identical motors, different speed
November 13, 2012
Hi all, I have 6 identical motors, or so I thought until I powered them all on at the same time for the first time and realised they all spin at different speeds.
Has anyone else observed similar behaviour either when using multiple identical motors, and/or when using the Arduino Motor Shield?
I am using the Arduino Ethernet + Motor Shield rev3, with 3 motors connected in parallel to Channel A and 3 motors connected in parallel to Channel B. Each motor is connected to a wheel.
My arduino code sends a forward + full speed to both channels.
All 6 wheels started spinning. Wahoo!
Then I noticed one wheel was spinning considerably slower than the rest.
I powered off, put all the wheels in the same position and marked one spoke on each wheel, making sure all spokes were aligned. I powered on, and sure enough I observed all 6 of the motors are spinning at slightly different speeds, and one running considerably slower than the others.
I hooked up my multimeter, and I measured 7.6v from the battery, and 6v across each of the 6 motors' terminals.
One other thing I dont understand is where the 1.6v disappeared to (7.6 at battery vs 6v at motor). Perhaps into powering the motor shield itself? I would have expected no significant voltage drop at the shield itself.
Motor shield specs etc are at http://arduino.cc/en/Main/ArduinoMotorShieldR3