Uno + 4 Wire Stepper Motor + 12V Power Supply

Question

Hello, I currently have a NEMA 17 stepper motor with an EasyDriver hooked up to an Arduino Uno with a 12 Volt power supply. Eventually, we are going to attach a load cell with a strain meter and will want to have the force to always be at 8 lbs. The stepper motor will be coupled with a vertical stage dial that will rotate depending on if the force is above or below 8 lbs. As of right now, I was wondering if it is possible to code the arduino to turn the stepper motor "counter clockwise" if the 12V power supply is under 12V and "clockwise" if it is over 12V just to practice for when the strain meter comes in. Is there a way for the arduino to read how many volts are output from the power supply? That is where I'm stuck right now. Thanks!

colecago · Answer

Use a voltage divider on one of the ADC's to get a voltage in the range your Arduino can read (3.3V or 5V depending on your Arduino). Basically two resistors in series between 12V and ground and you take your signal in the middle between the two resistors.

Vout = 12V * R2/(R1 + R2) (with R2 being the resistor tied to ground)

You should add a capacitor to that ADC line to get down some of the power supply noise as well.