AXBB Unable To Output Full 10v With VFD

[KLewtak]

Hello Everyone,

I've encountered an issue with my AXBB-E controller and my VFD (FULING DZB280 3.7kw)/Spindle (3.2kw 24000RPM @ 400hz) setup. The entire system is powered by two independent power supplies. The first is 24 volt/5 amp which powers both the VFD as well as the AXBB-E controller. The second is 5 volt/2 amp which is only connected to the 5 volt input on the controller.

As the title states, I am unable to get the controller to output it's full 10 volt analog signal when it is connected to the VFD. I also tested the controller with the 5v jumper enabled and it is unable to output the expected 5 volt analog signal. Not only this, but the output voltage is not stable when the controller and VFD are connected. When measured with a multi-meter, I see 4.78-4.80 volts when the VFD is hooked up and running, less than half of the expected voltage. With the VFD is disconnected from the controller I am able to measure a stable, full 10 volts. This is also noticeable when I try to target 340HZ on the VFD. It will get to that frequency but then proceed to waver between 338HZ and the desired 340HZ.

The big question is what could cause this? Any help with figuring this all out is greatly appreciated!

-Kacper

[beefy]

Put a multimeter (on the amps scale) in series with the 10v output wire.

Is the current flowing more than what the controller can give out. This could potentially be what is causing the voltage to drop.

[Greolt]

The entire system is powered by two independent power supplies. The first is 24 volt/5 amp which powers both the VFD as well as the AXBB-E controller.

I am not familiar with that particular VFD, but not sure why you are powering it with 24v

[cncdrive]

The output of the AXBB-E is an operational amplifier in voltage follower connection.
Such circuit has a gain of 1 and a low impedance output, so it's voltage will be stabile in the operational range of what the OP-AMP is rated for.
If I recall what is in the AXBB-E is rated for -20/+10mA, so the VFD should not load the output more than that.
If it does could cause a voltage drop. So, it would be good to know the internal circuitry of the VFD on the analog input.
It might pull the output to 0volts internally with too strong resistor which causes more current flow out of the AXBB-E analog output and voltage drop then happens because the OP-AMP is overloaded.
But to make sure we should see the circuit diagram of the analog input of the VFD, however I can't think of any other possible reasons for this problem.

[KLewtak]

The entire system is powered by two independent power supplies. The first is 24 volt/5 amp which powers both the VFD as well as the AXBB-E controller.

I am not familiar with that particular VFD, but not sure why you are powering it with 24v

My mistake, the VFD is powered by 220VAC. The 24VDC only goes to the AXBB controller.

The output of the AXBB-E is an operational amplifier in voltage follower connection.
Such circuit has a gain of 1 and a low impedance output, so it's voltage will be stabile in the operational range of what the OP-AMP is rated for.
If I recall what is in the AXBB-E is rated for -20/+10mA, so the VFD should not load the output more than that.
If it does could cause a voltage drop. So, it would be good to know the internal circuitry of the VFD on the analog input.
It might pull the output to 0volts internally with too strong resistor which causes more current flow out of the AXBB-E analog output and voltage drop then happens because the OP-AMP is overloaded.
But to make sure we should see the circuit diagram of the analog input of the VFD, however I can't think of any other possible reasons for this problem.

The measured current between the controller and the VFD is 20mA which would explain why my voltage dropped by half. Upon further research I have found that the VFD circuitry is set for 0~10V/4~20mA. After putting a 1.2k resistor into the circuit, the current dropped to ~9ma and the controller was able to maintain steady voltages at all ranges from 0-10VDC. Not sure if this is the proper solution to this type of problem, but for now it seems to work wonderfully. Thanks for the help and insights!

-Kacper

[tangent1001]

I'm having a similar issue. I have my PRO4848 from CNCRP wired up and moving. I removed the jumper from the board for 10V PWM and I am getting 4.81 volts off of the analog output. Only difference is I am seeing 4.8VDC even if the analog output wire is disconnected. Can someone help? Are my power supplies too weak? Im running 24V @ 3.75 Amp and 5V. Cant see the 5 volt supply sticker but it is almost certainly more than 500mA. I'm so close to being finished and I wanted to make some chips this weekend.

Many Thanks

[cncdrive]

Try to add a series resistor like the other poster in this thread.

[tangent1001]

I did. I didn't have a 1.2k ohm but I did have a 2.2 k ohm and used that. Still 4.8 volts. Also like I said it measures the same when I disconnect the wire entirely.

[dezsoe]

From the AXBB manual:

If the jumper is removed then the range is 0-5V and if the jumper is on then the voltage is 0-10V.

[tangent1001]

From the AXBB manual:
If the jumper is removed then the range is 0-5V and if the jumper is on then the voltage is 0-10V.

I got really excited when I saw your comment. It would be nice if I was just being a moron and read the manual wrong. Sadly you got it backwards. Below is copy pasted from the manual. Are there conflicting manuals out there? I got this from CNC drive website.

"
8.2 .Analog port.
The analog port contains 2 analog inputs and 1 analog output.
8.2.1 .Analog output.
There is one analog output on the board (marked with A01) which can output 0-10V voltage
levels or 0-5V voltage levels. The voltage range is selectable between the 0-10V or 0-5V
with the J1 jumper on the board. If the jumper is removed then the range is 0-10V and if the
jumper is on then the voltage is 0-5V. The analog output can be used for example to control
the speed of a spindle motor using a variable frequency drive with analog voltage input
interface. The jumper can be accessed with the top cover of the controller removed.
"