24.7 V max safe on Duet Ethernet?



  • I know the TMC 2660 drivers are only good up to 25 V. Upon start up, and after jogging a few of the axes, the reported peak voltage has gone as high as 24.7 V. Is this too close for comfort? It typically rests at 24.5 or 24.6.



  • 2660s can handle 30v max, the 25v rating on the Duet is to provide headroom.

    https://www.trinamic.com/fileadmin/assets/Products/ICs_Documents/TMC2660_datasheet.pdf



  • Oh sweet. Thank you!



  • @elmoret

    But this can be only fed via the main-inlet on the pcb/board, and the board has a max 25Vdc rating?


  • administrators

    @lb said in 24.7 V max safe on Duet Ethernet?:

    @elmoret

    But this can be only fed via the main-inlet on the pcb/board, and the board has a max 25Vdc rating?

    25V is the recommended maximum normal input voltage. When stepper motors brake, they feed energy back into the supply rails, so the voltage may rise a little. That's why we allow some headroom. Also, the firmware constantly measured the VIN voltage, and if it exceeds about 28V then it shuts down the drivers in an attempt to protect them. So you can expect skipped steps if the voltage exceeds about 28V.

    As well as the stepper drivers, the fan mosfets are also rated at 30V. All other components connected to Vin are rated at 35V or more.



  • @dc42 said in 24.7 V max safe on Duet Ethernet?:

    @lb said in 24.7 V max safe on Duet Ethernet?:

    @elmoret

    But this can be only fed via the main-inlet on the pcb/board, and the board has a max 25Vdc rating?

    25V is the recommended maximum normal input voltage. When stepper motors brake, they feed energy back into the supply rails, so the voltage may rise a little. That's why we allow some headroom. Also, the firmware constantly measured the VIN voltage, and if it exceeds about 28V then it shuts down the drivers in an attempt to protect them. So you can expect skipped steps if the voltage exceeds about 28V.

    As well as the stepper drivers, the fan mosfets are also rated at 30V. All other components connected to Vin are rated at 35V or more.

    Ah - cool! At least your pcb seems to have arrived long ago in the age of energy-saving where breaking it is not "killed as heat" in a "breaking-resistor"... Would it make sense for the duet3 to have some sort of "breaking-capacitor" with feedback 🙂 ? O.K. my wishlist is going wild here I think 🙂 And it is a topic for a diffrent thread...


  • administrators

    @lb said in 24.7 V max safe on Duet Ethernet?:

    Ah - cool! At least your pcb seems to have arrived long ago in the age of energy-saving where breaking it is not "killed as heat" in a "breaking-resistor"... Would it make sense for the duet3 to have some sort of "breaking-capacitor" with feedback 🙂 ? O.K. my wishlist is going wild here I think 🙂 And it is a topic for a diffrent thread...

    The Duet WiFi/Ethernet has 700uF of capacitance on the VIN rail to absorb the energy.


 

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