1. HARDWARE TESTING OF DIGITAL INPUT & OUTPUT CARDS FOR DATA ACCUSITION & CONTROL SYSTEMS A Mini Project Report submitted in partial fulfillment for the award of the degree Bachelor of Technology in Electronics and Communication Engineering Submitted by GAURAV BHATNAGAR (06621A0467) VENKATESWARAN SREERAM (06621A04B8)

2. Chapter 1: Introduction 1.1 DIGITAL INPUT AND OUTPUT CARDS: Digital I/O devices process digital signals and the output results in digital format. A digital I/O module has both input and output functionality and is used for data acquisition. This module includes on-off signals used in communication, user interface, or control. It provides integrated signal conditioning, reduction in wiring/cabling requirements and ease of installation. A digital I/O card is a specially made device for automation and control of industrial equipment, and is usually used in machine vision and automation applications. Digital I/O devices can be designed and manufactured to meet most industry specifications.

3. DATA ACQUISITION AND CONTROL SYSTEMS It generally refers to an industrial control system: a computer system monitoring and controlling a process. The process can be industrial, infrastructure or facility based as described below: Industrial processes include those of manufacturing, production, power generation, fabrication, and refining, and may run continuous,batch, repetitive, or discrete modes. Infrastructure processes may be public or private, and include water treatment and distribution, wastewater collection and treatment, oil and gas pipelines, electrical power transmission and distribution, civil defense siren systems, and large communication systems.

4. Functionality of Digital Input Card (DI) 2.1 FEATURES OF THE DIGITAL INPUT CARD It has 8 channels. It has 8 inputs and 8 outputs. Each channel is optically isolated from each other. Operating voltage is +17 to +28 V. It supports 8 relay output / transistor output channels.

5. The DI8 is an 8 channel isolated digital input board. The optically isolated inputs of the DI8 consist of a dual channel OPTO-coupler with a resistor for current limiting. The DI8 can be used to sense DC signals from TTL levels up to 24Vand to isolate the computer from large common-mode voltages, ground loops and voltage spikes that often occur in industrial environments. The output signal from the opto- coupler is given to the bounce eliminator which removes the flickering effect caused due to the electro-mechanical nature of the relay.

6. Diagram for 8 channel data input card

7. OPTO-COUPLER In electronics, an opto-isolator (or optical isolator, optocoupler, photo coupler, or photoMOS) is a device that uses a short optical transmission path to transfer a signal between elements of a circuit, typically a transmitter and a receiver, while keeping them electrically isolated — since the signal goes from an electrical signal to an optical signal back to an electrical signal, electrical contact along the path is broken. The opto-isolator is simply a package that contains both an infrared LED and a photo detector such as silicon diode, transistor Darlington pair, or SCR. The wave-length response of each device is tailored to be as identical as possible to permit the highest measure of coupling possible. The opto-coupler that is used in the DI8 card is the

8. APPLICATIONS 1) Opto couplers are used to isolate low-current control or signal circuitry from transients generated or transmitted by power supply and high-current control circuits. The latter are used within motor and machine control function blocks. 2) Medical equipment often uses opto couplers. 3) Where electrical safety is paramount, opto-couplers can totally isolate circuitry which may be touched by humans from mains electricity 4) Opto-isolators can help cut down on ground loops, block voltage spikes, and provide isolation

9. BOUNCE ELIMINATOR The bounce eliminator which is commonly used in the DI8 input card is the MC 14490.It is also called as MC 14490 Hex Contact Bounce Eliminator. It is a 16 pin device. The MC 14490 is constructed with complementary MOS enhancement mode devices, and is used for the elimination of extraneous level changes that result when interfacing with mechanical contacts. The digital contact bounce eliminator circuit takes an input signal from a bouncing contact and generates a clean digital signal four clock periods after the input has stabilized. The bounce eliminator circuit will remove bounce on both the "make" and the "break" of a contact closure

10. Features of bounce eliminator Diode Protection on All Inputs Six Debouncers Per Package Internal Pull-ups on All Data Inputs Can Be Used as a Digital Integrator, System Synchronizer, or Delay Line Internal Oscillator (R-C), or External Clock Source TTL Compatible Data Inputs/Outputs Single Line Input, Debounces Both "Make" and "Break" Contacts Cascadable for Longer Time Delays Schmitt Trigger on Clock Input (Pin 7) Supply Voltage Range = 3.0 V to 18 V Pb-Free Packages are Available