7i77 axis enable

Hello All,

I'm finally moving away from doing hardware work on my machine to playing with servo setup and integrating everything.

It seems it's best practice to have the 7i77 switch the enable on the servo drives on/off as required, presumably so things like the watchdog will be able to monitor the system and prevent servo drives from being enabled but uncontrolled. Sounds logical....

Well being not a genius at any of this, the actual implementation seems difficult and I'm going to need some guidance.

I have an Automation Direct SVA-204A drive manual here: cdn.automationdirect.com/static/manuals/sureservomanual/ch2.pdf page 28 diagram CN1-DI_3 seems like ti might be relevant?

So my expectation seeing as this is an enable, aka output from the 7i77's perspective is that it's going to feed it's field power (24v) out of TB5 pin1, and that should return to common on TB5 pin 0. That is to say if the halmeter for hm2_5i25.0.7i77.0.1.analogena says True I'd expect 24v to be present across TB5 pins 1 and 2.

I can toggle hm2_5i25.0.7i77.0.1.analogena using the machine power button but 24v is never present when measured with my multimeter. So either things are borked or I don't understand. Help me out here please.

The 7I77 enable outputs are floating switches, they are totally isolated from field power and logic power
Each enable output switch has a pair of pins ENAN+ and ENAN- (N being the channel number)

If you wire your drive so it has active high (sinking) enable inputs as shown in DI_3
you would connect the ENAN+ terminal to +24V and the ENAN- wire to the drives enable
input

The servo enables on a 7i77 behave like a simple switch (except that you need to have the polarity right or you'll wreck them)
So unless you are supplying voltage to one side of the enable, there will be no voltage present at TB5-1 and 2

So on your drive you would connect the com0 to the 7i77 TB5-2, and DI1 to TB5-1. (ala pg 2-27 of your linked to manual. Using the drives default setting of sourcing inputs.)

Just poking around with this more.

If I measure across ENA1+ and ENA1- I get ~19kohms resistance when hm2_...analogena true, open circuit (effectively) when false.

The drive is currently configured (or not, regardless, it is doing it) 24v on it's Digital Input 1 (configured as enable pin).

So If I just wire that 24v(from DI1) to ENA1+ and ENA1- back to COM- on the drive. I seem to get a circuit that works. Any negative to doing this?

Edit, reply doesn't seem to quote or reference which post you're replying to, or I'm blind. For clarify this is a reply to Todd, and the word above could probably be reversed.

Thanks, I posted below pretty much the same findings after PCW gave me more insight. But the polarity of what you're saying seems to be the reversed?

TB5-2 is ENAN+ so I'd expect it to wire to DI1?

It should work, but if you want to use any of the 7i77s other digital outputs to send a digital signal to the drive you may want to switch them to sinking inputs like Peter suggested.

dberndt wrote: Edit, reply doesn't seem to quote or reference which post you're replying to, or I'm blind. For clarify this is a reply to Todd, and the word above could probably be reversed.

Thanks, I posted below pretty much the same findings after PCW gave me more insight. But the polarity of what you're saying seems to be the reversed?

TB5-2 is ENAN+ so I'd expect it to wire to DI1?

For quoting you have to choose "quote" from the drop down menu when you press "action", then you can edit what you want quoted or delete what should not be included between the [quote=.....signs.
You might be correct that you need to reverse the enable output pins from the mesa board, you just explained it as you did and PCW was right to conclude you have active high enable on the drives.
Usually (almost always) they are active low.

Thanks all. I think I'm sorted for now. I'm not sure I like how the drive is wired up and powering it's limit switches and such, but it's working fine and I don't think I'm going to mess with it now, unless a solid reason to pops up. Functionally it's doing everything I need it to at this point. I guess the negative to the current setup is the drive's inputs are setup as sourcing and the 7i77s outputs are setup as sourcing, not ideal if I have to connect anything else which at this point I don't believe I do.

Next topic. Servo ready. So I can look at some diagrams and scratch my head for a bit and plumb the servo ready from the drive into say TB8-1. I'm not sure I'll ever have an actual use for this, as I'd expect the servo to be ready before the software is issuing commands anyways. But is there a best practice here, where in software would I plumb servo ready to? What would it accomplish/restrict?

I also have a servo fault input into the servo drive I could hook up, it should cause the servo to come to a halt when flipped. Given that the 7i77 is already driving the enable pin, is there any reason to hook this up? If so what bit of software would I hook it up to?

Also because I'm doing torque control, I've up my servo thread rate to be 250,000 instead of 1,000,000 based on what I've read on PID tuning of torque mode setups. It seems to have helped some, but PID tuning is black magic to me still at this point so maybe it really hasn't. As a byproduct however every once in a while I'll get an error about realtime processing from the hm2....sserial.0.port or some such thing and further to that the message say it won't be repeated but will be counted in hm2....sserial.0.port.errorcount (or some such thing), and when I look for that device with hal monitor, it's not there, something with a similar name is there, but when I monitor that it has 0 errors. Sorry about the names, I realize this is pretty much the worst bug report ever, but the machine with the details is in the garage and off. I'll grab exact naming in future, hopefully just the description is enough for someone to point me in the right direction on this. Should I care?

Servo tuning looks like black magic till you actually start tuning, then step by step everything starts to become clear and after a while it takes about 20 minutes to have a fine tuned servo.
As for serial errors, set a higher servo thread, till you get no errors and then start tuning.
Regards,
Tom

Hello everyone!

I'm on the process of making wiring drawings between my analog drives to a Mesa 7i77. I'm a bit confused about the connections.

I haven't received the actual card yet due to bureaucratic delays, but time presses and I may have to present my project (diploma thesis) without a connected and working set-up. However, I was requested to include all basic wiring drawings in my writing, at least the way I believe they will have to be done... (drive-to-mesa, switches-to-mesa, encoders-to-mesa etc.).

Following the drive and mesa 7i77 manuals I think my connections will look like in the picture bellow. I m also uploading a second picture that explains the 4 drive input pins I'm using. Can anyone at least verify that I m getting the concept right? Using just a power supply, I connected drive pin 27 to the +24V pole and pin 25 to GND and the drive was enabled, I also made the motor rotate by supplying a small voltage to pins 30 and 32 just to test its function.

Thanks in advance!