Easy driver with step-up converter

My project uses a bare bones Atmega328 chip and 4 AA batteries. It needs to spin a stepper motor (sparkfuns 10487 12 v stepper) intermittently.

So I got Pololus item 2117, a step-up converter w 12 V output. I measure 12v with no load, but when I hook it up to M+ on the easy driver board, voltage drops to 10v or less, and the motor wiggles but won't quit spin.

I'd appreciate any advice about how to make this setup work, or about a different setup. Thanks!

You need to provide a link to the datasheet for the motor. I can't find a sparkfun product with that number.

The Pololu page for that step up device only describes the max input current at 1.4 amps.

If you are stepping up from 6v that means the output current will be less than 0.7 amps. How many amps does the motor need? Can the AA batteries comfortably provide 1.4 amps? - and for how long?

Are the same batteries powering the Atmega 328 - that could also be a problem. How are you regulating the voltage?

You have not said what stepper motor driver you are using.

Stepper motors are very inefficient. You need a proper power supply and a 12v stepper would work better with a 20v+ power supply.

See stepper motor basics for more background info.

...R

Trying to power a step up converter like this from the same batteries as an ATmega chip is likely to be a poor choice. Sounds like this module isn't up to the load.

Do you mean the 10847 Sparkfun motor? That's not 12V, is 2A, 1.5 ohm bipolar motor, beyond the current range an EasyDriver can manage. Or do you mean the 10848, which is a 12V 0.4A unipolar motor.

Note that they both have 6 wires, but the 12V one is clearly meant for unipolar use with its 30 ohm windings, whereas a 1.5A motor is bipolar only (unless you are really twisted!).