# How does the motor shield determines how much voltage to supply to a motor?

Can i connect 6v DC motor and 12v DC motor, or 6v DC and 12V stepper to adafruit motor shield v1, and an external 12v power supply? also, how does it determine how much voltage needs to be supplied to a motor? is it done by code, when we set the speed of the motor, or the frequency?

do i have to take care of how much voltage i am supplying to the motor shield?

## 1 Answer

Can i connect 6v DC motor and 12v DC motor to adafruit motor shield v1, and an external 12v power supply?

No.

how does it determine how much voltage needs to be supplied to a motor?

It doesn't. It supplies whatever voltage you supply through the power input.

You must match the power supply to the motor. The motor shield is merely a switch that turns the power on and off in the right way to change the speed and direction of the motor.

• can i ask one more thing, when we set the speed and frequency of the motor in the code, what is the motor shield actually doing, is it changing the voltage, or the pwm signal? Jun 4 '20 at 10:23
• It's turning the power on and off very rapidly. The speed at which it turns the power on and off is set by the PWM frequency. The on and off times are set by the PWM duty cycle. Due to the low-pass filter-like nature of an inductive load like a motor the end result is the appearance of a reduction of both voltage and current to the motor, resulting in a change in the overall power and thus speed of the motor. However I would not recommend relying on low PWM duty cycles as a way of "underpowering" a 6V motor from 12V as it is all too easy to get it wrong and smoke the motor.
– Majenko
Jun 4 '20 at 10:26
• got it. does it mean that i can't connect a dc motor and stepper at the same time, if the voltage ratings are different? Jun 4 '20 at 10:27
• That is correct. For a 12V power supply you need 12V motors. Or a 12V to 6V voltage regulator (switching regulator ideally) and a second motor shield that you would then run at 6V.
– Majenko
Jun 4 '20 at 10:29