All ABOUT DIODE

Diode is a two-terminal electronic component with asymmetric conductance , it has low (ideally zero) resistance to current flow in one direction, and high (ideally infinite) resistance in the other. Today most diodes are made of silicon, but other semiconductors such as selenium or germanium are sometimes used. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals.

 

FUNCTIONS

The most common function of a diode is to allow an electric current to pass in one direction (called the diode’s forward direction), while blocking current
in the opposite direction (the reverse direction). This unidirectional behavior is called rectification, and is used to convert alternating current to direct current, including extraction of modulation from radio signals in radio receivers—these diodes are forms of rectifiers .

Symbol of diode

CONNECTING DIODE PROPERLY

I hope you understand the positive and negative terminal of diode.

DIFFERENT TYPES OF DIODES

There are different types of  diodes and each of them have different function.

Zener diodes are used to regulate voltage.

avalanche diodes are used to protect circuits from high voltage surges.

varactor diodes are used to electronically tune radio and TV receivers.

tunnel diodes , Gunn diodes, IMPATT diodes are used  to generate radio frequency
oscillations.

light emitting diodes(LED) are used to produce light.

We will be using LEDs and photodiode or LDR in our projects, so here is the note on two. To know more about LED check out my Light Emitting Diode (LED) post or Connecting LED Properly post, to know more about LDR click here

Light-emitting diodes (LEDs)

In a diode formed from a direct band-gap semiconductor, such as gallium arsenide, carriers that cross the junction emit photons when they recombine with the majority carrier on the other side. Depending on the material, wavelengths (or colors) from the infrared to the near ultraviolet may be produced. The forward potential of these diodes depends on the wavelength of the emitted photons: 2.1 V corresponds to red, 4.0 V to violet. The first LEDs were red and yellow, and higher- frequency diodes have been developed over time. All LEDs produce incoherent, narrow- spectrum light; “white” LEDs are actually combinations of three LEDs of a different color, or a blue LED with a yellow scintillator coating. LEDs can also be used as low-efficiency photodiodes in signal applications. An LED may be paired with a photodiode or phototransistor in the same package, to form an opto- isolator .

Photodiodes

All semiconductors are subject to optical charge carrier generation. This is typically an undesired effect, so most semiconductors are packaged in light blocking material.
Photodiodes are intended to sense light( photodetector ), so they are packaged in materials that allow light to pass, and are usually PIN (the kind of diode most sensitive to light). A photodiode can be used in solar cells , in photometry, or in optical communications . Multiple photodiodes may be packaged in a single device

Most popular 1N-series diodes

We will be using 1N-series diodes. The standardized 1N-series numbering EIA370 system was introduced in the US by EIA/JEDEC (Joint Electron Device Engineering Council) about 1960. Among the most popular in this series were:
1N34A/1N270 (Germanium signal),
1N914/1N4148 (Silicon signal),
1N4001 -1N4007 (Silicon 1A power rectifier) and
1N54xx (Silicon 3A power rectifier)

If you want to know more about diode let me know it through the comments.

SPEAKER

A loudspeaker (or “speaker”) is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by.vacuum tube made loudspeakers more generally useful. The most common form of loudspeaker uses a paper cone which is vibrated by an attached voice coil electromagnet between the poles.of a permanent magnet, but many other types exist. Where high fidelity reproduction of sound is required, multiple loudspeakers may be used, each reproducing a part of the audible frequency range. Miniature loudspeakers are found in devices such as radio and TV receivers, and many forms of music players. Larger loudspeaker systems are used for music, sound reinforcement in theatres and concerts, and in public address systems.

Here is the picture of a 8R speaker we which we will be using in our project.

Symbol of speaker

The most common type of driver, commonly called a dynamic loudspeaker, uses a lightweight diaphragm , or cone , connected to a rigid basket, or frame, via a flexible suspension, commonly called a spider, that constrains a voice coil to move axially through a cylindrical magnetic gap. When an electrical signal is applied to the voice coil , a magnetic field is created by the electric current in the voice coil, making it a variable electromagnet. The coil and the driver’s magnetic system interact, generating a mechanical force that causes the coil (and thus, the attached cone) to move back and forth, thereby reproducing sound under the control of the applied electrical signal coming from the amplifier .

Modern driver magnets are almost always permanent and made of ceramic, ferrite, Alnico, or, more recently, rare earth such as neodymium and Samarium cobalt. The size and type of magnet and details of the magnetic circuit differ, depending on design goals.

MUSICAL BELL

Today we are going to make a simple circuit that uses very few components and it produce sweet melody sound. This circuit uses a 3 terminal IC UM66. Usually this IC is used in greeting cards to make melody sound. The UM66 IC looks like a transistor with 3 terminals but it is a complete miniature tone generator with a tune and they come in variety of different tunes.

We have used a BC 548 NPN transistor for amplification and a 220R resistor to limit the base current. You can even include a switch in the circuit to keep the IC play the full music. Make sure that you do not give more than 4.5 V to UM 66.

I have marked the IC UM66 and BC 548 transistor on the image below to clear your doubts.

Here is an another angle of breadboard arrangement.

Here I have marked the pins of UM66. I hope this is useful.

COMPONENTS REQUIRED :-

1. UM66 IC
2. BC 548 transistor
3. 220R resistor
4. Speaker or buzzer
5. Battery 3V
6. Switch

CONNECTIONS :-

(MOST IMPORTANT :- Identify emitter, base, collector of transistor and pin number of IC UM66)

1. Connect a 220R resistor between pin1 of IC UM66 and base of transistor(connect middle pin of both transistors and IC).
2. Connect pin3 of IC UM66 and emitter pin of transistor to the base negative rail.
3. Connect pin2 of IC UM66 to the positive rail.
4. Take the speaker or buzzer and connect it between the collector pin and positive rail.
5. Now connect the battery and hear the melody sound.

If the musical bell is not working check the emitter, base, collector pins of transistor and pins of IC UM66 are connected properly. Still not working leave a comment and I will help you.