Electronics Projects

Measuring Instruments:

Objectives:
  1. To study about electrical variables and electrical symbols
  2. To study about digital multimeter
  3. To study about Digital oscilloscope.
  4. To study about Power supplies.
Apparatus :
Theory
Electrical Symbols:



Digital Multimeter:
multimeter is the meauring instrument use to meaure voltage,current and resistance of electronics and electrical circuits.multimeter is bascally ab intergration of Ammeter,Voltmeter and Ohm meter.some of modren digital meter also conatins Frequancy meter.
Ammeter is used for measuring Current and volt meter used for measuring volt and Ohm meter is used for resistance measuring.Volt is measured in Volt, current measured ampere and resistance measured in ohms.








The Cathode Ray Oscilloscope:
We use CRO to visualize at the voltages that changes with the time such as Ac voltages and signal waveform from amplifiers.The voltages on the X-plate makes the electron beam sweep across the screen.This sets the time base.The two properties we need to know about the sine wave is its amplitude and frequency.

Procedure:
  1. Turn on the Oscilloscope and Disconnect any probes plugged into the Channel 1 input connector.
  2. Set all the levers and button as indicated ,if they are not already.
  3.  Set channel 1 coupling mode switch to ;ground;GND.
  4. Turn down the intensity knob,if necessary to avoid burning out the screen.
  5. They sweeping dot  should  be clear but not too bright.
  6. Since channel 1 is now grounded to zero volt,the oscilloscope should read zero on the vertical axix using the coordinate axes centered on the screen.

What the Oscilloscope Does: 
  1. The Oclilloscope graphs voltages vs time, by sweeping an electron beam across the phosphor screen.
  2. Wherever the beam hits the screen,its grow screen.
  3. for most measurement,the beam sweeps rightward at a constant rate.
  4. When beam gets to the right hand side of the screen ,it jumps back to the left hand side.in this way the horizontal axis shows time.
  5. When probes is plugged into channel 1 input connector,the vertical axis shows the potential difference---i.e ,the voltage between the two wires coming out of the probe.
Measuring DC Voltages,and using The Volts/Division setting of Oscilloscope:




















Measuring AC voltages,and the time/division setting of Oscilloscope:






















Entry Alarm Circuit
Introduction:

This is Infrared based broken beam alarm to protect doors and entry passages.
It gives a loud alarm when somebody crosses the Invisible Infrared barrier. It can protect the doors both day and night and is free from false triggering.
Components Used:
 IR LED, R1  1KΩ
VR1 is Variable 3kΩ, Green LED, Red LED
IR Receiver, R   1K Ω, Transistor  C945, Buzzer, 9 v Battery
Operation:
The circuit uses Infrared diodes to emit continuous IR rays which are not pulsed.

The IR Receiver is used as a light sensor.

Its positive is connected to the positive rail through VR1 and the Emitter has a Green LED to indicate standby mode.

This receiver conducts when IR light strikes on it.
 The degree of biasing depends on the intensity of photons.

T2 is the alarm driver and its base is connected to the IR Receiver. So that the base bias of T2 depends on the conduction of IR Receiver.

When the Infrared rays illuminate the IR Receiver, it conducts pulling the base of IR Receiver to ground level so that it remains off.

Red LED and Buzzer connected to the emitter of T2 remains off in this condition.

When a person crosses the IR beam, IR Receiver  turns off and its collector voltage becomes high.

T2 then conducts and activates Red LED and buzzer.

The circuit can be constructed on a small piece of Varro board. Assemble R1 and IR LEDs on a board. Fix IR LEDs on one side of the entry and the IR Receiver on the opposite side.
 Carefully align IR beam on the IR Receiver so that buzzer will be silent in the standby mode. Move hand across the beam, buzzer should sound.VR1 adjust the base bias of T2 to keep the buzzer off in the standby mode.
Application:
1.This is used in house protection as security alarm system.

2.Used in sensitive department for safety protection.

3.Automatic door activator.
Subscribe to: Comments (Atom)

Followers