ABSTRACT
In the world of automation today, the DAQS (Data Acquisition Systems) manufacturers face
a great deal of problems when it comes to the compatibility with the “in-use” control network
in a particular industry. Today, there exist many control networks each one having its own
advantages and disadvantages. So it is really a big headache for the DAQS manufacturers to
decide which type of networks their systems should support and which not. Our project,
STIM (SMART TRANSDUCER INTERFACE MODULE) intends to solve this problem by
presenting and implementing a solution that took its inspiration from IEEE P1451 proposals.
By designing a general standard communication protocol to be used between the DAQS and
HMI (Human Machine Interface), the DAQS will be able to work with any sort of control
network in any industry of the world. We prepared simulations, devised its hardware model
and displayed its results on LabView (HMI). We also proved that not only different types of
sensors can be used with such DAQS but also this system is network independent.
Another problem that arises in the field of instrumentation is the handling of huge paperwork
that is involved in storing sensor’s data and calibration information. Our project gives the
concept of TEDS (Transducer Electronic Data Sheet), which contains all the information
about the sensor / transducer in the EEPROM. Thus this datasheet can be downloaded,
uploaded and updated at any time with a single click and can be moved remotely with the
sensor. Now there is no need to remember the calibration dates, constants, segment ranges
and location of the sensor. You can view that right on your HMI and update it at any time.

1.2 GENERAL DESCRIPTION OF THE
BLOCK DIAGRAM
Transducers are connected with STIM through the common interface options like 4-20mA
current interfacing or 0-5V, 0-12V or 0-24V. It is important to use level shifter in case of
0-12V and 0-24V transducers before connecting them with STIM.
STIM (Smart Transducer Interface Module) contains a portion of memory to store
TEDS(Transducer Electronic Data Sheet) which contains general, callibration and location
information about the specific transducer they correspond to. STIM acquires the data and then
sends it to NCAP through the TII(Transducer Independent Interface) protocol. This is a
synchrounous serial protocol that we have developed in this project.
NCAP(Network Capable Application Processor) is a device that communicates with STIM over
the TII protocol on one side and on the other side it communicates with the HMI over the control
network that can be specific with the specifi industry.
HMI(Human Machine Interface) is a software program based upon Labview and is used to view
data acquisitions from the sensors. It has also the options for TEDS viewing, updating and
storing. One can create reports and logs based upon sensors acquistions.
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1.3 IEEE P1451 FAMILY OF
STANDARDS
IEEE P1451.1
It gives the concept of Common Object Model for the transducers and networks. It establishes modular,
flexible connections of network interfaces, transducers and control components in a Network Capable
Application Processor (NCAP). This allows any transducer to be used on any control network with an
appropriately configured NCAP.
IEEE P1451.2
It defines a standard synchronous serial communication protocol between the transducers and NCAP. It
also gives the concept of TEDS (Transducer Electronic Data Sheet) that is attached with the transducer
containing its general, calibration and correction information.
IEEE P1451.3
This standard proposes multi-drop transducer network i.e. different transducers sharing the same bus.
Thus this allows multiple channels sharing a single transmission medium with different time delays and
addressing possibilities.
IEEE P1451.4
It defines a MMI (Mixed Mode Interface) for transducers i.e. that not only the physical values can be
sent to the DAQ systems but also the digital values from the TEDS will be sent. This enables these
transducers to have a self-describing capability thus making them plug-n-play in the systems.

CHAPTER2
IMPLEMENTATION

2.1 CHOOSING PIC18F452 as STIM
It is a million-dollar question as why we have chose PIC as STIM? The answer to this question is
simple; due to its versatility. When we were searching for the best device that can work as STIM,
we wanted to go for one which has as many no. of features internal to it as possible
device that has many features inside it, for example it should have:
 independent ADC channels with good resolution
 sufficient amount of internal memory
 sufficient amount of programming memory
 ability to communicate over synchronous and asynch
 multiple external interrupts with priorities setting allowed.
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cient asynchronous serial protocols and
ultiple Figure 2: STIM device unknown
possible. STIM is a
ronous
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When we compared our requirements with different devices, we found PIC18F452 an exactly
matched device. Following is the description how this 40-pin device promises to fulfill the needs
of STIM:
 8 independent 16-bit ADC Channels with optional external references
 256 bytes of internal memory
 8k of programming memory
 Supports SPI (Serial Peripheral Interface), I2C (Inter Integrated Circuit and USART
(Universal Serial Asynchronous Receive and Transmit)
 3 external interrupts, INT0, INT1 and INT2 with INT0 has the highest priority while the
priority of INT1 and INT2 can be changed to 2nd order or 3rd order.
As one can see that PIC18F452 fulfils all the major requirements of an efficient STIM. One more
reason for using PIC microcontroller is the ease in programming. With its easy to understand
programming editors, it is very easy to program the IC to perform complex controlling functions.

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