Jaya Prakash Narayan College of Engineering ,Mahabubnagar: 2014

Thursday 21 August 2014

Scales in Engineering Drawing

Engineering Drawing - Scales

Dimensions of large objects must be reduced to accommodate on standard size drawing sheet. This reduction creates a scale of that reduction ratio, which is generally a fraction. Such a scale is called reducing scale and that ratio is called representative factor.

Similarly in case of tiny objects dimensions must be increased for above purpose. Hence this scale is called enlarging scale.
Here the ratio called representative factor is more than unity.

Representative factor (r.f.) = Dimension of drawing / Dimension of object

Length of scale = r.f. * max. Length to be measured.

Types of scales:

Plain scales ( for dimensions up to single decimal)
Diagonal scales ( for dimensions up to two decimals)
Vernier scales ( for dimensions up to two decimals)
Comparative scales ( for comparing two different units)
Scale of cords ( for measuring/constructing angles)
Plain scale

Plain scale: - This type of scale represents two units or a unit and its sub-division.

Problem:- Draw a scale 1 cm = 1m to read decimeters, to measure maximum distance of 6 m. Show on it a distance of 4 m and 6 dm.

Construction:-

Calculate r.f. = Dimension of drawing / Dimension of object
r.f. = 1cm/ 1m = 1/100
length of scale = r.f. x max. Distance
= 1/100 x 600 cm
= 6 cms

B) Draw a line 6 cm long and divide it in 6 equal parts. Each part will represent larger division unit.
C) Sub divides the first part which will represent second unit or fraction of first unit.
D) Place (0) at the end of first unit. Number the units on right side of zero and subdivisions. On left-hand side of zero. Take height of scale 5 to 10 mm for getting a look of scale.
E) After construction of scale mention its rf and name of scale as shown.
f) Show the distance 4 m 6 dm on it as shown.

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Article by

Department of HUMANITIES AND SCIENCE

Jaya Prakash Narayan College of Engineering

Software Testing Quality and Challenges in Software Testing

When a program is executed, the developers of the program are concerned with the correctness and performance of the implementation of the program. Software engineers must ensure that the software systems must achieve an appropriate level of quality.

The software quality assurance is defined as the measuring and monitoring the strength of development process. It is also known as verification. i.e. verifying the process is nothing but SQA.

There are two types of factors in software quality.

(1) Technical factors

(2) Non-technical factors

The technical factors are concerned with the following

(1) The software should meet with the customer requirements (i.e. functionality of s/w)

(2) The software should meet with the customer expectations (i.e. usability, reliability and performance)

The non-technical factors are concerned with the following

(1) The cost to purchase the license of software

(2) The time to release into the market

Hence to achieve the good quality software, generally the following principle is followed.

SQA+SDLC+SQC.

The actual testing takes place at SQC (Software Quality Control).

The quality is defined as matching with the customer expectations and customer requirements.

Now we deal with the validation of the process.

The validation means that the actual testing of software from the end user point of view.

It checks that whether the product is fit to use or not. (In verification, we check that whether the product is fit to specification or not).

Challenges in Software Testing

In general, the test engineers face the following challenges or risks during testing.

(1) Lack of time

(2) Lack of resources

(3) Lack of skills

(4) Delay in delivery

(5) Lack of communication.

To overcome the above mentioned challenges in testing, generally the testing teams follow the ad hoc testing styles.

There are different types of ad hoc testing styles.

(1) Buddy testing

(2) Monkey testing

(3) Exploratory testing

(4) Pair testing

(5) Be bugging

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Article by

Dept. of CSE

Jaya Prakash Narayan College of Engineering

A Highly Efficient Solar Lantern by Texas Instruments

A Street Light Solution - System Block Diagram

A Highly Efficient Solar Lantern Block Diagram

TI had designed solar lantern solution specifically for Indian rural market with circuit protections, more shelf life, user control interface with dimming feature and the most important thing, very high power efficiency providing great backup time.

Key Solution Features:

Boost Drive Stage for 3W (3 LEDs in Series)

Stand-by current < 500uAReverse

Polarity protection for Battery and Panel

4 Stage Charging profile for Battery

User interface in form of Keys and Indication LEDs

Under-voltage Cutoff

TI Hero Products in this Solution

MSP430G2231

TLV70433

TPS61165

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Article by

Dept. of ECE

Jaya Prakash Narayan College of Engineering

How A Cell Phone Call Works

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Article by

Dept. of ECE

Jaya Prakash Narayan College of Engineering

Family of Microcontrollers

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Article by

Dept. of ECE

Jayaprakash Narayan Educational Society Group of Institutions

Golden Rules For Electronic Circuit Design

- All components must conform to the specified temperature range. For resistors, de-rating of power rating at peak temperature must be considered. For capacitors de-rating of capacitance, leakage and increase in ESR at peak temperature may be important. For other components such as diodes and transistors, parameters such as recovery times and current gain vary with temperature and must be considered at extreme temperatures. In summary, no design calculation must be left to chance (as is often the case with designs put together in haste), temperature effect calculations are indispensable to success.

- Devices connected to interfaces must be well protected from ESD (Electrostatic Discharge) damage. ESD damage may occur at the time of prototype construction, during manufacturing or during use. Contrary to common misconception ESD at the time of production may not render a device defunct, but may cause progressive deterioration which may result in field failure. Therefore built in ESD protectors are necessary and Mansi Engineering ensures that all its designs incorporate them where necessary. IEC 61000-4-2 is a widely accepted ESD test conformance standard. ESD protectors include MOVs, TVS diodes, ESD Protection Clamping diodes and the newly introduced Polymer based devices. Selection of the right type of protector depends on capacitance that can be tolerated without signal deterioration and other factors such as tolerable leakage current, cost, pin outs and board area required. In addition, ESD protectors must be placed as close as possible to the signal entry location and as far away as possible from the device being protected so that the resulting large trace impedance attenuates the high frequency ESD energy as it travels towards the protected device. Zener or TVS diodes must be placed between power supply lines and ground to absorb ESD energy traveling via other protector diodes towards power supply line, while the device is powered off.

- Terminals connecting to inductive sources must be protected from switching overshoots or undershoots using clamping diodes or other devices. Long traces that carry heavy currents may act as sufficiently large inductors to cause unwanted switching transients and therefore protection is necessary.

- Signal lines must be well protected from radiated and conducted EMI. Ferrite beads and capacitor filters are effective means to block EMI.

- Within limits of budget, every design must incorporate sufficient protections from wrong connections, such as battery polarity reversal and accidental grounding of an output line. Large resistors are recommended to be used in series with microprocessor outputs driving drivers that drive large inductive loads. This ensures that the processor is well protected from switching transients.

- Functioning of the system at power up must be analyzed. For example it is important to deploy pull-up resistors on microprocessor output signals that need to be high on power up. Similarly functioning of relevant parts when powering down deliberately or accidentally, must be analyzed. For example, when processor state saving is involved during power down, a power down detect functionality might prove indispensable.

- For EMC, it is recommended to use inductors (preferably shielded) to slow down sharp current rise and fall times. Sharp current transients cause a sharp varying and traveling electromagnetic field.

- It is important to assign test points to relevant nets. Especially all ground and power nets, bias or threshold points and other serviceable signals must have a test point, which add convenience during testing and troubleshooting. Test points may be free vias with suitable drill size to accept and retain stainless steel needles or header leads.

- Having an on board power on LED indicator has its own importance. It warns the engineer and people around that the circuit is live and prevents accidents."

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Article by

Dept. of ECE

Jaya Prakash Narayan College of Engineering

Jaya Prakash Narayan College of Engineering ,Mahabubnagar

About us :

Vahini Educational Society, registered in the year 1997 has established Jayaprakash Narayan College of Engineering (JPNCE) by experienced Academic Visionaries and Industrialists with a view to provide high quality education in the technical field and follow principles, morals, ethics and ideals of Bharat Ratna Lok Nayak Late Sri Jayaprakash Narayan. Hence the college is named after him. This college is located in the rural area in Mahabubnagar District and it is the first college to be established in Mahabubnagar district. There are total 7 colleges in the district and this college is reckoned by all stake holders as one of the best colleges of the district. The college is about 8 Kms from Mahabubnagar and 100 Kms from Hyderabad, & 75 Kms from Rajeev Gandhi International Airport, Hyderabad & is well connected by Rail, Road and Air.

Mahabubnagar is one of the backward districts of Andhra Pradesh and is coming up in the industrial field in the recent years. A few Technical Educational Institutes are also established in the district. Jayaprakash Narayan College of Engineering is the first technical institution to be established in the year 1997 to produce engineers required for the local development and in addition, providing opportunities for the students in this area. There are large numbers of reputed giant industrial establishments existing in this rural area such as M/s. HBL Power Systems Ltd., M/s. Saint Gobain, M/s. Pitti Laminations etc. A branch of Remote Sensing Agency, a Govt. organization is also available within 50 Kms from the college. This institute is preparing graduates to be useful for employment in the above organizations and there is a close collaboration with some of the industries in choosing the students of Jayaprakash Narayan College of Engineering to suit to their needs. There is an impressive Industry-Institute Interaction taking place for the growth of this region. Many of the I.T. professionals graduated from this institute are being absorbed by multi national companies like M/s. Satyam Computers, M/s. CMC, M/s. Wipro Computers etc. and also abroad. Electronic Engineers produced by this college are getting absorbed in organizations like ECIL, Hyderabad and other Electronic Industries within India and outside. The graduates produced by EEE Dept. of the college are being absorbed in APSEB and other Electrical Industries. Recently, Govt. of A.P. has decided to develop Fab City in the region which provides lot of opportunities for the students of Computer Science Engineering, Electronics & Communication Engineering and Electrical & Electronics Engineering branches. For all the ongoing development, core infrastructure in Mechanical and Civil Engg is also in high demand.

With recent relocated International Airport being established, situated about 70 kms from Mahabubnagar District, Industries & Infrastructure development activities have been on exponential rise in the district. JPNCE has been continuously making efforts to bring in the best facility in the campus through entering into MOUs with well performing Institutes like NIT, Warangal and also with many local industries & industries in Hyderabad. The effect of this has created increased enthusiasm and awareness amongst students who are bringing laurels by securing First Prize at Technical Symposium inside and outside the state of A.P.

VISION :

To Develop this rural Technical Institution to the level of International Recognition.
To Achieve Academic Excellence.
To Prepare the Students and staff to meet the Global needs of Industry and Society.

MISSION :

To Mould the Students to achieve 100% Employability
To Achieve Deemed University Status & Self Sufficiency.
To Include Ethical, Moral & Value – based Educational System in the Institution.

Quality Policy :

The Institute is committed to Academic Excellence and Overall Personality Development of the Students.
To Adopt innovative techniques in feedback practices for achieving continual improvement.
To Imbibe ethical practices among staff and students creating social awareness and responsibility.

Jaya Prakash Narayan College of Engineering