National Instruments Network Card FP RLY 420 User Manual

OPERATING INSTRUCTIONS

FP-RLY-420

8-Channel, SPST Relay Module

These operating instructions describe the installation, features, and

characteristics of the FP-RLY-420. For details on configuring and

accessing the FP-RLY-420 over a network, refer to the user manual

for the particular FieldPoint network module you are using with

the FP-RLY-420.

Features

The FP-RLY-420 is a FieldPoint relay output module with the

following features:

•

Eight Single-Pole Single-Throw (SPST) relay channels

Switching capacity 3 A at 35 VDC or 250 VAC

On/Off LED indicators

Hot plug and play operation

3,000 V input to output isolation

Double insulated for 250 V safe working voltage

–40 to +70 °C operation

Power Requirement

The FP-RLY-420 is powered via the local backplane bus from the

FieldPoint network module. The FP-RLY-420 is a high-power

consumption module and requires more than the nominal power

allocated to an I/O module from the network module. In some

applications, this could limit the number of I/O modules that you

can connect to a single network module.

When defining a FieldPoint system that uses an FP-RLY-420

module, you must calculate the power consumption. First refer

to the specifications section in the user manual for your network

FieldPoint ™ is a trademark of National Instruments Corporation. Product and company names

mentioned herein are trademarks or trade names of their respective companies.

321904B-01

Field Wiring

The terminal base has connections for each of the eight relay

channels and an external supply to power field devices. Each relay

channel of the FP-RLY-420 has two terminals: N.O. (Normally

Open) and I.C. (Isolated Common). The external supply is not

needed for the internal operation of the FP-RLY-420; however,

you may connect an external supply to power field devices by

connecting to the V and C terminals of the terminal base. If you

connect an external supply to the V and C terminals, the total

current supplied cannot exceed 6 A.

Table 1 lists the terminal assignments for the signals of each

channel.

Table 1. Terminal Assignments

Terminal Numbers

Chan-

V_sup

nel

N.O.

I.C.

COM

FP-RLY-420

Figures 2a and 2b show examples of basic wiring connections.

–

sup

Load

N.O.

I.C.

COM

N.O.

I.C.

Load

–

sup

N.O.

I.C.

N.O.

I.C.

–

Load

COM

a. Total Current Less

Than 6 Amps

b. Total Current Greater

Than 6 Amps

Figure 2. Basic Field Connection (Two Channels Shown)

Relay Output Circuit

The outputs of the FP-RLY-420 consist of Form A

electromechanical relays. The power-up state is off (open) to

ensure safe installation. In the ON state, the N.O. and I.C. contacts

connect together to form a short circuit. Choose the impedance of

the loads so that the current switched by any one channel in the ON

state is no more than 3 A.

In the ON state, there is an effective resistance of 100 mΩ between

the N.O. and I.C. terminals, which causes a voltage drop. For

example, if the current is 3 A, the voltage drop across the N.O.

and I.C. terminals is 0.3 V.

FP-RLY-420

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Figure 3 shows the diagram of one channel’s relay output circuit.

sup

N.O.

I.C.

COM

Figure 3. Relay Output Circuit

The maximum switching capacity of each relay is 3 A up to

250 VAC or 35 VDC. To switch greater DC voltages, refer to

Figure 4.

2.5

Safe Operating

Current

Region

1.5

(Amps)

20 40 60 80 100 120

DC Volts

Figure 4. Maximum Current vs. DC Volts

Contact Protection for Inductive Loads

When inductive loads are connected to the relays, a large

counter-electromotive force may occur at relay switching time

because of the energy stored in the inductive load. These flyback

voltages can severely damage the relay contacts and greatly

shorten the life of the relay.

It is best to limit these flyback voltages at your inductive load by

installing, across your inductive load, a flyback diode for DC loads

or a metal oxide varistor (MOV) for AC loads. Refer to the next

section, Guidelines for Selecting Contact Protection Circuits, for

more information.

FP-RLY-420

In addition, the FP-RLY-420 contains its own internal protection

MOV to prevent excessively high voltage from being applied

across the contacts. The MOV is located between the N.O. and I.C.

contacts of each relay, but National Instruments still recommends

the use of a protection circuit across your inductive load.

Guidelines for Selecting Contact

Protection Circuits¹

Proper selection is critical as the use of a contact-protection device

can extend contact life. When mounting the protection device,

always locate it near the immediate area of the load or contact.

Typically you should mount a protective device within 18 in. of the

load or contact.

Typically, contact-protection circuits are provided for an overview,

but you should thoroughly examine the circuit you are planning to

use. For more specific information on any of these circuits, contact

the Technical Services Department at American Zettler, Inc.

Diode and Zener Diode Circuit

Diagram

Notes

Use in DC applications only.

Use when diode circuit causes too long

release time.

Load

Use zener diode with zener voltage about

equal to power supply voltage.

This section has been reprinted with permission from American Zettler, Inc.

FP-RLY-420

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Diode Circuit

Diagram

Notes

Use in DC applications only.

Compared to RC type, circuit delays release

time (2 to 5 times values stated in catalog).

For larger voltages, use diode with reverse

breakdown 10 times circuit voltage and

forward load circuit.

Load

For smaller voltages, use reverse breakdown

voltage of 2 to 3 times power supply voltage.

CR Circuits

Diagram

Notes

Circuit A is suitable for AC or DC

applications, but if used with AC

voltage, impedance of the load

should be smaller than the CR

Load

circuit’s. Do not utilize for timer

loads, as leakage current can cause

faulty operations.

Circuit B is suitable for AC or DC.

If the load is a relay or solenoid,

release times lengthen. Effective

when connected to both contacts,

Load

power supply voltage across the

load is 100 to 200 V.

Varistor Circuit

Diagram

Notes

Effective for AC and DC

applications.

Circuit slightly delays release time.

Effective when connected to both

Load

contacts, power supply voltage

across the load is 100 to 200 V.

FP-RLY-420

In-Rush Current

The type of load and its in-rush current characteristics, together

with switching frequency, can cause contact welding. For loads

with in-rush current, measure the steady state current and in-rush

current to determine the proper relay. Some typical types of loads

and the in-rush current they create are summarized in the following

chart.

Type of Load

Resistive load

In-Rush Current

Steady-state current

Solenoid load

10 to 20 times the steady-state current

5 to 10 times the steady-state current

10 to 15 times the steady-state current

Motor load

Incandescent lamp load

Mercury lamp load

Approximately 3 times the steady-state

current

Sodium vapor lamp load

Capacitive load

1 to 3 times the steady-state current

20 to 40 times the steady-state current

5 to 15 times the steady-state current

Transformer load

Status Indicators

Figure 5 shows the module label and status indicators. You can

remove the insertable label to see wiring diagrams for the input

channels.

Figure 5. Status Indicators and Module Label

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After the module has been inserted into a terminal base (and

power is applied), the green POWER indicator lights and the

FP-RLY-420 informs the network module of its presence. When

the network module recognizes the FP-RLY-420, the network

module sends initial configuration information to the FP-RLY-420.

After receiving this initial information, the green READY

indicator lights and the FP-RLY-420 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.

Isolation and Safety Guidelines

Caution Read the following information before

attempting to connect ANY circuits that may contain

hazardous voltages to the FP-RLY-420.

This section describes the isolation of the FP-RLY-420 and its

compliance with international safety standards. The outputs are

isolated from the backplane of the terminal base with an isolation

barrier designed and tested to protect against fault voltages of up to

3000 Vrms. In addition, the FP-RLY-420 provides double

insulation (compliant to 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. You should never attempt 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 (as the FP-RLY-420 is) for such an

application.

Even when a product like the FP-RLY-420 is used in applications

with hazardous potentials, follow these guidelines to ensure a safe

total system:

•

The safety isolation of the FP-RLY-420 is from input to output,

not between channels on the same module. If any of the

channels on a module are wired at a hazardous potential,

ensure that all other devices or circuits connected to that

module are properly insulated from human contact.

FP-RLY-420

•

Do not share the external supply voltages (V and C on the

terminal base) with other devices (including other FieldPoint

devices) unless those devices are also isolated from human

contact.

As with any hazardous voltage wiring, ensure that all wiring

and connections meet with applicable electrical codes or

common sense practices. Mount terminal bases in an area,

position, or cabinet that prevents accidental or unauthorized

access to wiring with hazardous voltages.

•

The isolation of the FP-RLY-420 is certified as double

insulated for normal operating voltages of 250 Vrms. Do not

use the FP-RLY-420 as the sole isolating barrier between

human contact and working voltages of more than 250 Vrms.

Specifications

The following specifications are typical for the range

–40 to +70 °C, unless otherwise noted.

Input Characteristics

Number of channels..........................8

Relay type.........................................1 Form A (SPST)

Nonlatching

Maximum Switching Capacity (Resistive Load)

AC ..............................................3 A at 250 VAC

DC ..............................................3 A at 35 VDC

2 A at 40 VDC

1 A at 55 VDC

0.4 A at 120 VDC

Note Above 55 °C ambient, max. 1.5 A per channel.

Minimum switching voltage.............10 mA at 5 VDC

On resistance.....................................100 mΩ

Off state leakage ...............................0.3 µA at 250 VAC

Expected Life

Mechanical .................................20 × 10⁶operations min.

Electrical (at 30 cpm) .................300,000 operations at 3 A,

35 VDC

100,000 operations at 3 A,

250 VAC

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Maximum switching frequency

Mechanical .................................20 operations per second

Electrical.....................................1 operation per second at

maximum load

Relays operate time...........................6 ms typical, 8 ms max.

Relays release time ...........................3 ms typical, 4 ms max.

Relay bounce time ............................3 ms max.

Contact material................................Gold-plated silver cadmium

oxide

Isolation (CH–GND and CH–CH)....3,000 Vrms

Safety isolation, working voltage

(CH–GND only) ...............................250 Vrms, designed per IEC

1010 as double insulated

Physical

Indicators ..........................................Green POWER and

READY indicators, 8 green

output state indicators

Weight...............................................160 g (5.6 oz.)

Power Requirements

Power from network module ............1700 mW

Environment

Operating temperature ......................–40 to +70 °C

Storage temperature..........................–55 to +100 °C

Relative humidity..............................5% to 90% noncondensing

CE Mark Compliance

This product meets applicable EU directive(s) as follows:

Safety isolation .................................EN 61010 (double insulation

for 250 Vrms working

isolation, installation

category II)

EMC Directive

Immunity....................................EN 50082-1:1994

Emissions ...................................EN 55011:1991 Group I

Class A at 10 m

FP-RLY-420

Mechanical Dimensions

Figure 6 shows the mechanical dimensions of the FP-RLY-420

installed onto a terminal base. Dimensions are given in inches

[millimeters].

4.22 [107.19]

4.31

[109.5]

3.60 [91.44]

Figure 6. Mechanical Dimensions

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