Arduino ASCOM focuser kit

Maybe you remember the ASCOM jolo focuser project – now it has the production implementation! Some of my astro colleagues took a chance and we made an action. 15 circuit boards has been ordered and 10 ready to use kits have been made. 5 other users ordered just clean boards to make the kit by theirselves. You can see how the device look like:

foc-4The reference solution uses L298 stepper driver and works with half steps by default. You can find all the documentation, schematics, source code and PCB project at . 


There were some problems with first revision of PCB thats why you can see a few wires around the Arduino board 🙂 

Clear skies!

20 thoughts on “Arduino ASCOM focuser kit

  1. Hi Lukasz, may I ask you for echnical help with my focuser? Could you provide me your e-mail so I can describe it and send some photos? Or could you send me empty e-mail to streicher (at) seznam (dot) cz .Thank you and have a nice day 🙂



  2. Hello Lukasz,
    thank you very much for sharing your job. I tried the version 1.5 with some problems ..(excuse me for this long silence)… but version 2.0 works very well. I have just a little question, when the focuser is idle the motor become hot, there is a mean, in the arduino code, to stop the current into the motor when the focuser does not move ?
    Thank you again

  3. Hello Pascal,

    By default the motor is idle it should not be powered. There is a setting in ASCOM driver – Stepper duty cycle, check if you have set it to 0%


  4. Thank you for this quick answer, the stepper duty cycle was already set to 0% …I use an ln2003an as driver (nor an l298) may be saomething with that but not sure.

  5. Hmm, can be – you may try to find some info about AccelStepper library working with LN2003 driver, I dont remember if I tested this combination 🙁

  6. ok I will take a look to the library and the connection to my motor, I use an hybrid stepper motor but quickly (too?) connected as unipolar …. Once checked, I will let know and certainly I will have some questions more.
    Thank you.

  7. Hi Lukasz, apparently it seems difficult to drive an bipolar motor with my driver, I don't know exactly why it works … I have to look at the code and try to understand or change the driver, the problem is I would like keep the motor powered by the usb (it is possible, I have one based on PIC that work well), REgards. Pascal

  8. Hello Pascal, – I think I misunderstood you, I thought you have unipolar stepper and ULN2003 driver – that should work. I don't think it is possible to drive bipolar motor with ULN2003 driver in easy way 🙁

  9. sorry I misunderstood you too, I though your motor controller was for bipolar motor only … I actually connected an unipolar motor, and it works normally except the little problem in idle state, I do not thought your controller can work with the both motor type. So the idle problem could be solved by modifying the code ….. I hope. Thank to your patience.

  10. Witam Cię, muszę przyznać że stworzyłeś kawałek porządnej maszynki. Projekt mnie zaciekawił i już jestem w trakcie budowy, Arduino już zakupiony, mam tylko jedno pytanko:
    W moim układzie chcę zastosować driver A4988, w dokumentacji ASCOM Jolo Focuser 2.1 – 11 opisałeś podłączenie innych sterowników podając że w przypadku sygnału ENABLE nalezy wykorzystać Pin D6 modułu ARDUINO. Ze względu, że całość buduję sam, to czy można wykorzystać pin D11, który jest wykorzystywany w przypadku sterownika L298, tylko go zanegować dla A4988? Chodzi mi o to, że nie wiem czy po zmianie w AccelStepper, z HALF4WIRE na DRIVER, pin D11 pracuje nadal jako sygnał ENABLE czy jest przeniesiony faktycznie na D6. Nie chciałbym tracić wyjścia PWM.
    Pozdrawiam, i raz jeszcze wielki szacun za stworzony projekt.

  11. Cześć Artur,
    To niestety błąd w dokumentacji. Do sterowania A4988 używasz dwóch pinów – STEP i DIR i dodatkowo ENABLE – nie wiem skąd mi w dokumentacji tam wzięło się pin D6. Jeśli chcesz sterować wejściem ENABLE przez PWM to musisz użyć jednego z pinów 3, 5, 6, 9, 10 albo 11 – na innych nie ma sprzętowego wsparcia dla PWM. Jeśli chcesz tylko włączać/wyłączać ENABLE stanem wysokim/niskim to wystarczy dowolny pin Arduino.
    Trzymam kciuki 🙂

  12. Hello Lukasz,
    here are some news, I finally succeeded to shut down the power in my unipolar motor, just adding single code line : stepper.disableOutputs(); after line 16, in the stepper panel. May be this can interest you or other people who want to use unipolar motor. I have also tried with an bipolar motor but using an L293d driver, this driver had integrated diode and permit to do very compact usb powered controller using an arduino nano board. Thank you again for sharing your work. Sincerely. Pascal

  13. Hello Lukasz,
    I used your code without modification excepted the code line I added to disable the arduino outputs. The ULN2003 was classicality wired with the four entries (A2 to A5 plus Vcc and Gnd) and it works perfectly (wire connected to D11 is of course useless with this configuration). The 5v from usb is enough for my nema14 unipolar motor. I adjust the settings from the driver. Great thanks to you.

  14. Hello Lucaz
    First many thanks for sharing a great project.
    I built my focuser based on your design with some minor modifications (USB powered stepping motor and controller). It works great and I based it on your 2.0 code in GitHub.
    One thing I haven't been able to get running yet however us the temperature compensation. Although I do enter the required values in the driver it seems like it is not compensating even if the temperature changes (the DS1820 delivers the correct temp however).
    I'm using the 2.0 ascom driver as well.
    Do you know what I might be doing wrong or should I use another driver SW?

    Many thanks!

    Best Regards

    Ps: you can see images of the project here (sorry for the Swedish).

  15. Hi Claes,

    Nice to hear that you made it running 🙂 As for temperature compensation – it must be enabled in the controlling software, so if you use MaxIm (as I noticed on your screenshots) you need to enable checkbox "Temp. tracking". Let me know if that helped.


  16. Hello Lukasz,
    first : Happy new year ! second, one question … I am trying to make a focuser with an arduino micro pro board (based on the Atmega32U4, like the Leonardo model) this board is very interesting because it is very small and has an micro usb port integrated, the problem is your ascom driver cannot establish the connection with the board, do you have an idea? I can modify a little bit the arduino for matching to this different board but I am not able to modify the ascom driver, if you have a solution it will be welcome. Thanks.

  17. Thanks for the answer.
    Got it and will test later.
    I just noticed you updated the main branch with version 2.2. The HW I made is using the 2.0 version (no LCD) and this was partly due to Library errors in the 2.2 branch (in the i2c LCD library).
    Would you please let me know the main differences between 2.0 and 2.2 (also can you omit the LCD in the HW and still use 2.2)?

    Many thanks!

    Best Regards

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