High RPM DC Motor and MD10 Shield Controller

Help & Support Robot Parts
1

Hi,

I’m trying to set up the controller (specs below) but having issues controlling it at low pwm. The motor is rated for high rpms (specs below).

Using the Ardurino Uno to control the shield I have no issues running the motor in either direction under no-load with a pwm (acceleration) setting of 10.

When applying load the motor stalls…setting the pwm higher (50) will start the motor turning but then stalls again…of course I can go to a higher pwm but then I’m rotating too fast.

my questions are as follows:

  1. if the motor has a high current rating, with the shield md10 capable of 10-15A why is it stalling at low pwm? (I’m lifting 15lbs using a 6:1 pulley system which reduces the load down to about 3lbs).

  2. Do I need to change out the motor to a lower rpm? in the range of 50-100 rpm so the controller has the current drive to prevent the stall at 10rpm?

Controller Specs

SHIELDMD10
Shield come with these features:
● Bidirectional
control for 1 brushed DC motor.
● New!! Support motor voltage ranges from 7V to 30V.
● Maximum current up to 10A continuous and 15A peak (10 seconds).
● 3.3V and 5V logic level input.
● Solid state components provide faster response time and eliminate the wear and tear of
mechanical relay.
● Fully NMOS HBridge
for better efficiency and no heat sink is required.
● Speed control PWM frequency up to 10KHz.
● Stackable I/O header pin.
● Selectable digital pins for PWM and DIR.

Motor Specs

[font=Helvetica Neue, Helvetica, Arial, sans-serif][highlight=#ffffff]
]Voltage: 12 volt DC/:m]
]No load RPM: 5,310 (+/- 10%)/:m]
]Free Current: 2.7 amps/:m]
]Maximum Power: 337 Watts (at 2655 rpm, 172 oz-in, and 68 amps)/:m]
]Stall Torque: 2.42 N-m, or 343.4 oz-in/:m]
]Stall Current: 133 amps/:m][/highlight][/font]

2

Hi,

As we replied in our Support Center :
At low RPM, DC Motors needs more torque to be able to rotate (you can google “RPM vs torque DC motor”).
The RB-And-128 DC Motor you have, consumes 2.7Amps free running current but consumes a lot more when a load is attached to it or when it starts to rotate.
To approximate this amount of current drawn by the motor, a rule of thumb is to calculate 20%-25% of the stall current which is 133Amps.
Therefore, the current consumption of the RB-And-128 with a nominal load should be around 26.6-33.25Amps which is too high for the RB-Cyt-132 drive to handle.
The RB-Cyt-132 is capable to provide only 13Amps continuously (30Amps peak for 10 seconds).
It has probably an overcurrent protection feature to prevent the FETs from burning when the motor draws more current than it can provide and therefore it shuts down.
You have 2 options :

  1. Either change the motor for one that runs at slow RPMs and consumes less than 13Amps.
    We suggest you to take a look at our DC Motors comparison table.
  2. Or change the motor controller for one that can provide more than 30Amps continuously. Suggestion : 30A 5-30V Single Brushed DC Motor Driver