Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
spindle-mosfet-control [2020/10/22 06:18]
mrscott [Spindle control with a Mosfet] Reference Wikipedia Flyback_diode.
spindle-mosfet-control [2020/10/22 06:31]
mrscott [Spindle control with a Mosfet] Add more high-side inductive load switching article references.
Line 3: Line 3:
 If you are not using a VFD, and your spindle motor is a DC motor of low enough power (voltage and current, **including** any current extremes when stalled), you can control it directly using the MOSFETs on the Smoothieboard. If you are not using a VFD, and your spindle motor is a DC motor of low enough power (voltage and current, **including** any current extremes when stalled), you can control it directly using the MOSFETs on the Smoothieboard.
  
-MOSFETs are present on-board, but have limited current capacity ( up to 12A ) and need to be protected by a 'flyback' diode when controlling a motor, electromechanical relay or other inductive load.  See [[https://en.wikipedia.org/wiki/Flyback_diode|Wikipedia Flyback_diode]].+MOSFETs are present on-board, but have limited current capacity ( up to 12A ) and need to be protected by a 'flyback' diode when controlling a motor, electromechanical relay or other inductive load.  See [[https://en.wikipedia.org/wiki/Flyback_diode|Wikipedia Flyback_diode]] and [[https://electronics.stackexchange.com/questions/358210/driving-inductive-load-from-ic-with-mosfet|Driving inductive load, Electronics StackExchange]].
  
 Motors have the property of inductance, which is the electrical equivalent of inertia.  The motor current will continue to flow after the MOSFET is switched off, because the energy stored in the inductor by the current does not instantly disappear.  The current will decrease as the stored energy is dissipated.  This current flow results in the voltage across the motor reversing and increasing (or "spiking") until the current finds a path to flow.   Motors have the property of inductance, which is the electrical equivalent of inertia.  The motor current will continue to flow after the MOSFET is switched off, because the energy stored in the inductor by the current does not instantly disappear.  The current will decrease as the stored energy is dissipated.  This current flow results in the voltage across the motor reversing and increasing (or "spiking") until the current finds a path to flow.