Dynomotion

Group: DynoMotion Message: 8868 From: Hugh Sontag Date: 1/7/2014
Subject: Setting up KFLOP / Snap Amp for a stepper motor
Hi Tom,

I'm attempting to set up a stepper motor for our Z axis with KFLOP and a Snap Amp. So far, I haven't seen the motor move at all, and I'm interested in what you might suggest to figure out why.

The Z axis is assigned as channel 3. The same channel on the Snap Amp that I'm using previously drove a BLDC motor successfully.

I connected one coil to OUT4 - OUT5, the other coil to OUT6 - OUT7 on SnapAmp 1. The stepper has a max coil current of 7 amps.

I tried both "Microstep" mode and also "CL Micro" mode with P, I and D set = 0. Neither mode shows any movement when trying a "Move" on the Step Response window.

- I double-checked the motor connections to SnapAmp 1. An ohmmeter verifies that the coils appear to be wired to the leads connected to the Snap Amp.

- No current is shown (less than 0.2 amps, looks like noise) during a "Move" for the axes.

- The power supply is at 57 V throughout the move.

I've attached some screen shots, and data from a test "Move".

I'll use a power supply tomorrow to verify the stepper's ability to move if a coil is energized. I suspect that will just show that the stepper is in fact functional. Another of 4 motors in the same shipment works with the power supply.

What would you suggest to get the stepper running?

Thanks,
Hugh





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Group: DynoMotion Message: 8869 From: Tom Kerekes Date: 1/7/2014
Subject: Re: Setting up KFLOP / Snap Amp for a stepper motor [1 Attachment]
Hi Hugh,

Your configuration looks all correct to me.  Except that your invDistPerCycle is very small.  We usually leave that set to 1.0 which makes the KMotion Units "cycles" (50 per rev).  But that should work and wouldn't explain no current to the motors.

Did you enable SnapAmp by running the C program to set the Allowed peak current and Voltage clamping?  Did the fault LED on SnapAmp go off?

Regards
TK

Group: DynoMotion Message: 8870 From: Hugh Sontag Date: 1/7/2014
Subject: Re: Setting up KFLOP / Snap Amp for a stepper motor
Thanks for the suggestions. I didn't run a C program after turning on the KFLOP, so that could easily be the problem.

So I need to set the peak current limit and voltage clamping for the SnapAmp, I can do that.

The invDistPerCycle was left over from the configuration of the BLDC motor, so I'll go ahead and set it to 1.0. I think that this must go hand in hand with the Encoder Input Gain for the "CL Microstep" mode, which is what I want to use once I have the motor working open-loop.

We discussed the "CL Microstep" mode previously, and you told me that the Encoder Input Gain should be 50/8192 for a 2048 PPR encoder with quadrature. Is that in fact correct only if the invDistPerCycle is 1.0?

Thanks,
Hugh


On Tue, Jan 7, 2014 at 8:48 PM, Tom Kerekes <tk@...> wrote:
 

Hi Hugh,

Your configuration looks all correct to me.  Except that your invDistPerCycle is very small.  We usually leave that set to 1.0 which makes the KMotion Units "cycles" (50 per rev).  But that should work and wouldn't explain no current to the motors.

Did you enable SnapAmp by running the C program to set the Allowed peak current and Voltage clamping?  Did the fault LED on SnapAmp go off?

Regards
TK

Group: DynoMotion Message: 8871 From: Tom Kerekes Date: 1/7/2014
Subject: Re: Setting up KFLOP / Snap Amp for a stepper motor
Hi Hugh,

Yes that assumes invDistPerCycle is 1.0

Regards
TK