Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: THicks1971 on December 26, 2011, 07:43:43 PM

Title: Axon
Post by: THicks1971 on December 26, 2011, 07:43:43 PM

I was reading on your home page about the Axon microcontroller and from what I see, it has PWM on a few channels. Can this be used to drive a stepper? either type, unipolar or bipolar?

Title: Re: Axon
Post by: Admin on December 27, 2011, 05:37:34 AM

Steppers don't use PWM.

You need a stepper driver to drive a stepper. The microcontroller then controls the stepper driver.

Title: Re: Axon
Post by: THicks1971 on December 27, 2011, 06:24:57 AM

Any recommendations on a particular stepper driver modual?

Title: Re: Axon
Post by: Admin on December 27, 2011, 07:34:50 AM

What's the current and voltage of your stepper motor?

Title: Re: Axon
Post by: Webbot on December 27, 2011, 12:12:52 PM

Tutorial: http://www.societyofrobots.com/member_tutorials/node/120 (http://www.societyofrobots.com/member_tutorials/node/120)

Title: Re: Axon
Post by: Soeren on December 27, 2011, 08:24:07 PM

Hi,

Quote from: Webbot on December 27, 2011, 12:12:52 PM

Tutorial: http://www.societyofrobots.com/member_tutorials/node/120 (http://www.societyofrobots.com/member_tutorials/node/120)

Just to point you towards a bit on the L297, in your stepper tutorial, that needs correction:

Quote from: http://www.societyofrobots.com/member_tutorials/node/168

When we ask the L297 to perform another step then: it applies voltage to the coils and as the current increases then so does the sensed voltage. This is compared against a reference voltage on pin 15. As soon as the sense voltage exceeds this reference voltage then the voltage is removed from the coils until we ask for another step. So the reference voltage on pin 15 (maximum of 2.5v) controls the maximum current supplied to the motors and should be just enough to make the motor 'step' - at which point the current consumption is turned off. Its a closed loop feedback system!!

It is a closed loop system for sure, but it doesn't work as a simple current turn off.

When the current level triggers the "over current sense", the L297 goes into Chopper/PWM mode and adjust the current to the maximum allowed (By V_ref). It does so by modulating either the phase lines or the inhibit lines, depending on the logic level on Control (pin 11).

Title: Re: Axon
Post by: THicks1971 on December 28, 2011, 05:50:09 AM

Thanks for the info. I am using a 12v 600ma stepper from Jameco. I believe the L297 was the answer I was looking for. Thanks