DMM DYN 4 servos + Mesa 5i25 & 7i77 XYZ+A Cnc 5x10

So I changed the wiring and tested...
Now I believe the drive is constantly disabled. I can freely spin the motor shaft by hand while servo is powered which would normally suggest that the drive is disabled. Before that the shaft was locked.
Also, even though the servo is disabled (shaft moves freely) I can still get LinuxCNC to give it signal and make it spin. Weird. I'm quite confused now and not sure what is going on with the enable/disable in the drive.

ok it looks like it is actually a disable input.
I don't know why they say active high, but the sample diagram shows sinking input.



maybe a way to invert the enable on the 7i77?

For a disable input you need an external inverter like a normally closed relay:

+24V --> Relay-COM --> Relay-NC --> Disable-Input

and perhaps drive the relay coil from one of the field I/O outputs

Another possibility is wiring the disable input with a say 1K 2W
pull-up resistor to +24V and then grounding it with the 7I77s ENA pins:

+24V --> 1K Resistor.1 --> 1K Resistor.2 --> Disable-Input & 7I77ENA+
7I77ENA- --> GND

Edit:
The reason you can't simply invert the enables is that the 7I77s non-powered
and startup state should disable the drives and this is not easy to do with OPTOs
which are 'OFF' when not powered

Form B OPTOs = normally closed are available but rather exotic and
this would require a special 7I77 version.

Thanks for the replies guys.

I will work on the machine today as I have some free time... I am going to search the parts bin for a good relay to try and invert the ENA signal.

I spent the weekend working on the mechanical side, mainly on the Z-axis... I configured the servos and will need to tune them soon.

Anyways, I have not worked on getting the enable signal to work correctly as I got side tracked working on other parts of the machine.
I have attached a wiring diagram of how I think I could get the enabled reversed for disable. I would like to see if the way I have it wired in the diagram would work correctly... I thought it would be best to ask you guys before I do it so that I do not damage the 7I77 board or drive by doing something wrong.

@PCW I understand the way you suggested to wire up the relay but would I not need to wire the coil to the ENA- so that the drive will enable when Linuxcnc sends out a enable command? I might not be understanding something correctly.

Thanks!

That looks good to me, but I would wait for a more confident answer.

What do you mean when you say the neutral is bonded to earth.

If it's a 120V input power supply, it should have L1 and L2 inputs connected to 120V and Neutral. The case should be connected to ground.
You aren't supposed to have neutral and ground connected together anywhere but at the main service entrance.

Also, I wouldn't think jp4 pin 1 should be connected to earth ground.
It is used as a reference for the monitors on pins 8, 20, and 21.

you may want to ask dmm about that.
I would leave disconnected unless you are going to wire the monitors up, in that case I would connect it directly to the field power supply negative terminal.

Hi Alan,

What I meant is that the 24v dc common is bonded to ground, this is to help reduce noise in the system. I've been told it is good practice to bond all low voltage dc psu commons to earth ground. There are no high voltage lines tied to the machine ground as that is not a good idea.

Thanks.

In regards to pin 1 ground, I had the same assumption. Pins 1,9,12 are all tied to the JP4 connector shell internally in the drive so I assumed It would be fine to use pin 1 to connect the cable shield since they have it tied to the connector shell anyways.

I saw your post on cnczone, made me think about it more

Dmm calls the enable input active high. When described as disable input on the other diagram, it shows ground to activate.

So.. instead of 24v being switched by the relay to jp4 pin3, It makes sense to me to send ground down that wire to the relay contacts.

Normally closed relay, ground passing through - Disabled.
relay active, open circuit, drive pulls the line high - Enabled.

maybe try that?