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DIY focuser issues

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DIY focuser issues was created by Mindaugas

Hi guys,
I hope you're all safe and happy holiday season to you all!

The problem I am facing is that my step motor (Nema 17) doesn't react at all to any command on Ekos. My setup is: control (Ekos on raspberi pi4) , motor is connected to arduino nano (have both (and tried) controllers: A4998 and DRV 8825). Tried few build like this github.com/Hansastro/Focuser link1 and Arduino Focuser Pro (v.1) . Everything connects perfectly, no errors . Moonlite focuser library starts without a problem, but when I try to focus in or focus out , motor seems want to start (does small 'tick') but thats it. Ekos shows that focuser reached desired position , no errors in logs either. Tested motor itself with other simple code , it is working normally. Just don't understand what could be wrong here . Thanks for any idea/suggestion in advance!

regards,

Mindaugas
3 years 3 months ago #64734

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Replied by Jose Corazon on topic DIY focuser issues


Try reducing the current limit using the small pot on the DRV8825, If the current limit is too high, the motor may seize up, if it is too low it may be missing steps. You want the current limit set so your Vref is ~0.3V.
Is the motor getting hot when connected? That is an indication that the current limit may be too high.

Jo
3 years 3 months ago #64735

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Replied by Mindaugas on topic DIY focuser issues

Thanks for suggestion, but Vref is 0.26V. But yes, it gets hot if it stays idle.
3 years 3 months ago #64737

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Replied by Jose Corazon on topic DIY focuser issues

It shouldn't get hot. Mine stays quite cool, but then I am using the MyFocuserPro code.
I would try reducing the current limit further, i.e. turn the pot all the way to the left, then increase from there until the focuser starts moving (upon input).
Another thing to consider is input voltage. The DRV8825 needs at least 8 V, as I recall.
The following user(s) said Thank You: Mindaugas
3 years 3 months ago #64739

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Replied by Mindaugas on topic DIY focuser issues

No, no difference... lowered Vref to 0.15V . But maybe there is something wrong with board? Btw I am using this one of these type of boards www.amazon.com/Stepper-Motor-Driver-Cont...graver/dp/B074FT52T3 . Plus when I connect focuser on Ekos, on Arduino Nano Rx and TX leds starts blinking. Maybe that would help .. (plus there is constant DC12 V connected)
Last edit: 3 years 3 months ago by Mindaugas.
3 years 3 months ago #64743

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Replied by Jose Corazon on topic DIY focuser issues

I am using this controller and then just use jumper cables to make the connections from the Arduino to the controller:
www.amazon.com/gp/product/B07L74WZPS/ref..._title?ie=UTF8&psc=1

Blinking LEDs on the Arduino may mean that you are drawing too much current on the motor and the input voltage on the Arduino is no longer sufficient to drive the board. I had that problem with another stepper setup (not focuser). I had to lower the current limit even further for it to run.
3 years 3 months ago #64748

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Replied by Alan Archer on topic DIY focuser issues

Have you tried the Arduino IDE Serial Monitor to send the Moonlite commands to the focuser module and see if the motor responds. I use the Hans Astro Focuser and it has worked for a few years now without issue using the Moonlite driver in Indi. The Moonlite focuser commands are available on line. If it doesn't respond when you try that it's probably a wiring error.

Another thing to look at is the step settings Half Step Full Step & the step speed if you try to drive the stepper motor too fast it will not move.

The flashing Tx & Rx lights on the Arduino are fine, they're supposed to do that, it's an indication they're transmitting & receiving data. If the power light is flashing then you do have a supply voltage problem. Make sure to power the Arduino from a stable 5 volt supply & the stepper driver from a minimum 12 volt supply.

Regards

Alan
3 years 3 months ago #64888

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Replied by Jose Corazon on topic DIY focuser issues


Alan,

Looks like the motor is trying to move as it makes a clicking sound when triggered, but then seizes up. It also gets hot, so that all suggests that it is being triggered by the Arduino. I agree, there could be a wiring problem, perhaps the polarity of one of the coils is reversed?
It should be fine to power the Arduino from Vin at 12V, no separate PS should be needed (at least all my stepper setups work that way).
I have not used Hans Astro Focuser yet, though. MyFocuserPro works fine for me, so kyb could try using that code (may have to change the wiring according to pin output, though).

Jo
3 years 3 months ago #64889

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Replied by Alan Archer on topic DIY focuser issues

Jo,
If the wiring on one of the coils on the stepper motor is reversed the motor would still work fine with a 4 wire stepper, it would just run in the opposite direction. If the motor clicks it could be it's trying to step too fast, (a good way to test this is to change the step mode to half step and see if that makes a difference) or if it's connected to the focuser it may be binding & causing it to miss steps because of the excessive load. The locking up will be it's energised coils holding it's position after completing the move. I noticed some DIP Switches on the driver board maybe they set the step mode rather than the usual on board mode pins. (might be worth a read of the documentation on the boards.)
I've not used those particular board with my build, I used the Pololu A4988 for my focuser, but I also have DRV8825 & Easy Driver boards for experimenting with.

I must admit I power my arduino nano from the usb connection and power the A4988 board from the 12 volt supply, it never fails to work.

I also have a MyFocuserPro2 build from an ASCOM set up I used before I moved to Indi, I've updated the firmware on it and have tried it with the Indi driver & it appears to work really well, never used it for real, but I have it there ready if I ever setup a second rig, if we eventually get any decent clear weather in the UK to justify it.
3 years 3 months ago #64895

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Replied by Alan Archer on topic DIY focuser issues

Jo,
I've had a good look at the board being used, it will not work without a modification to the Arduino sketch, the driver pins for the stepper drivers will not be the same as the pins used Hans Astro build.

It could be done without too much trouble if there was a full schematic for the board so we knew which pins from the arduino are connected to which pins on the driver

Alan
3 years 3 months ago #64896

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Replied by Jose Corazon on topic DIY focuser issues


Alan, you are correct, the focuser would just run backwards if the polarity of one of the wires is reversed. That is an unlikely reason, but also a good opportunity to check all the wiring nonetheless.
The MyFocuserPro works GREAT with Indi, temperature probe triggered refocusing and all. Perfect with the Linear algorithm. I use nothing else these days, nails perfect focus every time.

Jo
3 years 3 months ago #64902

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Replied by Jose Corazon on topic DIY focuser issues


It should say in the sketch for the Hans Astro build what the pinOuts are. I don't think a full schematic of the board would be necessary. It would be a simple matter of changing them at the beginning of the sketch for the MyFocuserPro. Only 3 pins for ENABLE, STEP and DIR would need to be redefined.
Last edit: 3 years 3 months ago by Jose Corazon.
3 years 3 months ago #64904

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