controlling 3.1 volt steppers with adafruit motorshields v 2.3

I have tried to make a schematic:

The gray area represents the adafruit motor shield.

If the voltage is not HIGH enough a resistor will not INCREASE the voltage as far as I can see. Let me refer you to Robert Peter Oakes

Clem

Hi Clem.

The Idea is to decrease the voltage.

My idea is, using calculations, that if:

3.125 V = 2.5 A * 1.25 Ω

Which gives the voltage of the stepper.

My consideration is if I put a 3.55 resistor in serie, as in the schematic in a former post, will this resistor obtain the excess voltage?

By calculation:

12 V = 2.5 A * (1.25Ω + 3.55Ω)

where the 3.55Ω resistor is the one I'm talking about.

Is it possible to do it that way?

Or will the resistor consume too much energy?

Perhaps it's better to crate a voltage divider to reduce the voltage?

The voltage divider is better way to go sending one end to ground. I have seen this for 5 volt connections to a 3.3 volt pins on Raspberry Pi. But Too much voltage does not divide well. 12 volts to 3 volts will heat up the circuit too much.

Clem

In most stepper motor controllers (Modern ones), you do not limit the voltage by setting up a divider (R1, R2 ) as they manage the pulse width in the same way as driving an LED with PWM, it is more about the current going through the Motor, its inductance will limit this automatically and is often set-up in the configuration of the controller

So having a motor with only 1.25Ohms DC resistance means nothing to a pulse, its inductive reactance is what will matter and that to a pulse can be much higher than the DC Ohms

It would be common to see a stepper like this having say a 12V supply but still driven directly from the controller with no additional limiting resistors, you can often have a current sense resistor that provides feedback to the controller so it can manage the average current / power through the motor

In most stepper motor controllers (Modern ones), you do not limit the voltage by setting up a divider (R1, R2 ) as they manage the pulse width in the same way as driving an LED with PWM, it is more about the current going through the Motor, its inductance will limit this automatically and is often set-up in the configuration of the controller

So having a motor with only 1.25Ohms DC resistance means nothing to a pulse, its inductive reactance is what will matter and that to a pulse can be much higher than the DC Ohms

It would be common to see a stepper like this having say a 12V supply but still driven directly from the controller with no additional limiting resistors, you can often have a current sense resistor that provides feedback to the controller so it can manage the average current / power through the motor

I always learn more with you Peter. Thanks for stepping in.

Clem