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How should I regulate the power for my motors? Answered

Hello, I am planning on building a stepper motor driver using Tom McWire's design. I want to control 3 motors which are rated for 7 volts, 350mA, and 20 ohms. I plan on using a 12 volt 5amp power supply. I am trying to figure out what kind of resistor I should use so that I do not fry my motors. Maybe I am missing something, but this is the way I am looking at it.... If the motor is using 7 volts and the power supply is 12 volts, that means i have 5 volts left to use. 5v over .35amps (the amount the motor uses) is 15ohms. (14.28 rounded up) That also means it uses 1.75 watts (5*.35). Would a 15ohm 2 Watt resistor be sufficient or am I looking at this all wrong? Thank you for your help in advance, folks :-D

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lemonie

10 years ago

You'd be better with a 7V supply. The resistance / impedance of motors is variable, and you don't really want to be dumping a lot of power as heat.

Power Supply Instructables

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TheLostAmish

10 years ago

lol. I really hope I'm right, cause I just bought all the parts for it