Stepper drive connection

[cch1955]

I am using Automation Direct Surestep driver. The unit has optoisolated inputs. I am supplying +24v from PLC pwr supply to Step+ and Direction+ terminals.
See  http://web2.automationdirect.com/static/manuals/surestepmanual/ch2.pdf page 9 for PLC connection with 24volt outputs. I use 2200ohm limiting resistors as shown. Out 1 to direction-, out5 to step-. I notice when stepping and direction line is high, both led on output are dim. When only step led on, normal brightness. I susspect 2200 ohms is not right value for resitor driving isolated inputs.  Ideas? Concerns?
thanks

[support]

There is no reason for the behavior you observed if the resistors are wired properly. Please check your wiring again to ensure that each resistor is connected between the out1 and DIR- and out5 and STEP-.  If the LED is dimly lit it seems to suggest that the load (which is the stepper driver inputs in this case) is drawing some current out of the PLC outputs and cause the LED to partly lighted up. Please check if the PLC's +24V and 0V are separate from the Stepper driver power supply to the motor coils.

[cch1955]

In more testing: The wiring is as shown. Stepper has own linear and noise is not on output lines from stepper.

With scope check while running simple reversing stepper move, when out1 is at 21v(off) the out5 led is much brighter. Wave form of out 5 shows change from peaks of 21v down to 15v when direction bit goes high (led on, pulled down to ovdc).
I am also seeing 7 volt drop of the full pulled up voltage level of 20volts of the direction bit when out5 is stepping and direction bit not set. I also see "digital noise" for want of a better term on the direction line when stepping and direction bit set. the form matches the stepping form and has peaks about 10v above 0v. The direction line of the stepper is very confused by the noise. The optoisolator on the stepper drive has 220ohm resistors on both sides internally. Any Ideas? I am thinking of adding optoisolator on outputs from TriPLC to the stepper driver to isolate further. Comments?

[support]

When the PLC output #1 or #5 is turned ON, it WILL pull its output pin down to less than 1V and the output LED must light up normally.  I really don't see how the output LED can be affected by the connection of the load. If you remove the screw terminals from the I/O pins, does the output light up normally now?

Alreadys remember that the PLC output is to "sinks" current only and you must NOT use the PLC's internal pull up to 24V as a "sourcing" output to the stepper driver. Otherwise that will be showing up as dim LED because the PLC output is actually in the OFF state and not driving the load.

[cch1955]

After much cheching and head scratching I figgured this out. I did not have the MCR (master control relay) input tired to 24vdc. After running the problem back to the outputs on the PLC, I started looking for reasons.

I think it would be good of TRi-PLC to mention in the Outputs section of your docunmentation that the MCR input must be tied to 12-24vdc to enable the outputs. If not enabled, outputs can function in a random manner depending on extrenal circuts. I was able to toggle one bit on and off, but any more would cause problems and strange wave forms.

 Hope this helps someone else.

[support]

It wasn't mentioned in your earlier post that it was a T100MD2424+ so we missed  that part of consideration. The connection to MCR was mentioned in an earlier section in the T100MD2424+ installation guide, but I think you do have a good point here. However, it will likely to only affect to first time user of this model. Most people who forgot to connect this MCR to +24V also realize that all outputs and status LEDs were not lit even when their outputs are already turned ON and would seek for a solution. All outputs except 5 and 6 are controlled by the MCR.

[cch1955]

Yes I thought the output LED not coming on was unusual when not connected to a output device. I thought this could have been due to having LEDs on PLC wired same as terminal 9no internal pull up to 24vdc) and would require output connection to 24vdc in order to light up when bit was set.  A schematic of the board would be nice in the documentation or on the website, I could have eliminated this assumption early on.