Gate Alarm Circuit

Gate Alarm Circuit

A cheap and simple gate alarm made from a single CMOS Integrated Circuit.

Figure 1 represents a cheap and simple Gate Alarm, that is intended to run off a small universal AC-DC power supply.

IC1a is a fast oscillator, and IC1b a slow oscillator, which are combined through IC1c to emit a high pip-pip-pip warning sound when a gate (or window, etc.) is opened. The circuit is intended not so much to sound like a siren or warning device, but rather to give the impression: “You have been noticed.” R1 and D1 may be omitted, and the value of R2 perhaps reduced, to make the Gate Alarm sound more like a warning device. VR1 adjusts the frequency of the sound emitted.

IC1d is a timer which causes the Gate Alarm to emit some 20 to 30 further pips after the gate has been closed again, before it falls silent, as if to say: “I’m more clever than a simple on-off device.” Piezo disk S1 may be replaced with a LED if desired, the LED being wired in series with a 1K resistor.

Figure 2 shows how an ordinary reed switch may be converted to close (a “normally closed” switch) when the gate is opened. A continuity tester makes the work easy. Note that many reed switches are delicate, and therefore wires which are soldered to the reed switch should not be flexed at all near the switch. Other types of switches, such as microswitches, may also be used.

Guide to the Arduino Nano

Guide to the Arduino Nano

Connecting the Arduino Nano 2.2 to a computer with a Mini-B USB cable. Note the blue power LED underneath the board.

To connect the Arduino Nano to your computer, you’ll need a Mini-B USB cable. This also provides power to the board, as indicated by the blue LED (which is on the bottom of the Arduino Nano 2.x and the top of the Arduino Nano 3.0).

If you have an Arduino Nano 3.0, you’ll need to select Arduino Duemilanove or Nano w/ ATmega32 from the Tools > Board menu. If you have an Arduino Nano 2.x, select Arduino Diecimila, Duemilanove, or Nano w/ ATmega168. Select the correct serial port selected from the Tools > Serial Port menu. Then simply press the upload button in the Arduino environment. The board will automatically reset and the sketch will be uploaded.

How To Get Arduino Running on Windows

How To Get Arduino Running on Windows

How To Get Arduino Running on Windows

This document explains how to connect your Arduino board to the computer and upload your first sketch.

These are the steps that we’ll go through:

1. Get an Arduino board and cable
2. Download the Arduino environment
3. Install the USB drivers
4. Connect the board
5. Run the Arduino environment
6. Upload a program
7. Look for the blinking LED
8. Learn to use Arduino

1 | Get an Arduino board and cable

In this tutorial, we assume you’re using an Arduino Duemilanove or Diecimila. If you have another board, read the corresponding page in this getting started guide.

The Arduino is a simple board that contains everything you need to start working with electronics and microcontroller programming. This diagram illustrates the major components of an Arduino Diecimila. (The Arduino Duemilanove is almost identical.)

You also need a standard USB cable (A plug to B plug): the kind you would connect to a USB printer, for example.

2 | Download the Arduino environment

To program the Arduino board you need the Arduino environment.

Download: the latest version from the download page.

When the download finishes, unzip the downloaded file. Make sure to preserve the folder structure. Double-click the folder to open it. There should be a few files and sub-folders inside.

3 | Locate the USB drivers

If you are using a USB Arduino, you will need to install the drivers for the FTDI chip on the board. These can be found in the drivers/FTDI USB Drivers directory of the Arduino distribution. In the next step (“Connect the board”), you will point Window’s Add New Hardware wizard to these drivers.

The latest version of the drivers can be found on the FTDI website.

4 | Connect the board

On the Diecimila, the power source is selected by the jumper between the USB and power plugs. To power the board from the USB port (good for controlling low power devices like LEDs), place the jumper on the two pins closest to the USB plug. To power the board from an external power supply (6-12V), place the jumper on the two pins closest to the power plug. On the Duemilanove, the power source is selected automatically (there is no power selection jumper). In any case, connect the board to a USB port on your computer.

The green power LED (labelled PWR) should go on.

The Add New Hardware wizard will open. Tell it not to connect to Windows update and click next.

Then select “Install from a list or specified location (Advanced)” and click next.

Make sure that “Search for the best driver in these locations is checked”; uncheck “Search removable media”; check “Include this location in the search” and browse to the location you unzipped the USB drivers to in the previous step. Click next.

The wizard will search for the driver and then tell you that a “USB Serial Converter” was found. Click finish.

The new hardware wizard will appear again. Go through the same steps. This time, a “USB Serial Port” will be found.

5 | Run the Arduino environment

(Mac OSX): Copy the Arduino application to your Applications directory. Double-click the Arduino application.

(Windows): Open the Arduino folder and double-click the Arduino application.

6 | Upload a program

Open the LED blink example sketch: File > Sketchbook > Examples > Digital > Blink.

Select the serial device of the Arduino board from the Tools | Serial Port menu. On Windows, this should be COM1 or COM2 for a serial Arduino board, or COM3, COM4, or COM5 for a USB board. To find out, open the Windows Device Mananger (in the Hardware tab of System control panel). Look for a “USB Serial Port” in the Ports section; that’s the Arduino board.

You’ll need to select the entry in the Tools > Board menu that corresponds to your Arduino. For newer Arduino boards with an ATmega328 (check the text on the chip on the board), select Arduino Duemilanove w/ ATmega328. Previously, Arduino boards came with an ATmega168; for those, select Arduino Diecimila or Duemilanove w/ ATmega168.

Now, simply click the “Upload” button in the environment. Wait a few seconds – you should see the RX and TX leds on the board flashing. If the upload is successful, the message “Done uploading.” will appear in the status bar. (Note: If you have an Arduino Mini, NG, or other board, you’ll need to physically present the reset button on the board immediately before pressing the upload button.)

7 | Look for the blinking LED

A few seconds after the upload finishes, you should see the pin 13 (L) LED on the board start to blink (in orange). If it does, congratulations! You’ve gotten Arduino up-and-running.

8 | Learn to use Arduino

• Examples: try these example programs.
• Reference: read the reference for the Arduino language.

The text of the Arduino getting started guide is licensed under a Creative Commons Attribution-ShareAlike 3.0 License. Code samples in the guide are released into the public domain.

Arduino

Arduino

Getting Started with Arduino

What is Arduino?

Arduino is a tool for making computers that can sense and control more of the physical world than your desktop computer. It’s an open-source physical computing platform based on a simple microcontroller board, and a development environment for writing software for the board.

Arduino can be used to develop interactive objects, taking inputs from a variety of switches or sensors, and controlling a variety of lights, motors, and other physical outputs. Arduino projects can be stand-alone, or they can be communicate with software running on your computer (e.g. Flash, Processing, MaxMSP.) The boards can be assembled by hand or purchased preassembled; the open-source IDE can be downloaded for free.

The Arduino programming language is an implementation of Wiring, a similar physical computing platform, which is based on the Processing multimedia programming environment.

Why Arduino?

There are many other microcontrollers and microcontroller platforms available for physical computing. Parallax Basic Stamp, Netmedia’s BX-24, Phidgets, MIT’s Handyboard, and many others offer similar functionality. All of these tools take the messy details of microcontroller programming and wrap it up in an easy-to-use package. Arduino also simplifies the process of working with microcontrollers, but it offers some advantage for teachers, students, and interested amateurs over other systems:

• Inexpensive – Arduino boards are relatively inexpensive compared to other microcontroller platforms. The least expensive version of the Arduino module can be assembled by hand, and even the pre-assembled Arduino modules cost less than $50 
• Cross-platform – The Arduino software runs on Windows, Macintosh OSX, and Linux operating systems. Most microcontroller systems are limited to Windows. 
• Simple, clear programming environment – The Arduino programming environment is easy-to-use for beginners, yet flexible enough for advanced users to take advantage of as well. For teachers, it’s conveniently based on the Processing programming environment, so students learning to program in that environment will be familiar with the look and feel of Arduino 
• Open source and extensible software- The Arduino software and is published as open source tools, available for extension by experienced programmers. The language can be expanded through C++ libraries, and people wanting to understand the technical details can make the leap from Arduino to the AVR C programming language on which it’s based. SImilarly, you can add AVR-C code directly into your Arduino programs if you want to. 
• Open source and extensible hardware – The Arduino is based on Atmel’s ATMEGA8 and ATMEGA168 microcontrollers. The plans for the modules are published under a Creative Commons license, so experienced circuit designers can make their own version of the module, extending it and improving it. Even relatively inexperienced users can build the breadboard version of the module in order to understand how it works and save money.

Rain Alarm

Rain Alarm

This circuit gives out an alarm when its sensor is wetted by water.
A 555 astable multivibrator is used here which gives a tone of about 1kHz upon detecting water.
The sensor when wetted by water completes the circuit and makes the 555 oscillate at about 1kHz.

The sensor is also shown in the circuit diagram.
It has to placed making an angle of about 30 – 45 degrees to the ground. This makes the rain water to flow through it to the ground and prevents the alarm from going on due to the stored water on the sensor.
The metal used to make the sensor has to be aluminium and not copper. This is because copper forms a blue oxide on its layer on prolonged exposure to moisture and has to be cleaned regularly.
The aluminium foils may be secured to the wooden / plastic board via epoxy adhesive or small screws.
The contact X and Y from the sensor may be obtained by small crocodile clips or you may use screws.

Theft preventer alarm

Theft preventer alarm

 This circuit utilising a 555 timer IC can be used as an alarm system to prevent the theft of your luggage, burglars breaking into your house etc. The alarms goes ON when a thin wire, usually as thin as a hair is broken.
The circuit is straightforward. It uses a 555 IC wired as an astable multivibrator to produce a tone of frequency of about 1kHz which gives out a shrill noise to scare away the burglar.
The wire used to set off the alarm can be made of a thin copper wire like SWG 36 or higher.
You can even use single strands of copper form a power cable.

The circuit operates on a wide range of voltages from 5V to 15V.
The speaker and the circuit could be housed inside a tin can with holes drilled on the speaker side for the sound to come out.

Capacitor Theory

Capacitor Theory

A capacitor basically consists of two plates with an insulator in between,
although in practice the ‘plates’ are normally rolled up in a can to save space.
It can be used in a circuit to store charge for small periods of time.

Charge stored in a capacitor:

Charge Q = CV where C is the capacitance in Farads

charge Q is measured in coulombs (C)

Energy stored in a capacitor:

Energy stored, W = ½ QV = ½ CV² joules

Capacitance:

If the dielectric (the material between the plates) is a vacuum, Capacitance
C = e₀ (A / l) where A is the area of the
capacitor plates, and l is the distance between them.

e₀ is the permittivity of free space
(8.85X10-12)

If the dielectric is another material, capacitance is given by:

C = e_re₀
(A / l) where e_r is the relative
permittivity, which varies between materials.

Capacitors in Series:

Putting capacitors in series reduces the overall capacitance:

(1/C) = (1/C₁) + (1/C₂) + (1/C₃) …..

Capacitors in parallel:

Putting capacitors in parallel increases the total capacitance:

C = C1 + C2 + C3 …..

Note that the series and parallel capacitance formulae are the opposite of
those for resistance.

Capacitor Markings

Capacitor Markings

Capacitors are often marked with codes to show the value, tolerance and
material. This is particularly true for small types such as ceramic disc or
polystyrene where there is little space for full markings.

Value Codes:

The capacitance value is often marked using a 3 digit code. This works in the
same way as resistor coding but using numbers instead of colours. The first 2
numbers give the value and the last number is the multiplier.

These give the
value in Picofarads (pF), e.g. code 103 = 1 0 000pF (=0.01uF – see Capacitance
Conversion Table). Alternatively the value may be marked directly, for
example 2n2 is 2.2 Nanofarads (nF).

Tolerance Code:

A single letter is often used to indicate the tolerance of the component.
These can be translated using the following table:

Material Code:

The dielectric material is often marked in abbreviated form. The table below
shows the meaning of these abbreviations.

Capacitance Conversion Table

Capacitance Conversion Table

Different types of capacitors often have their values marked in different orders of magnitude. It is sometimes necessary to convert between them:

AC Power

Apparent Power, S – appears on the hypotenuse of the power triangle.

Apparent power is given by:

Apparent power = V I

= Voltage * Current

Units are volt -amps (VA)

True power is given by:

I²R = S cos f = VI cos f

This is the power in the resistive part of the circuit

Units are Watts (W)

Given by:

I²X_L = S sin f = VI sin f

and: I²X_C = S sin f = VI sin f

where X_L and X_C are inductive reactance and capacitive reactance respectively, and f is the phase angle.

Units are volt-amps reactive (VAr)

Power Factor = True Power / Apparent Power = P / S = cos f

True Power  = Apparent Power * Power Factor

= VI cos f