Compute Value and Wattage of Current-Limiting Resistors:Note: For L/R systems only. :This is a basic application of Ohms Law for a series circuit. :Your resistor must drop the difference in voltage between :the voltage at which your stepper is rated and your supply voltage: ::Resistor voltage drop = Supply voltage - stepper rated voltage :Applying Ohms Law, divide by the rated current to get the resistance: ::Resistor value = Resistor voltage drop / stepper current :Finally, and very importantly, you need to know how much wattage :you will be dissipating as heat, which your resistors must be rated to handle: ::Resistor wattage rating = Resistor voltage drop * stepper current :For example: Steppers rated at 2.5V @ 5A, with a 26V power supply ::Resistor voltage drop = 26V - 2.5V = 23.5V ::Resistor value = 23.5V / 5A = 4.7 Ohms ::Resistor wattage rating = 23.5V * 5A = 117.5 Watts |