How to connect the 73xx inhibit and command signal outputs to third party drives.
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The 73xx series family of controllers is designed to interface with any stepper or servo motor drive that takes either a step and direction, CW/CCW or +/-10 volt torque command signal. Many drives however, use optocouplers in their step, direction and enable inputs that may require connecting the signals from the 73xx in ways that might not be obvious to first time users. The following document addresses the most common scenarios for these signals:
Section 1: For the 733x and 734x Series Controllers with a UMI-7764
The digital outputs for inhibit, step and direction signals on the 734x are current sinking or open collector outputs. This type of output can sink a significant amount of current (~64 mA) but can only source a small amount (1.5 mA max). On the other hand, a very common way for third party drives to provide isolation between the controller and drive on their digital inputs is to implement it through an optocoupler circuit. In order to operate, an optocoupler usually requires that the signal that will activate it provide current in the order of 7.15 mA. In a scenario where the two previous circumstances are present the effect may sometimes be that the 734x controller sends out a step and direction or inhibit signal, and the third party drive will not see any transition at all, thus producing no response to the command.
In order to connect the signals properly, it is recommended to follow these steps:
Step 1.- Configure the polarity of your controller’s inhibit output signal to active low for proper operation of the UMI. This configuration can be performed from the Measurement and Automation Explorer, under the Axis Settings Section as Figure 1-1 shows.
The Motion Controller should be initialized any time changes are made to these settings by clicking on the
button at the top of the Measurement and Automation Explorer screen. Refer to the NI-Motion Controller Installation and Configuration Document for more information.
Step 2.- Connect the 733x or 734x controller to the UMI-7764 using a 68 pin VHDCI connector to 68 D-type connector cable (p.n. 186381-02) and connect an external 5v 1A power supply to the UMI power inputs.
Step 3.- Identify if the third party equipment's inputs (step, direction, and enable or shutdown, and digital inputs) implement optical isolation by means of an optocoupler or any similar circuit requiring the command signal to source current. This information is usually provided by the manufacturer in the product manual, usually through a diagram. These input are usually differential inputs and the third party drives will usually provide Step+, Step-, Direction+, Direction-, Enable+ and Enable - terminals.
Step 4a.-For each axis on the 73xx or the UMI, connect the Step, Direction, and Inhibit Out signals to the negative terminal of their respective input on the third party drive (for example Inhibit Out Enable -/Shutdown -). If the optocoupler input does not include its own current-limiting resistor, you must provide an external resistor in series with the 734x output. (Note: To prevent damage to the 734x, or other motion hardware, use a resistor that limits the current to a value below the maximum specifications of the controller and other hardware). Then, connect the positive terminal of the third party drive's input to a power supply capable of sourcing the voltage and current necessary for the signal to be driven as specified by the manufacturer. An easy and very common way to do this for people using the UMI-7764 to interface third party drives, is to use the same power supply connected to the UMI as the voltage source for the other signals. This source is available at the +5v screw terminal of each axis in the UMI. Figure 1-2 shows this process for the Step signal.
Figure 1-2a
Step 4b.-As an alternative to step 4a, you can also connect the Step, Direction and Inhibit Out signals from the UMI to the external +5v power supply by using a 300 ohm pull up resistor as well as to their respective terminal on the third party drive. The same way as described in step 4a, you can use the external power supply used to power the UMI as the source for these signals. Then connect the negative terminal on the third party drive’s signal to a ground terminal on the UMI. Figure 1-2b describes this process for the Step signal.
Figure 1-2b
Step 5.- Connect the Fault signal from the third party drive to the Inhibit input signal on the UMI. Make sure that the Inhibit input and inhibit output polarity switches (S1 and S2) on the UMI are set to match the polarity of the Fault and Enable signals on the third party drive (active high or active low). In order to do this, refer to figure1-3. This figure shows the polarity configuration switches for the Inhibit In (S2) and Inhibit Out (S1) Signals on the UMI-7764.
IMPORTANT NOTE: The inhibit input, inhibit output and inhibit all signals on the UMI appear with a bar over their name. This only means that the signals are configured for active low operation (signal pulled low to be considered active) by default. The UMI internally pulls up these signals to +5v through a 3.3k pull-up resistor when nothing is connected to them.
Configuring the inhibit inputs for active low operation sets the UMI into a mode where if there are no connections on the inhibit input terminals of an axis, the signal will be considered inactive by the UMI and will not cause the inhibit output to go active. In order to be active, the inhibit input signal needs to be pulled low by the third party drive’s fault signal.
Configuring the inhibit inputs for active high operation sets the UMI into a mode where if there are no connections to the inhibit input terminals of an axis, these signals will be considered active by the UMI because of the internal pull-up resistor and will cause the inhibit output signal to go active. In order to be inactive, the inhibit input signal needs to be pulled low by the third party drive’s fault signal.
The inhibit all input is an active low input by default and its polarity can not be changed. Pulling this input low sets all of the inhibit outputs on the UMI to their active state and takes precedence over the states of the individual axis inhibits.
The inhibit outputs on the UMI will be toggled to their active state either individually or as a group when any of the following occur:
| Third Party Drive or 733x/734x Action | UMI-7764 Effect | UMI-7764 Action | Third Party Drive Effect |
| Axis 1 Drive Fault Signal Generated (Pulled high or low depending on drive configuration) | Inhibit In Axis 1 set to Active (Pulled high or low depending on switch S2) | Inhibit Out Axis 1 set to Active (Pulled high or low depending on switch S1) | Axis 1 Drive Disabled. |
| Axis 2 Drive Fault Signal Generated (Pulled high or low depending on drive configuration) | Inhibit In Axis 2 set to Active (Pulled high or low depending on switch S2) | Inhibit Out Axis 2 set to Active (Pulled high or low depending on switch S1) | Axis 2 Drive Disabled. |
| Axis 3 Drive Fault Signal Generated (Pulled high or low depending on drive configuration) | Inhibit In Axis 3 set to Active (Pulled high or low depending on switch S2) | Inhibit Out Axis 3 set to Active (Pulled high or low depending on switch S1) | Axis 3 Drive Disabled. |
| Axis 4 Drive Fault Signal Generated (Pulled high or low depending on drive configuration) | Inhibit In Axis 4 set to Active (Pulled high or low depending on switch S2) | Inhibit Out Axis 4 set to Active (Pulled high or low depending on switch S1) | Axis 4 Drive Disabled. |
| Kill Command Executed or Following Error occurred on 73xx Axis 1 (Pulled low) |  |
Inhibit Out Axis 1 set to Active (Pulled high or low depending on switch S1) | Axis 1 Drive Disabled. |
| Kill Command Executed or Following Error occurred on 73xx Axis 2 (Pulled low) | |
Inhibit Out Axis 2 set to Active (Pulled high or low depending on switch S1) | Axis 2 Drive Disabled. |
| Kill Command Executed or Following Error occurred on 73xx Axis 3 (Pulled low) | |
Inhibit Out Axis 3 set to Active (Pulled high or low depending on switch S1) | Axis 3 Drive Disabled. |
| Kill Command Executed or Following Error occurred on 73xx Axis 4 (Pulled low) | |
Inhibit Out Axis 4 set to Active (Pulled high or low depending on switch S1) | Axis 4 Drive Disabled. |
| Drive E-Stop or External E-Stop Activated (Optional, has to be pulled low). | Inhibit All Set to Active (Pulled low) | Inhibit Out Axis 1 though 4 set to Active (Pulled high or low depending on switch S1) | Axis 1 through 4 drives Disabled |
| 73xx Controller Disconnected | |
Inhibit Out Axis 1 though 4 set to Active (Pulled high or low depending on switch S1) | Axis 1 through 4 drives Disabled |
Once all the command and inhibit connections are made, the connections from any 73xx controller to a servo or stepper drive that requires step and direction or CW/CCW command signals should look as shown in Figure 1-4a (for step 4a) or 1-4b (for step 4b). The connections from a 734x or 735x controller to a servo drive requiring a +/-10V command signal are shown in Figure 1-5a and 1-5b.
Figure 1-4a
Figure 1-4b
Figure 1-5a
Figure 1-5b
The connections described above will take advantage of the fact that the external supply sources enough current to flow through the optocoupler when the 73xx signal is at a logic low, thus turning it on. When the signal from the controller is floating, an internal 3.3kohm resistor pulls it up to 5v. This makes the difference in potential 0 across the optocoupler and turns it off.
For more details on all of these connections, refer to the Related Links Section.
Section 2: For the 735x Series Controllers with a UMI 7764
The digital outputs for inhibit, step and direction signals on the 735x can be configured either as open collector or totem pole configurations. This configuration can be performed from the Measurement and Automation Explorer, under the Axis Configuration and Axis Settings Sections as shown in Figures 2-1 and 2-2. The Motion Controller should be initialized any time changes are made to these settings by clicking on the
button at the top of the Measurement and Automation Explorer screen. Refer to the NI-Motion Controller Installation and Configuration Document for more information.
When the step, direction and inhibit lines are configured for open collector configuration, or if the signals on the power drive require more than 16 mA of current from the controller signal in order to work, follow the connection steps described in Section 1.
When the step, direction and inhibit lines are configured in totem pole mode, the outputs have the capability of sourcing up to 16mA current, which should be drive most optocoupled inputs on third party drives.
To connect signals in the totem pole mode, follow these steps:
IMPORTANT NOTE: Since the 735x series controllers can have up to 8 axis of motion, more than one UMI may be needed for connecting all of the drives. If the Motion I/O connector for axis 5-8 is used with the UMI, the connections and behaviors that follow are the same than those described for axis 1 through 4 below.
Step 1.- Configure the polarity of your controller’s inhibit output signal to active low for proper operation of the UMI. This configuration can be performed from the Measurement and Automation Explorer, under the Axis Settings Section as Figure 2-3 shows.
The Motion Controller should be initialized any time changes are made to these settings by clicking on the
button at the top of the Measurement and Automation Explorer screen. Refer to the NI-Motion Controller Installation and Configuration Document for more information.
Step 2.- Connect each Motion I/O on the 735x controller to the UMI-7764 using a 68 pin VHDCI connector to 68 D-type connector cable (p.n. 186381-02) and connect an external 5v 1A power supply to the UMI power inputs.
Step 3.- Connect the Step, Direction, and Inhibit Out signal from the 735x to the positive terminal of their respective input on the third party drive (for example, Inhibit Out Enable +/Shutdown +). Then, connect the negative terminal on the signal input of the third party drive to a ground terminal on the UMI. If the optocoupler input does not include its own current-limiting resistor, you must provide an external resistor in series with the 7350 output. To prevent damage to the7350 or other motion hardware, use a resistor that limits the current to a value below the maximum specifications of the controller and other hardware. Figure 2-4 describes this process for the Step signal.
Figure 2-4
Step 4.- Connect the Fault signal from the third party drive to the Inhibit input signal on the UMI. Make sure that the Inhibit input and inhibit output polarity switches (S1 and S2) on the UMI are set to match the polarity of the Fault and Enable signals on the third party drive. Refer to figure2-5 to locate these switches on the UMI-7764.
IMPORTANT NOTE: The inhibit input, inhibit output and inhibit all signals on the UMI appear with a bar over their name. This only means that the signals are configured for active low operation (signal pulled low to be considered active) by default. The UMI internally pulls up these signals to +5v through a 3.3k pull-up resistor when nothing is connected to them.
Configuring the inhibit inputs for active low operation sets the UMI into a mode where if there are no connections on the inhibit input terminals of an axis, the signal will be considered inactive by the UMI and will not cause the inhibit output to go active. In order to be active, the inhibit input signal needs to be pulled low by the third party drive’s fault signal.
Configuring the inhibit inputs for active high operation sets the UMI into a mode where if there are no connections to the inhibit input terminals of an axis, these signals will be considered active by the UMI because of the internal pull-up resistor and will cause the inhibit output signal to go active. In order to be inactive, the inhibit input signal needs to be pulled low by the third party drive’s fault signal.
The inhibit all input is an active low input by default and its polarity can not be changed. Pulling this input low sets all of the inhibit outputs on the UMI to their active state and takes precedence over the states of the individual axis inhibits.
The inhibit outputs on the UMI will be toggled to their active state either individually or as a group when any of the following occur :
| Third Party Drive or 735x Action | UMI-7764 Effect | UMI-7764 Action | Third Party Drive Effect |
| Axis 1 Drive Fault Signal Generated (Pulled high or low depending on drive configuration) | Inhibit In Axis 1 set to Active (Pulled high or low depending on switch S2) | Inhibit Out Axis 1 set to Active (Pulled high or low depending on switch S1) | Axis 1 Drive Disabled. |
| Axis 2 Drive Fault Signal Generated (Pulled high or low depending on drive configuration) | Inhibit In Axis 2 set to Active (Pulled high or low depending on switch S2) | Inhibit Out Axis 2 set to Active (Pulled high or low depending on switch S1) | Axis 2 Drive Disabled. |
| Axis 3 Drive Fault Signal Generated (Pulled high or low depending on drive configuration) | Inhibit In Axis 3 set to Active (Pulled high or low depending on switch S2) | Inhibit Out Axis 3 set to Active (Pulled high or low depending on switch S1) | Axis 3 Drive Disabled. |
| Axis 4 Drive Fault Signal Generated (Pulled high or low depending on drive configuration) | Inhibit In Axis 4 set to Active (Pulled high or low depending on switch S2) | Inhibit Out Axis 4 set to Active (Pulled high or low depending on switch S1) | Axis 4 Drive Disabled. |
| Kill Command Executed or Following Error occurred on 73xx Axis 1 (Pulled low) | |
Inhibit Out Axis 1 set to Active (Pulled high or low depending on switch S1) | Axis 1 Drive Disabled. |
| Kill Command Executed or Following Error occurred on 73xx Axis 2 (Pulled low) | |
Inhibit Out Axis 2 set to Active (Pulled high or low depending on switch S1) | Axis 2 Drive Disabled. |
| Kill Command Executed or Following Error occurred on 73xx Axis 3 (Pulled low) | |
Inhibit Out Axis 3 set to Active (Pulled high or low depending on switch S1) | Axis 3 Drive Disabled. |
| Kill Command Executed or Following Error occurred on 73xx Axis 4 (Pulled low) | |
Inhibit Out Axis 4 set to Active (Pulled high or low depending on switch S1) | Axis 4 Drive Disabled. |
| Drive E-Stop or External E-Stop Activated (Optional, has to be pulled low). | Inhibit All Set to Active (Pulled low) | Inhibit Out Axis 1 though 4 set to Active (Pulled high or low depending on switch S1) | Axis 1 through 4 drives Disabled |
| 73xx Controller Disconnected | |
Inhibit Out Axis 1 though 4 set to Active (Pulled high or low depending on switch S1) | Axis 1 through 4 drives Disabled |
Once all the command and inhibit connections are made, the connections from a 735x to a servo or stepper drive that requires step and direction or CW/CCW command signals should look as shown in Figure 2-5. The connections from a 735x to a servo drive requiring a +/-10V command signal are shown in Figure 2-6.
Figure 2-5
Figure 2-6
For more details on all of these connections, refer to the Related Links Section.
Related Links:
7344/34 Hardware User Manual
7342 Hardware User Manual
7350 Hardware User Manual
UMI-7764 User Manual
NI-Motion User Manual
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