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Messages - pterodyne

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For a complete after market solution, check out:


I have two of these.  Not astro eq, but eqmod compatable.  Somewhat different design than astroEQ or Onstep, but works great.  Ive actually gotten the best performance per amp out of EQDrive than anything else.  Can't really say why other than he uses a different kind of driver altogether.  For example, I can drive my harmonic drive mount at 2500x sidereal with this setup, whereas astroEQ and onstep the best was about 350x - 500x.  Same motors and powersupply.

Sorry Tom, just trying to help people out. Delete this post if you don't want discussion of other

I never had a workable solution even trying to trick the config.  In the end, I couldn't use the higher uStep modes like 64 - 256 because the slew speed ended up being too slow without gear changing.  Short of desoldering the switches and some how configuring the modes that way, Im not sure this is a workable solution.

Tom, can you confirm, the reason for the slow speeds with gear ustep changing disabled is because of the mega CPU?  cant deal with the number of pulses per rev?  I ask because I have a little more flexability with these drivers in the Onstep project using the same mega.  E.g. 1.1Dps slew rate with the mega and the drivers hard coded to 128uStep.

Ugh.. well that was short lived.  It was slewing around great.  I parked it because I had an axis reversed.  Closed out of eqmod, loaded the config utility, and it no longer saw the com port.  So I unplugged and re plugged a few times, still no com port.  And a windows message that the USB device was not recognized.  Then on 2 other computers, the same.  I guess don't buy cheap clone boards.  Not even sure who made the original.

I can confirm that this works.  Im using it on the harmonic drive mount from other posts.  Currently using ramps 1.4 MKS Gen L with TMC2130 drivers (configured not in SPI mode).

Really much thanks. 

As a side note, my board for whatever reason needs to have the reset button pressed at the exact moment.  The technique I used is hold the reset button down, release and hit the "done" button in the config utility at the same time.  Anyone seen this?  Mine is a "biqu" no name brand from amazon with CH340 usb chipset. Ive read about it on other forums, but it's hard to say because most of the references are to Mega 2560 clones, not RAMPS all in one boards.

Well these drivers have dip switches so other than de soldering those I'm going to have to live with no control of the modes.  Short of modifying the config utility which I'm sure is considerable project for you, using these specs:

1.8 degree steppers
200:1 harmonic drive
4:1 pulley motor reduction
driver with dip switches to set up to 1/256 ustepping. (I need at least 32. 64 or higher would be better.)

I'm not completely sure what numbers I need to put into the config utility to trick my system into working.

I'm pretty sure gear changing should be disabled.  Not sure about multiplying the Motor gear ratio part.  I think I understood your original post years ago when I was in the early stages of this project, but at that spec had no motor gear..

As to the config utility at some point yes it would be awesome to choose a custom driver and ustep mode, and also be able to configure the pins.  Certainly I have little concept of the time involved. 

Thanks as always!


This is awesome.  Ill test it out as soon as I get a chance..


Tom, Im wondering if you saw the last two posts? 

Id love to see a build of this that doesn't require me to compile the firmware separately :)    I have a MKS Gen L with Onstep On it.. I would be great to be able to switch back and forth.

Tom, as a side note :)

feature request if it would work.  A driver choice of "custom" that allowed you to pick from 1/1 to 1/512 uStep modes. then the rest of the maths are handled by the correct entry of motor step angle, worm gear etc..

Just a thought.

Got it working with onstep and TMC2100.. Still wanting eqmod though.  I bought these drivers:


they do up to 256 microstepping.

Tom, you had previously stated:

You could also then do a quick 'hack' to get AstroEQ to work without firmware modifications by selecting a microstepping mode in the config utility to be 1/4 stepping (as it will disable the microstepping mode change for high-speed movements), and set the gear ratio box to be the difference, so for example if you set the driver to 1/100 stepping, the fake gear ratio would be 100/4 = 25.
In the calculations, the microstepping mode and gear ratio are only ever multiplied together, so if you make one half what it should be, you can double the other the compensate.

Now unlike the original example I am not using a 1:1 motor gear, the specs are:

1.8 degree steppers
200:1 harmonic drive
4:1 pulley motor reduction
driver with dip switches to set up to 1/256 ustepping.

So for the configuration utility Im assuming I leave uStep gear changing Disabled.

Motor step angle 1.8
worm gear ratio 200
that leaves Gear ratio and microstepping level.

if I wanted to use 256 (probably anything 32 or better is fine, but for this exercise), I would put the Motor microstep level at 4 uStep, multiply my actual motor gear by 4 (4*4=16) then divide the actual driver uStep mode by the result. 

as in:
Motor gear ratio 4*uStep mode of 4=16
driver uStep mode of256/16=16 final calulated motor gear ratio.

Tom does this pan out?

Ive attached a snip of the config utility.

So this didn't end up being a good solution.  The motor had too much vibration during tracking.  Not sure why.  Same motors with other drivers (8825 etc) even at 16uStep were pretty smooth.  Tried adjusting current through the full range, no help.

Back to onstep for now.  I have a RAMPS MKS V1.4 all in one board with onstep.  Maybe Ill try that.  In theory I could change the pins in the firmware...

Im trying this mount with a 3axis TB6600 stepper driver from sainsmart and an AstroEQMega.  Really easy to setup, I didn't even put the EN line in.  Just DIR/PUL on both axis, 5V from the Mega 2560.  Can anyone think of a reason I have to have EN?  The drivers get disabled when an axis is given a command rather than enabled.  It obviously will use more power when idle with the axes always enabled.

AstroEQ Support / Re: RA Motor hot even when not slewing
« on: August 19, 2018, 23:24:11 »
Thanks...  Ill just leave it for now..

AstroEQ Support / RA Motor hot even when not slewing
« on: August 19, 2018, 19:46:26 »
I have my losmandy titan astroEQ running ok. Unfortunately I am back home in south Baja California and I remembered something I forgot to fix.  I noted that my RA motor gets somewhat hot just sitting there, not tracking or slewing.

I have VREF set to 1, and very large heat sinks (NEMA 23).  The DEC motor doesn't get hot slewing or not.  I also have made the fast decay hack by shorting thew two appropriate pins on the RA axis only.  In another thread Tom suggested replacing the DRV8825 for a similar problem.  Unfortunately I am over 3000KM from the observatory now, and my remote hands person probably couldn't replace the DRV 8825.  It seems to be operating fine however as far as tracking and slewing. 

SO the real question is, should I try to address?  Is the motor in any danger (fairly expensive stepperonline motor)? driver (who cares).  Id say I probably need to remove the diode too as it is always really hot.

I can touch both the motor and the heatsink ok without burning but I don't have a ir thermometer.


Capabilities Question / PEC and VSPEC
« on: August 07, 2018, 20:48:19 »
Tom, as always thanks for your time and dedication to this project!

Something I haven't messed with yet, but plan to now that my Titan mount is astroEQ based:

Because our AstroEQ mounts have various and different worms/gears/pulleys/ratios and microstepping modes, does eqmod PEC routines work as expected?  What if anything should change about the workflow as described in the VSPEC manual?

Thanks for suggestions!

Bryan Ramsey

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