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.