I/O connections


The Nix Servo Drive provides various inputs and output terminals for parameter observation and drive control options. These inputs can also be used for some feedback purposes (see Feedback connections).

The input and output pins are summarized below:

Motor brake input

Digital outputs (GPO1 and GPO2) can also be used as a motor brake output.

Alternative assembly options

Under a custom purchase order, Nix Servo Drive can be provided with some alternative I/O:

  • 2 x ±10 V differential 12 bits analog inputs
  • 2 x 0 ~  5 V single ended 12 bits analog input
  • Torque Off input

Wiring recommendations

Wiring recommendations for I/O signals are the same than for feedback signals. Detailed information about good wiring practices can be found in Feedback wiring recommendations.

General purpose single ended digital inputs interface (GPI1, GPI2)

The general purpose non-isolated digital inputs are ready for 5 V levels, but are 24 V tolerant. Next table show their electrical specifications.

Specification

Value

Number of inputs

2 (GPI1, GPI2)

Type of input

Single ended
ESD protected
Low-pass filtered

ESD capability

IEC 61000-4-2 (ESD) ± 15 kV (air), ± 8 kV (contact)

Input current

0.17 mA @ 5 V; 1 mA @ 15 V

High level input voltage

4 V < Vin < 24 V

Low level input voltage

0 < Vin < 1 V

Input impedance30 kΩ

1st order filter cutting frequency (-3 dB)

100 kHz

Sampling rate1 ksps

Max delay

2 μs

General purpose inputs electrical equivalent circuit is the following:

NixLowSpeedGPIDiagram

Next figure shows an example of how to connect a switch to the GPI, using +5V_OUT (pin 16) pin as a supply source.  

NixLSGPI

Non-isolated I/O

Nix Inputs and outputs are not isolated. The ground of the Nix Servo Drive and the ground of the devices connected to I/Os must be the same. Otherwise inputs or outputs may be damaged.

Nix Servo Drive general purpose inputs can be used for connecting three-wire sensors. Next figures illustrate the connection of PNP and NPN three-wire sensors in input GPI2 (same wiring can be used for GPI1). Pin 16 (+5V_OUT) can be used as a supply source.

NixLSGPIsensor

NixLSGPIpullUp

GPI Pull-up resistors

Pull-up resistors ensure the desired logic state when the sensor (transistor or relay) is in off-state.

NPN pull-up resistor value must be chosen in order to ensure  ≥ 4 V at the GPI pin considering the 30 kΩ input resistance. For a  sensor supply of 5 V, 1 kΩ is recommended. For a sensor supply of 24 V,  10 kΩ is recommended. 

High-speed digital inputs interface (HS_GPI1, HS_GPI2)

The high-speed (HS) non-isolated digital inputs are ready for 5 V levels but are 24 V tolerant. Next table show their electrical specifications.

Defect logic value

Nix high-speed inputs are default low-level (OFF). When no signal or load is connected, the board will detect a logic low.

Specification

Value

Number of inputs

2 (HS_GPI1, HS_GPI2)

Type of input

ESD protected
Differential and single ended

ESD capability

IEC 61000-4-2 (ESD) ± 15 kV (air), ± 8 kV (contact)

Input current

2 mA @ 5 V; 5 mA @ 15V

High level input voltage

(HS_GPI+ - HS_GPI-) > 150 mV

Low level input voltage

(HS_GPI+ - HS_GPI-) < -600 mV

Maximum working input voltage±24 V
Maximum recommended frequency10 MHz
Sampling rate20 Msps

Total rising delay

65 ns

Total falling delay

55 ns

Maximum common mode voltage (VCM)-7 V ≤ VCM ≤ 12 V

Next figure shows the circuit model for high-speed digital input. Input is composed of a 3-resistor differential divider, with 10 kΩ resistors, resulting in a total input impedance of 30 kΩ. This bias resistors allow both single ended and differential input operation. Noise immunity can be improved by reducing input impedance with a termination resistor between HS_GPI+ and HS_GPI-.

High-speed digital inputs electrical equivalent circuit is the following:

NixHSInputsDiagram

Non-isolated I/O

Nix Inputs and outputs are not isolated. The ground of the Nix Servo Drive and the ground of the devices connected to I/Os must be the same. Otherwise inputs or outputs may be damaged.

Next figure illustrates how to connect high-speed differential signal to HS_GPI1 (same wiring can be used for HS_GPI2).

NixHSGPIdiff


Single ended operation

In order to use the high-speed digital input in single ended mode, connect the negative terminal (HS_GPIx-) to 2.5 V. This voltage can be achieved with a voltage divider from +5V_OUT.

Voltage_divider_NIX

For a 24 V input, the negative terminal (HS_GPIx-) can be connected to 5 V (+5V_OUT).


The following figure shows how to connect high-speed single ended signal to HS_GPI2 (same wiring can be used for HS_GPI1).

NixHSGPIsingle  

Nix Servo Drive high-speed digital inputs can be used for connecting three-wire sensors. Next figures illustrate the connection of PNP and NPN three-wire sensors in input HS_GPI2 (Same wiring can be used for HS_GPI1). Pin 16 (+5V_OUT) can be used as a supply source.  

NixHS_GPIsensorPNP
 

NixHSGPIsensor

HS_GPI pull-up resistors

Pull-up resistors ensure the desired logic state when the sensor (transistor or relay) is in off-state.

NPN pull-up resistor value must be chosen in order to ensure a positive value in the differential receiver while consuming low current. For a  sensor supply of 5 V, 1 kΩ is recommended. For a sensor supply of 24 V, 47 kΩ is recommended.  


The connection of a NPN three-wire sensor with a noise filter is shown in the next figure.

NixHSInput_SingleEndedFilter

Analog inputs interface (AN_IN1, AN_IN2)

Nix Servo Drive has two 12-bit analog inputs, a single ended one (AN_IN1) and a differential one (AN_IN2). Each one of them has a different input voltage range. Next table summarizes the main features of the analog inputs:

Specification

Analog input 1

Analog input 2

Type of inputs

Single ended
ESD protected

Differential
ESD protected

ESD capability± 4 kV (contact)

Analog input resolution

12 bits

Maximum operating voltage

0 ~ 5 V

±10 V

Maximum common mode voltage (Analog input 2)-±10 V
Maximum voltage on any pin (referred to GND)7 V24 V
1st order filter cutting frequency (-3dB)4.2 kHz4.4 kHz
Sampling rate (max)10 ksps

Next figure shows the circuit model for the analog input 1: 

NixAnalogSinInputsDiagram

Next figure shows the circuit model for the analog input 2: 

NixDifferentialAnalogInput

Extending AN_IN1 voltage range

To get a 0 ~ 10 V input range in AN_IN1 input, place a 30 kΩ resistor in series with the input.

Non-isolated I/O

Nix Inputs and outputs are not isolated. The ground of the Nix Servo Drive and the ground of the devices connected to I/Os must be the same. Otherwise inputs or outputs may be damaged.

Next figure illustrates how to connect an analog single ended source to the Nix Servo Drive analog input 1.

NixAnIn1conn

Next figure shows how to interface differential and single ended voltage sources to the differential analog input 2. The differential analog input is typically used as a command source or feedback signal. 

NixAn2Diff

NixAn2Sing

Digital outputs interface (GPO1, GPO2)

Nix Servo Drive has two digital non-isolated outputs. Digital outputs are based on an open drain MOSFET with a weak pull-up to 5 V, and are 24 V tolerant and short-circuit protected. Next table shows their main features:

Specification

Value

Number of outputs

2

Type of output

Open drain output with weak pull-up to 5 V
ESD protected.
Overload, short circuit and over-temperature protected with auto restart (self protected MOSFET).

ESD capability

IEC 61000-4-2 (ESD) ± 15 kV (air), ± 8 kV (contact)

Maximum supply output

30 V (5-24 V typical)

Maximum sink/source current

Source: low current @ 5 V: 5 mA
Sink: 500 mA @ 5 or 24 V

ON-OFF delay

124 μs @ 30 V and Rload = 100 kΩ
20 μs @ 5 V and Rload = 100 kΩ

OFF_ON delay

15μs @ 30 V and Rload = 100 kΩ
50 μs @ 5 V and Rload = 100 kΩ

Max working frequency

1 kHz

Next figure shows digital output circuit model. 

NixGPODiagram

Non-isolated I/O

Nix Inputs and outputs are not isolated. The ground of the Nix Servo Drive and the ground of the devices connected to I/Os must be the same. Otherwise inputs or outputs may be damaged.

Wiring of 5V loads

Loads that require 5V as high-level voltage can be connected directly to the digital output. A wiring example for GPO2 is shown in the next figure (same wiring could be used for GPO1). 

Nix5VGPO

Wiring of 24V loads

Loads that require 24V as high-level voltage can also be interfaced with GPO. For this option, an external power supply is needed. The load can be connected with a pull-up to 24V or directly switched with the GPO. Next figures show two example connections to GPO2 (same wiring could be used for GPO1). 

Nix24VGPOpullUp


Nix24VGPOload

Interfacing inductive loads

The switching of inductive loads (like relays or motor brakes) can cause inductive kicking, that is a sudden voltage rise when the current through the inductor is falls to zero. In order to avoid this voltage rise, it is recommended to place a diode in anti-parallel with the load (known as freewheeling diode).

Standard rectifier diodes such as 1N4002 or 1N4934 are appropriate for the application.

An alternative to the freewheeling diode is to place a varistor or an RC snubber in parallel with the load.

An example of how to connect an inductive load to GPO2 is shown in the next figure (same wiring could be used for GPO1). 

Nix24VGPOinductive

Motor brake output (GPO1, GPO2)

Electromechanical brakes are needed in critical applications where the disconnection of the motor or a lack of electric braking could be dangerous or harmful (i.e. falling suspended loads). Nix Servo Drive can use the digital outputs (GPO1 and GPO2) as a brake output. This output consists on an open drain MOSFET (1 A  and 24 V). Further specifications can be found in Digital outputs interface.

Motor brake operation

For brake operation of a GPO, this function has to be configured through Motion Lab.

The brake operation is usually configured for normally locked electromechanical brakes; that is, brakes that by default block the movement of the motor shaft. For this reason, the switch is controlled with inverted logic, being activated to allow the rotation of the shaft. This kind of brakes increase the safety of the application, because in a drive power failure, the switch would be opened and therefore the brake activated.

Next figure show how the typical connection using the main supply as brake power supply.

NixBrakeGPO

Free-wheeling diode

It is recommended to use a freewheeling diode in anti-parallel with the brake to prevent inductive kicking (voltage rise when current through the brake inductance falls to zero). Standard rectifier diodes such as 1N4002 or 1N4934 are appropriated for the application.



Torque off input (custom purchase order)

As assembly option (custom purchase order), the Nix Servo Drive can be provided with a torque off input. This input is used to prevent motor torque in an emergency event while Nix remains connected to the power supply.

The torque off input can be implemented through input GPI2. When a LOW level voltage is detected in this input, the transistors of the power stage are turned off and a STO fault is notified. During this state, no torque will be applied to the motor no matter configuration, or state of a command source. This will slow down the motor shaft until it stops under its own inertia and frictional forces. This input should not be confused with a digital input configured as enable input, because enable input is firmware controlled and does not guarantee intrinsic safety as it can be reconfigured by a user.

Not a Safe Torque Off

The torque off input is not a safety critical torque off input (Safe Torque Off). It should not be used for safety critical applications.

GPI2 input reads a logic low state (0 V < Vin < 1 V) by defect, so the input must be connected to a logic high level (4 V < Vin < 24 V) to activate the power stage. Next figures show two examples of connection of the torque off input, a self-supplied option and an external supplied option.

NixInputTorqueOff

NixTorqueOffInputExternal