Dynomotion

Group: DynoMotion Message: 1809 From: bouseman_73 Date: 9/18/2011
Subject: buzzing and oscillation motor
Hi Tom
I have strange problem. I use DC brush motor (40v, 100w) + AMC drive (30a8T, www.a-m-c.com)+ KFlop+Kanalog. Motor is controlled by analog 0...10v. When I turn power ON, motor begins buzzing and oscillating and it's going on until Kflop initialization (d1, d2 leds flashing) will be done. Right after KFlop initialization is finished (d1, d2 leds ON) motor works good, without any buzzing or oscillating. If I turn power on motor + drive (without KFlop), it's also works good.
How can i fix it?

thank you in advance
Slava
Group: DynoMotion Message: 1810 From: Tom Kerekes Date: 9/18/2011
Subject: Re: buzzing and oscillation motor
Hi Slava,
 
I'm not sure what might be causing the buzzing.  Probably with KFlop/Kanalog powered off or uninitialized the Analog Outputs are floating and so then pick up noise.  You may want to check the shielding on your wiring.  The Kanalog outputs will float until KFLOP initializes and turns on the +/-15V Generator on Kanlog that is used for the Analog Circuits.
 
But regardless it is best to keep the Amplifier disabled until you are ready to enable the Servo loop.  Even without the buzzing it is almost impossible to have a high gain amplifier sit still by commanding the input to 0V because there will always be some small offset or noise.  So the axis may slowly creep until the Servo is enabled.
 
It looks like your Amplifier has an Inhibit input that if pulled to ground should disable the drive.  They don't provide details other than it is a 5V TTL signal that will be high if left open.  So I would assume there is an internal pull up resistor.  So a solution would be to somehow keep this pulled low until your KFLOP Init.c program would set it high and then Enable the Servo.
 
The first 8 IO on both JP4 and JP6 of KFLOP have fairly strong (150 ohm) pull down resistors.  So those pins are guaranteed to remain low with power off and throughout the boot process.  Setting those pins to a 3.3V TTL high should also be a valid 5V TTL high so it should enable the drive properly.
 
Another option is to use two relays connected to Kanalog.  One driven from SWE that guarantees all the Kanalog outputs are initialized to their default state, and another that can be switched by your Init.c program.
 
Hope this helps.
 
TK