

 

I wouldn't say that the 8.2/2.8V thing is anything other than coincidence.  Most of the 12V should be getting to the motors, I believe the drivers chop/cut the power (on/off quickly) to keep the motors from overheating (and more.)

 

Perhaps someone who understands this stuff better than I can chime in, but I'll take a stab at an explanation for the 1A supply reading:

the motor should only need a fraction (about 1/3?) of it's rated current since it's running at 12V not 3.8 (this could be expressed as a power/watts relationship also)... so about 1/3 of 2A = 0.66A + some losses as heat at the DRV8825... and you have a bit less than 1A at 12V.  There are two coils in that motor but both aren't run at 100%, does this factor in as 2 x RMS(0.707, per phase) when micro-stepping so 0.66*1.4=.93A + resistive losses at the DRV8825, etc = 1A?  This concept is approximately correct I expect.

 



#147 hjd1964

hjd1964

    Ranger 4

  • *****
  • Posts: 368
  • Joined: 24 May 2012

Posted 08 March 2015 - 12:35 PM

The problem with the GM-8 and the G11 is that the side mounted drives interfere with full motion. I've got some Meade LX90 drives that have some potential. just a sketch:

Converting it to the Autostar system with the LX90 drives?



#148 hjd1964

hjd1964

    Ranger 4

  • *****
  • Posts: 368
  • Joined: 24 May 2012

Posted 08 March 2015 - 01:19 PM

 

Hi Howard,

 

thanks for the explanation - as a person with a biological background rather than an electronics one I'll take your word for it !!

 

It seems to be working fine, but the slewing speed is a little slow about 1/2 rev per second so I will need to play with settings to speed things up a bit to get to the 2 deg second target I'd like.

 

It would be nice if the ascom driver could handle the initialization - rather than needing your chart program or an android ap (I have a Windows phone!).... My old laptop is filled t the limit with Pinpoint, The Sky 6, Skytools 3, and Astroart.... It would be nice to avoid having to try to fit an extra charting program on to initialize the drive..... I have been using a borrowed android tablet to play....... but this must go back soon.

 

I'm also very appreciative of Steve for doing the boards, and you for doing the development work on the software.... Much applause from a non techie person here....

 

cheers

Gary

 

A MaxRate value of 32 is what I use to get 2.5 deg/sec. on my G11.

 

I'm not a big fan of ASCOM control panels cluttering up my screen, I like control in one application so that's what I did...

 

However, alignment of OnStep really needs just a few commands :A1# :A2# :A3# :A+# .  If using ASCOM's POTH a simple jscript or vbscript could be written to send the required commands (it would take just a few lines of code I believe.)

 

For example:

Use a script to start a two-star align, send ":A2#" using ASCOM's CommandBool().

Use your program of choice to goto a suitable star and center the star with guide commands.

Use a script accept the alignment star, send ":A+#" using ASCOM's CommandBool().

Use your program of choice to goto a suitable star and center the star with guide commands.

Use a script accept the alignment star, send ":A+#" using ASCOM's CommandBool().

Done.

 

Orly was wanting PEC control from ASCOM and this could be accomplished in a similar way.  I'll get around to throwing something together soon if no one else picks it up.  Perhaps a stand-alone windows application.

 

A jscript would look something like this (hacked jscript example provided with ASCOM install.)  Probably doesn't work, but it should be close:

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

var H = new ActiveXObject("ASCOM.Utilities.Chooser");
// WScript.Echo("Pick driver in the Chooser. Then click Properties to activate its SetupDialog if required");

// Make chooser for Telescopes

H.DeviceType = "Telescope";

// I added "POTH Hub" below so drvrID is returned immediately

// if an empty string were passed it brings up the chooser dialog

var drvrID = H.Choose("POTH Hub");

if(drvrID === "") WScript.Quit(); // Cancelled chooser
var T = new ActiveXObject(drvrID); // Create instance of selected driver

// Start align one-star

var result=T.CommandBool(":A1#",true);

T = null;

H = null;

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


Edited by hjd1964, 08 March 2015 - 01:24 PM.


#149 pbunn

pbunn

    Vanguard

  • *****
  • Posts: 2,000
  • Joined: 29 Sep 2010

Posted 08 March 2015 - 02:46 PM

Got a link to the Marlin Jones NEMA 11 steppers? I can't find it listed. I hope they aren't sold out.

 

Pat



#150 hjd1964

hjd1964

    Ranger 4

  • *****
  • Posts: 368
  • Joined: 24 May 2012

Posted 08 March 2015 - 08:55 PM

Got a link to the Marlin Jones NEMA 11 steppers? I can't find it listed. I hope they aren't sold out.

 

Pat

 

Still there, now don't go buying them all before I get my spares. :)

 

http://www.mpja.com/...tinfo/31129 MS/

 

I just finished initial testing of my TAK EM10 with these motors, ended up settling on 2.4 degree/sec. gotos (@24VDC) with these motors.  I wired for bipolar not half-coil since I wanted the low speed torque.  I get nervous when I stall during 3 deg/sec. slews so experimenting ended there. 

 

Still have to see what tracking looks like.

 

NOTES:

If anyone gets these... be sure NOT to push/pull on that output shaft getting that spur gear off, use a gear puller ** very important **

These motors need a lead assembly, make the cables or buy them.  I bought mine from Oriental Motor, they were $5ea and they charged me no shipping.


Edited by hjd1964, 08 March 2015 - 09:01 PM.



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics