Engine management system is used for managing the ignition and airfuel requirements of an engine. In the case of a four stroke multicyUnder petrol engine, each cylinder has a piston performing all the four stroke (suction, compression, working or expansion and exhaust strokes) and the piston rod of each piston connected to a common crankshaft, and their power stroke at different times resulting in continuous power for rotation of the crankshaft.
The power and speed of an engine are functions of ignition timing and air fuel mixture. Henc, by controlling the the ignition timing and air fuel mixture it is possible to control the speed and power of the engine. In modern cars the ignition timing, opening and closing of valves at appropriate time, quality of air fuel mixture are controlled by microprocessor with the help of sensors. Fig. 1.16 illustrates the basic concept of engine management
In modern washing machine mechanical system is replaced by digital device i.e., a micro controller and the sequence of instruction i.e. program embedded in the microcontroller. The amount of detergent, amount of water, pH value are all sensed by the sensor and these sensed quantities or signals are input to the microcontroller. Based on the input and the software embedded, the corresponding output of the micro controller to carry out the different sequence of operations. The sequence of contrail can be varied by varying the software embedded at the manufacturing level of the washing machine. Figure 1.15 illustrates the block diagram of a microcontrolled based automatic washing machine.

For ignition timing the crankshaft drives a distributor which makes electrical contacts for each spark plug in turn a timing wheel. This timing wheel generates pulses which are input to the microprocessor. The microprocessor as per the program adjusts the timing at which high voltage pulses are sent to the distributor so that spark occurs at the right time resulting in complete combustion of the fuel. The quantity of air-fuel mixture entering the cylinder during suction stroke is again controlled by the microprocessor by varying the time for which the solenoid is activated to open the intake and the throttle position. The quantity of fuel injected into the air stream (to form air fuel mixture) is sensed by a sensor of the mass flow rate or calculated from other method, and then input to the microprocessor which in turn gives an output to control the fuel injection valve. This is only a very brief description of the engine management system using microprocessor.

ELEMENTS OF CNC MACHINE

INTRODUCTION
The primary function of any machine tool is to impart the required shape and dimensions to a work piece with the desired accuracy by removing excess material from the work piece in the from of chips or particles.
A computerized or computer numerical control (CNC) is a control system that utilizes dedicated, program stored computer or microcontroller to perform some or all the basic numerical control functions. A machine tool incorporating such a control system is called CNC machine. Fig. 4.1