Connecting NI-7358 and UMI-7774 to a sinusoidal commutation driver

[serkanb]

Hello,

I'm using NI-7358 PCI motion control card and UMI-7774 to drive a brushless servo motor driver Advanced Motion Controls S16A8 External Sine Commutation driver. (It doesn't have isolated ground.)

It's inhibit input like below:

                                ^ 5V

                                 |

                                 >

                                <  10K

                                 |

 (-INH / EN ) o----------------> to control logic

　

GND              o----------------

                                              |

                                          --------

                                            ----

                                              -

　

UMI's inhibit output is connected the drivers inhibit input directly. But there is something wrong with this connection. Control card's inhibit output always stays energized so that driver always stays disabled. (When inhibit input is connected to ground directly it's working properly)

When inhibit signal is active (axis is killed) UMI's inhibit output is 3.5V.

When inhibit is deactived (axis is started) UMI's inhibit output is 4.9V.

NI7358 inhibit is configured active low

UMI 7774 is configured active low

Driver is configured as active low.

　

I tried both open collector and totem pole configurations of NI7358. Results were the same.

Could you help me please.

Kind regards...

PS: AMC driver's manual: http://www.a-m-c.com/download/datasheet/s16a8.pdf

[Justin__D]

Hi serkanb,

This link explains how the inhibit lines can be set up with third party drives.  It refers to the 7764, but should still be similar to the 7774.

http://zone.ni.com/devzone/cda/tut/p/id/3442

[serkanb]

Hello Justin

Thanks for your reply.

This document explains the connection to a driver which has a optocoupler input but my driver doesn't have optocoupler input.

Inhibit output's voltage level is not able to reduce less then 3.5V. So that I tried below connection.

                                            --------------------------------------o  (inhibit/enable)

Inhibit   50K   npn BC337      /

o----------^~v------------------------|

                                          \

                                           |

                                           |

                                         ----- GND

                                          ---

                                           -

This time it's able to send 0V to driver but it always stays enabled now.

Could you tell me what's the problem here?

[Justin__D]

Hi serkanb,

I have a couple of things I would like you to try.

1.  What do the lights on the UMI indicate when you change the Inhibit Output Settings in MAX (enabled or disabled)?  When you change these settings make sure you initialize the drive after changes.

2.  If you have the drive inhibit line connected directly from the UMI to the drive what are the results of changing these inhibit output settings?  Are there any LEDs on the drive to indicate if it is enabled or not?

3.  What happens if you reverse the polarity in MAX and/or the UMI?

[serkanb]

Hello,

>>1.  What do the lights on the UMI indicate when you change the Inhibit Output Settings in MAX (enabled or disabled)?  When you change these settings make sure you initialize the drive after changes.
 
inhibit disabled from MAX ------>   UMI Disable led is always on

inhibit enabled from MAX ------->   UMI Disable led is on when axis is killed

                                                 UMI Disable led is off when axis is started


>>2.  If you have the drive inhibit line connected directly from the UMI to the drive what are the results of changing these inhibit output settings?  Are there any LEDs on the drive to indicate if it is enabled or not?

When the inhibit line is connected to drive directly, it's enable led is always red (it means disable) since it configured as active low. When I change its polarity to active high it always indicates green (enabled) whether the UMI's inhibit line is low or high.

When inhibit signal is active (axis is killed) UMI's inhibit output is 3.5V.  When inhibit is deactived (axis is started) UMI's inhibit output is 4.9V.

>>3.  What happens if you reverse the polarity in MAX and/or the UMI?

Drive is always green or red according to drive's inhibit polarity.

[Justin__D]

Hi serkanb,

How are you measuring the voltage from the drive inhibit?  Are you measuring the 4.9V and 3.5V when the drive is connected?

I'm still looking into if we need an additional resistor or not and how we need to tie that together.

[serkanb]

Hi Justin,

I'm measuring inhibit voltage when UMI is directly connected to diver.

(between "inhibit output" and "iso common")

I can see 0V and 5V when UMI is not connected to driver.

[Kevin_H.]

Justin is out of the office right now, I just wanted to let you know I'm looking into your issue and will be in touch with him until he's back. 

[serkanb]

Hello,

I'm still in trouble with this issue.

Could you help me please?

[Highland_Controls]

It looks like you need a pull-down resistor on the inhibit line.  I would try a 10k resistor.