User Manual

Many motor controllers or speed controllers can have peak current ratings that are substantially

higher than the continuous current rating; this is not the case with these motor drivers, which have a

30 A continuous rating and over-current protection that can activate at currents as low as 30 A (50 A

typical). Therefore, the stall current of your motor should not be more than 30 A. (Even if you expect

to run at a much lower average current, the motor can still draw short bursts of high currents, such as

when it is starting, if special steps are not taken.)

If your motor has a stall current over the driver’s continuous current rating of 12 A per channel, we

recommend you take extra steps to make sure that your motor will not be exposed to loads that will

cause it to exceed 12 A for prolonged periods of time (or you take extra steps to keep the motor drivers

cool, such as increasing air flow or adding heat sinks). Exceeding 12 A for long durations should not

damage the shield, but it will eventually activate the driver’s thermal protection, which might result in

inadequate performance for your application.

It is not unusual for the stall current of a motor to be an order of magnitude (10×)

higher than its free-run current. If you do not know your motor’s stall current, you can

approximate it by measuring the current it draws while held stalled at a lower voltage

(such as when powered from a single battery cell) and then scaling that value linearly

with voltage. For example, the stall current of a motor at 6 V is six times the stall current

of that motor at 1 V. Another, less accurate method is to use a multimeter to measure

the resistance between the motor terminals and then use Ohm’s law to compute the stall

current I at voltage V: I = V/R. This last method generally is not as reliable because it

can be difficult to measure such small resistances accurately.

Occasionally, electrical noise from a motor can interfere with the rest of the system. This can depend

on a number of factors, including the power supply, system wiring, and the quality of the motor. If you

notice parts of your system behaving strangely when the motor is active, first double-check that your

power supply is adequate, then consider taking the following steps to decrease the impact of motor-

induced electrical noise on the rest of your system:

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