4 brush-less DC motors with integrated drive electronics

[vumbl]

Hi Guys,

I'm in need of a little help with a project I'm working on.

I need to be able to drive 4 brush-less DC motors with integrated drive electronics using an Arduino Uno.

The motors: http://goo.gl/SFTFJH

I'm currently using the Arduino and the Adafruit Motor Shield v2 (http://goo.gl/8tpeX1) to drive 4 normal DC Coin Motors (http://goo.gl/mk5noa), but as far as I'm aware this is useless with the brush-less motors so I'm a little stuck.

I want to be able to:

• - Drive the 4 motors separately to each other
  - Drive the motors 2 or more at the same time
  - Be able to change speed (not sure that’s even possible)
  - Not purchase another motor driver if one can be built with the components
  - Use Arduino (This is a must)
  - Use these particular brush-less motors (This is a requirement)

Note this passage from the motor website: “BEING ELECTRONICALLY COMMUTATED, THIS MOTOR WON'T WORK IF CONNECTED BY REVERSE POLARITY. NOTE ALSO THAT THIS VIBRATION MOTOR CAN NOT BE CONTROLLED BY PWM - IT MUST HAVE A STEADY 3V DC SUPPLY.”

My contact from Precision Micro-drives was kind enough to send me a drawing and a link to explain how he would do it using MOSFET, however I'm afraid this is out of my league and I'm in need of someone to explain how all the components are working and why etc.



I'm aware this is a big ask but I'm keen to learn, please make the assumption you are talking to a student as I have only a limited knowledge. This isn't for production, but so I can use the prototype to communicate with smartphones to test a couple of things (More my area, I work with code).

Kind regards,
Sam.

[adafruit_support_bill]

You could still use the motor shield to drive those motors. As long as you always set the direction to FORWARD and the speed to 255, there will be no reverse polarity or PWM.

If you prefer to use transistors, this guide explains how the circuit works. https://learn.adafruit.com/adafruit-ard ... -dc-motors

As with the motor shield, to prevent PWM, always set the speed to 255.
Or, instead of the analogWrite(motorPin, speed); used in the code, simply do a digitalWrite(motorPin, HIGH);

[vumbl]

Thanks for your reply.

Very interesting. The motors are only 3V so would I need to set the speed: myMotor->setSpeed(85);?

[adafruit_support_bill]

Very interesting. The motors are only 3V so would I need to set the speed: myMotor->setSpeed(85);?

No. As I said, to prevent PWM, you must always set the speed to 255.

To give the motor 3v, you need to remove the VIN jumper from the motor shield and connect a 3v power source to the External Power terminals.

[vumbl]

Ok that's great thank you.

If I was to run 2 motors at the same time would the 3v supply not work?

[adafruit_support_bill]

Those motors only pull 65mA. As long as your power supply has enough current, the same supply should be able to run all 4 motors.
2xAA or AAA batteries will easily handle it.

[vumbl]

Brill thanks.

One final question and I'll leave you alone. Any idea how to control speed (if you can) or do you think it's on or off with these?

[adafruit_support_bill]

From the chart on the spec sheet, it looks like it will respond somewhat to a change in voltage (1.6v-3.6v). It should be possible to design a filter to derive a steady voltage from the PWM outputs of the motor shield.