Build a Simple Home Alarm Circuit Using 555 ICs

This is a Simple Home Alarm Circuit Using 555 ICs. This schema can be simplified by using a single 74C14 IC. This IC is also known by the following numbers: 40106, 40014, and 74HC14.  These are CMOS chips and are characterised by low current consumption, high input impedance and a supply voltage from 5v to 15v. (Do not substitute 7414 or  74LS14. They are TTL chips and operate on 4.5v to 5.5v and have low impedance inputs.)

 Simple Home Alarm Circuit Diagram

The 74C14 contains 6 Schmitt Trigger gates and 4 of these gates (Schmitt Inverters) are used in this schema.
The schema consists of a number of "building blocks" and the first consists of two transistors in a very clever "bootstrap" arrangement. The first transistor is turned on via the 3M3 and 47k. The second transistor is not turned on and the output is HIGH.

A small signal from the electret microphone will consist of positive and negative excursions and the negative excursion will turn the first transistor OFF. This will turn the second transistor ON and the left lead of the 100n will be pulled towards the 0v rail. The 100n is uncharged and the right lead will also be pulled towards the 0v rail and the input of the  74C14 will see a LOW. This will make the output HIGH and turn on the BC547 transistor.

When the second transistor turns ON, it also pulls the 2u2 down and this removes the "turn-on" voltage to the first transistor. The two transistors remain in this state for a few seconds while the 2u2 discharges and the voltage on the base of the first transistor rises. When this happens, the two transistors change state and the 2u2 charges. When the schema is waiting to detect audio, the 2u2 is charged via the 47k on the base of the first transistor and 47k collector resistor of the second transistor (plus the base-emitter voltage drop of the first transistor).

Simple Home Alarm Circuit Diagram A

 To exit the property, the EXIT button is pressed and this puts a HIGH on pin 1 of the IC so that any signal from the electret mic is not passed to the siren. The EXIT delay is determined by the value of the 100u and 2M2. Normally-open and normally-closed switches will also send a LOW to trigger the siren.

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Basic Of Power Supply Wiring diagram Schematic

I was a fan and an electronics Technician. Almost all electronic devices use Power Supply. If you want to know more about the Basic Of Power Supply Circuit Diagram , you can browse the articles in this blog. Here I am trying to write an article about the Power Supply. 

All electronic equipment requires power supplies, either from the battery or use electricity in your home. Electronic equipment usually requires certain power supply consumption. Suppose the voltage for charging mobile phones require only 5 Volt, may not 220V of electricity in your home is connected directly to your cell phone, of course it should be through the Power Supplies that have been adapted to the voltage consumption phone or other electronics, if directly connected to your mobile home electric / electronic you will explode. Except electronic equipment that is equipped with the power supply in it such as a TV, tapecorder, personal computers, VCD, etc. 

Lets see Basic of Power Supply Circuit Diagram below Electronic equipment typically uses direct current (DC) and the voltage and current of the adjustable electrical equipment condition. In the picture I show a basic schematic schema Power Supply is comprised of a transformer is used to reduce the voltage of 220V at the primary and 6V - 12V on the secondary.

So, electronic equipment required for basic of the Power Supply is:
1. Transformer (TRANSFORMER), in this case a 220V input and 12V as output
2. Silicon diodes
3. capacitors
4. Electrolyte capacitors

Basic of Power Supply Circuit, by Bustamsyah

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Crossover For Subwoofer

The crossover network is intended for use when an existing audio installation is to be extended by the addition of a subwoofer. Often, this additional loudspeaker is one that has been lying around for some time. If its frequency response extends down far enough, all is well and good, but a filter is then needed to cut off any frequencies above, say, 150 Hz. Often, a subwoofer network is an active filter, but here this would necessitate an additional power supply. The present network is a passive one, designed so that the speaker signal of the existing system can be used as the input signal.

Crossover For Subwoofer Circuit diagram:

 Crossover Circuit Diagram For Subwoofer

Since the bass information is present in both (stereo) loudspeakers, the signal for the sub woofer can simply be tapped from one of them. The network is a 1st order low-pass filter with variable input (P1) and presettable cut-off frequency (P2). The signal from the loudspeaker is applied to terminal ‘LSP’. Voltage divider R1-R2-P1 is designed for use with the output signal of an average output amplifier of around d 50 W. The crossover frequency of the network may be varied between 50 Hz and 160 Hz with P2. The values of R3, P2, and C1, are calculated on the assumption that the subwoofer amplifier to be connected to K1 has a standard input resistance of 47 kΩ.

If this figure is lower, the value of C1 will need to be increased slightly. It is advisable to open the volume of the subwoofer amplifier fully and adjust the sound level with P1. This ensures that the input of the subwoofer amplifier cannot be overloaded or damaged. Make sure that the ground of the loudspeaker signal line is linked to the ground of the subwoofer amplifier. If phase reversal is required, this is best done by reversing the wires to the subwoofer. If notwithstanding the above additional protection is desired at the input of the subwoofer amplifier, this is best effected by ‘overload protection ’ elsewhere in this site.

Author: T. Giesberts Copyright: Elektor Electronics

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Low Cost Universal Charger Wiring diagram Schematic

Here is the ambit diagram of a low amount accepted charger for NiCD - NiMH batteries. This ambit is Ideal for car use. It has adeptness to transform a mains adapter in to a charger . This one can be acclimated to allegation cellular phone, toys, portables, video batteries, MP3 players, ... and has selectable allegation current. An LED is amid in ambit to announce charging. Can be congenital on a accepted purpose PCB or a veroboard. I achievement you absolutely like it.

Low Cost Universal Charger Circuit Diagram Prt

R1 = 120R-0...5W
R2 = See Diagram
C1 = 220uF-35V
D1 = 1N4007
D2 = 3mm. LED
Q1 = BD135
J1 = DC Input Socket

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Schematic Power Amplifier with IC TDA7370

Here..... this circuit is stereo power amplifier , based on IC TDA7370, its nice Intregated Power amplifier , He does not have hre slightest sound buzzing , although power amplifiers without additional reinforcement , such as filters , tone control, etc.

Voltage                      : 9 to 24 volts
Max. Power Output  : 2 x 20 Watts
Impedance                : 4 Ohms

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Build A Voltage Inverter using IC NE 555

In many diagram we need to generate an internal adjustable voltage. This schema shows how it is possible to use a trusty old NE555 timer IC and a bit of external schemary to create a voltage inverter and doubler. The input voltage to be doubled is fed in at connector K1. To generate the stepped-up output at connector K2 the timer IC drives a two-stage inverting charge pump schema.

The NE555 is configured as an astable multivibrator and produces a rectangular wave at its output, with variable mark-space ratio and variable frequency. This results in timing capacitor C3 (see schema diagram) being alternately charged and discharged; the voltage at pin 2 (THR) of the NE555 swings between one-third of the supply voltage and two-thirds of the supply voltage.

Voltage Inverter Circuit Using IC NE555

The output of the NE555 is connected to two voltage inverters. The first inverter comprises C1, C2, D1 and D2. These components convert the rectangular wave signal into a nega-tive DC level at the upper pin of K2. The second inverter, comprising C4, C5, D3 and D4, is also driven from the output of IC1, but uses the negative output voltage present on diode D3 as its reference potential. The consequence is that at the lower pin of output connector K2 we obtain a negative volt-age double that on the upper pin.

Now let us look at the voltage feedback arrangement, which lets us adjust this doubled negative output voltage down to the level we want. The NE555 has a control voltage input on pin 5 (CV). Normally the voltage level on this pin is maintained at two-thirds of the supply voltage by internal schemary. The voltage provides a reference for one of the comparators inside the device. If the reference voltage on the CV pin is raised towards the supply voltage by an external schema, the timing capacitor C3 in the astable multivibrator will take longer to charge and to discharge. As a result the frequency of the rectangle wave output from IC1 will fall, and its mark-space ratio will also fall.

The source for the CV reference voltage in this schema is the base-emitter junction of PNP transistor T1. If the base volt-age of T1 is approximately 500 mV lower than its emitter voltage, T1 will start to conduct and thus pull the voltage on the CV pin towards the positive supply.

In the feedback path NPN transistor T2 has the function of a voltage level shifter, being wired in common-base configuration. The threshold is set by the resistance of the feedback chain comprising resistor R3 and potentiometer P1. When the emitter voltage of transistor T2 is more than approximately 500 mV lower than its base voltage it will start to conduct. Its collector then acts as a current sink. Potentiometer P1 can be used to adjust the sensitivity of the negative feedback schema and hence the final output voltage level.Using T1 as a voltage reference means that the schema will adjust itself to compensate not only for changes in load at K2, but also for changes in the input supply voltage. If K2 is disconnected from the load the desired output voltage will be maintained, with the oscillation frequency falling to around 150 Hz.

A particular feature of this schema is the somewhat unconventional way that the NE555’s discharge pin (pin 7) is connected to its output (pin 3). To understand how this trick works we need to inspect the innards of the IC. Both pins are outputs, driven by internal transistors with bases both connected (via separate base resistors) to the emitter of a further transistor. The collectors of the output transistors are thus isolated from one another [1].

The external wiring connecting pins 3 and 7 together means that the two transistors are operating in parallel: this roughly doubles the current that can be switched to ground.The two oscilloscope traces show how the output voltage behaves under different circumstances. The left-hand figure shows the behaviour of the schema with an input voltage of 9 V and a resistive load of 470 Ω connected to the lower pin of output connector K2. The figure on the right shows the situation with an input voltage of 10 V and a load of 1 kΩ on the lower pin of output connector K2. The pulse width and frequency of the rectangle wave at the output of IC1 are automatically adjusted to compensate for the differing conditions by the feedback mechanism built around T1 and T2.

Because of the voltage drops across the Darlington out-put stage in the IC (2.5 V maximum) and the four diodes (700 mV each) the schema achieves an efficiency at full load (470 Ω between the output and ground) of approximately 50 %; at lower loads (1 kΩ) the efficiency is about 65 %. Link

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Capacitive Sensor

The purpose of this schema is to animate shop-windows by means of a capacitive sensor placed behind a post-card-like banner. The card is placed against the glass inside the shop-window, and the visitor can activate the relay placing his hand on the card, from the outside. Especially suited for toy-shops, the schema can activate model trains, small electric racing cars, lights etc. Further applications are left at users imagination. Adopt it to increase the impact of your shop-window on next Christmas season






Parts:

R1,R2_____1M 1/4W Resistors
R3,R4____47K 1/4W Resistors

C1_______10µF 25V Electrolytic Capacitor
C2______470pF 630V Ceramic or Polyester Capacitor

D1-D3____1N4002 100V 1A Diodes

Q1-Q3_____BC337 45V 800mA NPN Transistors

RL1_______Relay with SPDT 2A @ 220V switch
Coil Voltage 12V. Coil resistance 200-300 Ohm

J1________Two ways output socket

Sensor____Aluminium or copper thin sheet with the dimensions of a post-card,
glued at the rear of the same (about 15x10.5 cm.)

Thin screened cable




Q1, Q2 & Q3 form a high impedance super-Darlington that drives the relay, amplifying the 50 or 60Hz alternate mains-supply frequency induced in the sensor by the human body. C1, D2 & D3 ensure a clean switching of the relay. Power supply can be any commercial wall plug-in transformer adapter with rectifier and smoothing capacitor, capable of supplying the voltage and current necessary to power the relay you intend to use.
Note:

* For proper operation, schema ground must be connected via a small value, high voltage-rating capacitor to one side of the mains supply socket. The "Live" side is the right one.

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