Servo Pulse and Direction - LS Electric L7C & L7P Servo System at AutomationDirect

?The LS Electric L7C Servo System can be  controlled by three types of pulsed inputs:   pulse and direction where one signal provides  the movement pulses and the other provides the   direction of rotation; clockwise/counter  clockwise where one signal provides pulses   for one direction and the second signal  provides pulses for the other direction;   and quadrature phasing where if one pulse  train leads the other, the motor rotates   in one direction and when the phasing flips,  the motor runs in the other direction.   In this video, we’ll do the  pulse and direction example   because it’s the most common and the other two  use basically the same configuration and setup.   First, we have to connect our controller  – usually a PLC – to the servo.   Getting the wiring right is really important  so we’re going to spend a few minutes on that.   If you are already familiar with wiring, you can  skip ahead until the red wiring banner in the   upper right corner goes away. You have two options.   You can connect via differential pair line  drivers. That’s easy, just connect plus to   plus and minus to minus for both signals.  It’s the most robust and it allows the drive to   accept signaling up to 1 megabit per second. You can also connect via open collector like this.   The current flows from the 24-volt supply  through an internal current limiting resistor,   through the led in the optoisolator, to the  open collector transistor which switches the   signal to ground to turn on the optoisolator. I got these wiring diagrams from the L7C Servo   Quick Start Guide which I can’t recommend enough  – it has everything you need to know to get up and   running quickly. You can download that from  the drive’s page at automationdirect.com.   This is for a 24-volt system like a PLC. What if  you have a 12-volt or a 5-volt system? No problem.   Instead of connecting this guy, the L7C Servo  Drive gives you direct access to the optoisolator   LEDs. Just connect these through an appropriate  current limiting resistor and you are good to   go. These are the recommended resistor values.  You could even wire it this way for 24 volts   by supplying your own 1.5K ohm resistors  instead of using the built-in ones here.   We’ll be using the internal resistors via the PCOM  signal in this demo because it is so much easier.   This open collector signaling can handle up to  200 thousand pulses per second. And you’ll want   to keep the wires to less than around 10 meters.  The differential signaling can typically be   used out to around 30 meters. That depends on  your signaling rate and system configuration,   of course, so consider these rough estimates. In all cases, please, do yourself a favor   and use a good low capacitance  data cable with a shield. And,   connect that shield to the drive's frame ground  only. Don’t connect the other end of the shield.   Why? Because when you connect the other end of  the shield you create a close circuit that current   can flow though. So when outside electromagnetic  interference hits the shield, it creates currents   in the shield. That creates fields inside the  shield that can couple currents into your signal   wires which can actually cause more problems than  no shield at all! By only connecting the shield at   one end, you break that path so current can’t flow  and create disruptive fields inside the shield.   And that applies to both kinds of wiring. There is one thing you need to be aware of   with the L7C Servo System. If you use the optional  terminal block to access the drive’s I/O’s, while   the 50-pin cable is shielded, it doesn’t give you  a chassis ground connection at the terminal block which means the shielding stops here. So how do  you shield these wires if you can’t extend the   drive’s chassis ground from the terminal block? Easy. Just connect their shield to the PLC's   chassis ground. But, make sure you  don’t connect the shields here,   otherwise, you’ll get that current path again  and all of the issues that come along with it.   Of course, AutomationDirect has really good  cost-effective cables for these kinds of   applications. Here are some suggestions to  get you pointed in the right direction.   I have our demo set up as an open-collector from  a BRX PLC and I would recommend using this part   number or something like it for the cable. I am using the handy terminal block you can get for the   L7C servo, so my shields are connected like this. If you are using differential pair, I would   recommend a cable like one of these for a  good low capacitance high data rate cable.   The only real difference is the color-coding  of the wires and this one which is foam   polypropylene - is has the lowest capacitance  so it won’t round off your signals as much at   higher data rates. At the lower bit rates we’re  using that isn’t really a factor. And remember,   at AutomationDirect you can order only  the length you need and there are no cut   charges or shipping on orders over $49. I hate spending so much time on wiring,   but if you don’t get that right you’re setting  yourself up for all kinds of frustration.   Ok, that was the hard part. Once  you have the wiring complete,   setting up for pulsed signaling is easy. I’m going to go to the setup menu   and return to factory setting so you  know exactly where I am starting from.   Of course, we always power cycle the drive  or just reset the drive’s controller after a   factory reset to make sure everything is totally  cleared out and we get a good clean start.   Go to the setup wizard. I’m only going to cover  the stuff significant to pulsed input here   and breeze through the rest. If you need  to see how to set up the other stuff,   then check out the quick start videos  where we walk you through all of that.   Let’s go online and read the current drive  configuration which should be the default since we   just did a factory reset. Encoder setup is fine.  We want pulsed input which is the default. Here   are the three choices – A/B quadrature, clockwise  counter-clockwise and pulse and direction. You   can also specify inverted versions of those if  your signaling happens to be upside down. We’ll   be using pulse and direction for this demo. You can also filter the incoming pulses. We’re   using open collector in this example which has  a max pulse rate of 200,000 pulses per second,   so this cutoff is way above that. We could  probably even lower that some if we wanted to.   We don’t really need to worry about filtering  noise for this demo, so I’ll leave that alone.   Rotation direction doesn’t matter for this demo.  I’m going to change the electronic gearing so   instead of using the native pulses per revolution,  the system will use 100,000 pulses per revolution,   just to keep things simple in our demo. This stuff is all fine for our example.   Digital inputs. All we really need  for this demo is the servo enable,   and the inhibit signal which I’ll put on Input  3 because I have something wired to Input 2   for other videos. I’ll disable the rest. We’re not going to use any outputs in this   demo so I’ll disable those. We’re not using homing.   Write all of that to the drive. Wait for  the confirmation and we’re good to go.   And again, we always reset the controller –  or do a power cycle - after making changes   to ensure everything gets cleared  out and we get a good clean start.   I’m using a BRX PLC to generate the pulses simply  because that’s what I had laying around and it’s   super easy to set up for motion. Here’s the wiring  diagram I am using for our open collector example.   If I wanted to do differential pair, I would need  to add this BRX I/O module. There’re other videos   showing you how to set up the BRX PLC for motion,  so we’re not going to spend time on that here.   I have the BRX PLC set up so that on the first scan  the axis gets configured, and whenever C0 is   toggled, the BRX PLC will send 100,000 pulses to  the servo which since we set the servo to 100,000   pulses per revolution should give us one complete  revolution. I love that I can do all of my motion   with just one instruction in the BRX PLC. The PLC is online and running, so in the   Servo’s DriveCM software, I’ll go to the  digital inputs and enable the servo.   Back in the DoMore Designer software, I’ll  toggle C0, and yep, the servo motor rotated   one full rotation. Exactly what we expected. If I enable the inhibit, and toggle C0 to send   the pulses, nothing. The inhibit signal prevents  the pulses from getting to the drive’s controller.   But, it doesn’t release the holding torque  from the motor – only the servo output enable   can do that. Release the inhibit, toggle  C0, and we are back up and running.   That’s all there is to it. The Drive CM software  makes configuring the L7C Servo for pulsed input   super easy. Just make sure you  pay attention to the wiring   and you’ll be up and running in no time. What if you need encoder feedback at your PLC   for position verification or  to trigger some other action?   Easy. Back in the setup wizard, on this page, you  set the number of pulses the drive will output per   revolution – you’ll usually set that to the same  thing as your electronic gearing - and you can   set up the format of the encoder output signals.  You then connect the dedicated encoder output pins   on the drive back to your controller. Program  your controller accordingly and you’re done!   That should be enough to get you  started with using pulsed inputs   on the LS Electric Servo Systems. Click here to learn more about the   LS Electric Servos. Click here to learn about  AutomationDirect’s free award-winning support   options. And click here to subscribe to this  YouTube channel and click that little bell   icon so you will be notified when we  publish more videos like this one.