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A modified LaserGRBL board to be used with a spindle

LaserGRBL Board Refitted for Spindle Control

Prototyping a Spindle Controller from a LaserGRBL Board

Mar 20, 2024

in: lasers, automation, manufacturing

This article will guide you through a simple yet effective way to modify a laser GRBL board to drive a spindle motor. By utilizing an IRLZ44 MOSFET and an NTE598 diode, you can control a spindle up to approximately 36 volts and 12 amps. This is an easy project to enhance your CNC.

Materials Needed

You will need the following:

  • Laser GRBL board
  • IRLZ44 MOSFET (IRLZ34 or similar also allowed)
  • NTE598 Diode (Any 10A diode will work)
  • Soldering iron and solder
  • One length of wire; any will do (this carries no significant current)
  • Some amount of high current, thick wire (as needed)
  • JST plug rated for your spindle current (Or any other 2-pin plug that can carry high current)

These materials should be available at any local or online electronics retailer.

Connecting the MOSFET

Connect the MOSFET as follows:

  • Gate to Laser PWM: Locate the laser PWM pin on your GRBL board. Use a small piece of wire to connect it to the gate (G) pin of the IRLZ44 MOSFET. This is what allows you to control the spindle motor’s speed through the laser control commands.
  • Source to Ground: Connect the source (S) pin of the IRLZ44 to the ground. It’s crucial to make this connection right at the power plug to ensure a stable and reliable ground connection.
  • Drain to Spindle Motor: Connect the drain (D) pin of the MOSFET to the negative terminal of the JST plug.
a LaserGRBL board with a black wire connected to the laser PWM pin

Connect the length of wire to the board's PWM pin

a LaserGRBL board with an IRLZ44 MOSFET added next to the power transistor, with a wire connecting Gate to the laser PWM

Connect the MOSFET as described above

a LaserGRBL board with an IRLZ44 MOSFET added next to the power transistor, high current wires coming from the MOSFET's source and drain pins

Connect the spindle to the MOSFET

Next, connect the NTE598 Diode.

Connecting the NTE598 Diode

Connect the diode as follows:

  • Connect the anode of the NTE598 diode to the drain of the IRLZ44 MOSFET.
  • Connect the cathode of the NTE598 diode to the positive of the power plug. The diode is here to eat up reverse current spikes when the motor stops, which can cause the Arduino on the GRBL board to glitch.

Make sure the direction of the diode is correct!

a LaserGRBL board with an IRLZ44 MOSFET added next to the power transistor and a NTE598 diode between drain and a power connector

Solder the diode between the power connector and MOSFET drain; make sure the direction is correct

Now we connect power.

Connecting Power

Finally, connect the positive terminal of the power plug to the positive terminal of the JST plug.

Finishing and Testing

After completing the connections, test the board without connecting the spindle. Ensure it can power up and receive signals. Then, connect JST plug to the motor. If your power supply has sufficient output wattage, this is all you need to do. Be sure to test your power system with the spindle unloaded before testing on a workpiece, for safety.

Powering Larger Spindles

If you want to use a separate power supply for the spindle you can. Just connect the power supply grounds together, and then connect the positive terminal of the JST plug to the spindle’s power supply. Ensure that any connections used to carry spindle current are solid, and any wires used are rated for the high current being carried.

Refer to the American Wire Gauge Chart, provided by many wire manufacturers.

https://www.powerstream.com/Wire_Size.htm