Stepper motor voltage: NEMA17 + EasyDriver *SOLVED*

Projects General Guidance
1

Hi All,

I'm in the process of making a CNC machine, I am using NEMA 17 stepper motors with EasyDriver boards to run them.

The problem I am facing is my stepper motor's rated voltage is 3.4 volts and the EasyDriver requires a minimum input of 7 volts for the motors.
What's really confusing me is there are lots of tutorials on how to hook up EasyDrivers to NEMA 17 motors and most of them use 12V inputs on the EasyDriver, but when you look at all the different types of of NEMA17 from RepRap's reference NEMA 17 Stepper motor - RepRap, hardly any of them are rated at 12V most are rated at 2-4 Volts.

My feeling is I am misinterpreting the meaning of "Rated Voltage" in this context, I mean the motors are pretty beefy size wise and 3.4 volts seems quite low for something this big.

Here is a link to my motor's spec http://www.ebay.co.uk/itm/CNC-Nema17-for-1-7A-3400g-cm-40mm-length-4-Lead-2-phase-Longs-Stepper-Motor-/280871522245?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item41653f4fc5

Here is a link to the EasyDriver boards I have http://www.ebay.co.uk/itm/EasyDriver-drive-stepper-motor-driver-board-/220922508583?pt=LH_DefaultDomain_0&hash=item337001f527

The sentence "EasyDriver-board voltage regulator chip can be set to 3.3V or 5V, directly with the 4-wire stepper motor and micro-controller and precisely control the stepper motor movement"

Implies it takes the input voltage (whatever that is) and supplies 3.3 or 5.5 volts to the motor, is that a correct interpretation ?

I would really appreciate if anyone can clarify exactly how many volts im supposed to supply to the easy driver boards whilst not frying my Motors!

All help appreciated.

2

Well my research skills clearly aren't very good today, my question is answered on the EasyDriver FAQ

"Q1) My motor says it can only take 2.1V at 2A. Will the EasyDriver (running from up to 30V) blow up my motor or damage it in any way?
A1) Nope. You're safe. Motors are specified with DC flowing through their coils. But what we are concerned with is maximum current. The voltage spec of the motor doesn't really matter, using the EasyDriver. (Or any chopper driver, for that matter.) The EasyDriver will ramp up the voltage to the coil until the current reaches the maximum set with the pot (max of 750mA). Then it will cut the power to the coil until the current dips down again, then re-apply power, over and over again, about 20,000 times per second. Any motor that's rated for 150mA/coil (or more) will work with the Easy Driver just fine, no matter what it's voltage rating. Note that if your motor is rated for less than 750mA/phase, you should adjust the current set pot on the EasyDriver to dial down the maximum coil current to match your motor."

Q1 as well! I cant even use "it was obscured in documentation" as an excuse :slight_smile: Leaving this post as a reference for anyone else who might get stuck.

3

eci22:
Leaving this post as a reference for anyone else who might get stuck.

Thanks for doing that, it surely helped me :smiley:

4

If your motor requires 2 amps an Easydriver won't be suitable as it can only supply 750mA. You need a BigEasydriver or better still a Pololu DRV8825.

...R