A Problem With Resonance

[MoonlightMedia]

Sorry if you have seen this post before but I think this is the right place to
put it.

The following Email was sent to Gecko SUpport -

Gentlemen,

I recently replaced two controllers with Gecko 201s. The previous controllers
had been serviceable until failure. The reason I chose Geckos was that the
prior vendor (overseas) no longer answers mail. I suspect they are out of
business.

The old controllers were configured as an 8x micro step structure driving bipolar 1.8 degree motors. These motors are being sourced with 35 volts and the Gecko 201s are set factory stock with approximately 3 amps current (24K resistors - OK a little under 3 amps) . The motors are rated at 4 amps max.

My problem is that I am getting resonance in the motor output. The way I have determined that it is resonance is as follows.

Using a single output (X Only) and plotting a straight line along the X Axis, everything works normally and sounds nice and smooth. This can be repeated forward and backward with no loss of steps and no jitter or other objectionable process. Jog works extremely well and is very quiet and smooth. I am running all of this under Mach III and on a Win 2K system.

If I plot a circle and look at he X Axis only (Y Axis disconnected) , the plot hesitates at about the 25 percent and 75 percent points along the X Axis. The motor jitters, reverses and steps erratically. This only happens at these points and is very repetitive. The same problem exists under identical (Axis Swapped) circumstances for the Y Axis and motor.

Since the 201s are preset for 10X step resolution, I thought this would not be an issue. I tried setting the midband disable but it does not help. Do you have any suggestions how to rectify this problem.

Again let me say that this was a running unit before I replaced my old controllers with the Gecko 201s. Any help would be much appreciated and I am prepared to set up any testing scenario you would like.

Bill

Moonlight Media LLC

[ger21]

Can you try increasing the acceleration? It might help you pass quickly through the resonant band.

If you don't here back from Gecko via email, give them a call. They are supposed to be extremely helpful.