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Semiconductors and Alarm Systems

Describes solid-state components. Often used when discussing transistors, which are commonly made of silicon. They can function as an insulator or a conductor dependent on changes in voltage. They are excellent switching devices, have no moving parts, able to change between conductive and nonconductive state very quickly. Semiconductors in their natural state, are neither good conductors nor good insulators, but they can be manipulated to display properties of either. This makes them essential in the design and operation of many electronic devices, including transistors, diodes, and integrated circuits. They are widely used in applications such as computers, smartphones, and communication systems, as they can control and regulate the flow of electrical current in a circuit, which is crucial in the functioning of these devices.

  • Are not good conductors.
  • Not good insulators.
  • Examples included.
    • carbon,
    • silicon
diodes and Leds
Diodes and Leds

LEDS

f bright lights turn you on, you can appreciate the curious behavior of semiconductors: They emit light when you apply an electric current to them. This light is generally very dim and only in the infrared region of the electromagnetic spectrum. The light-emitting diode (LED), such as the light that glows yellow or green when your computer is on, is a special type of semiconductor expressly designed to emit copious amounts of light. Most LEDs are engineered to produce red, yellow, or green visible light, but some special-purpose types
emit infrared, blue, and even white light.
LEDs carry the same specifications as any other diode, but they usually have a pretty low current rating. An LED has a PIV rating of about 100 to 150 volts, with a maximum current rating of under 50 milliamps. If more current passes through an LED than its maximum rating allows, the LED burns up. LED specifications indicate both the maximum current rating, usually referred to as forward current, and the peak current. The peak current is the absolute maximum current that you can pass through the LED for a very short period
of time. Here, short means short — on the order of milliseconds. Don’t confuse forward current with peak current, or you may wreck your LED.

You use a resistor, to limit the current to the LED. You select the value of the resistor to maintain the current below the maximum current rating of the LED. The calculation is simple, and for most LEDs and 5 or 12 volt circuits, you can use common resistor values that get
you in the right ballpark.

  • 3.3 to 5 Volts – 330 Ohms resistor
  • 6 to 9 Volts – 560 Ohm resistor
  • 12 to 15Volts – 1K Ohms resistor

You can always select a higher value resistor, which simply makes the LED glow less brightly. If you select a lower value resistor, you run the risk of burning out the LED. Because most LEDs cost just a few pennies a piece, you can experiment with resistors of different values and not break the bank. You want a more accurate calculation, you need to know the forward volt-
age drop through the LED, in addition to the LED’s maximum current rating.

LEDs, or Light Emitting Diodes, are commonly used in older alarm system installations as an indicator of the armed state of the system (Arm/Disarm/Alarm condition). However, due to their visible indication from outside the building, this practice has become less popular in modern installations. The advancement of technology has allowed for the use of smartphone apps to check the status of an alarm system, making LED indicators less necessary.

  • On older installations they are used for outside indication if the alarm system armed state (Arm/Disarm/Alarm condition).
  • On more modern installations people have stopped using the practise since the indication is visible from outside, hence burglars can also see if your system is armed or not. With the advancement in technology most people rely on smart phone apps to see the status of their alarm system.

Transistors

Transistors were developed as an alternative to the vacuum tube. The two main ways that you can use transistors (or vacuum tubes, for that matter) are to amplify a signal or to switch a signal on and off. Besides its small size, a transistor has another advantage — it uses less power than a vacuum tube to accomplish the same job. With creative connections in a circuit, you can also use transistors to switch or amplify voltages. This fancy circuit work can confuse you when you’re studying circuits involving transistors. Transistors are very complex little critters, so we just talk about the basic types you encounter when you begin working in the electronics world, what they look like.Millions of individual transistors make up the microprocessor.

In alarm systems, transistors are commonly used as switching devices. They control the flow of current in the system by switching between a conductive and non-conductive state based on changes in voltage. They are used in various applications such as amplifying signals, switching relays, and controlling the activation and deactivation of alarm components. The use of transistors allows for efficient and precise control of the alarm system, leading to improved stability and reliability.

Most of the time they were used to switch Relays.

transistors
semiconductor example transistors
transistors
semiconductor example transistors

Watch out for

Most semiconductor devices like LEDS and Diodes are polarity sensitive. If you connect them up to an existing alarm system, make sure you do not swap polarity. The LED in question will blow andstop working. Also remember your current limiting resistor. LEDS will also blow if the resistor is not in series.