Ardufocus - open source Moonlite compatible focuser

[jbrazio]

Hi

yes motor cabling is kinda of agnostic because you can always tell the firmware which connection (pins) it needs to use using the config.h file.

yes the latest fw is compatible as long as you don’t enable High Resolution mode and you have the capacitor on the reset line to prevent the DTR auto reset.

[Monk314]

Thank for you answer....

Here some pictures of my implementation. By the moment, I'm using ans old version of ardufocus, with a 8HS15-0604S motor and a A4988 driver. The motor shaft has a 16 tooth gear and the focuser shaft has a 48 tooth gear.

One of my requirements  was easy adaptation to different OTAs, and easy mount/unmount for use the OTA both in "manual" as "automate" modes....

Here is my ardufocus focuser both in a SW 120/600  and maksutov 127 OTAs.

Cheers!!

 

 

 

[jbrazio]

Interesting design ! Never thought of mounting it this way.

[jbrazio]

Due to popular demand and some work started by jkoenig72 Ardufocus now has support for manual focus using physical switches. You can operate it either manually or through ASCOM as the counters will always be in sync. The basic interface is two push buttons and one pot (speed adjust) but if you are using two motors you can add a third button to switch between the motors, it also support LED to display the active motor.

After two years into "beta" I am on the last mile to release the official 1.0 version together with a new PCB layout.

ardufocus.com

[NickK]

On 03/09/2018 at 12:21, jbrazio said:

Sorry for the late reply but for some reason I'm not getting e-mail notification of the subscribed topics.

@NickK In one hand powering down a stepper driver will make you lose accuracy exactly has you described, on the other hand leaving the driver in holding torque will make the motor heat. My main concern is not the driver itself but the motor, the 28BYJ-48 running at 12V gets pretty toasty. Has this is not a one size fits all situation I leave up to the user to choose by toggling MOTOR1_SLEEP_WHEN_IDLE. However there is a catch, you need to have full accuracy during an auto focus run, i.e. when you're moving on the focal axis and taking measurements and then moving back to the best position; you don't really need that much accuracy between runs, i.e. you auto focus now and then auto focus in one hour. For this reason even if you have MOTOR1_SLEEP_WHEN_IDLE enabled there is an undocumented flag that defines a timeout after the last move before the motor's power is cut, by default this is set to 5 seconds. This should be set to accommodate the time it takes for your setup to take a frame and analyse it before moving into the next position, this way your motor will be powered off during most of the session but still keep accuracy when it is really required to.

If the changes required to make the DRV8825 work are as trivial as increasing the delay after a sleep instruction then I suggest the following:
https://github.com/jbrazio/ardufocus/compare/patch/drv8825

@NickK could you please comment ? Thanks.

@swaxolez in fact there are two versions of the 28BYJ-48, the ULN2003 driver board is the same for both models. You must power the driver board either with 5V or 12V according with the motor type you have, however you should not power a 5V motor with 12V.

@jbrazio the motor heat on this is a factor of voltage and power. This is why I use the current chopper controller (DRV8825). It chops the current at a very high rate resulting in very little heating of the coils. The stepper is stone cold even after hours of movement at 12V with load on a 3.8V.

Could you add support for two limit switches? Open until the focuser approaches it's limit at either end, then closed stopping the focuser unless a command to move away from the limit is received. In original focuser I made the controller cycle limit to limit on startup/reset so that it knew the range and scale available.

For multi-night runs, the software may need to be checked to see if it allows a re-calibration step at the start of the session. The focuser could then re-check the limits.

Edited December 30, 2019 by NickK

[NickK]

Just rebuilding my OdroidC2 kstars and indi platform. I’ll switch to use this with my drv8825 and uno used for the focuser.

Should have this over the next couple of days.

[NickK]

Right ... getting to the end of of the ODroid C2 build..

I've created a virtualbox 64bit x66 ubuntu install for cross compiling to arm aarch64 Indi, kstars and this.. so will start playing with the focuser over the next week(s).

This will allow me to test using the Mac straight to the focuser (12 core Mac 32GB RAM is a lot faster!), then simply patch over the binaries.

Once it's working, I'll look at adding stop switching for limits.