all in one for fun circuit

Magic Lights Circuit using Bi-Colour LED

This is the magic lights circuit which use bi-colour LED as the output to provide the light. The circuit uses 14 bi-colour (red and green) LEDs having 3 terminals each. Various dancing colour patterns are generated utilizing this circuit considering that each LED can create three various colours. The middle terminal (pin 2) of the LEDs will be the common cathode pin that is grounded. When a positive voltage is applied to pin one, it emits red light. Similarly, when positive voltage is applied to pin 3. it emits green light. And when positive voltage is simultaneously applied to its pins 1 and 3, it emits amber light.

The circuit could be implemented for decorative lights. The IC1 (timer IC 555) is applied in astable mode of multivibrator to produce clock signal for IC2 and IC3 (CD4518) that are dual BCD counters.

The two counters of each one of these ICs have already been cascaded to acquire 8 outputs from each. The outputs from IC2 and IC3 are connected to IC4 through IC7 that are BCD to 7-segment latch/decoder/driver ICs. Therefore we acquire a complete of 14 segment outputs from each of the IC pairs composed of IC4 plus IC5 and IC6 plus IC7. While outputs from former pair are connected to pin No. 1 of all the 14 bi-colour LEDs through current limiting resistors, the ouputs of the latter pair are similarly connected to pin No.3 of all the bi-colour LEDs to acquire a magical dancing lights effect. 

Cricket Chirping Sound Generator

This is the circuit diagram of cricket chirping sound generator based on IC 4060, a 14 stage ripple counter and oscillator IC. A suitable audio wave form is produced by IC2 and related electronic components, driving the mini speaker through Q1. To allow a more real-life behavior, the chirp is interrupted in a pseudo-casual way by two timers built around IC1C and IC1D, whose outputs are mixed into IC1B and further time-delayed by IC1A, driving the reset pin of IC2.

Mice Repellent Circuit

This is the circuit diagram of mice repellent. Mice are animals that are very annoying, because sometimes he is damaging the object stored in the form of archives that are still valuable.

To drive out the mice, you can create an electronic circuit of mice repellent as shown above. With 50KHz frequency generated by the timer IC 555. The mice would run because his ears will feel sore due to the signal frequency.

The work of this circuit is very simple. The timer IC act as the frequency generator, while the frequency value is decided by C1 and C3. The output of 555 will be amplified by the SC1162 transistor and then fed to the speaker so the audio signal can be heard by the mice.

Parts List:

R1 = 1K8
R2 = 1K
R3 = 5K6
R4 = 480R
C1 = 2,2nF
C2 = 0,022uF/6V
IC = 555
Q = SC1162
SP = Speaker 4 ohm

Electronic Siren Circuit

This is the schematic diagram of electronic siren circuit. The sound produced imitates the rise and fall of an American police siren. When very first switched on, the 10uF capacitors is discharged and each transistors are off. When the push button switch is pressed to 10uF capacitor will charge via the 22k resistor. This voltage is applied towards the base of the BC108B which will turn on slowly. When the switch is released the capacitor will discharge via the 100k and 47k base resistors and also the transistor will slowly turn off. The change in voltage alters the frequency of the electronic siren.



Electric current drain is fairly high in this electronic siren circuit so a appropriate power supply is needed. The duration the tone takes to rise and fall is determined by the 10uF and 22k resistor. These values may possibly be varied for various effects.

Electronic Chirping Canary Circuit

Well, for those of you who want to make a small project, this alarm may be an option for you. This circuit will generate the canary chirping sound. The chirp sound of a canary is generated by the oscillation process by resistor R1 and capacitor C1. The capacitor, having a capacitance value of 100 uF, is charging through the resistor, having a resistance of 4.7 K ohms. During this stage, R1 is the bias for the transistor making it operate in the cut off. When the transistor is in cut off mode, the base-emitter voltage is very minimal for any considerable current to flow. This mode triggers the oscillation to end but will start again once the capacitor discharges across the transmitter’s base-emitter circuit.

The frequency of the chirp may be modified by changing the values of the resistor and capacitor. The charging of the capacitor occurs when operating the push button switch. By releasing the button, the chirping runs quicker whilst the oscillation weakens.

The loudspeaker is being driven and coupled to the circuit by the miniature audio transformer of LT700 which having a frequency of 1 kHz. This circuit can be supplied with 9V battery.

Electronic chirping canary circuit source: http://www.elecpod.com/circuit/av/2010/03011410.html

Really Simple LED Flasher with LM3909

This is a very -very easy and simple LED flasher circuit with only needs three components that are: a flasher IC, a LED and a electrolytic capacitor.

Component list:

LED1_________Red LED
C1___________100uf/16V
IC1__________LM3909

Very nice for electronics newbie.. :)

Light Detector

This is a circuit diagram of light detector. This circuit can be used as a sensor of automatic lamp switch, thic circuit also can be used for anti theft alarm circuit.

Schematic diagram:

Use variable resistor R1 to adjust the light threshold at which the circuit triggers. R1's value is chosen to match the photocells resistance at darkness. The circuit uses a CMOS 4001 IC. Gate U1a acts as the trigger, U1b and c form a latch. S1 to reset the circuit. You may used piezo buzzer or LED as output indicator, you may use both of them.

High Quality Intercom circuit

This is an intercom circuit which use LM380 as the audio amplifier and 2 transistors as the microphone pre amplifier. The sound quality will be good enough with low cost building.

This circuit consists of two identical intercom units. Each unit contains a power supply, microphone preamplifier, audio amplifier and a Push To Talk (PTT) relay circuit. Only 2 wires are required to connect the units together. Due to the low output impedance of the mic preamp, screened cable is not necessary and ordinary 2 core speaker cable, or bell wire may be used.

Detail explanation about this intercom circuit include the PCB layout, please visit this page

Running LED

This is the running LED circuit diagram. The LED will "running" (on) one by one. You can use this circuit for many purpose like motorcycle lamp, running character and much more.

Here the schematic diagram with IC timer 555:

And use this circuit use NAND logic:

Zone Alarm System

This is the circuit of alarm system with 5 independent zones. Suitable for a small office or home environment. It uses just 3 CMOS IC's and features a timed entry / exit zone, 4 immediate zones and a panic button. There are indicators for each zone a "system armed" indicator.

Zone 1 is a timed zone which must be used as the entry and exit point of the building. Zones 2 - 5 are immediate zones, which will trigger the alarm with no delay. Some RF immunity is provided for long wiring runs by the input capacitors, C1-C5. C7 and R14 also form a transient suppresser. The key switch acts as the Set/Unset and Reset switch. For good security this should be the metal type with a key.

Circuit works:
At switch on, C6 will charge via R11, this acts as the exit delay and is set to around 30 seconds. This can be altered by varying either C6 or R11. Once the timing period has elapsed, LED6 will light, meaning the system is armed. LED6 may be mounted externally (at the bell box for example) and provides visual indication that the system has set. Once set any contact that opens will trigger the alarm, including Zone 1. To prevent triggering the alarm on entry to the building, the concealed re-entry switch must be operated. This will discharge C6 and start the entry timer. The re-entry switch could be a concealed reed switch, located anywhere in a door frame, but invisible to the eye. The panic switch, when pressed, will trigger the alarm when set. Relay contacts RLA1 provide the latch, RLA2 operate the siren or buzzer.

Simple Electronic Buzzer

This is a simple electronic buzzer circuit diagram. Cheap and easy to build.
The 555 is used as astable multivibrator operating at about 1kHz and produces a shrill noise when switched on. The frequency can be adjusted by varying the 10K resistor. You may change the 10K resistor with variable resistor.

Multi tone alarm

This is a simple and easy to build multi tone alarm circuit that can be used in burglar alarms or sirens. The circuit is based on dual op-amp MC1458 and LM 380. The two op amps inside the MC 1458 are used to produce square and triangular waves.LM 380 is used to amplify the output.The first op amp IC1a is wired as an astable multi vibrator and second op amp IC1b is wired as an integrator, to make the square wave triangle.

The two output square ans sine can be selected using switch S1 to the input of IC2 which amplifies it to drive the speaker. POT R4 can be used for tone adjustment.

Notes .

• IC1a and IC1b are same. So their power supply is common.Wire exactly as shown in figure, nothing to care.
• C1 and C2 are ceramic, C3 is electrolytic capacitor.
• Pin 6 of IC2 (inv input) has no connection.
• A dual power supply is needed here.

Basic Analog Flip Flop Schematics

This schematics is a basic analog flip flop. As we know, there are analog flip flop which built using analog components like ordinary transistor and digital flip flop build using digital logic IC (integrated circuit) like TTL IC.

and here the result:

To control the speed of light's "on" and "off" in another word "control the flash rate", you can replace the Resistor 10K with variable resistor 20K or replace the electrolytic capacitor 100uF with other value.

Flip flop PCB layout:

Dancing Lights

This circuit is very simple... you can use this circuit for decoration purposes or as an indicator. Flashing or dancing speed of LEDs can be adjusted and various dancing patterns of lights can be formed.

The circuit consists of two astable multivibrators. One multivibrator is formed by transistors T1 and T2 while the other astable multivibrator is formed by T3 and T4. Duty cycle of each multivibrator can be varied by changing RC time constant. This can be done through potentiometers VR1 and VR2 to produce different dancing pattern of LEDs.

Flashy christmas light

This simple and inexpensive circuit built around a popular CMOS hex inverter IC CD4069UB offers four sequential switching outputs that may be used to control 200 LEDs (50 LEDs per channel), driven directly from mains supply. Input supply of 230V AC is rectified by the bridge rectifiers D1 to D4. After fullwave rectification, the average output voltage of about 6 volts is obtained across the filter comprising capacitor C1 and resistor R5.

Just a minute scoring board circuit

You can use this circuit for quiz contests wherein any participant who presses his button (switch) before the other contestants, gets the first chance to answer a question. The circuit given here permits up to eight contestants with each one allotted a distinct number (1 to 8). The display will show the number of the contestant pressing his button before the others. Simultaneously, a buzzer will also sound.

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bassic of resistor

A resistor is a two-terminal electronic component designed to oppose an electric current by producing a voltage drop between its terminals in proportion to the current, that is, in accordance with Ohm's law: V = IR. The resistance R is equal to the voltage drop V across the resistor divided by the current I through the resistor.

Resistors are characterized primarily by their resistance and the power they can dissipate. Other characteristics include temperature coefficient, noise, and inductance. Practical resistors can be made of resistive wire, and various compounds and films, and they can be integrated into hybridprinted circuits. Size, and position of leads are relevant to equipment designers; resistors must be physically large enough not to overheat when dissipating their power. Variable resistors, adjustable by changing the position of a tapping on the resistive element, and resistors with a movable tap ("potentiometers"), either adjustable by the user of equipment or contained within, are also used.

We will now explain how to work out resistance values by using the colour bands. Hold the resistor so the fourth band is GOLD. The first two bands of colour provide the two digits in the answer and the third band provides the number of zeros. The answer will be in OHMS.
Here are the resistors used in the projects and their colour bands:

In a moment we will show how the colours are worked out but first we will discuss resistors in general.
PREFERRED VALUES
The value of a resistor is measured in ohms. A low value resistor may be 10 ohms or 22 ohms. A high value resistor may be 100,000 ohms, 330,000 ohms 1,000,000 ohms or even higher.

This is an enormous range and we need this range for electronics. If we had a resistor of each value from 1 ohm to 5 million ohms we would need 5 million types! This is impractical and the designers of circuits have found that in most cases, the value of a resistor can be 10% higher or lower than a specified value and the circuit will work perfectly ok. So the manufacturers of resistors worked out a range of values to provide designers with a complete coverage without the need for too many types.

This is called the range of PREFERRED VALUES and starts at 10 ohms (there are also lower values). The next value is 12 ohms, then 15 ohms, 18 ohms, 22 ohms, 27 ohms 33 ohms 39 ohms 47 ohms 56 ohms 68 ohms and 82 ohms. This is the first 12 values and they may seem like unusual values but each value has been worked out on a 10% tolerance scale. The next values are 100ohms, 120 ohms, 150 ohms, 180 ohms and you can see a pattern emerging - they follow the first group except they are ten times greater. Each group is called a decade and the next decade is 1000ohms, 1200 ohms, 1500 ohms, 1800 ohms etc.

In the old days, when a manufacturer made a batch of resistors, he could not control the final value. So he simply made resistors and tested them just before adding the bands of colour. He did not want to throw any resistors away so when making 100 ohm resistors, for example, he had some at 100 ohms, some at 101 ohms, some at 125 ohms, some at 80 ohms and lots of other values.

Every resistor between 90 ohms and 110 ohms would be banded as 100 ohms. Resistors from 111 ohms to 133 ohms would be banded 120 ohms and in this way the value of any resistor would be either the exact value or only 10% away from the exact value. In electronics, most circuits will work perfectly ok with a resistor that is slightly higher or lower than the stated value. Electronics is not that critical. We are really talking about the old days of radio and the use of valves - where the resistor values were not very critical. Modern electronics (digital electronics) is somewhat more critical and resistors are much more accurate as you will see by the gold band on the resistors in the kit. Gold represents a tolerance of 5%.
RESISTOR COLOUR CODE
Resistors have always been the most difficult component to identify in electronics and that's why they need a lot of study. Once you master the colour code you will feel much happier.

To the casual observer, any circuit board is a mass of "little coloured things" called resistors, with no indication of what value they represent. Once you know the resistor colour code you will be able to work out the values and relate them to a circuit diagram.

That's why it is so important to master this part of electronics. The resistors required for the experiments in this section are contained in a kit of parts and must be separated from the rest of the components and correctly identified.

This is the first thing you will be doing so you don't fit the wrong value in any of the projects.
If you fit the wrong value, the circuit may not work and some of the other components may be damaged. Later on you can experiment with changing resistor values but at this stage you should only fit the specified values.
IDENTIFYING THE RESISTORS
Separate the resistors from all the other components and place them on the bench so that the gold band is to the right.

The gold band indicates the resistors have a tolerance of 5%. In other words they are more accurate than older-style 10% types. This gold band does not concern us in this course but it DOES tell us which way around to hold the resistor so that the colour bands can be read correctly. Only 10 different colours are used for ALL resistors.

The following table shows these 10 colours and the number given to each:

READING THE VALUES
Hold the resistor so that the 3 colour bands are to the LEFT and the right hand band is either gold or silver.

The first colour gives the first DIGIT of the resistance. The second colour give the second DIGIT in the answer. The third colour gives the number of zero's in the answer. There are only 12 resistors in each decade and they have the following first two colours:

All you have to do is add the number of zero's to get the resistance. Use this table to give the number of zero's:

For example, what is the value of a resistor with colour bands:
red red black
2 2 Ohms
Answer:
22 ohms. This is written 22R

What is the value of a resistor with colour bands:
red red red
2 2 00
Answer:
2,200 ohms. This is written 2k2

A resistor with colour bands:yellow purple orange
4 7 ,000
This is written 47k.

A resistor with colour bands:
orange white brown
3 9 0
This is written 390 ohms or 390R.
STANDARD FORM
To make it easy to recognise the value of a resistor, it is important to present the value in a STANDARD FORM - an easily recognised form. This involves using the letters: R, k and M to represent ohms, kilo ohms and Meg ohms (instead of writing lots of ,000's).

For example a 4,700,000 ohm resistor is 4.7 Meg and the decimal point is replaced by the letter M to give 4M7.

A 2,200 ohm resistor is 2.2k and this is written as 2k2. A 100,000 ohm resistor is written as 100k. A 10 ohm resistor is written as 10R, as the letter R represents ohms. The letter R was possibly chosen as a short form of "Resistance."

A 2.2 ohm resistor is written as 2R2. A 1,000 ohm resistor is written as 1k, and so on.
WHAT DOES A RESISTOR DO?
This is not an easy question to answer because a resistor is able to do many things, depending on where it is placed in a circuit, its value and the surrounding components. Every resistor carries out a particular task, and sometimes it does more than one task.
To keep things simple we will cover only a few tasks. In future pages we will cover more features.
1. ZERO OHM RESISTORS AS A LINK
We have already shown that resistors are marked with coloured bands to show the value of the resistance in OHMs and they have a value from .22 ohm (actually from zero ohms - a zero ohm resistor is used as a LINK on a PC board and the purpose of this component may be to act as a bridge to jump over other tracks on the board or it may be a temporary component that can be removed and changed at a later date. It can also be a "test point" where the resistor (link) is removed for testing or calibration.

Resistors can be as high as 10M or greater, depending on the purpose.
This is an enormous range and depending on the value of the resistor and the other component(s) around it, so its function will be determined.
2. THE RESISTOR AS CURRENT LIMITING
Whenever a resistor is placed in a circuit, the current flow through that part of the circuit will be less when the resistor is fitted.

Some components, such as Light Emitting Diodes, will take too much current if they are connected directly across a battery or power supply.

To prevent them burning out, a resistor must be connected in series with one of the leads.
This has already been covered in previous pages.
3. THE RESISTOR AS A VOLTAGE DIVIDER
The resistor can also act as a voltage divider. When two resistors are placed in series, the voltage at their join is a percentage of the voltage across them. The actual voltage can be determined by mathematics or experimentation. For example, If two equal-value resistors are connected in series to a 12v supply, the voltage at their mid point will be 6v. The value of the resistors can be adjusted so that the "pick off" voltage is 9v, or 11v or any voltage up to 12v.
4. THE RESISTOR IN A TIMING CIRCUIT
The resistor can also be used to create a TIMING CIRCUIT by combining it in series with a capacitor. This will be covered later in the course.

The resistor limits the current into the capacitor so that it takes a PERIOD OF TIME to charge. Whenever you see a resistor and capacitor in series you can be fairly certain they form a timing circuit. There are lots of other functions for a resistor including a fusible resistor that is simply designed to burn out if the current through it gets too high, and these will be covered in future pages.

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the understanding of capacitor

A capacitor is a passive electrical component that can store energy in the electric field between a pair of conductors (called "plates"). The process of storing energy in the capacitor is known as "charging", and involves electric charges of equal magnitude, but opposite polarity, building up on each plate. A capacitor's ability to store charge is measured by its capacitance, in units of farads.

Capacitors are often used in electric and electronic circuits as energy-storage devices. They can also be used to differentiate between high-frequency and low-frequency signals. This property makes them useful in electronic filters. Practical capacitors have series resistance, internal leakage of charge, series inductance and other non-ideal properties not found in a theoretical, ideal, capacitor.

The capacitor is used in almost every electronic circuit. It is a very important component and it does many different things, depending on where it is placed.

A capacitor is basically a device that stores a charge of electricity.
It has two or more plates that are separated by air or a non conducting medium such as plastic.

A basic capacitor is shown in the diagram below with the corresponding circuit symbol.

Capacitors can be large or small and the size is the result of the value of the capacitor as well as the voltage it is capable of withstanding.

There is a lot to learn about capacitors and we will only be discussing the very basics.
There are many types of capacitors, here are 5 of the most common types:

AIR - such as a tuning capacitor in a radio.

GREENCAP - a polyester capacitor.

CERAMIC - a ceramic insulating material that produces a very compact
capacitor

MONOBLOCK - also called monolithic - a multi-layer ceramic capacitor

ELECTROLYTIC - aluminium plates with a moist insulating medium. This type of capacitor has a very high capacitance in a small space.

The diagram below shows a single-ended electrolytic, suitable for mounting on a printed circuit board and the symbol.

The unit for capacitance is the FARAD. But one Farad is an enormous value and we don't use values this large in electronics. The value we use is the micro-farad. A microfarad is one-millionth of a farad.

For some circuits we need capacitors of more than 1 microfarad capacitance and for others we need less than 1 microfarad.

For a power supply we need electrolytics of 10 microfarad, 100 microfarad, 1,000 microfarad and even 10,000 microfarad. The letter to signify microfarad is "uF" or simply "u". Thus 1microfarad is 1u, 10 microfarad is 10u etc.

For audio work we need smaller values such as .1microfarad and .01 microfarad.
In electronics, we try and avoid using the decimal point as it can be rubbed off components and omitted from photocopies of circuit diagrams.

To get around this we use sub-multiples and the sub-multiple of microfarad is nanofarad.

1,000 nanofarad = 1 microfarad.
Thus .1u = 100 nanofarad.
The letter to represent nanofarad is "n".
Thus .01u = 10n

For radio frequency work, even smaller values of capacitance are needed.

The nanofarad is divided into 1,000 parts called picofarad. Thus 1,000 picofarad = 1nanofarad.

The picofarad is written pF or simply "p."
Thus 1,000p = 1n.

Some capacitors are physically very small and there is very little space to write the component value. To get around this, manufacturers have produced a numbering system using 3 digits.

It is based on picofarads. A 100 picofarad capacitor is written as 101, A 1,000 picofarad capacitor is written 102, A 10 nanofarad capacitor is written 103 and 100 nanofarads is written 104. The third digit represents the number of zero's.

For example: 1n = 1,000p = 102.
10n = 10,000 = 103
100n = 100,000 = 104



WHAT DOES A CAPACITOR DO?
Capacitors do lots of things and it depends where they are positioned in a circuit, the value of the surrounding components and the value of the capacitor.

One of the things that makes the study of a capacitor complex is the current flowing into it starts off very high and gradually reduces as the capacitor charges.

In addition, the voltage across the capacitor does not increase evenly, it rises rapidly at first then gradually slows down. Some of these facts have already been covered and at this stage it only important to know that the charging is not linear.

The capacitor can also be used as a timing component. This has been covered in the oscillator circuits where the value of the capacitor determines the frequency of the oscillator.

The capacitor is basically a device that stores a charge of electricity, but depending on where it is placed in a circuit, it can be used as a reservoir device, a blocking device or a device to pass AC signals. It can be used for filtering, stage separation, decoupling, timing, and even amplifying! (In a tuned circuit it creates amplification when connected to a coil - but this is mainly due to one of the incredible properties of a coil).

It will take a lot more projects to cover all these features.

You can hear the result of a time delay circuit in the Simple Siren project (Project 4) and if you think of the electrolytic as a miniature rechargeable battery, charging and discharging as we have shown in the animations, you will be a little closer to "seeing" how the circuit operates.

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Simple Battery Charger with LM350

The schematic diagram can be used for charging the 12V lead acid batteries.

The circuit is designed as a constant voltage source with a negative temperature coefficient. The transistor Q1 (BD 140) is used as the temperature sensor. The transistor Q2 is used to prevent the battery from discharging through R1 when the mains power is not available. The circuit is designed based on the voltage regulator IC LM350. The output voltage of the charger can be adjusted between 13-15 V by varying the POT R6.

The LM350 will try to keep the voltage drop between its input pin and the output pin at a constant value of 1.25V. So there will be a constant current flow through the resistor R1. Q1 act here as a temperature sensor with the help of components R6/R3/R4 which more or less control the base current of Q1. As the emitter/base connection of transitor Q1, just like any other semiconductor, contains a temperature coefficient of -2mV/°C, the output voltage will also show a negative temperature coefficient. That one is only a factor of 4 larger, because of the variation of the emitter/basis of Q1 multiplied by the division factor of P1/R3/R4. This results in approximately -8mV/°C. The LED will glow whenever the mains power is available.

The transistor Q1 must be placed as close as possible to the battery.
Use a 20 to 30 V / 3A DC power supply for powering the circuit.
This circuit is not possible for charging GEL type batteries as it draw large amounts of current.

Here the LM350 pin layout:

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easy USB Battery Charger for Lithium Ion Battery

This schematic diagram is used for charging lithium ion battery. The power source is from a computer's USB port. With this circuit, you do not need to build power supply circuits for charging your battery.

A USB port is a great power source for charging a single cell li-on battery. It is capable of supplying maximum 5.25V and 500 mA. The circuit above is a USB powered single cell li-on battery charger. LM3622 is used as the controller. This special purpose IC has a precise end-of-charge control and low battery leakage current about 200nA.

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how to NiCad Battery Charger

This simple and low cost battery charger uses a single transistor as a constant current source. The voltage across the pair of 1N4148 diodes biases the base of the BD140 medium power transistor. The base-emitter voltage of the transistor and the forward voltage drop across the diodes are relatively stable. The charging current is approximately 15mA or 45mA with the switch closed. This suits most 1.5V and 9V rechargeable batteries.

The transformer should have a secondary rating of 12V ac at 0.5amp

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sample 6V Gel Cell Charger Circuit

This is the diagram of 6V Gel Cell charger. The circuit is using NE555 timer as oscillator and TPI31T switching transistor. The schematic diagram designed by Tony Van Roon.



Parts List:

R1 = 22 ohm, 1W R2 = 270 ohm R3 = 220 ohm *R4 = 715 ohm, 1% *R5 = 3.57K, 1% *R6 = 1.40K, 1% *R7 = 1.47K, 1%

C1 = 100nF C2 = 100nF D1 = 1N4001 T1 = TIP31A, B, C (or equivalent) U1 = Timer IC NE555V (or equivalent) S1 = Toggle switch, ON-OFF

* Resistors type are carbon, 1/4 watt, 5% tolerance, unless otherwise indicated.



6V Gel Cell Charger circuit source page

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another Multi tone alarm schematic diagram

This is a simple and easy to build multi tone alarm circuit that can be used in burglar alarms or sirens. The circuit is based on dual op-amp MC1458 and LM 380. The two op amps inside the MC 1458 are used to produce square and triangular waves.LM 380 is used to amplify the output.The first op amp IC1a is wired as an astable multi vibrator and second op amp IC1b is wired as an integrator, to make the square wave triangle.

The two output square ans sine can be selected using switch S1 to the input of IC2 which amplifies it to drive the speaker. POT R4 can be used for tone adjustment.

Notes .

• IC1a and IC1b are same. So their power supply is common.Wire exactly as shown in figure, nothing to care.
• C1 and C2 are ceramic, C3 is electrolytic capacitor.
• Pin 6 of IC2 (inv input) has no connection.
• A dual power supply is needed here.

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Simple fire alarm circuit with IC timer NE555

Here the simple file alarm circuit based timer ID NE555. The works is simple, the lamp give light to the LDR (Light Depending Resistor) as light sensor. When the light from the lamp covered with smoke then the LDR will change its resistance value and then activated the alarm.

The thermistor offers a low resistance at high temperature and high resistance at low imperature. This phenomenon is employed here for sensing the fire.

The IC1 (NE555) is configured as a free running oscillator at audio frequency. The transistors T1 and T2 drive IC1. The output(pin 3) of IC1 is couples to base of transistor T3(SL100), which drives the speaker to generate alarm sound. The frequency of NE555 depends on the values of resistances R5 and R6 and capacitance C2.When thermistor becomes hot, it gives a low-resistance path for the positive voltage to the base of transistor T1 through diode D1 and resistance R2.

Capacitor C1 charges up to the positive supply voltage and increases the the time for which the alarm is ON. The larger the value of C1, the larger the positive bias applied to the base of transistor T1 (BC548). As the collector of T1 is coupled to the base of transistor T2, the transistor T2 provides a positive voltage to pin 4 (reset) of IC1 (NE555). Resistor R4 is selected s0 that NE555 keeps inactive in the absence of the positive voltage. Diode D1 stops discharging of capacitor C1 when the thermistor is in connection with the positive supply voltage cools out and provides a high resistance path. It also inhibits the forward biasing of transistor T1.

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fire alarm system

The works is similiar from previous circuit. the LDR sending the light from lamp. When light from lamp blocked by smoke, the alarm will be activated.

When there is no smoke the light from the bulb will be directly falling on the LDR. The LDR resistance will be low and so the voltage across it (below .6V). The transistor will be OFF and nothing happens. When there is sufficient smoke to mask the light from falling on LDR, the LDR resistance increases and so do the voltage across it. Now the transistor will switch to ON. This gives power to the IC1 and it outputs 5V. This powers the tone generator IC UM66 (IC2) to play a music. This music will be amplified by IC3 (TDA 2002) to drive the speaker.

The diode D1 and D2 in combination drops 1.4 V to give the rated voltage (3.5V ) to UM66 .UM 66 cannot withstand more than 4V.

Notes.

• The speaker can be a 8Ω tweeter.
• POT R4 can be used to adjust the sensitivity of the alarm.
• POT R3 can be used for varying the volume of the alarm.
• Any general purpose NPN transistor (like BC548,BC148,2N222) can be used for Q1.
• The circuit can be powered from a 9V battery or a 9V DC power supply.
• Instead of bulb you can use a bright LED with a 1K resistor series to it.

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Sound Effects Alarm Generator alarm system

This schematic in very simple and easy to made. The IC produces all the sound effects, the output at Pin 3 being amplified by the transistor. A 64 ohm loudspeaker can be substituted in place of the 56 ohm resistor and 8 ohm loudspeaker. The 2 pole 4 way switch controls the sound effects. Position 1 (as drawn) being a Police siren, position 2 is a fire engine sound, 3 is an ambulance and position 4 is a machine gun effect. The IC is manufactured by UMC and was available from Maplin electronics code UJ45Y. At the time of writing this has now been discontinued, but they have have limited stocks available.

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Water Activated Alarm || simple circuit uses timer IC

This simple circuit uses timer IC to generate frequency. Emitter current from transistor BC 109C powered the IC to work, so the transistor work similiar as switch work. Under dry conditions, the transistor will have no bias current and be fully off. As the probes get wet, a small current flows between base and emitter and the transistor switches on. A larger current flows in the collector circuit enabling the 555 osillator to sound.

An On/Off switch is provided and remember to use a non-reactive metal for the probe contacts. Gold or silver plated contacts from an old relay may be used, however a cheap alternative is to wire alternate copper strips from a piece of veroboard. These will eventually oxidize over but as very little current is flowing in the base circuit, the higher impedance caused by oxidization is not important. No base resistor is necessary as the transistor is in emitter follower, current limit being the impedance at the emitter (the oscillator circuit).

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simple water alarm system

More explanation about water level circuit, please go to this page.

Description:
This circuit will trigger with any fluid with a resistance under 900K between the maximum separation distance of the probes. Let me explain further. The circuit uses a 4050B CMOS hex buffer working on a 5 volt supply.

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Zone Alarm System schema

This is the circuit of alarm system with 5 independent zones. Suitable for a small office or home environment. It uses just 3 CMOS IC's and features a timed entry / exit zone, 4 immediate zones and a panic button. There are indicators for each zone a "system armed" indicator.

Zone 1 is a timed zone which must be used as the entry and exit point of the building. Zones 2 - 5 are immediate zones, which will trigger the alarm with no delay. Some RF immunity is provided for long wiring runs by the input capacitors, C1-C5. C7 and R14 also form a transient suppresser. The key switch acts as the Set/Unset and Reset switch. For good security this should be the metal type with a key.

Circuit works:
At switch on, C6 will charge via R11, this acts as the exit delay and is set to around 30 seconds. This can be altered by varying either C6 or R11. Once the timing period has elapsed, LED6 will light, meaning the system is armed. LED6 may be mounted externally (at the bell box for example) and provides visual indication that the system has set. Once set any contact that opens will trigger the alarm, including Zone 1. To prevent triggering the alarm on entry to the building, the concealed re-entry switch must be operated. This will discharge C6 and start the entry timer. The re-entry switch could be a concealed reed switch, located anywhere in a door frame, but invisible to the eye. The panic switch, when pressed, will trigger the alarm when set. Relay contacts RLA1 provide the latch, RLA2 operate the siren or buzzer.

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Light Detector diagram

This is a circuit diagram of light detector. This circuit can be used as a sensor of automatic lamp switch, thic circuit also can be used for anti theft alarm circuit.

Schematic diagram:

Use variable resistor R1 to adjust the light threshold at which the circuit triggers. R1's value is chosen to match the photocells resistance at darkness. The circuit uses a CMOS 4001 IC. Gate U1a acts as the trigger, U1b and c form a latch. S1 to reset the circuit. You may used piezo buzzer or LED as output indicator, you may use both of them.

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gate alarm circuit

Here the simple gate alarm circuit that built based on CMOS IC 4093B. With CMOS IC, this circuit must be work with small universal 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.

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simple and easy emergency light and alarm circuit

This is a simple and easy emergency light and alarm circuit. This circuit is permanently plugged into a mains socket and NI-CD batteries are trickle-charged. When a power outage occurs, the lamp automatically illuminates. Instead of illuminating a lamp, an alarm sounder can be chosen.

When power supply is restored, the lamp or the alarm is switched-off. A switch provides a "latch-up" function, in order to extend lamp or alarm operation even when power is restored.

Component parts list:

R1 = 220K
R2 = 470R
R3 = 390R
R4 = 1K5
R5 = 1R
R6 = 10K
R7 = 330K
R8 = 470R
R9 = 100R
C1 = 330nF/400V Polyester Capacitor
C2 = 10µF/63V Electrolytic Capacitor
C3 = 100nF/63V Polyester Capacitor
C4 = 10nF/63V Polyester Capacitor
D1-D5 = 1N4007
D6 = LED Green
D7 = 1N4148
Q1,Q3,Q4 = BC547
Q2,Q5 = BC327
SW1,SW2 = SPST Switches
SW3 = SPDT Switch
LP1 = 2.2V or 2.5V 250-300mA Torch Lamp Bulb
SPKR = 8 Ohm Loudspeaker
B1 = 2.5V Battery (two AA NI-CD rechargeable cells wired in series)
PL1 = Male Mains plug

Circuit Works:
Mains voltage is reduced to about 12V DC at C2's terminals, by means of the reactance of C1 and the diode bridge (D1-D4). This avoids the use of a mains transformer.

Trickle-charging current for the battery B1 is provided by the series resistor R3, D5 and the green LED D6 that also monitors the presence of mains supply and correct battery charging.
Q2 & Q3 form a self-latching pair that start operating when a power outage occurs. In this case, Q1 biasing becomes positive, so this transistor turns on the self latching pair.

If SW3 is set as shown in the circuit diagram, the lamp illuminates via SW2, which is normally closed; if set the other way, a square wave audio frequency generator formed by Q4, Q5 and related components is activated, driving the loudspeaker.

If SW1 is left open, when mains supply is restored the lamp or the alarm continue to operate. They can be disabled by opening the main on-off switch SW2.

If SW1 is closed, restoration of the mains power supply terminates lamp or alarm operation, by applying a positive bias to the Base of Q2.

Notes:

• Close SW2 after the circuit is plugged.
• Warning! The circuit is connected to 230Vac mains, then some parts in the circuit board are subjected to lethal potential!. Avoid touching the circuit when plugged and enclose it in a plastic box.

Emergency Light and Alarm circuit source: http://www.redcircuits.com/Page45.htm

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a touch activated alarm system

This is a touch activated alarm system. Your alarm system will be activated when someone touching the "trigger". You may use this circuit at your home door, your vehicle etc.

Parts list:

R1 = 100K R2 = 56K R3 = 10M R4 = 220K P1 = 100K D1 = 1N4004

T1 = 2N3904, or equivalent U1 = 555 Timer* C1 = 47μF/16V** C2 = 33μF/16V** Re1 = Relay***

Notes:

*The 555 can be a LM, NE, or MC(cmos) type, they're all pin-compatible.

**C1/C2's working voltage ought to be elevated to 25V in the event you decide to go with a 12V power source. Rule of thumb: the operating voltage of capacitors are at least double the supplied voltage, in other words, if the power source is 9 Volt, your capacitor(s) is a minimum of 18V. Transistor T1 could be any approximate substitute.

*** Use any appropriate relay for the project and if you're not tight on area, use any size. I've build this specific circuit to prevent students from fiddling using the security cameras in pc labs at the University I'm employed. I made sure the metal casing was not grounded. But as being the schematic shows you are able to essentially hook it as much as any type of metal surface. I utilized a 12-vdc power supply. Use any suitable relay to deal with your specifications. A 'RESET' switch (Normally Closed) can be added between the constructive and also the 'arrow-with-the-+'. The trigger (touch) wire is connected to pin 2 of the 555 and will trigger the relay, using the body resistance, when touched. It is apparent that the 'touching' component has to be clean and can make good contact using the trigger wire. This particular circuit might not be suitable for all applications. Just in case you wonder why pin 5 is not listed within the schematic diagram; it is not really required. In particular noisy circumstances a little ceramic capacitor is placed between pin 5 and ground. It will no harm to put one or leave it out.

Additional note: For those of you who didn't discover, there's an approximate 5-second delay build-in before activation of the relay to avoid false triggering, or perhaps a 'would-be' thief, and so on.

Circuit design by Tony van Roon.

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Electronic Chirping Canary Circuits

Well, for those of you who want to make a small project, this alarm may be an option for you. This circuit will generate the canary chirping sound. The chirp sound of a canary is generated by the oscillation process by resistor R1 and capacitor C1. The capacitor, having a capacitance value of 100 uF, is charging through the resistor, having a resistance of 4.7 K ohms. During this stage, R1 is the bias for the transistor making it operate in the cut off. When the transistor is in cut off mode, the base-emitter voltage is very minimal for any considerable current to flow. This mode triggers the oscillation to end but will start again once the capacitor discharges across the transmitter’s base-emitter circuit.

The frequency of the chirp may be modified by changing the values of the resistor and capacitor. The charging of the capacitor occurs when operating the push button switch. By releasing the button, the chirping runs quicker whilst the oscillation weakens.

The loudspeaker is being driven and coupled to the circuit by the miniature audio transformer of LT700 which having a frequency of 1 kHz. This circuit can be supplied with 9V battery.

Electronic chirping canary circuit source: http://www.elecpod.com/circuit/av/2010/03011410.html

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bassic how to make motor cicle alarm

This is a very basic motorcycle alarm design circuit which can be used to secure your motorcycle with very low in cost.

Design schematic:

Circuit Number Five uses a SPCO/SPDT relay - but you actually only require to make use of a SPST relay. In case you are going to make use of the veroboard layout supplied - you will require to make use of the style of relay specified. But you are able to develop the alarm making use of whatever style of relay you've accessible.

Circuit Notes:
Any number of normally-open switches might be employed. Fit the mercury switches to ensure that they close when the steering is moved or when the bike is lifted off its side-stand or pushed forward off its centre-stand. Use micro-switches to secure removable panels and also the lids of panniers and so on. When 1 of the trigger-switches is closed - the relay will energize as well as the siren will sound.

You are able to select what will happen up coming. Should you develop the circuit as shown, the siren will continue to sound until you turn it off - or until the battery is exhausted. But, in the event you leave out D3 - the siren will stop sounding right away the trigger-switch is re-opened.

Whilst you are inside earshot of your machine - the former configuration is greatest. You are able to usually turn off the alarm your self. But in case you are going to be away from your bike for any length of time - and you do not wish to trigger a nuisance - then the latter configuration is possibly much more suitable. In the event you consist of a SPST switch in series with D3 - you'll be able to pick the behaviour that finest suits the circumstances at any given time.

Components placement:

Relay coils and some sounders generate high reverse-voltage spikes which will destroy sensitive electronic components. D1 and D2 are there to short-circuit these spikes just before they are able to do any harm. Even though there's absolutely nothing within the alarm circuit itself that might be damaged - I've no concept what other electronic equipment may be connected to the exact same power supply. So I included the two diodes as a precaution. If you are satisfied that there is absolutely nothing on your bike that may be damaged in this way - you'll be able to leave out the two diodes.

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Electronic Siren Circuit schema

This is the schematic diagram of electronic siren circuit. The sound produced imitates the rise and fall of an American police siren. When very first switched on, the 10uF capacitors is discharged and each transistors are off. When the push button switch is pressed to 10uF capacitor will charge via the 22k resistor. This voltage is applied towards the base of the BC108B which will turn on slowly. When the switch is released the capacitor will discharge via the 100k and 47k base resistors and also the transistor will slowly turn off. The change in voltage alters the frequency of the electronic siren.



Electric current drain is fairly high in this electronic siren circuit so a appropriate power supply is needed. The duration the tone takes to rise and fall is determined by the 10uF and 22k resistor. These values may possibly be varied for various effects.

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