Remote Operated Lighting System

Circuit Design

How to Design Basic Electronics Circuit using Diode, Precision Potentiometer, Capacitor etc

Circuit Design is one of the basic and yet technical aspect of electronics in our schools and life as an electronics hobbyist. As we shall be working with component such as Diode anode cathode,Principles of Diode forward bias, Diode characteristic, Capacitors, Wire Wound Resistors and Precision potentiometer.

The art of electronics and ability to imagine or been creative is an important skill in science. Innovations, ideas, research and persistent has brought about the existence of certain component in engineering and science as a whole. Today, I will be giving you a concept of knowing what you want to do and how to go about it.

For instance, you came back home after the day’s job, tired and hungry. Reaching out to the wall switch to put on your lighting system and television set, it seems it’s another form of work. The thought of having a system where you could just be on your sofa and put on your room lighting system, security light outside, television set and so on.

First, in wanting to construct a unit that will receive infra-red (IR) signal from your TV remote control, you need a component that can receive these IR signal (Infra-red ray), then convert it to switch ON or OFF a relay. Since a relay can be use as a switch, the relay will now serve as the contact-maker or switch-operator for you.

Having gotten an idea of your intention, its time to look for these component. The first stage is the stage that will receive the IR ray, but this stage cant stand alone without a “Pulse stretcher”. A Pulse stretcher is a monostable multivibrator. Once triggered, it remains ON for duration of time determined by the RC-network known as the frequency determining network. This is necessary because the stream of pulse “IR ray” coming from the IR transmitter in the TV remote is a stream of multiple rays oscillating from 300Hz up to 33 KHz depending on certain factor. BUT, we only needed ONE ray to drive the next stage. So, we improvise a stage that will help us eliminate other rays while allowing ONLY on ray to pas through. The output of the second stage (Pulse Stretcher) is then connected to a unit that will be doing the changing of “state” for us. It’s called A Bistable Multivibrator. We will use a decade counter CD4017 connected in such a way as to serve as a Bistable Multivibrator for us. Such that, when it receives a pulse of IR ray, its OUTPUT will be High (ON) or Low (OFF).

This On or off state will be connected to the base of a transistor that will energize a relay. GBAM!!! Simple? Let’s find out

- Infra-Red Receiver

Infra red receiver is common in the market. Below is a popular type of IR Receiver and its pin configuration (arrangement).

As seen from the diagram above, the first pin from your left with the device facing you directly is Pin 1 (Connected to GROUND), Pin 2 (Connected to Positive Supply- VCC) and Pin 3 (Connected as output to the next stage) Output.

So, from my diagram, the terminal of the NAND gate i used, the first pin connected upward is the Positive VCC, The centre connecting to the next stage is Output while the last terminal going Ground is Ground.

The first terminal or pin is tagged “Pin 1”. Pin 1 is the “Ground”. So, during our construction, we will connect pin 1 to the ground or neutral potential of our power supply unit (Battery).

Next, Pin2 is “+V” known as the positive terminal or positive pin for our power supply unit. Also, we shall connect a regulator (Zener Diode) rated at 5.1V to provide a stable voltage not beyond 6V.

Next, Pin 3 (Output) will be connected to the next stage as our source of signal input for that stage.

Below is a circuit diagram with precise and correct component values that has been assembled and tested for quality reason to enable you put something of this form together. I shall be using “Multism 10” in drawing the circuit diagram.

I was unable to get the symbol of IR receiver in Multism 10 component list, so i used a NAND-gate logic circuit symbol in representing IR Receiver. ok! For those of us that doesnt known what a NAND Gate symbol is, its the symbol at the begining of the diagram with a little circle ball at the back connecting to the next stage been the Pulse Stretcher.

Please note that, D1 and K1 are poitns where you will connect your load or socket or Bulb, while the other end is your source of power say PHCN as the case may be.

Dont forget to connect pin 8 of CD4017 to ground and pin 14 to supply (VCC).
Feel free to leave your questions as the need arise.

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RESISTOR

What is a Resistor?

A resistor is simply a conductor that opposes the flow of electric current to one (1 A) amperes when a voltage of (1V) one volt pass through it. Also, a resistor is an active element which can either be a carbon type or choke or wired-wound type. This component that renders a resistance to the flow of electric current plays a major role in the electronics industry today. Below is a symbol of a resistor and structural view as likely available in the markets.

The amount of resistance introduced by the resistor is what determines the amount of current flow through the conductor or circuit. This amount or level of resistance is measured by a rate of unit known as Ohms. And the standardized abbreviation in representing a resistor is R. Ohms law states that. The resistance of a resistor is dependent on the composition of material it’s made up of also known as its resistivity, also its dimension and object temperature involved. The Resistivity of a resistor is defined in terms of the ohms resistance per cubic centimeter of that substance at a temperature of 20 degree Celsius.

Applications of Resistor

A Resistor can be applied in various ways in both electronics industry and circular world at large.

-A resistor can be use as heating element in households.

In areas of cold temperature such as homes in parts of the world as Russia, Germany, and certain parts of United states, heating elements are use to keep the room temperature at a safe level needed for the body. Below shows a heating element design for homes.

- In Incandescent Lamps:

resistors are designed to produce illumination in glass tubes to provide light for visual and even around the premises for security surveillance. Below is a basic incandescent lamp

- Electronics circuitry:

where adjustment is needed to regulate the inflow of current. Certain resistors made adjustable known as rheostat or variable resistors, when adjusted they offer certain level of resistance to current flow in increasing and decreasing pattern respectively depending on the intention of the circuit designer. Variable resistor are also use in volume control in audio systems where the level of audio signal is to be regulated in amplifiers both in home-theaters, radio systems, transmitters and so on. Below shows the symbol of a variable resistor and its structural diagram.

-In Dimmer.

Certain room lighting system requires dim light (low illumination or intensity of light in the room). Variable resistors are applied to regulate or adjust the rate of flow of current in the circuit of the Dimmer thereby providing a Dull Like illumination suitable for sleeping mood at night.

Resistor Color Code

Resistors are made such as to have values of resistance in order for anyone to be able to identify and apply it independently. This is made possible by coloring. Commonly used resistors are those with four (4) colors. The last color hereby denotes its tolerance.

The color codes are arranged much that the colors seem closer to one part of the terminal than the others. Below shows a resistor and its color code written on it. The side of color closer to the terminal I indicate the start point or point to begin counting from for identification. The last color is known as the tolerance. As we humans have limit to which we can admit or accommodate things in life, so also a resistor has a limit known as tolerance to which it can withstand certain amount of current been passed through it.

The color band of the resistors and their equivalent digits are listed below:

B- Black- 0, B- Brown- 1, R- Red- 2, O- Orange- 3, Y- Yellow- 4, G- Green- 5, B- Blue- 6, V- Violet- 7, G- Gray- 8, W- White- 9,

Tolerance: Gold=±5%, Silver= ±10%. Note also that the first and second colors are the digits of the resistor value. The third color is the multiplier x10, and the fourth digit is the tolerance.

Below shows the diagram and color band on the resistor and how to calculate a certain resistor:

For instance, a resistor having colors of Red, Green, Yellow and Gold. The resistance values will be calculated as:
Red=2, Green=5, Yellow=10¬4¬¬ ¬Gold= ±5% 2 and 5 multiply by10¬4¬¬ ¬¬ ±5% 25*10¬4¬¬ ohms ±5% 250000 ohms ±5% = 250KΩ, ±5% = 12500Ω
Therefore, the total resistance becomes 250kΩ + 12500Ω = 262500Ω and 250KΩ-12500Ω= 237500Ω This means that, the resistor can tolerate between 262500Ω and 237500Ω.

These are just the few types of resistor whose resistance can be calculated using color code. There are some that their values are written directly on their body. Examples of those are Choke resistors. The picture below shows such resistor.

Other types such as potentiometer used as volume controls, their resistance value are written on their body in the form of multiplier such as 503 = 50kΩ, 104 = 100KΩ and so on.

Thanks for taking time to read through, I wish we make it a date next time as I keep you updated on basic electronics components, uses and circuits idea and applications generally.

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Diode

What is a Diode?

In my last article, i wrote a little on Transistor, its application and composition. Today, we will glance at a little of other semiconductor device in electronics.

A Diode is a semiconductor device that is made up of a P-N junction (positive-negative junction), sandwiched together. It is represented by the symbol shown below:

A diode only allows the flow of electric current in one direction i.e. when forward biased as shown in the diagram below. First, forward biasing a diode has to do with connecting or providing a signal source to the Anode (positive terminal) of the diode, while the cathode is then connected to the negative potential or ground of that same arrangement known as circuit in electronics terminology. This signal source could be a varying voltage from a transducer such as a microphone, thermistor (temperature-voltage converting device), a signal generator or even a DC power source such as the one used below and so on.

When a diode is reverse biased, current will not flow because it has a very high resistance when reverse biased. In the forward biased mode, current (conventional current) flows from the anode (positive terminal) to cathode (negative terminal). While electrons will migrate from the cathode (negative terminal) to the anode (positive terminal) of the semiconductor diode.

When you look closely to a practical diode, as in the most commonly used once such as IN4001 etc, there is a white coated ring like mark at one corner of the diode. This mark denotes the position of the cathode (negative) terminal while the other end that has uniform color with the rest part of the device is the anode (positive) terminal.

Applications of a Diode

A diode has vital and divers application in electronics circuit or in the field of science and technology in large. Among a few are in Logic circuits- where the presence and absence of a signal or voltage is denoted or represented as a 1 or 0. Diodes are used as OR Gates and other combination to form a complex unit. In Power Supply Units- Diodes are used in power supply circuits as rectifiers- It converts alternating signal (ac voltage) to direct current voltage (DC Voltage). Since it is said that current only flows in one direction, when the alternating signal is fed to it positive terminal known as the anode, current is allowed to flow through thereby forming a positive waveform at the output point. In Radio communication circuitry- Diodes are use as detectors for radio receivers (Amplitude Modulation Detector) in decoding or retrieving the signal received from the transmission end. In other circuits it could be manipulated to serve as a detector for heat and so on. The applications is much that diodes are now been use in television screen in their other forms as Light Emitting Diode. Light Emitting Diode- a Light Emitting Diode is just another form of a semiconductor diode been made to emits light when it is forward biased. This has brought further research work into complex designs as liquid displays and L.E.D television screens.

Another form of a semiconductor diode is a Zener Diode. In my next article I shall discuss more on it.

Watch out for my next article. Look forward to seeing you.
This is an update of my previous discussion on Diode.

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