[erikjgreen]

Hi, all;

This previously was stuck on the tail end of an older question I asked, so I want to separate it out in another thread in the hope that someone can give me a hand. Background first:

I'm trying to bench test some aerotech ba20-320 drives. These are old school analog servo drives that take +/-10V input and can run brushless or brushed servos. Amps are 20 peak, volts up to 320. I have the drive connected to a compatible servo on my bench. I also have the following connected:

* Tachometer to the tach inputs on the drive
* Drive enable (limit switches are inverted by jumpers for now)
* 9v battery/potentiometer to command input, other end of differential input tied to GND per manual
* Servo power wires to A and C terminals (A and C are used for brushed drives and B is open)

I've set all the jumpers in the drive to the "brushed" setting. Additionally I've set jumpers to enable tach feedback (as opposed to encoder). I've set the DIP switches for the drive to allow full current and full peak current. The drive can handle up to 20 amps peak for 2 seconds, and continuous is 10 amps. The servo is larger than this, it can handle up to 21 max amps (it's a SEM MT30). However, I have a 10 amp fuse inline with live power which comes off the inside of a 240->110 step down transformer (this drive can be line powered per the manual, but I wanted isolation). DIP switches are also set to velocity mode. I've tried both supplying a command signal with a 9V battery and also the drive's internal "test" mode.

After all that, I can't get any servo movement. I do hear harmonics a bit when the drive is enabled, but no power is output to the drive.

So my question is, what is a normal bench test config for an analog servo drive? If you've tested a drive this way, could you please let me know what sort of connections usually have to be made - power, servo, tach, limits, etc? If a connection says it's "active low" vs. "active high" then it should be active when grounded (to the drive's common ground) right? Do you just connect wires to the drives one-off, or do you have a "test rig" you use?

I'm tearing my hair out trying to figure out what these drives want in order to operate.

Thanks,
Erik

[Al_The_Man]

I have used many a A-M-C drive of all models and usually they are very simple, especially the DC brushed variety.
The main thing is to make sure the enable light is on, most drives have a internal jumper to set high or low enable, the same thing for the FWD REV L.S. input, although the these will not cause the enable to go out when tripped.
These limits and enable are referenced to the common terminal.
I have a test +-10v analogue source made up from a couple of 9v batteries and a 5k pot.
I haven't got the manual in front of me, but I seem to recall it is the A & B for DC brushed, and 60deg commutation?
Al.

[erikjgreen]

Hmm... from the look of the manual it's A+C. Here's the one I'm reading:

http://www.aerotechmotioncontrol.com...BA10_20_30.pdf

According to figures 2-7 and 2-8 it's wires A and C, or at least that's how it looks to me. I don't see it mentioned anywhere else?

I'll check the outputs just in case with the amp powered up, to see if there's any current there.

Right now I've got it configured so that both limits and enable are tied to ground, the limits are set to be active when given +5v through a resistor. The enable is default, and the LED does light up. Power, tach, and servo are connected.

I've tried switching between test mode per the manual and using a 9 volt bat with a 5k pot... neither works.

I'm stumped.

Erik

[erikjgreen]

Okay... I went through all the switches and checked them... apparently the "new" servo drive I'd bought had been taken out of the box and configured for sinusoidal commutation. Once I moved those jumpers back the servo started dancing around nicely.

I'm going to try connecting the thing in torque mode now (the way I want to use it) and see if it still turns, then I'll check the other drives.

I do have a question though... should a 5k pot and a 9v battery produce the full speed range? I only seem to get a little variation. I'm guessing I need to do the math and see if I'm getting the full voltage range?

Thanks,
Erik

[Al_The_Man]

I was thinking AMC all along, for using a 9v battery and pot for testing, ground pin 21, connect battery across the pot and battery -ve goes to 21 and the slider to pin 8.
Al.

[erikjgreen]

Thanks, Al.

I got all three drives tested today, all work as advertised (in torque mode with +/-10V command) once I figured out the minimum wiring needed:

* Servo power on pins A+C (dunno why I put A+B above, that's a typo)
* Ground servo case to drive case
* command signal from battery/pot (jumper other half of diff. signal input to GND, - side of signal input to common pin)
* Ground enable signal (jumper enable pin to GND)
* switch limit inputs to "active on 5v" and ground them
* AC power through fuse to drive incl. ground connection
* CLAMP DOWN servo

(also servo configuration - set current limits, disable test mode, and set torque mode + jumpers for brushed motor)

Erik