Block diagram of a general purpose oscilloscope and its Basic operation

Block diagram of a general purpose oscilloscope:

the basic block diagram of a general purpose oscilloscope.

A general purpose oscilloscope consists of following parts.

1. Cathode ray tube                                                                        

2. Vertical amplifier

3. Delay line

4. Time base circuit

5. Horizontal amplifier

6. Trigger circuit

7. Power supply.

1. Cathode Ray Tube:

Cathode Ray Tube is the heart of the oscilloscope. When the electrons emitted by the electron gun strikes the

phosphor screen of the CRT, a visual signal is displayed on the CRT.

2. Vertical Amplifier

In Vertical Amplifier,The input signals are amplified by the vertical amplifier. Usually, the vertical amplifier is a wide

band amplifier which passes the entire band of frequencies.

3. Delay Line

Delay Line as the name suggests that, this circuit is used to, delay the signal for a period of time in the vertical section of CRT. The input signal is not applied directly to the vertical plates because the

part of the signal gets lost, when the delay Time not used. Therefore, the input signal is delayed

by a period of time.

4. Time Base Circuit

Time base circuit uses a uni junction transistor, which is used to produce the sweep. The saw

tooth voltage produced by the time base circuit is required to deflect the beam in the horizontal

section. The spot is deflected by the saw tooth voltage at a constant time dependent rate.

5. Horizontal Amplifier

In Horizontal Amplifier,The saw tooth voltage produce by the time base circuit is amplified by the horizontal amplifier before it is applied to horizontal deflection plates

6. Trigger Circuit

In theTrigger Circuit The signals which are used to activate the trigger circuit are converted to trigger pulses for the

precision sweep operation whose amplitude is uniform. Hence input signal and the sweep

frequency can be synchronized.

7. Power supply:

The Power supply voltages require by CRT, horizontal amplifier and vertical amplifier are provided by the power supply block.

 Power supply block of oscilloscope is classified in to two types

(1) Negative high voltage supply

(2) Positive low voltage supply

The voltages of negative high voltage supply is from -1000V to -1500V and the range of positive

voltage supply is from 300V to 400V approx.

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Traffic Light System proposal

Arduino Traffic Light System

This circuit was tested and worked properly!

 

Here is a traffic light system based on Arduino that can be use in a 3-way ond 4-way intersections. It has an additional blinking orange led that is used to signal when the pedestrians can cross the street. The code is a little bit complicated but I think you can understand how it works, right?

Check out this video below to see how the traffic lights system is working.
The code is written based on 4 situations:

1. the first traffic light (TF1) has the red signal and the pedestrians ON; the second one (TF2) has green ON.
2. TF1 has red and yellow ON; TF2 has yellow ON
3. TF1 is green now and TF2 is red and pedestrians ON
4. TF1 is yellow and TF2 is red and yellow

The schematic is too easy, all you have to do is connect the leds in series with a 470Ω resistor between the ground and the Arduino pins mentioned in the code.

Code of the Arduino Traffic Lights Sketch

// Source: http://www.electroschematics.com/10178/arduino-traffic-light-system/
int trafficLights1[] = {2,3,4,5};	// red, yellow, green, pedestrians led pins
int trafficLights2[] = {6,7,8,9};	// red, yellow, green, pedestrians led pins
int situations = 4;
int duration[] = {8000,3000,10000,3000}; // duration of each situation
long previousCars = 0;
long previousPeds = 0;
long interval = 300;	//blink interval for pedestrians
int ledState = LOW;
int state;
int i = 0;

void setup()
{
  for(int i = 0; i < 4; i++) {
	  pinMode(trafficLights1[i], OUTPUT);
	  pinMode(trafficLights2[i], OUTPUT);
  }
	Serial.begin(9600);
}

void loop()
{	
	unsigned long currentMillis = millis();		
	if(currentMillis - previousCars < duration[i]) {			
		situation(i);		
	} else { 
		previousCars = currentMillis; 
		if(i >= situations) {
			i = 0;
			} else {
			i++;
		}		
	}
}

void activateTrafficLight1(String lights, int pedestrians) 
{	
	for(int x = 0; x < 3; x++) 
	{
		if(lights[x] == '0') state = LOW;
		if(lights[x] == '1') state = HIGH;
		digitalWrite(trafficLights1[x], state);	
	}
	if(pedestrians == 1) {
		blinkPed(trafficLights1[3]);
	} else {
		digitalWrite(trafficLights1[3], LOW);
	}
}

void activateTrafficLight2(String lights, int pedestrians)
{	
	for(int x = 0; x < 3; x++)
	{
		if(lights[x] == '0') state = LOW;
		if(lights[x] == '1') state = HIGH;
		digitalWrite(trafficLights2[x], state);
	}
	if(pedestrians == 1) {
		blinkPed(trafficLights2[3]);
	} else {
		digitalWrite(trafficLights2[3], LOW);
	}
}

void situation(int i)
{
	switch(i){
		case 0: 
			activateTrafficLight1("100",1); // 100 means red ON, yellow OFF, green OFF
			activateTrafficLight2("001",0); // the second parameter is for pedestrians
			break;							// 1 is ON and 0 is OFF
		case 1: 
			activateTrafficLight1("110",0); // 110: red ON, yellow ON, green OFF
			activateTrafficLight2("010",0);
			break;	
		case 2: 
			activateTrafficLight1("001",0);
			activateTrafficLight2("100",1);
			break;
		case 3:	
			activateTrafficLight1("010",0);
			activateTrafficLight2("110",0);
			break;	
	}
}

void blinkPed(int ped) {
	unsigned long currentMillis = millis();
	if(currentMillis - previousPeds > interval) {		
		previousPeds = currentMillis;		
		if (ledState == LOW)
		ledState = HIGH;
		else
		ledState = LOW;
		digitalWrite(ped, ledState);
	}	
}

RF based electronics notice board,sms tranmission

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 RF based notice board

Introduction

Single or Multi electronic notice boards with operating distance up to 1000meters using RS485 protocol

Notice boards play a vital role mostly in educational institutions. The events, occasions or any news, which has to be passed to the students, will be written on the notice boards present in every floor in the colleges or schools. The present system is like, a person will be told the news and he has to update this news on all the notice boards present in the college or school. This will be seen mostly during the examination seasons.

The time table or the schedule of the exams has to be given to the students. This will be done by writing the details on the notice boards. But this process consumes a lot time to update the news on all the notice boards and there may be chances that the person responsible may commit some mistakes or he may be absent sometimes. So, this may create disturbances and the entire schedule may be disturbed. To avoid all these, electronic Notice Board have been designed which completely eliminates the manual work.
   Here we are using RS48.  It is an  alternative for RS-232 for long distance. RS-232 only up  to 15m. but in MAX 485 up to 1500m limit. in addition we connect up to 32 devices.                           If your control system needs to receiving and sending data in the same time you must use full duplex transmission mode. It is possible (and in real world this is the most popular case) that control system first sends request message to ROV (e.g. get temperature) and than waits for the response. In this scenario, there is no possibility that control system and ROV sends data in the same time, so half duplex communication is sufficient.  For full duplex communication you need 4 wires, for half duplex only 2 wires. MAX485 is providing half duplex mode. If you need to use full duplex you must use 2 units (or full duplex chip).