sinking/sourcing motion control signals

[M0Reng]

Hi,

attached diagrams that i collect from the umi7774 manual, my 3'rd party servo drive, and diagram from knowledgebase of "how to connect 73xx to third party drive" (http://zone.ni.com/devzone/cda/tut/p/id/3442).

The diagram from the umi7774 manual is example of Fault signal, they mention that is same for Step(CW) signal as weel.

But, the Step(CW) signal dont have Step(CW) - like the Fault has (+/-). 

Can someone point on the right diagram?

what i think is that i need to use the "Example 2" in the servo drive manual (the top right in the attached image, second example)

and it make sence because its very similar to the diagram from the knowledgebase (the bottom right in the attached image)

because the umi7774, has only Step(CW) which is sourcing (?? please tell me if i wrong here...)

and the Step signal in the Servo-Drive is 'Open-collector", that means Sinking (?? again, please tell me if i wrong here...)

the connection i need to make for the step signal is:

[Servo Drive, pin 7] Step  <to>  [Servo Drive, pin 3] +12V   (built into the servo amplifier)

[Servo Drive, pin 8] /Step <to>  [UMI-7774/Axis 1/Control connector] Step (CW)

[Servo Drive, pin 2] GND  <to>  [UMI-7774/Axis 1/Control connector] digital ground (?? or analog ground)

Your help is appreciated!

Message Edited by MotiM on 10-11-2008 07:27 AM

[ben64]

Hello MotiM,

The Fault has + and - because it is a feature of the UMI that you can use to implement external fault detection circuitry according to your needs. The examples at the left shows two ways of connecting external circuitry to the Fault+ and Fault- lines depending on the fact that the external circuitry is sinking or sourcing current.

The STEP(CW) signal is coming from a controller like the PCI-7330 and I think it is just passing through the UMI (I think there is a reference to this in the UMI user manual). I think what you have to do is to connect the step(cw) signal to the step- input of your drive (pin 😎 through a resistor (the one labelled optional on the lower right figure of your attachment). You should also connect the digital ground of the UMI to pin 2 of your third party drive.

 The step(cw) will sink current when it is in its LOW state, this current is approximateley (12V)/(1k+150+R) and R should be calculated to be high enough to turn ON the optocoupler. Now you have to calculate the value of the resistor so that when the step(cw) signal is in a HIGH state (5V) the current is NOT high enough to turn ON the optocoupler, that current is approximately (12V-5V)/(1k+150+R).

Hope this help.

Ben64

[M0Reng]

Dear Ben64,

thank you for your reply.

first, i'm happy to read that the pin connection that i write in my post is correct.

1)  i tought that the Fault+,Fault- is also signals that i need to connect to the servo drive,

     in my case, the Yaskawa servo drive has ALM+,ALM- signals for alarm (when there is some fault in the drive)  

     do i need to connect this signals to the Fault+,Fault- or to the "Enable" of the Axis?

2)  i need to read again your post regarding the calculation of the resistor R that i need to use when
     connecting the Step(CW) to the Step- of the servo drive.

     You write that i need resistor R that the current is :  I = (12V-5V)/(1k+150+R)

     But what is the current in this equation?  if i understand the diagram from the servo-drive manual,
     the current need to be 9mA.
     if you look in the umage i attached in my first post, in the upper right figure (example 2),

     its writing there (the arrow from servo-drive, pin8  to the Step(CW) ) "About 9mA"   

    So, R is :    9mA = 7V/ (1000+10+R)

     is that correct?

Thanks for helping in this.

MotiM

[ben64]

MotiM,

The current is approximately 9 mA when the step(cw) is in a low state, that is the current is 12V/(1K+150). Now if you don't add an additional resistor the current through the optocoupler will be approximately 7V/(1k+150) = 6 mA when step(cw) is in HIGH state and it may be high enough for the optocoupler to still be ON, you will have to look at your driver specs.

I suggest you connect the alarm to the fault inputs, it will disable your drive if an alarm is triggered. Again you will have to look at your drive specs to figure out if the faults inputs should source or sink your alarm signal.

ben64

[ben64]

MoyiM,

I just saw that there is also a 3.3k resistor on the UMI side in the step(cw) circuit so the optional resistor may not be required after all, you'll have to do the check.

Ben64

[M0Reng]

Dear ben64,

Thank you for your replies.

i really appreciate your help,

its very important to me to understand the wiring and to configure the motion perfectly.

the use of resistor is something that i dont think about, and i'm glad that you let me know that

i need to use this option in some cases.

i will read again all the UMI-7774 manual and the Servo Drive Manual

and i hope that now after reading your comments i'll put more attention and hopefully undersand better the wiring

between the umi abd the servo drive.

Thank you!

MotiM