[ka67_72]

I need some help with wiring/configuration of my amps and motors. I'm using AMC B25A40E amps http://www.a-m-c.com/download/legacy/b25a40k.pdf
with Rutex R2040 step/dir to analog cards. I have US digital differential encoders going to the Rutex. Using a DATAQ DAQ to monitor voltages, I can see the Rutex is outputting signals to correct for error. The motor I'm trying now is a Pacific Scientific PMC5FB-00101-01. It has what appear to be three hall sensors spaced sixty degrees apart. I've tried two amps configured the same way with similar results. They are in current mode with the pots adjusted according to the info from AMC. I've changed the order of the motor and hall wiring to every combination I can figure and the best I've got the motor to do is return to zero if I only move it a few degrees by hand. Otherwise it just freaks out. The Rutex can get it to jerk left and right then the amp takes over and jumps around regardless of input voltage. Then it locks the motor down until I return the input voltage to zero. If I disconnect the halls from the amp, it thinks I have a brush motor connected and outputs a +/- voltage, that corresponds to the input, across Motor A and B terminals. This leads me to believe it understands the Rutex. Any help would be appreciated.

Thanks,
Kevin

[Al_The_Man]

First, I would get the motor and drive working with an analogue signal into the drive, use a battery box or pot across a 9v battery etc.
Use 120deg commutation and with power on the hall sensors but the motor power disconnected, turn the armature by hand in both directions and the drive LED should stay green, if it goes to red, then the commutation sequence is wrong.
Once the LED stays green, then connect the motor power and try varying the speed in both directions, if it stutters or takes off or behaves oddly in one or both directions, then you have to try the six different armature connection commutations until the motor is controlled properly, once it is OK then you can connect the feedback loop.
Then the condition may occur where the encoder phasing is wrong.
i.e. the commanded direction contradicts the encoder direction.
Then you can either change the A & B pulse if single ended, or the A & /A if differential.
BTW, the hall spacing depends on the pole count, this will vary the amount of electrical revolutions per mechanical revs.
Al.

[ka67_72]

Al,
Thanks for the response. Do I need to have the battery hooked to the Ref in when I'm testing the halls. I checked it in all six positions twice without one hooked up. In two configurations I can turn it one direction without the light going red, but it comes on in the other direction. In the other four it blinks in both directions. The red blips on so faintly I didn't see it at first so I switched to 60 degree and tested. In that, all six give 120 degrees of red, 120 of green, a short flash of red, and the last 120 of green.

Thanks,
Kevin

[Al_The_Man]

The battery box is just for testing the motion once the halls are OK.
The drive/halls should have power but motor power leads disconnected.
Turn the shaft slowly and the LED should stay permanently green in both directions.
I would set the drive to 120deg.
You have to get the hall combination right before proceeding.
Al.

[ka67_72]

Al,
The best I can get is all green in one direction with a short red flash once every 360 in the other. It will do this in two of the six configurations. The rest go red in both directions. I've attached the waveform output of my halls. They're triangular. I don't know if this is a problem. The noise on 3 is from my daq. If I swap 2 and 3 it goes away.

Thanks,
Kevin

[Al_The_Man]

You should have clean square wave out of you commutation sensors.
They are of such a width that you can measure with a meter at very low rpm.
Do you have true halls or commutation track equivalent on the encoder?
How are you powering your Hall inputs to the drive or encoder?
If the encoder is powered separately, you only take the three hall connections and Common to the drive from the encoder.
Al.

[ka67_72]

Al,
The signal I attached before is from the sensors that came on the servo. Power is coming from and signal is going to the amp. There are three chips standing on a ring about 60 degrees apart. The middle one is turned backwards from the others. They surround a ring magnet mounted to the servo shaft. I just assumed these were hall sensors. The chips have three leads (power, ground, signal). They are marked 95A 513. I haven't found any info on the chips or these two servos. I have adapted a US Digital E5D-720-312-I encoder to the servo. http://www.usdigital.com/products/e5/ The encoder is just hooked to the Rutex.

Thanks,
Kevin

[Al_The_Man]

OK you have the older style discrete Hall effect devices.
The fact they are 60 degrees apart do not mean they are 60deg commutation as is set and implied on the drive, i.e. 60/120.
The spacing of the halls depend on the electrical difference.
IOW if you have a 8 pole motor, there will be 4 electrical (360deg) rotations per one mechanical rotation.
If you put a meter on one of the hall effect outputs, and find that the output goes high four times every mechanical rotation then this is a 8 pole motor.
Three times will be a 6 pole motor.
If you are not getting a nice square wave, you may need a pull up resistor on each outputs, 1k~5k.
Al.

[Al_The_Man]

Here is a link for the sequence on a 4 pole motor, if you step through, you will notice the commutation is 120deg and there are two electrical rotations per mech. rev.
http://users.tinyworld.co.uk/flecc/4...otor031102.swf
Al

[ka67_72]

Al,
Each hall output only goes high once per rotation. Reading through the AMC documentation it says the hall input has a max low of 1.5V and a min high of 3.5V. Without resistors, I'm currently going from 1.8V to 4.3V. I'll play with some resistors to get it down.

Thanks,
Kevin

[Al_The_Man]

The most important is to get the wave shape right, the ones shown in post#5 look terrible.
You should get a nice square wave, I would tend to try an interface IC before resistors, or use three 2n7000 for example as buffers.
The motor appears to be a 2 pole motor which is very unusual, you may get quite a bit of 'cogging' at low rpm.
Al.

[ka67_72]

OK. I'll order those from digikey ,set these two motors aside, and start on one of the others. I have two with frameless resolvers, and one with a tachsyn. Which do you want to tackle first?

Kevin

[Al_The_Man]

AFAIK you will need AC sinusoidal with resolver commutation drives.
Al.

[ka67_72]

Al,
I have the 2N7000's on order. I'm going to scrap the other three motors, try to find a good source for some new BLDC motors with normal halls, and use the encoders I've already bought. I'll probably just buy one for my Y axis to get running and buy the A and B ones later.

Thanks,
Kevin

[Al_The_Man]

Al,
I have the 2N7000's on order. I'm going to scrap the other three motors, try to find a good source for some new BLDC motors with normal halls, and use the encoders I've already bought. I'll probably just buy one for my Y axis to get running and buy the A and B ones later.

Thanks,
Kevin

You may find that BLDC motors with actual hall effect sensors are hard to come by, they were replace quite some years ago with the encoder track type, which has a reputation of being a better, more precise method.
I would also look for 6 or 8 pole motors.
Incidentally, renco have encoders for sale on ebay for $20.00, some with commutation tracks, single ended output though.
Al.

[ka67_72]

Al,
Can you recomend some sources for new, ready to go motors that will work with my amps?

Thanks,
Kevin

[Al_The_Man]

Well with those amps, you have quite a wide range, anywhere from 120vdc to 400vdc. 12amp operating.
In the past I have succesfully used CMC, Aerotech, Applied Motion, Tamagawa, with the AMC amps.
Al.

[ka67_72]

Al,
I just understood what you meant about the Renco encoders. I can use them for my commutation and use the US Digitals I have for the controller. The remaining motors I have are four pole. To keep me from having any more spare parts, how many pole pairs do I need to specify for the Rencos.

Thanks,
Kevin

[Al_The_Man]

Renco specify the commutation by resolution/(pole pair) at the end so a 4 pole motor would need a /2.
Al.

[ka67_72]

Al,
The Rencos worked for my 4 pole motors. I have them tuned on the bench. So I have Y, A, and B working. Now I'm back to my hall commutated x and z axis motors. I'm using the 2N7000s. I've attached the screen capture of them in action. I'm measuring the voltage drop across the FETs. Whenever the middle one is low, the fault light comes on. What do you think?

Thanks,
Kevin