This is a fantastic project; many thanks for all your hard work.
I've been using a Seletek Armadillo to control my focusser until recently when the stepper driver has stopped working. Rather than replace it, I fancy making my own (I do have electronic and arduino experience)
Could I just clarify what board you would recommend. I have a 200mm Reflector with a relatively light camera. Currently I use a sm-42BYG011 as the motor but it only has 200 step/rev (1.8 degree/step) so I think I will need to replace it with either a Nema17 PG5 or 27 or a Nema 14. I was thinking of using a DRV8825 controller. I'm considering a Rotary encoder and a LCD but won't need either Bluetooth or WiFi as I can connect it direct to the OBs PC via USB
What does the HW203 stand for?
Many thanks
Rob
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A drv8825 controller with a NEMA14 0.9 hybrid is a good choice for most solutions. You indicate that you are using a small 200 step motor now, so a NEMA14 0.9 gives you 400 steps.
I dont like the rotary encoder - there is too much lag. If you rotate too fast or too much the focuser cannot keep up.
HW203 - The orginal DRV8825 boards made were replaced with a newer version, and there was a slight change to signal wires. The replaced DRV8825 then became knownas DRV8825HW203 which is the boards recommended now,
Regards
Robert
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Thanks for your quick and thorough response. Still a little undecided on which version to go for although I think I agree with you as regards the RE.
Looking at my 'spares' box I've got a number of Nano/Uno's, some voltage regulators and some stepper drivers off a 3D printer build (I think 4988's not DRV8825). So I think I'll knock together a breadboard test bed. The 4988 are pin identical to the DRV so I can switch that really easily for minimal cost
My current motor is connected to the fine focuser so actually has a 10 : 1 and did get good accuracy. It also seems able to hold the weight;a relatively light imaging train (an Atik 314L and electronic Filter wheel). This obviously already has the appropraite coupling and bracket. However the Nema 14 is much more powerfull should I change anything in the future. The other motor is extremely light (and cheap) if it is up the the job
I also have pcb etch facilities and 3d Printing so I should really make my own circuit and fitting although the professionally made ones look fantastic..
The bit that I've always struggled with is the Windows software side and the ASCOM interface so I'm so grateful that you have developed that side.
I'll let you know how I get on
Rob
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Rob (and all)
This is a fantastic project; many thanks for all your hard work.
I've been using a Seletek Armadillo to control my focusser until recently when the stepper driver has stopped working. Rather than replace it, I fancy making my own (I do have electronic and arduino experience)
Could I just clarify what board you would recommend. I have a 200mm Reflector with a relatively light camera. Currently I use a sm-42BYG011 as the motor but it only has 200 step/rev (1.8 degree/step) so I think I will need to replace it with either a Nema17 PG5 or 27 or a Nema 14. I was thinking of using a DRV8825 controller. I'm considering a Rotary encoder and a LCD but won't need either Bluetooth or WiFi as I can connect it direct to the OBs PC via USB
What does the HW203 stand for?
Many thanks
Rob
Depends on all the calculations of cfc, step size etc.
See
https://www.youtube.com/watch?v=J6vh_iS2JsE
and the pdf
A drv8825 controller with a NEMA14 0.9 hybrid is a good choice for most solutions. You indicate that you are using a small 200 step motor now, so a NEMA14 0.9 gives you 400 steps.
https://www.omc-stepperonline.com/hybrid-stepper-motor/nema-14-bipolar-09deg-11ncm-1558ozin-04a-10v-35x35x28mm-4-wires-14hm11-0404s.html
I am also experimenting with this stepper,
https://www.ebay.com/itm/GM12-15BY-DC5-12V-2-phase-4-wire-Permanent-Magnet-Stepper-Gear-Motor-Metal-Gear/163265164855?hash=item26035cb637Ⓜ️mxSamepmNSuM3gOSv0XX71A:rk:5:pf:0
10mm shaft with 1:298 gearing. The sm motor you use provides 0.23N holding force, this GM motor 1:298 provides 1.2N holding force. This will give you a lot of steps per revolution.
I dont like the rotary encoder - there is too much lag. If you rotate too fast or too much the focuser cannot keep up.
HW203 - The orginal DRV8825 boards made were replaced with a newer version, and there was a slight change to signal wires. The replaced DRV8825 then became knownas DRV8825HW203 which is the boards recommended now,
Regards
Robert
Robert,
Thanks for your quick and thorough response. Still a little undecided on which version to go for although I think I agree with you as regards the RE.
Looking at my 'spares' box I've got a number of Nano/Uno's, some voltage regulators and some stepper drivers off a 3D printer build (I think 4988's not DRV8825). So I think I'll knock together a breadboard test bed. The 4988 are pin identical to the DRV so I can switch that really easily for minimal cost
My current motor is connected to the fine focuser so actually has a 10 : 1 and did get good accuracy. It also seems able to hold the weight;a relatively light imaging train (an Atik 314L and electronic Filter wheel). This obviously already has the appropraite coupling and bracket. However the Nema 14 is much more powerfull should I change anything in the future. The other motor is extremely light (and cheap) if it is up the the job
I also have pcb etch facilities and 3d Printing so I should really make my own circuit and fitting although the professionally made ones look fantastic..
The bit that I've always struggled with is the Windows software side and the ASCOM interface so I'm so grateful that you have developed that side.
I'll let you know how I get on
Rob
Just remember the VDD pin on the A4998