Advanced Search

Another thing I noticed is that when looking at the circuit diagram the +24 volt input is not connected to anything, the same on the PCB this pin is not connected either, only -24 volts is connected to the current limiting resistors at the inputs of the optocouplers of the inputs.

The CAT3000 definitely doesn't work with Linuxcnc with the latest version. If I connect it to TwinCAT, there's no problem. I can go to OP state, the inputs and outputs work, the encoder too, but with LNC, nothing works; it doesn't go to OP state. Something very strange is that many Enable pins are generated, 8 in total for each Enable, as seen in the photo. I don't know if the problem could be the ethercat-conf file.

You could run a unipolar analog drive (0 to +10V) with direction control by using the
abs component on the output of the position PID loop in LinuxCNC. The abs component
has a sign output that could be used for direction control.
 

Dear members,

my milling machine has four 12 VDC Tacho-motors for the axes  The direction change is done by a switch and by relais. It is not a CNC control, it is a distance-control managed by a Heidenhain TNC113 for each axis seperately only in sequence - not in parallel. So it is easy to change the motor running direction by a switch or by a relais. The motor amplifier accepts as external signals only 0 to 10 VDC and an "Enable".
 

The question is how to handle the MESA output which ranges from -10VDC to  + 10 VDC to have the motors run-direction changed.

The only other option of aan amplifier which I found is from RS Components, which has a direction switch. But it works also only with a signal voltage of 0 to 10 VDC.
 
I there any helpfull idea how to realise the controls without relais?

Thanks a lot and best regards

Hartwig

 

Sorry, I have pasted print-screens, are not shown but are creating a lot of senseless Text.

I will repeat my post in a proper format.

Best regards

Hartwig

The problem is, if the drives are enabled and powered when the step/dir signals decay 
there is a point where even 10mv of switching noise (at the drive PWM frequency so maybe 20 KHz)
will be interpreted at step signals, especially if there in no hysteresis past the optocoupler in the drive.

For actual servo drives, I would use a 7I96S isolated output to enable the drives.

Looks like the swap kills the problem completely. Although I still prefer the relay solution.

There isn't a lot of noise on the step line, +/-50mv which shouldn't be enough to cause steps I would think?

satiowadahc wrote:

Quick confirming I leave the step + disconnected?

Yes.
-
Personally i would find the source of interference and remove or fix it, start by checking grounding and signal cable shielding.

Quick confirming I leave the step + disconnected?

Even with the noise - it over accelerated the motors passed the over torque limit which stopped them.

Adding the relay was my first step and that works pretty well. Has 8ms of reaction time which motors on a test bench show about 30degrees.

I'll try the pin inversion right now in addition.

Thank you!

I suspect that the drives see marginal output levels + drive generated noise as a series of steps.
Marginal output levels are possible with a slow ramp of the power as it drops to 0

Estop should really drop primary power to the drives but not control power. 

Suggestions:

1. Use one 7I96S isolated output to enable all drives. This will go false (off)  on power loss or watchdog bite
so the step/dir states during power-up/power down will not matter.

2. Use the STEP- and DIR- pins (and invert them in hal)

#1 is a more reliable choice

Hi, Troubleshooting a series of mishaps in design.Background.

Problem 1. Operators using power switch as an e-stop.
Problem 2, Killing control power on this machine doesn't kill power to the drives and motors - Welp adding another relay now.
Problem 3, Mesa step and direction signals go high on power loss until the caps die out. (Which is what I'm actually curious about in this thread)
Problem 4, Teknic eclipse drives read a high step as a series of pulses. (Following up with them on that).

7i96s is wired with Step connecting to Step input on eclipse drive and Dir connected to Direction on eclipse. One motor has a RC delay timer on the enable, as the brake takes a moment to engage or the Z-Axis falls under its own weight. While waiting for the brake it jerks very violently.

Is there a way to make the Mesa card step and direction go low on power loss? 

Scope - Green is step, purple is enable delay, 100ms/div
 

I am going to see what we can squeeze out of the Nano9K for now, but its nice to know we can use something with a lot of direct IO in the future if needed. That 20K Lite board is a pretty solid option.

Cheers.
Russell.

1. I would use a good commercial power supply. The 7I97T draws only about 400 mA but the 5V also powers
the encoders which will add to this, I would suggest 2A.

2. The 7I97T has local +- analog power supplies so only requires +5V

3. ENA+ to KL8, ENA- to KL5,  AOUT to KL7,  GND to KL2


The real problem  I see here is the these are unidirectional drives, and reversing with a relay will not work
when trying to hold position at low speeds (the relay is too slow)

What machine is this for and are these the original drives?

Because these drives would make sense for constant speed use but not position control.

The milling machine has been working great so I haven't done any changes to it for several months. However one thing that has been on my mind for a while is that I have no idea how hot it gets inside of the control cabinet during long milling sessions.

A quick search for temperature display brought up this unit on AliExpress for a very low price:

www.aliexpress.com/item/1005005993184685.html

I bought one and it arrived a couple weeks later, here is how it looks installed in the cabinet.

 

 

 

 

It's gonna be interesting to see how hot it actually gets inside the cabinet.