Re: OnStep to Servo or External Step/Dir drive

Dave Cook

Watching this with interest.  I'm re-motoring some older Byers drives into the modern world - I also found the Stepperonline 16-bit servos (note that per spec they only support 32k actual resolution though) and am thinking of giving them a whirl since they're much less expensive than DMM/Clearpath.  You need 300-500KHz pulses to drive them full rate so we're definitely in Teensy-land.  My fallback would be some of the small DMM 60V servos which would be fantastic, as well as 65% faster than the Stepperonline ones.  I integrated much larger DMM servos on my CNC mill conversion and they have been nearly flawless, but I think a lot of people would appreciate a sub $100 per channel option.

Re: STEPPERONLINE Nema 17 Bipolar Stepper 400 steps choice with TMC2130 #tmc2130

Sean Sadler

Hello, I'm new to the forum, but I saw this post and wanted to offer this...

I've used Trinamic TMC2130's for several years now on my DIY 3D printer, so I can say with certainty that they will drive a 2-amp motor.  For your reference, here is the datasheet for the TMC2130 from Trinamic's website, in which they specify a 2-amp load is nominal with a 2.5-amp peak load.

Re: Vixen GP-DX motorization for Mak 180 #drv8825 #tmc5160 #esp32 #ds3231

Antoine Cesbron


Parts are ordered, I buy the controller (TMC5160), but wait for the focuser stepper, I'll manage it in a second time.

I have question about "Soft limits".
As a drawing is easier than long words story, I quickly draw "my balcony" (the EQ mount come from GradCAD) to show you what I plan to do and to show the limits I'm talking about.

(This is 3D PDF, you have to accept to open it.)
On "OnStep_EQ_AZ_Limits_1.pdf" you can see the risk that the ocular touch the balcony if I want to continue turn left.
To continue to turn left, I have to "full rotate" to be safe "OnStep_EQ_AZ_Limits_2.pdf".

Is it possible to set "Soft limits" in a case like mine ?
Two axis positions at a time need to be used to check  limits.
Ex :
If altitude is lower than "X deg", Azimuth can rotate 360 deg (useless but permitted)
When altitude reach "X1 deg", Azimuth rotation is maxi "Y1 deg".
When altitude reach "X2 deg", Azimuth rotation is maxi "Y2 deg".
When altitude reach "X3 deg", Azimuth rotation is maxi "Y3 deg"...

It can permit to avoid ocular hitting the balcony.
The other interrogation is, did OnStep can manage those informations on a Goto request ?

Excited to receive the Teensy to start playing with software !
And excited to take skills in software development, because finally, all my requests are reachable with the right code.
Thanks for your help.

Equipment for EM200

man yokotsuna

Hi There,

Recently, the OnStep made in China has become a hot topic.
Actually, I also made equipment like the attached image using OnStep.
I already made equipment for EM10 as well as EM200.

The drive parts of TAK's equatorial mounts have special dimensions, and it is not possible to build a satisfactory drive system with a combination of ready-made parts.

Sanryu co Ltd can manufacture stepping motors that rotate at high speed, but need to order 100 at a time.
Also, the diameter of the spur gear hole of EM200 is 4mm and 6mm, and it is difficult to match the shaft diameter (5mm) of many stepping motors.

Most of all of the parts, including the PCB, are custom-made.

Are there any restrictions on supplying such equipment for a fee? I support the idea of open source and can open all information about equipment on this forum.

I would appreciate it if anyone could answer the above questions.


Thank you Onstep Team! #EQ5 #blackpill

Douglas Cook

Tonight has been a good night.

Controller board fired up, connected to Nema 17 steppers custom mounted to EQ5 stand.
My 11 year old, downloaded the Onstep Android App onto his trusty tablet, connected to the Onstep Wifi, scratched his head, pressed a few buttons and nothing happened.
Once we figured out 'the old man' had his Stepper connections back to front, William whipped out the tablet again and low and behold the mount came to life and appears to be behaving as expected.

The look of absolute awe on his face was priceless.

We are both very happy! Conversely, my wife does not know what all the fuss is about and concerned why William is late for bed ;-)

I expect we will now spend the next week or so with more head scratching, hopefully resulting in a properly calibrated setup......

Thanks to all for your support.

Re: WeMos D1 Mini Pro

Douglas Cook

Quick update for all - Soldering to the 'RF shielding can' works well and creates a good anchor point to allow the use of a more substantial coax such as RG316.

Re: STEPPERONLINE Nema 17 Bipolar Stepper 400 steps choice with TMC2130 #tmc2130

Drew 🔭📷🚴‍♂️

I use the 2A version on my LXD75, so it should also work for you. I found the 1.68A version wanting at high speed.  I get 5 degree/second slews with my MaxESP3 board. I use TMC5160 drivers. Beware of the newest ones, they are too large for the MaxESP3 board and almost all the OnStep boards.

Get the full D-cut version. I have had several instances where I needed it to properly position the pulley. Doesn't seem to cost more.

Re: Vixen GP-DX motorization for Mak 180 #drv8825 #tmc5160 #esp32 #ds3231

hitosi sato

To calculate the focuser setting, CFZ is calculated from the distance the tube moves in one rotation of the focus knob and the F value of the optics.
You need to have about 10 steps within the CFZ distance to get a precise focuser setting.
I used the "Myfocuserpro" document as a reference.
If Crayford Focuser has a fine knob, 28BYJ-48 might work.
In any case, you need to find the required number of steps from CFZ.


STEPPERONLINE Nema 17 Bipolar Stepper 400 steps choice with TMC2130 #tmc2130

Ming Lei

I saw total 4 models on its website. The model with 1.68A is the popular choice though I don’t why. I like to buy the 2A model to get more torque. I also don’t know what the full D-cut is for; judging from the spec and photo, I can see the cut side of the motor shaft extends to the full length of the shaft.

There is also 0.9A model but I think it is a bit underpower for TMC2130. Is TMC2130 sufficient to get the best performance out of the 2A model?

Maxpcb2 GPS


Hi, preparing the maxpcb2 i would like to use a NEO 6 gps module at the place of the clock. Since the footprint on the pcb is not designed for a gps i was wondering if anyone has integrated that composent in the box ?  The solution could be a small pcb redirecting the pins but there are certainly other solutions.
Thank you

Re: any advice on GX12 aviator connectors


Thank you gentlemen i see what you mean and the idea is nice !

Re: Chinese ONSTEP

Ken Hunter

On Wed, Sep 21, 2022 at 06:42 AM, George Cushing wrote:
2.4Mhz external antennas
Sorry... A 2.4 MHZ antenna is a BIG DEAL...
and not that cheap. I believe you are quoting
a 2.4GHZ model instead.

Re: Vixen GP-DX motorization for Mak 180 #drv8825 #tmc5160 #esp32 #ds3231

Antoine Cesbron

Thanks for your replies. 
I have time and will re-think about my focuser solution. 

I'll look for a 400 steps, micro sized motor.
I can spend 20 bucks in a better controler and motor (I'll buy another TMC5160 to have the 3 sames drivers in the setup).

Re: Vixen GP-DX motorization for Mak 180 #drv8825 #tmc5160 #esp32 #ds3231

George Cushing

I found these NEMA 14 and 17 400 step motors for under $5. The 17s were stage lighting take offs.


Re: web server ( including smart web-server) and com port conflict in windows 10

George Cushing

Google "Smart Web Server."

Re: Chinese ONSTEP

George Cushing

In the way back "EQ-3s" and the CG-4 had some differences, mainly because there were many EQ-3 types on the market and it was difficult to tell them apart. When SW introduced the EQ3-2 it was the same CG-4 mount they had been making for Celestron to replace the Vixen Polaris.

I'm trying to convert a EQM3-5 Pro with a dead Skyscan. This variation on the EQ3-2 has a new 180T RA gear set but the same old 65T Dec. Dec can be removed for use as a RA only camera mount. The conversion is going to use the existing motors and external gear reduction units.

Still trying to confirm the ratios of the gear boxes, but they look the same as those of the EQ3-2 Synscan Pro goto kit.


Re: Chinese ONSTEP

George Cushing

2.4Mhz external antennas and cables are about a buck and a half by 40 units. Probably most of the cost is in the brass SMA male/female RF coax connectors. The actual antenna is just a length of wire.

Re: Flashing ESP8266 D1 Mini AT command firmware


Would someone be kind enough to send the AT command, AT+GMR to their WiMos D1 Mini and kindly post the results back here?

thank you

Re: Vixen GP-DX motorization for Mak 180 #drv8825 #tmc5160 #esp32 #ds3231

hitosi sato

Hi Antoine

I'm sure you already know this, but just in case, here's a tip about the 28BYJ-48 modification.
This motor is a 5-wire uni-polar motor, so you need to make some modifications to run it with a bipolar driver such as the DRV8825.
There is a lot of information on YouTube etc., so I won't go into details.
You need to open the blue cover and cut one wiring pattern on the small PCB.
The red wire is not connected to the motor driver, and the remaining 4 wires are connected to the driver.
This motor has an internal reduction gear, and it has 2048 steps per revolution for full step operation, but there is some backlash.
If the performance is not enough, it would be better to replace it with a 200-step motor for better results.
Hence it is better to have a motor driver with good micro stepping performance.
The DRV8825 is not recommended because it does not perform finer than 1/8 micro step.

My focuser has worked well enough for my limited use.
I plan to install it on my Crayford Focuser to test its performance.


Re: Vixen GP-DX motorization for Mak 180 #drv8825 #tmc5160 #esp32 #ds3231

Dave Schwartz

On my original generic EQ-5 conversion I used 138mm belts. The brackets (from Thingiverse) didn't provide any extra spacing between the motor and the worm block but I used a large washer about 2mm thick to get the right spacing.

On a Meade LXD55 conversion I am just completing, the brackets I designed (uploaded into the Files area) provide a 3mm spacing from the worm block but I had to use 140mm belts, which makes sense due to the 1mm extra distance.

These mounts are both Vixen GP clones.

Based on this experience, I would say that the length of the belt is 134mm plus twice the thickness of any shim or bracket wall between the motor and worm block.

Fortunately, when I found that 138mm was too tight for my new brackets, I had 140mm belts on hand because I had to do the purchase multiple times to get it right when doing my EQ-5. With shipping from China being much less reliable now than then, I would recommend you by multiple sets of belts bracketing the value you think you need... the cost of the belts you don't need is your insurance against having to wait for multiple orders.

On 2022-09-20 1:12 p.m., Antoine Cesbron wrote:
Thinking of it, using as you, the 48T:16T belt gear is far enough.
Maybe you know the right belt length for Vixen GPDX mod?
I'll receive it in two weeks, I can't measure now.

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