National Instruments FieldPoint FP-PWM-520 Operating Instructions Manual

Page 1
OPERATING INSTRUCTIONS
FP-PWM-520
8-Channel, 5 or 24 V PWM Output Module
These operating instructions describe the installation, features, and characteristics of the FP-PWM-520. For details on configuring and accessing the FP-PWM-520 over a network, refer to the user manual for the particular FieldPoint network module you are using with the FP-PWM-520.

Features

The FP-PWM-520 is a FieldPoint pulse-width modulated (PWM) output module with the following features:
Eight PWM output channels
0 to 100% duty-cycle capability with 12-bit resolution
One millisecond period resolution
Overcurrent protected outputs
Sourcing outputs compatible with sinking inputs or 24 VDC devices
On/off LED indicators
Hot plug and play operation
3,000 Vrms input-to-output isolation
Double insulated for 250 V safe working voltage
Independent configuration of the output period for each channel from 1 to 65,535 ms in 1 ms increments
FieldPoint is a trademark of National Instruments Corporation. Product and company names mentioned herein are trademarks or trade names of their respective companies.
322139B-01 © Copyright 1998, 1999 National Instruments Corp. All rights reserved. June 1999
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Installation

The FP-PWM-520 mounts on a FieldPoint terminal base (FP-TB-xx) unit. Because of its hot plug and play operation, you can install the FP-PWM-520 onto a powered terminal base without disturbing the operation of other modules or terminal bases. The FP-PWM-520 receives operating power from the terminal base.
To install your module, refer to Figure 1 and complete the following steps:
1. Slide the terminal base key to either position X (used for any module) or position 4 (used for the FP-PWM-520 module).
2. Align the FP-PWM-520 alignment slots with the guide rails on the terminal base.
3. Press firmly to seat the FP-PWM-520 on the terminal base. When the module is firmly seated, the terminal base latch locks it into place.
Key
Latch
Alignment
Slot
Guide Rails
Terminal BaseI/O Module
Figure 1.
Install Your Module

Field Wiring

The terminal base provides connections for each of the eight output channels and for an external supply to power f i eld devices. Although the module does not need the external supply for its internal operation, the output channels source current from this external supply and require it to operate.
Each channel has one output terminal, V terminals, COM (internally connected to the C terminal); and a supply terminal, V
(internally connected to the V terminal).
sup
If you want to connect an external supply to power field devices, connect to the V and C terminals of the terminal base, or to the V
FP-PWM-520 2 www.natinst.com
; two common
out
sup
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and COM terminals for the individual channels. If the total current supplied by the FP-PWM-520 channels is more than 4 A, route the external supply to the V
and COM terminals. Otherwise, you can
sup
connect the external supply only to the V and C terminals. Figure 2 shows two examples of basic wiring connections.
CV
a. Total Current Less
Than 4 Amps
Figure 2.
V
out
COM
V
out
COM
CV
+
Load
Load
V
sup
V
out
COM COM
V
sup
V
out
COM COM
b. Total Current Greater
Than 4 Amps
Basic Field Connections (Two Channels Shown)
+
Load
Load
Table 1 lists the terminal assignments for the signals of each channel. T erminal assignments and wiring diagrams are also listed under the slide-in card on the front of the FP-PWM-520 module.
Table 1.
Terminal Assignments
Terminal Numbers
Channel
V
out
V
sup
COM
0 1 17 2, 18 1 3 19 4, 20 2 5 21 6, 22 3 7 23 8, 24 4 9 25 10, 26 5 11 27 12, 28 6 13 29 14, 30 7 15 31 16, 32
© National Instruments Corp. 3 FP-PWM-520
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Pulse-Width Modulated Output Circuit

The FP-PWM-520 PWM output channels have optically isolated sourcing outputs with overcurrent protection circuitry. In the ON state of the output period, a transistor is turned on between the positive external supply v oltage (the V and V output (V
) terminal. In the OFF state, this transistor is turned off,
out
allowing only a small leakage current to flow . Select the impedance of the loads driven by the output channels so that the current supplied by any one channel in the ON state is no more than 1 A.
The output channels need an external power supply of 5 VDC or between 10 and 30 VDC connected to the C and V terminals of the module.
In the ON state, the effective resistance between the output and the external supply voltage is 0.3 Ω, which causes a voltage drop. For example, if the external supply voltage is 5 V and the output current is 1 A, the output voltage is 4.7 V:
[5 V – (1 A x 0.3 Ω)=4.7V].
Figure 3 shows a diagram of the discrete output circuit of one channel.
terminals) and the
sup
Optical
Isolation
Figure 3.
V
C
Discrete Output Circuit
V
sup
V
out
COM

Overcurrent Protection

Overcurrent protection circuitry on each output deactiva tes the output if the current it sources to the V level. This level is always at least 1 A. A slightly higher inrush current that exists for a short time will not trigger the protection circuitry. If the protectio n circuitry disables an output that would otherwise be in the ON state, the status indicator for that channel is still lit, but the output transistor is turned off.
FP-PWM-520 4 www.natinst.com
terminal exceeds a safe
out
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Detecting an Overcurrent Condition

To determine whether an overcurrent condition exists, complete the following steps:
1. Use the FieldPoint Explorer to set the duty cycle to 100% for the channel in question.
2. Measure the voltage between the V
and COM terminals for
out
that channel. Under normal load conditions, the V
-to-COM voltage is
out
within 1 V of the supply voltage when the output is on continuously. Any voltage more than 1 V less than the supply voltage indicates an overcurrent condition. Typically, the V
-to-COM voltage is nearly zero if the protection circuitry
out
is activated.
The overcurrent protection circuitry resets when the output switches to the OFF state, when you disconnect field power from the module, when you remove the FP-PWM-520 from its terminal base, or when you turn off the network module. Unless you set the output duty cycle to 0% or 100%, the output channel switches to the OFF state once per output period during normal operation.

Remedying an Overcurrent Condition

To remedy an overcurrent condition, determine the cause of the overcurrent condition and disconnect the load that is causing the problem from the FP-PWM-520. The channel resets automatically when the load is removed.
Alternatively, if completely removing the channel load is not convenient, reset the channel in any of the following ways:
Use the FieldPoint Explorer to set the duty cycle to any value other than 100% and wait at least one output period for the channel to reset.
Use the FieldPoint Explorer to set the duty cycle to 0%. The channel resets immediately.
Disconnect the external power supply from the module.
Remove the FP-PWM-520 from the terminal base.
Turn off the network module that the FP-PWM-520 is connected to.
Normal operation can resume after you correct the overcurrent condition.
© National Instruments Corp. 5 FP-PWM-520
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Output Channel Operation

Each of the PWM output channels uses a period and a duty cycle setting to determine when to switch its output to the ON or OFF state.
The output period is the only configuration attribute for each channel. You can set the period to any value between 1 ms (1 kHz) and 65,535 ms (0.01525 Hz), in increments of 1 ms.
The output duty cycle is written as the data v alue for each channel. Y ou can set the duty cycle to any percentage v alue between 0% and 100%, with 12-bit resolution (4,096 discrete duty-cycle settings).

Status Indicators

Figure 4 shows the module label and status indicators. To see wiring diagrams for the input channels, remove the slide-in card.
Figure 4.
After you insert the module into a terminal base (and app ly power), the green POWER indicator lights and the FP-PWM-520 informs the network module of its presence. When the network module recognizes the FP-PWM-520, it sends initial configuration information to the FP-PWM-520. After receiving this initial information, the green READY indicator lights and the FP-PWM-520 is in its normal operating mode. In addition to the green POWER and READY indicators, each channel has a numbered, green, output state indicator that lights when the channel is in the ON state.
FP-PWM-520 6 www.natinst.com
Status Indicators and Module Label
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Isolation and Safety Guidelines

Caution
Before you connect any circuits that may contain hazardous voltages to the FP-PWM-520, read the following information.
This section describes the isolation of the FP-PWM-520 and its compliance with international safety standards. The outputs are isolated from the backplane provided by the terminal base with an optical isolation barrier designed and tested to provide protection against fault voltages of up to 3,000 Vrms. In addition, the FP-PWM-520 provides double insulation (compliant with UL and IEC safety standards) for working common-mode voltages of 250 Vrms. Safety standards (such as those published by UL and IEC) require the use of double insulation between hazardous voltages and any human-accessible parts or circuits.
Never try to use any isolation product between human-accessible parts (such as DIN rails or monitoring stations) and circuits that may be at hazardous potentials under normal conditions, unless the product is specifically designed for such an application, as is the FP-PWM-520.
When you use a product like the FP-PWM-520 in applications with hazardous potentials, follow these guidelines to make sure your total system is safe:
The safety isolation of the FP-PWM-520 is from input to output, not between channels on the same module. If an y of the channels on a module are wired at a hazardous potential, make sure that all other devices or circuits connected to that mo dule are properly insulated from human contact.
•Do not share the e xternal supply voltages (V, C, V
, and COM
sup
terminals on the terminal base) with other devices (including other FieldPoint devices), unless those devices are isolated from human contact.
As with any hazardous voltage wiring, make sure that all wiring and connections meet with applicable electrical codes and common sense practices. Mount terminal bases in an area, position, or cabinet that prevents accidental or unauthorized access to wiring that carries hazardous voltages.
The isolation of the FP-PWM-520 is certified as double-insulated for normal operating voltages of 250 Vrms. Do not use the FP-PWM-520 as the only isolating barrier between human contact and working voltages of more than 250 Vrms.
© National Instruments Corp. 7 FP-PWM-520
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Specifications

The following specifications are typical for a range –40 to +70 °C, unless otherwise noted.
Output
Number of channels..........................8
Output type .......................................24 VDC, sourcing
Supply voltage..................................5 VDC or 10 to 30 VDC,
user-provided
Output current...................................1 A, with built-in overcurrent
Output impedance.............................0.3
Pulse-width accuracy........................–1, +3 µs, any period and
Physical
Indicators ..........................................Green POWER and
Weight...............................................140 g (4.8 oz.)
Power Requirements
Power from network module............300 mW
protection circuitry, 8 A maximum for all channels
duty cycle
READY indicators, 8 green output state indicators
Environment
Operating temperature......................–40 to +70 °C
Storage temperature..........................–55 to +85 °C
Relative humidity..............................5% to 90%, non-condensing
CE Mark Compliance
This product meets applicable EU directive(s), as follows:
Safety isolation .................................EN 61010 (double insulation
FP-PWM-520 8 www.natinst.com
for 250 Vrms working isolation, installation category II)
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EMC directive
Immunity.................................... EN 50082-1:1994
Emissions ................................... EN 55011:1991 Group I
Class A at 10 m
Mechanical Dimensions
Figure 5 shows the mechanical dimensions of the FP-PWM-520 installed on a terminal base. Dimensions are given in inches [millimeters].
4.22 [107.19]
4.31
[109.5]
3.60 [91.44]
Figure 5.
© National Instruments Corp. 9 FP-PWM-520
Mechanical Dimensions
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