Using 7i76 to control spindle reverse with Danfoss DC150 DC controller

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24 Sep 2018 04:28 #117910 by acondit
I am getting ready to wire up the spindle control circuitry of the 7i76. I did the initial setup with pncconf and so far everything has just worked. My question is do I need to do anything special to insure the spindle has reached 0 rpm before allowing the relay to activate or is that all handled in the pncconf setup.
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24 Sep 2018 13:50 #117920 by PCW
I dont think pncconf makes any provision to ensure the the spindle has stopped before
reversing.

Do you have a spindle encoder? If not you will probably have to use a timer and some logic to prevent the direction from changing while the spindle is still rotating.

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24 Sep 2018 15:24 #117926 by acondit
Yes, I have a spindle encoder. It is homemade, 100 counts plus index. I used to just use Index plus A channel. I have just changed it over to use A, B and Z. I am getting a lot more variation in speed reported than when I used to run it as just index plus counter mode, so, I need to look at the outputs with halscope and see how they look. I may need to adjust the positions of the A and B detectors.
I think that I will hook up the spindle_ena switch and the spindle speed controls first and verify that they are working, before I hook up the direction relay.
Does the schematic look correct for the wiring?

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24 Sep 2018 17:57 #117929 by Grotius
Hi Alan,

I think you can program the Danfoss for speed up and speed down in second's. Usually 3 second's for up and 3 second's for down.
You can switch direction by linuxcnc imediatly. The Danfoss will do the rest.

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24 Sep 2018 21:09 #117935 by acondit
Grotius,
I looked in the Graham Transmissions Cycletrol 150 manual (I understand that Danfoss sold the DC controller line to Graham Transmissions, Inc.). I didn't find any such programming options. However, I did find that the braking option is supposed to bring the motor to a stop within 1/4 second (when the braking switch is closed).
So, the question remains, with an encoder will linuxcnc/mesa try to change the state of the dir switch before it detects 0 rpm? Or does it look for 0 rpm before changing the state of the dir switch?
Alan

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24 Sep 2018 21:34 #117937 by PCW
Any delay in changing the spindle direction must be specifically created
using components in the hal file, LinuxCNC will simply change the spindle
direction immediately on 'S' commands or when doing spindle synchronized moves like rigid tapping.

This will likely destroy your spindle motor drive, the relay, and possibly the spindle motor. You can get away with this with a VFD, since you can program the rampup/rampdown rates but not a relay reversing circuit which requires that the drive be totally off and motor stopped before reversing.

I would recommend that you test any hal control logic and relay operation thoroughly before connecting your spindle motor. Ideally someone with a similar reversing relay setup could provide a sample hal file since its fairly involved...

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24 Sep 2018 21:40 - 24 Sep 2018 21:49 #117938 by Grotius
Hi Alan,

Ai... That sound painfull. I always use Delta, they have around 8 parameter's of ca 200 that are usefull for me.
I alway's turn of the fan sound for the noise as first.

But okey. With braking you need separate device. I don't know how it's called, i think resistor or brake device to catch up the brake heat.

If i switched from m3 to m4 today several times, the program was not looking at spindle rpm. In my postgui there was also no
comment : spindle at speed. I think you have to connect the encoder and try it. But i think the code will be looking at your current rpm, only for thread milling i think it will look at the rpm.
But if you want to be sure and there is no other option...

If you have a simple led-indicator or rpm indicator, you can use a user defined macro to make your wishes.
In macro i think M101 and above you can say what you want to do. If it is too difficult for you.
I can help you with writing some code.

In the User Defined Macro code, you have a input, this is your encoder rpm or led indicator that say's we are zero.
After that state. On or Off bit input / state. You can say start spindle M3 or M4.
It's quite easy to do.
A other option is to make a wait command. You clock your spindle down time and use it as wait function.
In hal a time function is available. If not, i have a good one. Source Rodw.
Last edit: 24 Sep 2018 21:49 by Grotius.

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30 Mar 2023 22:41 #267944 by romafede
Hi, let me introduce myself, I'm Federico from Argentina, I'm building a cnc lathe with a Danfoss variator for spindle control, and I have the same problem. I am using Mesa 7i96S. I am new to Linuxcnc, I was reading many topics in this forum and I got here. How can I solve the change of direction M3 - M4? I appreciate any information...

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