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Caution Substitution of components may impair suitability for Class I, Division 2. Caution For Zone 2 applications, install the system in an enclosure rated to at least IP 54 as defined by IEC 60529 and EN 60529. Caution For Zone 2 applications, install a protection device across the external power supply and the COM pin. The device must prevent the external power supply voltage from exceeding 70 V if there is a transient overvoltage condition. Special Conditions for Hazardous Locations U
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Special Conditions for Marine Applications Some modules are Lloyd’s Register (LR) Type Approved for marine applications. To verify Lloyd’s Register certification, visit ni.com/certification and search for the LR certificate, or look for the Lloyd’s Register mark on the module. Caution To meet radio frequency emission requirements for marine applications, use shielded cables and install the system in a metal enclosure. Suppression ferrites must be installed on power supply inputs near power
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Connecting the NI 9478 The NI 9478 has a 37-pin DSUB connector that provides connections for the 16 digital output channels. 1 DO0 COM 20 2 DO1 COM 21 3 DO2 COM 22 4 DO3 COM 23 5 DO4 COM 24 6 DO5 COM 25 7 DO6 COM 26 8 DO7 COM 27 9 Vsup Vsup 28 10 Vsup Vsup 29 11 DO8 COM 30 12 DO9 COM 31 13 DO10 COM 32 14 DO11 COM 33 15 DO12 COM 34 16 DO13 COM 35 17 DO14 COM 36 18 DO15 COM 37 19 NC Figure 1. NI 9478 Pin Assignments NI 9478 Operating Instructions and Specifications 6 ni.com
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Each channel of the NI 9478 has a DO pin to which you can connect the load you want to control. Each channel also has a COM pin. National Instruments recommends you provide independent COM wiring for each channel to minimize current flow in the COM wiring. The COM pins are all connected together internally. You must connect an external power supply to the NI 9478. This power supply provides the current for the devices you connect to the module. Connect the positive lead of the power supply
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Connect the device to DO and the positive lead of the power supply. Refer to Figure 2 for an illustration of how to connect a device to the NI 9478. V sup Cable Clamp DO Device External + Power – Supply COM NI 9478 Figure 2. Connecting a Device to the NI 9478 You must connect the V pin to the power supply to enable a sup weak cable clamping diode that protects the module from cable inductance flyback. This flyback voltage results from small amounts of energy stored in the inductance of th
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Protecting the Module from Flyback Voltages If the module is switching an inductive or energy-storing device such as a solenoid, motor, or relay, and the device does not have flyback protection, install an external flyback diode as shown in Figure 3. Refer to the Using Long Cables section for more information about protection from cable inductance flyback. V sup Cable Device Clamp DO External + Power – Supply COM NI 9478 Figure 3. Connecting a Flyback Diode to the NI 9478 © National Instru
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Using Long Cables The inductance of the cabling that connects the NI 9478, the loads, and the external supply stores up energy when a channel is on and passing current through the cables. Each time a channel is turned off, the energy stored in the cables is released as flyback voltage and dissipates as heat in the NI 9478. The total power dissipated in the module increases with higher switching frequencies, higher currents, and longer cable lengths. The cable length is the total distance
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You can reduce the effective length of the cable by adding a capacitor close to the NI 9478 across the power supply leads and adding a diode from the digital output line to the V pin line. sup National Instruments recommends that you use a capacitor with a capacitance of at least 20 μF. In this case, the effective length of the cable is the distance from the output pin, through the new diode, through the capacitor, and back to the COM pin, as shown in Figure 5. V sup Load Cable Clamp Exte
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I/O Protection The NI 9478 provides protection against overcurrent and short-circuit conditions. Output Current Limit Thresholds The NI 9478 provides two configurable current limit thresholds for the module, Limit A and Limit B. The NI 9478 continuously monitors the current through each output channel and detects if the current exceeds either of the current limit thresholds. You can configure the current limit thresholds and check the current limit output status in software to determine if
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Some applications require a large inrush current when a channel is first turned on. If this inrush current exceeds the maximum current limit threshold, you may need to disable overcurrent protection by programming the channel to have no current limit. Refer to the software help for more information about configuring current limits. Visit ni.com/info and enter cseriesdoc for information about C Series documentation. Caution The NI 9478 is not protected against output overcurrent or short-c
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Overcurrent Refresh The NI 9478 provides an overcurrent refresh setting that enables a channel to automatically recover within the specified overcurrent refresh period if the channel exceeds its current limit threshold. If overcurrent refresh is disabled, the channel remains off after an overcurrent condition until software sends a command to turn the channel back on. Refer to the software help for more information about overcurrent refresh. Visit ni.com/info and enter cseriesdoc for info
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for that channel. Use the following equation to calculate the percentage of the total power budget each output channel uses in your application. 2 2 ⎛⎞ ⎛⎞ P = 4% I + 0.12%() length – 0.2 I + 0.04%() I + 1 freq ⎝⎠ out ⎝⎠ out out where P is the percentage of total allowable power the channel uses I is the output current in amperes while the channel is on out length is the total cable length in meters, shown in Figure 4 freq is the frequency rate in kHz at which the output channel goes through a
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Example One You are driving a load with 2.0 meters of cable through a cycle in which the NI 9478 is on and passing 1.25 A of current for 40 μs, then off for 10 μs. The output period is 50 μs (40 μs + 10 μs) so the output frequency is 20 kHz. The channel uses 14.8% of the total power budget, as shown in the following equation. 2 2 4%() 1.25 +[] 0.12%() 2.0 – 0.2() 1.25 + 0.04%() 1.25 + 1 20 = 14.8% NI 9478 Operating Instructions and Specifications 16 ni.com
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OPERATING INSTRUCTIONS AND SPECIFICATIONS
NI 9478
16-Channel, 0–50 V, Sinking Digital Output Module
with Programmable Current Limits
Français Deutsch
ni.com/manuals
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This document describes how to use the National Instruments 9478 and includes specifications and pin assignments for the NI 9478. Visit ni.com/info and enter rdsoftwareversion to determine which software you need for the modules you are using. For information about installing, configuring, and programming the system, refer to the system documentation. Visit ni.com/info and enter cseriesdoc for information about C Series documentation. Note The safety guidelines and specifications in this
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Safety Guidelines Operate the NI 9478 only as described in these operating instructions. Hot Surface This icon denotes that the component may be hot. Touching this component may result in bodily injury. Safety Guidelines for Hazardous Locations The NI 9478 is suitable for use in Class I, Division 2, Groups A, B, C, D, T4 hazardous locations; Class I, Zone 2, AEx nA IIC T4, and Ex nA IIC T4 hazardous locations; and nonhazardous locations only. Follow these guidelines if you are installing th
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Example Two You are driving a load with 2.0 meters of cable through a cycle in which the NI 9478 first is constantly on and passing 3 A of current for 0.25 seconds, then drives the load at 20 kHz with 1.25 A current for 1.25 seconds, then drives the load off for 4 seconds. While the NI 9478 is constantly on, the output frequency is 0 kHz and the 2 channel uses 36% (4% × 3 ) of the total power budget. Example One shows that while the NI 9478 is driving at 20 kHz, the channel uses 14.8% of
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Sleep Mode This module supports a low-power sleep mode. Support for sleep mode at the system level depends on the chassis that the module is plugged into. Refer to the chassis manual for information about support for sleep mode. If the chassis supports sleep mode, refer to the software help for information about enabling sleep mode. Visit ni.com/info and enter cseriesdoc for information about C Series documentation. Typically, when a system is in sleep mode, you cannot communicate with t
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Specifications The following specifications are typical for the range –40 to 70 °C unless otherwise noted. All voltages are relative to COM unless otherwise noted. Output Characteristics Number of channels..........................16 digital output channels Output type .......................................Sinking Power-on output state .......................Channels off Output voltage (V )...........................I R 0 0 0 External power supply voltage range (V )...........................
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1 Switched output current (10 kHz) , per channel All channels on...........................1 A max Four channels on ........................2 A max One channel on...........................4 A max 1 Switched output current (20 kHz) , per channel All channels on...........................0.75 A max Four channels on ........................1.67 A max One channel on...........................3.33 A max Output impedance (R ) .....................50 mΩ max 0 Reversed-voltage protection .............N
