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1 Asia Pacific Journal of Engineering Science and Technology 3 (3) (2017) Asia Pacific Journal of Engineering Science and Technology journal homepage: Full length article Microcontroller Based Photo-Electric Control System Chukwuedozie N. Ezema 1, *, Chinazam C. Ezema 2, ThankGod D. Ekwunife 3 1,2 Nnamdi Azikiwe University Awka Anambra State, Nigeria 3 Dodawn Computronix (Nig) Awka Anambra State, Nigeria (Received 21 September 2017; accepted 28 September 2017; published online 30 September 2017) ABSTRACT Street light has become part of our environment. Good street lighting provides and enhances safety in the community for residents, pedestrians and road users. Street lighting helps people feel safe and helps to reduce car crashes and crime. There are no specific hours for the lights to be on. Street lights are switched on and off by photo-electric control units, which react to changes in light levels. Thus the objective of this research is to design and implement a Photo-Electric Control System using AT89c51 Microcontroller and Light dependent resistor (Light/Dark Sensor). This was done by first comparing the different design approaches for each functional part to determine feasible and still affordable designs. The underlying hardware is complex and small, manufacturer-defined; power on reset routine must be run to place this hardware into an appropriate state before it can begin executing the user program. Running this reset routine requires that the microcontroller s oscillator is operating. Application software was used to implement street light Control function. Each individual module was designed separately. After successful simulation and testing, they were put together to create the finalized version. Then, analysis was performed on the entire materials comparable to components that are already available in the market. The outcome of the design implementation of the microcontroller based photo-electric control system was satisfactory. This study recommends that further research work be carried out to design and implement automatic lighting system with remote database capable of sending signal and situation reports regarding operational parameters such as battery life and maintenance tips. Keywords: Photo-Electric Control System; Microcontroller; Light Dependent Resistor 1. Introduction A Street light or lamp post is a raised source of light on the edge of a road or walkway, which is turned on or lit at a certain time every day [4,6,10]. Modern lamps may also have lightsensitive photocells to turn them on at dusk, off at dawn, or activate automatically in dark weather. Street lighting helps people feel safe and helps to reduce car crashes and crime. There are no specific hours for the lights to be on. A photo-electric cell, something that measures the level of * address: ecnaxel@gmail.com 2017 Author(s)

2 130 Chukwuedozie N. Ezema et al. Asia Pacific J. Eng. Sci. Tech. 3 (3) (2017) light, is used to make sure street lights come on when it starts getting dark and go off when it gets light. Street lights are designed to light the highway, including the footway [1, 3, 7]. This project is basically designed to automatically switch on/off street light when the environment is dark. A photo-electric cell (Light Dependent Resistor LDR) is used to measure the level of light, is used to make sure street lights come on when it starts getting dark and go off when it gets light [5,9,11,13]. The project is done for a complete understanding of how a street Light is controlled, the principles and processes involved. 2. Materials and Methods In this project, Design and Implementation of Microcontroller Based Automatic Street Light, an application software will be used to implement street light Control function. Each individual module was designed separately. After successful simulation and testing, they were put together to create the finalized version. 2.1 The MCU System Design Fig. 1 Block Diagram Overview of the Project The microcontroller switches on or off the street light through a relay when it receives signal from the LDR sensor circuit. The microcontroller basic operational circuit is used. The process of starting any microcontroller is a non-trivial one. The underlying hardware is complex and small, manufacturer-defined; power on reset routine must be run to place this hardware into an appropriate state before it can begin executing the user program. Running this reset routine requires that the microcontroller s oscillator is operating.

3 131 Chukwuedozie N. Ezema et al. Asia Pacific J. Eng. Sci. Tech. 3 (3) (2017) Where your system is supplied by a robust power supply, which rapidly reaches its specified output voltage when switched on, rapidly decreases to 0V when switched off, and while switched on cannot brown out (drop in voltage), then you can safely use low-cost reset hardware based on a capacitor and a resistor to ensure that your system will be reset correctly: this form of reset circuit is shown in Fig. 2. Where your power supply is less than perfect, and / or your application is safety related, the simple RC solution will not be suitable. Several manufacturers provide more sophisticated reset chips which may be used in these circumstances. Fig. 2 The RC Reset System All digital computer systems are driven by some form of oscillator circuit: the AT89C51 is certainly no exception. The oscillator circuit is the heartbeat of the system and is crucial to correct operation. For example, if the oscillator fails, the system will not function at all; if the oscillator runs irregularly, any timing calculations performed by the system will be inaccurate. Fig. 3 The Microcontroller Clock Input A simple way of improving the AT89C51 performance is to increase the clock frequency [1,14]. More modern (Standard) 8051 devices allow the use of clock speeds well beyond the 12 MHz limit of the original devices.

132 Chukwuedozie N. Ezema et al. Asia Pacific J. Eng. Sci. Tech. 3 (3) (2017) 129-140 2.2 The Input Interface Design Circuit The LDR is attached to a voltage divider circuitry.

4 132 Chukwuedozie N. Ezema et al. Asia Pacific J. Eng. Sci. Tech. 3 (3) (2017) The Input Interface Design Circuit The LDR is attached to a voltage divider circuitry. By using Kirchhoff s law the voltage obtained and which we can use to measure the level of light. As a result the system will automatically trigger the lights on during night and off during day time. 2.3 Choosing a resistor value The value of the resistor R will determine the range of the output voltage Vo. For best results you need a large 'swing' (range) for Vo and this is achieved if the resistor is much larger than the sensor's minimum resistance Rmin, but much smaller than the sensor's maximum resistance Rmax. You can use a multimeter to help you find the minimum and maximum values of the sensor's resistance (Rmin and Rmax). There is no need to be precise, approximate values will do. Then choose resistor value: R = square root of (Rmin Rmax). Choose a standard value which is close to this calculated value. 2.4 Swapping Over the Resistor and Sensor The resistor and sensor can be swapped over to invert the action of the voltage divider [1,12]. For example an LDR has a high resistance when dark and a low resistance when brightly lit, so: If the LDR is at the top (near +Vs), Vo will be low in the dark and high in bright light. If the LDR is at the bottom (near 0V), Vo will be high in the dark and low in bright light. 2.5 Using a Variable Resistor Fig. 4 Resistor A variable resistor may be used in place of the fixed resistor R. It will enable you to adjust the output voltage Vo for a given resistance of the sensor. For example you can use a variable resistor to set the exact brightness level which makes a chip change state. The variable resistor value should be larger than the fixed resistor value. For finer control you can use a fixed resistor in series with the variable resistor. For example if a 10k fixed resistor is suitable you could replace it with a fixed 4.7k resistor in series with a 10k variable resistor, allowing you to adjust the resistance from 4.7k to 14.7k.

5 133 Chukwuedozie N. Ezema et al. Asia Pacific J. Eng. Sci. Tech. 3 (3) (2017) If you are planning to use a variable resistor connected between the +Vs supply and the base of a transistor or comparator IC you must include a resistor in series with the variable resistor. This is to prevent excessive base current destroying the transistor when the variable resistor is reduced to zero. Fig. 5 LM324 Comparator LM324 Comparator used as buffer: Used to give signal to the microcontroller for a clean logic high or low for Street light switch ON/OFF. Fig. 6 Output Interface Design 2.6 The Output Interface Design (Display Unit) Driving a Relay with a Transistor (Transistor Switch) Driving a Relay, rated: 6V, 100 Ohm. Relay current, I = 6/ 100 = 60 ma The transistor has Beta (hfe) at least 100, for a collector current of 60 ma, to produce hard saturation; we want a forced beta of about 1/ 10 the active value. This means, transistor base current (I b ) is 60 ma/ 10 = 6mA and base-emitter drop = 0.7V. Hence, base bias resistor, Rb = (6 0.7)/ 6 ma = ohm. Since is not a standard resistor we can use1k standard. 2.7 The Power Supply (AC-DC) This module will consist of a center tapped Transformer that will step down the AC voltages from 220V to 12 Vrms. Then this will pass through a Full Wave Bridge Rectifier and a filtering capacitor to achieve close to DC voltage level.

6 134 Chukwuedozie N. Ezema et al. Asia Pacific J. Eng. Sci. Tech. 3 (3) (2017) Fig. 7 AC/DC Converter Schematic 2.8 Transformer Rating for Power Supply In the above diagram we have transformer rating of 0.5A (500mA) 12V secondary voltage. For the power supply this is a small transformer available at the market. And the research does not anticipate drawing the maximum current. To obtain the peak value of the output dc signal, we must multiply the transformer secondary rms voltage value by drop on diodes (there are two diodes on the current's path)., and subtract the voltage 2.9 Power Supply Rectifier Diode Rating With the full wave bridge rectifier, the current rating should be at least twice the load current maximum i.e. 2 x 0.5A or 1A good type to use is 1N4001-1N4007 rated 1A, 1000PIV, since research does not anticipate drawing the maximum current Power Supply Filter Capacitor Rating The value of the filter capacitors for the smoothing of the rectified voltage to minimal allowable ripple voltage can be computed using the formula below: Vr, value depends directly on the load current and inversely on the size of the capacitor. It can be estimated with this design formula:

7 135 Chukwuedozie N. Ezema et al. Asia Pacific J. Eng. Sci. Tech. 3 (3) (2017) Where f is the line frequency (60 Hz) and C is the capacitor capacity, its main parameter, usually measured in microfarads, nanofarads and picofarads For example, we have a 12VAC transformer, a diode bridge rectifier, and a maximum load current of 0.5 Amperes. Let's assume that the circuit we are going to feed requires that Vripple is not more than 2 Volt. We use the previous formula but reordered in this way. The nearest available size is 2200uF. Now we need to know what is the maximum voltage that the capacitor is going to be exposed to. We must consider the worst case, this is the V rectified peak in no-load condition, which means without deducting the voltage drop on diodes: Available commercial values are 16V, 25V, 35V, 50V, 63V... Well, 25V is ok for us. So, our capacitor is completely defined as "Electrolytic capacitor 2200uF x 25V". 3. System Implementation After successful simulation and testing, the project was put together to create the finalized version. Gathering of components from the specification in the circuit design precedes assembly or construction of the project. First, the component according to types and values were listed. The components were obtained at an electronic parts store in the market. Equivalents were sourced where necessary Resistors: Qty. Capacitors: Qty. 470 Ohms, 1/4W uf 25V 1 10K, 1/4W nf 1 1k, 1/4W 4 33pF 2 Transistor/Other Semiconductors: Qty. BC N4007 (Or Rectifier Module) 4 12 MHz Crystal 1 AT89C51 1 L LM324 1 Other Components: Qty 40 pin IC socket 1 Transformer 12V, 500mA 1 6 V Relay 2

8 136 Chukwuedozie N. Ezema et al. Asia Pacific J. Eng. Sci. Tech. 3 (3) (2017) Power Switch 1 Mains power cord 1 Vero Board (Big size) 1 Connecting Flexible wire 3yds 3.1 Hardware Implementation Strip/Vero Board Construction This involves the actual construction, which is the hard wiring of the circuit already prototyped. This consists of thin copper strips on one side and plain insulator board on the other side punched with hole at 0.1- inch matrix interval. Components are mounted on the plain side and soldered on the copper side. The copper strip runs from left to right and all components soldered on the strip are automatically joined together; where that is not required the strip is cut at appropriate point with drill or sharp object. All the components were mounted and soldered taking care that the transistors, electrolytic capacitors, diodes and the regulator were mounted the correct way round. While soldering the solder blobs should not touch the adjacent tracks otherwise there will be short circuit. Finally the IC should be mounted on the IC socket and tracks under the socket were cut to separate the pins. Input Interface Wiring Diagram The circuit arrangement below shows the input interface implementation wiring diagram. Fig. 8 Typical Input Transducer Microcontroller System Wiring Diagram Here we have the microcontroller system implementation wiring diagram. The relay transistor driver is connected at port p1.0 and the signal input port is at port p3.0.

9 137 Chukwuedozie N. Ezema et al. Asia Pacific J. Eng. Sci. Tech. 3 (3) (2017) The Output Interface Implementation Fig. 9 The Microcontroller System circuit The transistor relay driver wiring diagram make up the output wiring circuit.. Fig.10 Transistor Relay Driver

138 Chukwuedozie N. Ezema et al. Asia Pacific J. Eng. Sci. Tech. 3 (3) (2017) 129-140 4. System Testing and Integration 4.

10 138 Chukwuedozie N. Ezema et al. Asia Pacific J. Eng. Sci. Tech. 3 (3) (2017) System Testing and Integration 4.1 Software Implementation The code development is very much the same as for any computer. The microcontroller software development is based around a programming environment which will normally include: A text editor to develop the source program code An Assembler to produce a machine executable program with linked library modules Some form of debugging to allow the program to be tested Access to a programmer to program the target device. The job of the Assembler is to convert the source code produced by the programmer into an object code file [1, 3, 14]. It works by replacing each line of assembly instruction code with the corresponding machine code instruction that will be executed on the target microcontroller. The object code file cannot be executed on the target microcontroller. It needs to be passed through a program called a Linker. The job of the Linker is to take the object file produced by the Assembler and link it with standard library modules (that have already been pre-assembled into object files) to produce a complete working executable file that can be loaded into the memory of the microcontroller. Sometimes the Assembler and Linker are combined into one program so that assembling a source program automatically links it as well [12]. This is the case with the 8051 Assembler. Fig. 11 Stages in the Production of a Program Figure 11 below, shows the different stages in the production of a program. Note that the only stage that requires a lot of user input is the initial production of the user source code file. The rest of the program production involves using the Assembler and Linker tools. 'Filename' is the name of the program that the user is developing, thus the output of the Editor is the source file 'filename.asm'. The output of the Assembler is the object file 'filename.obj'.

11 139 Chukwuedozie N. Ezema et al. Asia Pacific J. Eng. Sci. Tech. 3 (3) (2017) The Linker links the 'filename.obj' with any Library object files that the program might use. It will also link any user object files that the user might want to include. The Linker output is the executable file to run on the target system. A program called a Loader or a microcontroller programmer takes your executable hex file from the hard disk and loads it onto the target microcontroller. 5. Conclusion Fig. 12 Flow Chart The system functioned satisfactorily. After sifting through many design options for all aspects of the device, the ones selected did the job, and did it well. The main feature of the system is that it has a dark/light activated sensor, which must agree to environmental condition before the street light can be activated. At dusk the LDR develops high resistance which makes the voltage divider circuit to output a logic high voltage and this is signals the microcontroller to switch on the street light. Likewise at dawn the sensor develops a low resistance a low logic voltage appears, and then the lights are switched off. This study recommends that further research work be carried out to design and implement automatic lighting system with remote database capable of sending signal and situation reports regarding operational parameters such as battery life and maintenance tips. References [1] Donald, B., Lighting Systems and Application. Ofor Education Limited. Lagos, , [2] Moris, M., Digital Design (Second Addition), 30-54, [3] Onovo, C., Electronic Devices and Circuit Theory. University Press Limited. Onotsha, 6-45, 2016.

12 140 Chukwuedozie N. Ezema et al. Asia Pacific J. Eng. Sci. Tech. 3 (3) (2017) [3] Maini, A.K., Hand Book of Electronics, 54-76, [5] Jacob, F., Handbook of Modern Sensors: Physics, Designs, and Applications, 3-16, [6] Ezugwu P. A., The 8051 Microcontroller. West Publishing Company, St Paul Minnesota, 14-32, [7] Ugwu, A. O. and R. F, Odoh., The 8051Microcontroller and Embedded Systems, Third Edition. Sunshine Inc, 2-9, [8] Paul, H. and H, Winfield., The Art of Electronics. Cambridge University Press, Second Edition, 6-22, [9] Sharma, M.C., Relays and Its Application BPB-Publishers, 56, [10] Abbas, V., Sensors: Advancements in Modeling, Design Issues, Fabrication and Practical, 17-22, [11]Muhammad, T., Ali M. & G. M, Janice, The 8051 Microcontroller and Embedded systems, Pearson Education, 7-12, 2002 [12] Kenneth, J. A., The 8051 Microcontroller. Parson Education Limited London, 17-22, [13] [14] ; Street Light Article

Microcontroller-Based Optical Displacement Weighing Scale

Microcontroller-Based Optical Displacement Weighing Scale Chukwuedozie N. Ezema *1, Chukwuebuka B Umezinwa 2 and Ernest O. Nonum 3 1 Department of Electronic and Computer Engineering, Nnamdi Azikiwe University