BLDC multi-motor speed control

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BLDC multi-motor speed control

BLDC multi-motor control

Q: I have a few of the BLF series Brushless DC motors. Now my application requires them to run at the same speed. Is there any way I can use a single control unit to adjust the speed on all of them at the same time?

A: There are two ways to achieve multi-motor speed control: by external potentiometer, or by external DC voltage.
If you are adjusting the speed with an external potentiometer, you need to use a common power supply line and a common speed control line for each driver. The resistance value is calculated using the formula below:

VRx = 20/n (K ohm), n/4 (W), where n is the number of drivers.

Also, to adjust the speed difference between motors, you can connect a 1.5 K ohm, ¼ W resistor to the VM terminal of the first driver, and a 5K ohm, ¼ w variable resistor to the VM terminal of each of the remaining drivers. Please see the circuit diagram below:

blf external pot.jpg (42.87 KiB) Viewed 3501 times

Another method is to use external DC voltage. You will need to connect all drivers using a common power supply line and common speed control line with a 5 VDC power supply. The power supply capacity is calculated using the formula below:
I = 1 mA x n, where n is the number of drivers. Please note a 1.5 K ohm, ¼ W resistor should be connected to the VM terminal of the first driver, and a 5K ohm, ¼ W variable resistor should be connected to the VM terminal on each of the remaining drivers in order to adjust the speed difference between motors. Please see the connection diagram below for external DC voltage speed control:

blf external DC.jpg (45.2 KiB) Viewed 3501 times

The BX, BLE, BLF BLV and BLH series brushless DC motors can be controlled by a single speed setting unit by using one of the two methods mentioned above. You can connect up to five driver/motor units for the BLF and BLH series. For the BLV, BX and BLE series, up to twenty driver/motor units can be connected. However, please note while the connection are the same for the BLV, BX and BLE series, the resistor on the first driver should be changed to 470 ohms, and the variable resistors on each remaining drivers should be 1K ohm.

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