User`s guide

7.2 TTL TO SOLID STATE RELAYS
Many applications require digital outputs to switch AC and DC voltage motors on and
off and to monitor AC and DC voltages. These AC and high DC voltages cannot be
controlled or read directly by the TTL digital lines of a PCI-DIO24.
Solid State Relays
, such as those available from Omega, allow control
and monitoring of AC and high DC voltages and provide 750V isolation. Solid State
Relays (SSRs) are the recommended method of interfacing to AC and high DC sig-
nals.
The most convenient way to use solid state relays and a PCI-DIO24 board is to pur-
chase a Solid State Relay Rack. A SSR Rack is a circuit board with output buffer
chips which are powerful enough to switch the SSR and sockets to plug SSRs into.
SSR Racks are available from Computer Boards and most manufacturers of SSRs. If
you have only a few outputs to control, you may also wish to consider the DR-OAC
or DR-ODC, single point, DIN mountable SSRs.
The high current outputs of the PCI-DIO24H and PCI-DIO24H/CTR3 boards are
suitable to drive SSR’ directly but the CMOS outputs of the PCI-DIO24 do not have
sufficient drive to connect directly to most SSRs. If you only want to drive one or two
SSRs with CMOS outputs, all you need is a 74LS244 output buffer chip between the
82C55 output and the SSR. Of course the SSR will need 5 volt power as well.
7.3 VOLTAGE DIVIDERS
If you wish to measure a signal which varies over a range greater than the input range
of a digital input, a voltage divider can drop the voltage of the input signal to the level
the digital input can measure.
A voltage divider takes advantage of Ohm's law, which states,
Voltage = Current * Resistance
Implied in the above is that any
variation in the voltage drop for the
circuit as a whole will have a
pro-
portional
variation in all the volt-
age drops in the circuit.
A voltage divider takes advantage
of the fact that the voltage across
22
Signal
High
Signal
Volts
Signal
Low
Vin
R1
R2
V1
V2
Vout
CIO-DIO24
Input
Groundt
SIMPLE VOLTAGE DIVIDER - Vin = R1+R2
Vout R2
22
7.3 VOLTAGE DIVIDERS
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22
7.2 TTL TO SOLID STATE RELAYS
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20
7.1 PULL UP & PULL DOWN RESISTORS
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20
7 ELECTRONICS AND INTERFACING
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18
6.3 PCI-DIO24H/CTR3
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17
6.2 PCI-DIO24H
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16
6.1 PCI-DIO24
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16
6 SPECIFICATIONS
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15
5.5 82C54 COUNTER CHIP
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14
5.4 INPUT PORTS
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13
5.3 OUTPUT PORTS
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12
5.2 82C55 DIGITAL I/O REGISTERS
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11
5.1 82C55 CONTROL & DATA REGISTERS
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10
5.1 BOARD CONTROL REGISTERS
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8
5 I/O REGISTER MAPS
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8
4 SOFTWARE
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7
3.4 COUNTER CONNECTIONS & SETUP
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6
3.3 SIGNAL CONNECTION CONSIDERATIONS
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5
3.2 CONNECTOR DIAGRAM - PCI-DIO24, -24H &
-24H/CTR3
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5
3.1 CABLES AND SCREW TERMINAL BOARDS
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5
3 I/O CONNECTIONS
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4
2.4 Testing The Installation
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3
2.3 RUN InstaCAL
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3
2.3 InstaCal
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3
2.2 DOS and/or Windows 3.1
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2
2.1 WINDOWS 95, 98 & NT
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2
2 QUICK START & INSTALLATION
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1
TABLE OF CONTENTS
1 INTRODUCTION
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