Analog and Digital I/O Module

1. ANALOG AND DIGITAL
I/O MODULE
Presented by: Shubham Patel
Roll no:22MEM3R14

2. MODULE: Connect the process to the data processing unit
Basic signals in real-time systems.
Introduction:

3. • Analog input signals are received from sensors and signal conditioners
and represent the value of measurand like flow, position,
displacement, temperature, etc.
• The role of a sensor is to measure the parameter for which it is
constructed and present an equivalent electrical signal as output.
• The signal conditioner takes as input the output of sensor and
suitably conditions it to be acceptable to real-time systems.
• The signal may be amplified, filtered or/and isolated in signal
conditioner depending on the sensor type and its electrical
characteristics.
Analog input signals:

4. Analog to Digital conversion:
1.Pulse code modulation.
2.Delta modulation.

5. • Digital input signals refer to the ON-OFF states of various valves, limit
switches, etc.
• Normally digital input signals are compatible to real-time systems and
can be inputted directly. In case some signal amplification/reduction
is required, signal conditioning unit is added, before real-time system
Digital input signals

6. • Definition: "Interrupts are the events that temporarily
suspend the main program, pass the control to the
external sources and execute their task. It then passes
the control to the main program where it had left off ”.
• The abnormalities may be in terms of:
• (a) Exceeding of certain limits of some parameters like temperature,
flow, etc. which may require to be controlled immediately.
• (b) Power failure in which case all the parameters must he stored and
work may be suspended.
Interrupt input signals:

7. Timer/counter input signals:
• The timer circuits may be used to initiate events at defined intervals.
• The counter circuits on the other hand, may be used to count the
occurrences of any defined event.
• The output of timer/ counter may be used as interrupt signal to real-
time system.
• Display output signals are used to drive the display devices like,
LED, LCD, VDU, Audio Alarms etc.
• The display of status of process, various control valves etc. is very
important to the operator.
• Apart from this, the limits set for various parameters at different
places in the process are also displayed for the benefit of operators
Display output signals:

8. An inside look of real-time systems

9. Analog input module:
• The module continuously scans the analog input signals in the pre-
defined order and frequency, converts them in to the digital and then
sends these values to processor.
• Depending on the application and sophistications, the analog input
module may contain local intelligence or may be commanded by the
master processor.

10. • The processor initiates multiplexer by sending the address of input
channel.
• The multiplexer connects the particular channel to the ADC.
• The processor sends the Start Convert signal to ADC. The ADC
converts the analog signal to digital, puts it at the output and issues
End of Conversion signal.
• The processor on receipt of the End of Conversion signal, reads the
ADC output and stores in memory.
• The operation is repeated by processor by sending the address of
next channel to multiplexer.
Analog input module with no local intelligence:

11. Analog input module with local intelligence
• The intelligence is provided by the processor and memory.
• The processor does the scanning of various channels and stores the
digital values in local memory.
• The interaction with main processor is achieved through Direct
Memory Access or Interrupts, initiated by main processor.

12. Digital input module:

13. Analog output module:
• The objective of analog output module is to provide appropriate
control signals to different control valves.
• The demultiplexer switches the digital output received from the
master processor to the output channel whose address is specified.
The digital to analog converter of particular channel will convert the
input digital value to equivalent analog signal which is connected to
control valve, motor etc.

14. Interrupt control module:
• Interrupt control module, basically provides interface between a
number of interrupting devices and master processor.
• The conflict between different devices needing the immediate
attention of master processor at the same time is resolved by
allocation of priorities to devices.

18. Program status world

20. References:
• [1] Benson, R.ICI Manuf. Technol., Wilton, UK, "Process controlthe future", IEEE Xplore,Aug. 1997,
pp. 161-166, ISSN. 0956- 3385.
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DTMF Technology", International Journal of Control and Automation, Vol. 4 No. 2, June, 2011,
pp.35-42.
• [3] Ayad Ghany Ismaeel, Raghad Zuhair Yousif and Essa F. Abdallh, "GUI Based Automatic Remote
Control of Gas Reduction System using PIC Microcontroller", IRACST – Engineering Science and
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System for Batch Tea Dryer", Journal of Agricultural Science, Vol.1, No.2, Dec. 2009, pp.101- 106.
• [5] Bhavina Patel, Vandana Shah and Ravindra Kshirsagar, "microcontroller based gesture
recognition system for the handicap people", Journal of Engineering Research and Studies E-
ISSN0976-7916, pp.113-115.
• [6] Amit Sachan, "Microcontroller Based Substation Monitoring and Control System with Gsm
Modem", IOSR Journal of Electrical and Electronics Engineering (IOSRJEEE) ISSN: 2278- 1676
Volume 1, Issue 6 (July-Aug. 2012), PP 13-21.
• Computer based Industrial control book by Dr Krishna Kant.

22. THANK YOU