Monthly Archives: February 2009

Types of Diodes

Diodes are an important part of today’s electronic components and are widely used for a number of applications. Accordingly, a large number of different types of diodes have been created to cater to their wide array of uses. The more popular types of diodes are described below.

Schottky Diodes: These diodes are made from a semiconductor to metal contact instead of semiconductor-semiconductor junction. This gives them a lower forward drop voltage as compared to pn junction diodes. They have a faster reverse recovery time and high switching speeds due to the low junction capacitance. They are used in voltage clamping applications and as low loss rectifiers.

LEDs (Light Emitting Diodes): These electronic components are formed from direct band gap semiconductors like gallium arsenide, and as the carriers cross the junction and recombine with the majority carriers, they emit photons. Infrared to ultraviolet wavelengths can be obtained depending upon the material used for making the LEDs. They are often used in signaling operations.

Varactor Diodes: These diodes are used as voltage controlled capacitors and have important applications in frequency locked loop and phase locked loops used in tuning circuits.

Zener Diodes: Zener diodes permit current to flow in the forward direction as in a normal diode, but where it differs is that it also allows current to flow in the reverse direction when the voltage exceeds the breakdown voltage also referred to as Zener voltage or the Zener knee voltage. It can be used as a precision voltage reference.

Avalanche diodes: These diodes are also used for conducting in the reverse direction once the reverse bias voltage increases the breakdown voltage. The reverse bias causes a wave of ionization, like an avalanche, and leads to a large current.

Tunnel diodes: These diodes have a negative resistance region of operation that is caused due to quantum tunneling. This allows for amplification of signals. These diodes offer most resistance to nuclear radiation.

Gunn Diodes: These diodes are similar to tunnel diodes except that they are made of different materials, like InP, GaAs, and exhibit negative differential resistance.

If you are just beginning to work with diodes, you might want to purchase a small amount of each type listed above. A good source for all diodes and other electronic components is West Florida Components.

Rotary Switches: Construction and Use

A rotary switch is a kind of switch that has a rotating shaft attached to a terminal. That terminal is able to make or break a connection to one (or more) other terminals. Rotary switches may feature different switch positions that can be set by rotating the switch spindle in one or another direction. Some common examples where a rotary switch might be used is in a multi-speed fan or as a band selector on multi-band radios. Until the early 1970’s, rotary switches were used as channel selectors on TV receivers.

In general, rotary switches can be found where ever there is a need to control a large number of circuits covering a range of currents, voltages and power requirements. Currently, you will find rotary switches in these applications:

  1. medical equipment
  2. computers
  3. industrial controls
  4. instrumentation
  5. communications equipment
  6. aircraft equipment

The construction and design of a rotary switch is centered around the center rotor. The rotor has a contact arm that projects out from its surface. Around the rotor are an array of terminals. These serve as the contact for the arm, or spoke. Since the switch has multiple layers, each layer permits the use of an additional pole. There is also a detent mechanism which will click into place as the switch is turned from one active position to another. The contact / sensor system and detent mechanism determine the number of possible switching combinations.

Grayhill Rotary Switch

Grayhill Rotary Switch




Above is an example of a Grayhill military rotary switch. You can see it has 5 decks. Each deck has 1 pole. Each pole has 9 positions.

This is an example of a 16 position rotary switch assembly 1-435304-1. This rotary switch assembly has a bar handle. It is a single pole but has 16 positions.

All About Self-Adhesive Rubber Feet


Square Rubber Bumpers

Square Rubber Bumpers

Self-adhesive rubber feet, also known as bumpers or bumpons, are a versatile product that can be used in many different ways around the house and workshop.The self-adhesive glue will stick to most surfaces including glass, wood, metals and plastics.

In the home, you can use rubber feet as dampers to cushion the closing action of cabinet doors or drawers in your kitchen, bathrooms and laundry rooms. The rubber bumpers will protect your expensive cabinet doors and drawers from hitting the frame of the cabinets and maintain the integrity of the wood by preventing vibrations when door meets the cabinet. Another way to use rubber bumpers in the kitchen is to attach them to the bottom of cutting boards to prevent the board from skidding, Many small kitchen appliances have rubber feet on the bottom to keep them from sliding.

There are other places in the home that rubber bumpons can be used. Put them on the underside of hanging pictures to help them grip the wall and help the frames stay in place without damaging the walls or the artwork.They can be adhered to speakers to protect the floor from scuffing and keep vibrations to a minimum. Your electronic equipment needs air to circulate between the cases. Using tall rubber feet as spacers will separate the equipment and allow air to circulate.

In the home office, rubber feet can be used on keyboards to grip the surface of the desk. Computers and laptops have rubber feet on the bottom which keeps them from sliding.If one of them is lost, your computer will be unbalanced and hard to use.

Rubber feet are often used with electronics projects. Once common place is on project boxes and pc cases. You will also find them on circuit boards.

In addition, rubber bumpers can be found in automotive applications, woodworking projects, glass projects such as coasters and stained glass window hangings.

Rubber bumpons are generally sold in three shapes: cylindrical, hemispherical and square.

Use the flat (cylindrical) rubber feet when you need increased load capacity. The hemispherical feet are most often used when increased sound dampening is required. Hemispherical rubber bumpers are favored for increased energy absorption.

The thin, low profile bumpers are great for increased load capacity. Their flat, wide surface helps absorb weight evenly. If you require air circulation, the taller, high profile rubber bumpons would be the best feet for the job.

Clear and black self-adhesive rubber feet are the most widely requested colors but many of the feet are also produced in gray.

Large Self-Adhesive Rubber Feet

Large Self-Adhesive Rubber Feet

Keep a supply of self-adhesive rubber feet in different shapes, sizes and colors around the house for the next time you need to use one of these versatile products.They are an inexpensive solution for many projects.

New Mystery Part: SCR5162-005 by Motorola

Sometimes we come across some new parts and there is no accompanying information. We search high and low for a data sheet but occasionally we are not successful.

One such part is the Motorola SCR5162-005. So far we know (think?) it’s a triac. But that’s all we got.

Do you know what it is? Do you have any specs for it? Let us know what you know and if we can verify the information, we’ll send you a $5.00 gift card to shop on our web site which is the best online store for electronic components.

BUZ11 – a Popular Power MOSFET

BUZ11

BUZ11

The BUZ11 is an N-Channel enhancement mode silicon gate power field effect transistor designed for applications such as switching regulators, switching converters, motor drivers, relay drivers, and drivers for high power bipolar switchng transistors requiring high speed and low gate drive power. The BUZ11 is also used for DC-DC and DC-AC converters and in the automotive environment for injection, ABS, airbags, lampdrivers and more.

It features:

  • 33A 50V
  • Nanosecond Switching Speed
  • Linear Transfer Characteristics
  • High Input Impedance

The BUZ11 is in a TO220 package.

If you are looking at the BUZ11 with the drain (flange) at the top, the left pin is the GATE, the middle is the DRAIN, and the right lead is the SOURCE.

Low Power Quad Op Amps – LM324AD of the LM324 Series

The LM324 series consists of four independent,
high-gain, internally frequency-compensated operational amplifiers
designed specifically to operate from a single power supply over a
wide range of voltages.

LM324AD

LM324AD

In the linear mode, the input common-mode voltage range includes
ground and the output voltage can also swing to ground, even
though operated from only a single power supply voltage.
The unity gain crossover frequency and the input bias current are
temperature-compensated.

The LM324 is available in 3 packages: DIP 14, SO14 and TSSOP14.