MECHANICAL PROPERTIES OF BLACK COTTON SOIL … · tests such as Atterberg limits, sieve analysis, Hydrometer analysis, specific gravity, compaction and California bearing ratio (CBR)

Proceedings of the Multi-disciplinary Academic Conference on Sustainable DevelopmentVol. 2 No. 2 July 10 – 11, 2014, M.L. Audu Auditorium, Federal Polytechnic, Bauchi

MECHANICAL PROPERTIES OF BLACK COTTON SOIL STABILIZED WITH CEMENT

J.O Uloko and N.D. Usman

Department of Civil Engineering Technology, Federal Polytechnic, Bauchi. Bauchi State, Nigeria.

ABSTRACTIn order to provided alternative building and construction materials that will be cheaper and affordable than concrete based materials, this paper presents the compressive strength of black cotton soils stabilized with cement as such an alternative. Preliminary engineering properties’ tests such as Atterberg limits, sieve analysis, Hydrometer analysis, specific gravity, compaction and California bearing ratio (CBR) were conducted on the soil to determine it as an occurring clay soil of black cotton soil type. The results obtained showed that the clay content is 44.4% as against 41.0% silt content and 14.6% sand. Also, the dark brown soil had liquid limit of 31%,plastic limit of 25%,plastic index of 6.0%,CBR of 9.2 and linear shrinkage of 8.9%,these properties in addition to others make the black cotton soil inadequate for both sub-base and base course material in pavement construction, hence the need for the stabilization. The soil was then stabilized with 2%,4%,6% and 8% cement and cured for 7,14 and 28 days before testing. After 28 days of curing the following compressive strengths were obtained 2.89N/mm², 3.94N/mm², 4.44N/mm² and 5.16N/mm². The results show that cements stabilized black cotton soil can be used for constructions respectively. Further investigation should be carried out on stabilization with other common stabilizers.Keywords: Black cotton soil, stabilized with cement, compressive strength, density properties, NBRRI, ASTM and BS (Standards)

INTRODUCTION:Black cotton soil or ‘’turf’’ are residual sub-tropical clays, which usually occur over volcanic rock such as basalt. The black or deep grey or brown color could be attributed to the presence of organic matter. They are rich in calcium carbonate with the mineral montmorillonite being the dominant constituent. According to Ola (1975), black cotton soils may contain as high as 68% clay and as low as 6% sand. So they are basically clayey soils, expansion of clays is a duly occurring material phenomenon that is caused by wetting of the soil consequently resulting in volume increase. Nowadays, it is well acknowledge that swelling of clays may include considerable distress and thus serious damage to civil engineering structure. Black cotton soil is highly plastic and expansive montmorillonite clay minerals. The presence of these clay minerals along with the flat terrain in which they occur, the attendant poor drainage and the distinct alternating wet and dry season makes the black cotton soil highly problematic as foundation for building and road structure. This is due to the characteristic phenomenon of high swelling on water absorption and high shrinkage on drying (Ibrahim, 1977), (Ola, 1978). The volume changes however, are contained to an upper critical zone of the soil, which are usually about 1.5m thick; below this layer the moisture content remain more or less the same (Ola, 1993). In Nigeria, black cotton soils are typically found in the low-lying area of the North east State of Borno, Gombe, Adamawa, Yobe and Taraba States. They occur in discontinuous sketches as superficial deposits; usually not more than 2m thick. Black cotton soils are also formed from weathering of sedimentary rocks, which are of volcanic origin. The turf and ashes are made of volcanic dust, which is essentially a collection of minutes particles of volcano glass, these materials readily weather to form montmorillonite clays which is chief clay minerals of the black cotton soils in area where the rate of evaporation exceed precipitation rate, poor leaching alkaline condition and retention of magnesium and calcium in the soil formation of black cotton soil is highly favored. According to Nigerian Building and Road Research Institute (NBRRI, 1983),’’black cotton soils are dark colored expansive clays, characterized by the phenomena of swelling on absorption of water and shrinking in drying. These characteristics make them highly problematic as foundation for both building and road structures, such soils are common products of tropical weathering and are encountered in several parts of the world.Also the laboratory test data show that all black cotton soils are not the same, the variations in their particles size distribution, clay and silt contents, liquid and plastic limits and swell potential are so wide that black cotton soil cannot be considered as just one type of soil. A road pavement constructed over an expansive black cotton soils are generally ‘’stabilized’’ with additives like lime and cement. These additives or stabilizers in essence replace the active sodium by the less active calcium ions, this paper is aimed at investigating the compressive strength of black cotton soil stabilized with cement.

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MATERIALS AND METHODSPreparation of materialsSoil: The soil used in this study is naturally occurring expansive soil black cotton soil (dark grey in colour) obtained along Km 24 Gombe – Biu road in Yamatu Deba Local Government Area of Gombe State using the method of disturbed sampling. The location lies within latitude 10° 19’N and longitude 11° 30’E. In terms of extent of deposit, black cotton clays are not restricted to the area of study but are wide spread throughout the North – Eastern Nigeria.Ordinary Portland cement (OPC) of “Ashaka cement” brand was used. It exhibited all the qualities requires of good cement by visual means, touch and hydration, which conforms to the specimen specification of BS 12 (1978)MixingMix proportion was specified by volume and the ‘’dry mix process’’ (Ndububa, 1995) was adopted. It involved thorough mixing of cement stabilizer with black cotton soil in their dry state before gradually adding water while the mixing process continued to a required consistence. However, the mix proportions used for the stabilizers were 2%, 4%, 6% and 8%of the total volume of the mixes respectively. The mixing was done mechanically and segregation was avoided.Compaction and curing The mixed materials were introduced into 150 x150 x150mm cube moulds in three layers with hand trowel; each layer was compacted with the aid of a 2.5kg rammer, three samples were prepared for each experiment from which average were determined. The specimen were demoulded after 24 hours and cured by Plastic sheeting with black polythene bag to ensure air tightness and prevent evaporation of water for the number of days of curing.Compressive strength testingThe compressive strength test was carried out in accordance with British Standard specification (BS 1881 1970) with a compressive machine, the compressive strength is the ratio of the crushing force and the cross-sectional area of the sample. Also weighing of specimen was conducted before crushing to determine the densities of the cubes.RESULTS AND DISCUSSION Preliminary tests results on the black cotton soil as shown in Table 1., shows that it is not suitable for use as a construction material for roads in its natural form based on the Highway Research Board (1943). The results shows that strength of black cotton soil stabilized cement increased with increase percent of stabilizer and age, the 28 days strength of 5.16 N/mm² for 8% BCSC exceeded the recommended strength of 2.5N/mm² for sand/Crete blocks (NSO, 1995) and also far exceeded the minimum recommended strength of 1.5N/mm² for building bricks (Ndububa, 1995). The densities also increased with percent of stabilizer increase which attests to the stronger bonding of particles as a result of the cement content.The results of the density and compressive strength tests are presented in Table 2 to 6, the results show that compressive strength increases with curing days and percent of stabilizer and the trend is as presented in figure 1, 2 and 3 respectively.Table 1: Summary of preliminary test results of untreated black cotton soilS/No. TEST/PROPERTY RESULT VALUE1. In situ moisture content (%) 31.42. Passing BS sieve 200 96.03. Specific gravity,Gs 2.344. Liquid limit, LL (%) 31.05. Plastic limit, PL (%) 25.06. Plasticity index PI (%) 6.07. Linear shrinkage LS (%) 8.98. Group index 229. Color Dark brown 10. Maximum Dry Density MDD (mg/mᵌ) 1.2111. Optimum moisture content OMC (%) 15.812. California Bearing Ratio CBR (%) 9.213. Unconfined Compressive Strength UCS (KN/m²) 6414. Free swell (%) 8015. AASHTO Classification A-7-616. Black cotton soil classification CH17. Sand content (%) 14.6

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18. Silt content 41.019. Clay (%) 44.4

Table 2: Compressive strengths and Densities of Plain Black cotton soil with 0 %Curing periods (days) Average cube density

(Kg/mᵌ)Average crushing load (KN)

Average compressive strength (N/mm)

7 1600 11 0.4914 1833 14 0.6128 2033 27 1.21

Table 3: Compressive strengths and Densities of Black cotton soil stabilized with 2% cementCuring periods (days) Average cube density



7 2033 49 2.1814 2167 57 2.5028 2267 65 2.89




7 2067 70 3.1114 2433 74 3.3028 2500 89 3.94




7 2567 92 4.0914 2700 96 4.2828 2900 100 5.16




7 2933 103 4.5114 3067 108 4.7328 3300 116 5.16

Fig. 1: Density of Black Cotton Soil Stabilized with Cement

Fig. 2: Compressive Strength of Black Cotton Soil Stabilized with Cement Cement

Fig. 3: Compressive Strength of Black Cotton Soil Stabilized with Cement Cement

CONCLUSION

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From the work carried out, The natural black cotton soil was classified as A-7-6 or CL in the AASHTO and USCS. Soils under these groups are of poor engineering benefit.The compressive strength of black cotton soil stabilized with cement met the standards for slope fills, building blocks, bricks and plastering, the results also showed the average densities of all the materials are above 1600 kg/mᵌ recommended for maximum density for light weight concrete (D of E, 1973). Therefore, they cannot be used as light weight building materials, in the case of road pavement constructions, plain black cotton soil will need be stabilized to meet the requirement for sub-bases.

REFERENCESAASHTO (1986) Standard Specifications for Transportation Materials and Methods of Sampling and Testing. 14th

Ed., Am. Assoc. of State Highway and Transport Officials (AASHTO), Washington, D. C ASTM (1992) Annual book of ASTM standards

B.S. 1377 (1990) “Methods of testing soil for civil engineering purposes”. British standards institute London. B.S. 1924 (1990) “Methods of testing for stabilized soils” British standards institute London. Moses, G. (2008) “stabilization of black cotton soil with ordinary portland cement Using Bagasse ash as

admixture” IRJI Journal of Research in Engrg. Vol.5 No.3 , pp. 107-115 Ndububa, E.E (1995): An appraisal of vegetable fibre reinforcement in construction. Thesis (M.Eng.)

University of Nigeria, Nsukka. Pp.95 NBRRI, (1983): Engineering properties of black cotton soils of Nigeria and related Pavement design.

Nigerian Building and Road Research Institute, Research Paper No., 1 – 20.Nigerian General Specification (1997) Bridges and Road Works. Federal Ministry of Works, Lagos, Nigeria

Ola, S.A.(1983)."The geotechnical properties of black cotton soils of North Eastern Nigeria" In: S.A. Ola (Editor. Tropical soils of Nigeria in Engineering Practice, A.A. Balkema, The Netherlands, Rotterdam,155-171.

Osinubi, K. J. (1997). 'Soil stabilization using phosphatic waste.' Proceedings 4th Regional Conference on Geotechnical Engineering, GEOTROPIKA '97, Johor Bahru, Malaysia, 11 -12 November, 225 – 244.

Osinubi, K. J. (1998a). “Influence of compactive efforts and compaction delays on lime treated soils”. Journal of Transportation Engineering, ASCE, Vol 124, No. 2, 149 – 155.

Osinubi, K.J. (2000a). “Stabilization of tropical black clay with cement and pulverized coal bottom ash admixture”. In: Advances in Unsturated Geotechnics. Edited by Charles D. Shackelford, L. Houston and Nien-Yui Chang. ASCE Geotechnical Special Publication, No.99, pp.289-302

Osinubi K. J. and Eberemu, A. O. (2005). “The use of blast furnance slag treated latrite in attenuation of ground contaminants.” Proc. Of The Nigeria Marterial Congress 2005 (NIMACON). Nov. 17th – 19th 2005. Zaria, Nigeria. pp. 28-35.

Osinubi, K.J., Ijimdiya, T. S. and Nmadu, I. (2008). “Lime stabilization of black cotton soil using bagasse ash as admixture.” Book of ABStracts of the 2nd International Conference on Engineering Research & Development: Innovations (ICER&D 2008), Benin City, Nigeria, 15-17 April. Technical Session 9B – Construction and Structures, Paper ICERD08058, pp. 217 – 427.

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DESIGN AND IMPLEMENTATION OF A MESSAGE CRAWLER DISPLAYWITH PS2 KEYBOARD INTERFACE

A.Y. Ibrahim, L.Maijama’a, M.G. Aliyu, M.Fatima

Electrical and Electronic Engineering Technology Department School of Engineering Technology. Federal Polytechnic, Bauchi, P.M.B 0231 Bauchi, Bauchi State, Nigeria.

ABSTRACTThis paper presents the design of a Moving Message Crawler Display System (MMCDS) also called Microcontroller Based Message Board (MBMB) via PS2 keyboard entry with serial communication using PIC16F876A microcontroller. The work is a solution to the problems of inadequate sign post and good direction guide in most complex building, high-ways and other public facilities like electrical polling units. Combinations of hardware and software components are used to achieve the desired result of high brightness, animated and attractive message display unit. Programming is used to intelligently steer the entire associated electronic circuits on how to interact with its externality. The software design is based on the assembly language written and tested with PIC microcontroller. Microcontroller digital electronic components combined with discrete electronic components are used with ULN 2803 driver to drive a display unit which is made up of high efficient and low power consuming Light Emitting Diodes (LEDs) as electronic display components. Both hardware and software of the developed prototype are fully functioning and the tests have been successful. In conclusion, the MMCDS system can replace the conventional entry methods.Keywords: MMCDS, PS2 keyboard, PIC Microcontroller, ULN 2803 Driver, and LEDs

INTRODUCTIONThe Message Crawler Display (MCD) is a mode of advertising system that has grown over the years. An important part of the system is a formation of LED’s arranged in a dot matrix formation and also a PS2 keyboard interfaced. LED technology is one of the most advanced technologies today as they are very efficient and requires very little power to produce a visible bright and eye catching light. The MCD uses this technology with an embedded controller technology to be able to display information from a distance. The crawling text, graphics, and animation capture the attention of the bystander in a dynamic way making the message more noticeable and more likely to be remembered. The message can be updated frequently and easily to keep the information current. The aim of this paper is to design and implement a microcontroller based message crawler with a PS2 keyboard interfaced. An additional electronic circuitry has been incorporated in the system to achieve amplification and switching so as to provide good resolution when viewing the display.

MethodologyThe Message Crawler Display (MCD) operates based on the instruction stored in the PIC memory. The microcontroller ,driver unit, counter unit and the system operating switch are powered from the power supply through LM 7805 regulator as shown in the system block diagram of Figure 1.The interfacing keyboard receives its power from the PIC. An input from the keyboard will be sent to the processing unit in the PIC to process as required by the program. The instruction program illustrated in Figure 2 will determine the sequence of operation. After being processed by the processor in the Central Processor Unit (CPU), it will send the output to the display unit through the drivers and the counters.

Data line

Microcontroller

PIC16F876A

LM 7805

Driver

Power Supply

Switch

LED Dot Matrix Display

Keyboard

Counter

LM 7805

SYSTEM INPUTS

PIC INPUT PORT

PROGRAM INSTRUCTIONS

SYSTEM INITIALISATION

CENTRAL PROCESSING UNIT

PIC OUTPUT PORT

Figure 1: System Block Diagram

Figure 2: PIC Process Diagram

Power SupplyThe power of the system is designed to work based on the following voltage level of 220V/15V A.C, 50HZ, 1A step-down transformer, a bridge rectifier with IN4007 diodes, a filter capacitor, LM7805 IC regulator and a green coloured LED for power indicators. The LM7805 IC regulator was used to supply the whole circuit with 5V in each stage of the design.TransformerBased on the transformer requirements the peak voltage Vm and maximum current Im is given by (1a and 1b ) respectively. (Boylestad and Nashelshky, 1996). Vm = √2 Vrms = 21.21V ... (1a)

Im=√2×Irms = 1.414A … (1b)

Where Vr.m.s and I r.m.s are the roots mean square voltage and current with the values of 15V and 1A respectively as chosen design parameters.RectificationPIV = Vpeak = Vm … (2)Hence a IN4007 with PIV =50V can be used from the output of the rectification is dc voltage Vdc

Vdc= 2πVm-2VD … (3a)

V d c = 12.11V

Idc =2πIm … (3b)

Idc = 0.900063A

Where Vm = 21.21V, Im = 1.414A and VD= 0.7V = Forward bias voltage drop of the 2 active diodes.

FilteringThe capacitor value was chosen on the basis that its value can hold the peak to peak voltage at ripple factor R f

of 0.05% of Vm

Vripple =Rf x Vd c … (4)

Vripples = 0.006055V.

Vripple= Idc4√3FC (Boylestad, and Nashelshky, 1996). ... (5) The

Capacitance value in Farad will be determine by (6)

C= Idc4√3FVRipples …

(6)Where F=frequency= 50HzC =4595µF.For proper filtering the standard value of capacitor used is 4700µF, 50V.Microcontroller UnitA microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications. The microcontroller used in this work is 16F876A which is serving as the central controlling unit for the entire system. Crystal OscillatorThe crystal oscillator provides resonant network that supply the necessary stable clock pulse to the microcontroller via pins 9 and 10 of the microcontroller. It also determines the execution speed of the microcontroller as it clocks it and emits pulse at fixed frequency. The crystal oscillator used is the LFX 351H, 4MHz for proper matching with microcontroller requirements.From the data sheet we got the value of the load capacitance CL of the crystal oscillator used for this work as 16pF. C1 and C2 need to match this load capacitance value using (7)

CL ꞊ C1×C2C1+C2 + CStray (Stitt, and Kunst,1991) …

(7)The stray capacitance in the circuit was to be in the neighbourhood of 2-5pF. Therefore since CL is already stated in the data sheet to be 16pF and we know Cstray to be approximately 5pF, all we need to test is the value for C1 and C2 to make sure that it will match CL taking into account Cstary.

Therefore, from (7), CL ꞊22pF×22pF22pF+22pF+5pF ꞊ 16pF

We take 22pF value that gives much better result.Display UnitThis unit used an array of LEDs with same rating arranged in dot matrix technique that has a dimension of 32X7 LEDs i.e. thirty two columns and seven rows to display seven character in the matrices as shown in Figure 3a.

Figure 3a: 5X7 LED MatrixOne current limiting resistor R is sufficiently used per row since all the LEDs have the same rating. Figure 3b and (8) are used to determine the value of R.

http://en.wikipedia.org/wiki/Integrated_circuit

http://en.wikipedia.org/wiki/Personal_computer

http://en.wikipedia.org/wiki/Microprocessor

http://en.wikipedia.org/wiki/Random-access_memory

http://en.wikipedia.org/wiki/Programmable_read-only_memory

http://en.wikipedia.org/wiki/NOR_flash

http://en.wikipedia.org/wiki/Input/output

D1

5V=VS

R

Id

Figure 3b: LED Circuit

R=Vs-VdId … (8)

R=500ΩWhere, Vd = 2.5V and Id =5 mA.The approximate value of the standard resistor R used is 1kΩ, 0.5w (standard value). Therefore resistors R1 to R7 are the same and equal to R. Figure 3c, (9) and (10) are used for the design of the circuit that switches ON of OFF the LEDs.

Figure 3c: Typical Transistor Switch

VCC=5V, VCE=250mV, VBE=700mV, IB=5mA, VB=2.5V, β=110, VE,R1=? VB<VBE , to operate as switch

R1=VBIB=2.5V5mA=500Ω

… (9)

VE=VCC-VCE=5-0.25=4.75V … (10)

This 4.75V is enough to light up an LEDDriver UnitThis is made up of ULN2803 octal peripheral driver arrays; it is an NPN Darlington transistors through which the anodes of the LEDs are provided with 0V as the output. Each transistor in the ULN2803 should be turned ON (one at a time) by the outputs of the HCT4017 counter chip. The design requires a HIGH logic level at the input of the switch in order to give out a LOW which will correspond to the 0V voltage rail. In essence, the transistor switch in this case acts as an inverting buffer or better said it operates in the active LOW mode. Once any output of the counter goes high, the corresponding transistor gives out a LOW to the cathodes of LEDs to which it is connected. All the row switches are identical; therefore the design for one will be the same for all columns as shown in Figure 4 and lighting pattern of LEDs in Table 1.

R3

R2

R1

Q3NPN

Q2NPN

Q1NPN

4017

CP1

CP0

MR

Q0

Q1

Q2

Q3

Q4

Q5

Q6

Q7

Q8

Q9

Q5-9

U1

Figure 4: Column Switch with LED and CounterTable 1: Lighting Patterns of LEDs

PIN1

PIN2 PIN3 IN4 PIN5

RB0RB1RB2RB3RB4RB5RB6

Figure 5: Implemented System Model

Transistors Q1, Q2&Q3 sink current from the cathodes of the LEDs of each row. This action completes the circuit

in order for a given LED to be lit. Table 1 shows the light up condition for RB7 – RBO from the controller when a letter such as “L”, when the first column is scanned, i.e. PIN1 is selected by the decoder controlled by the RA port of the PIC then at first a bit pattern corresponding to ‘11111111” is sent out on the RB ports of the PIC and subsequently the next column i.e. PIN2 is selected by the PIC and again the corresponding bit pattern is sent out through the RB ports in this case “00000001” and the process is repeated for the other levels but this is done at a very high speed such that human eye thinks all the LEDs are on at the same time.KeyboardThe keyboard is used in order to change the message in future. PS2 connector is the interface unit. The output of keyboard is given to microcontroller through an input interface. Input interface limits the incoming high voltage and current. To protect the microcontroller the incoming voltage should not exceed 5V. Microcontroller is a 28 pin IC, which contain 4 input-output port and its working frequency is 4MHZ. The output of the microcontroller is given to the led driver which is connected to the output interface, which transmits the information in the display panel.System software and Implementation

The rows data comes from the flash memory of the microcontroller; it can also be taken from an external EEPROM/Flash IC. In essence the character data (ASCII) are put into the flash memory. When any letter or number is pressed from the keyboard it clicks on it from the character data stored in the PIC16F876 microcontroller. The microcontroller consists of device that has a features an asynchronous Master Reset which clears the register, setting all outputs low independent of the clock. The ULN2803 serves as an interface, which drives the massage from right to left on the display unit. This will continue displaying and moving unless it is reset or put off. The software aspect of the project dealt with the coordination of the entire activities of moving message crawler system. Assembly language was utilized in the programming. Figure 5 shows the Implemented system model displaying some characters while Figure 6 shows the complete system circuit diagram.

Figure 6: Complete System Circuit DiagramResults and DiscussionHardware and software portion of the project are separated into stages while developing the overall system. The testing of the project started with the testing of power supply unit to ensure it could supply the required voltage (+5V) to the circuit. A test program was also used to test the hardware accuracy of the constructed dot matrix display to be sure the LED, s lighted up as it scrolled the characters across them. The project performs the required functions visualized at the proposal stage. However though satisfied with the software operation and simulation, less fulfilment was obtained from the illuminations received from the LED, s. It was discovered that the low illumination was as a result of the luminous intensity of the red LED, s selected at the beginning with luminous intensity of 5mcd at 10mA. So a standard bright red LED was selected with luminous intensity of 80mcd at10mA and was used.ConclusionFrom the paper objectives, skills were put together in order to complete this task; just like any other engineering design and construction exercise, the practical approximations and deductions cannot completely conform to that required theoretically. It is not professional to allow these variations go beyond tolerance.However, it is therefore right to conclude that this is a field of research that is worth investigating both in time and in resources.

REFERENCESAdo, G. (2011). Design and Implementation of a Moving Message Display, Abubakar Tafawa Balewa

University Bauchi: B.Eng Project Report (Unpublished)Agrawal H., Agrawal I.,Junagal K. and Tiwa M.(2013). Implementation of Moving Message Display Using

Microcontroller Controlled by PC. International Journal of Engineering trend in Electronics and Computer Science (IIETECS) vol. 2, Issue 4.

Ahmad, R. (2008). Design and Implementation of a microcontroller-Based moving message Display, Abubakar Tafawa Balewa Universit,y Bauchi: B.Eng Project Report (Unpublished)

Bello, A. M. (2010). Design and Implementation of a Moving Message Display, Abubakar Tafawa Balewa University, Bauchi: B.Eng Mini-Project Report (Unpublished)

Boylestad, R. L. and Nashelshky L. (1996).Electronics Devices and Circuit Theory,Prentice Hall:London. Forrest, M. M. (1984). Getting Started With Electronics, Highest Publications Limited: United States.Green, D. C. (1982). Digital Electronics Technology, Pitman Publishing Ltd: New Zealand.Horowitz, P. (1989). The Art of Electronics, Cambridge University Press: United States.Mims, M. (1984).The Engineering note book, Highest Publications incorporated, California U.S.A.Stitt, R. M. and Kunst, A. (1991). Signboard Design, Burr-Brown Application (Bulleting, Sept.1991)Theraja, B.L. &Theraja, A.K. (2002). A Textbook of Electrical Technology, S.Chand and Company Ltd:

New Delhi.

http://en.wikipedia.org/wiki/scrolling retrieved, 14th February, 2013. Blue Programmable LED Moving scrolling Message DisplayMain circuit diagram

Main circuit diagram

http://en.wikipedia.org/wiki/scrolling

Documents

MECHANICAL PROPERTIES OF BLACK COTTON SOIL … · tests such as Atterberg limits, sieve analysis, Hydrometer analysis, specific gravity, compaction and California bearing ratio (CBR)