500Watt Power Amplifier Circuit

In this post I will publish the circuit schematic diagram of Power Amplifier with 500watt output mono, yesterday happened to date July 18, 2012 order I able to make Power Sound System 1000 watts stereo output, which is used Sanken Transistor Final original eight seeds, serial 2SC2922 and 2SA1216, while the circuit schematic that I made here just next to it / mono with 4 Sanken transistors, lets see diagram skematic 500Watt Power Amplifier Circuit :

Power circuit requires consumption voltage polarity is 3 - 42Vol; + 42 Vol; CT 0 V and there is a safety fuse / voltage connecting Fuse Fuse is the only positive and negative voltage is connected, the source voltage / transformer CT minimum of 10A, AC Vol 220, 50 Hz.

Safe Oscillator For Watch Crystals circuit with explanation

This circuit was developed to allow watch crystals to be used in an existing CMOS oscillator circuit that was to run from a 12V supply. The problem is that these crystals only work up to a supply voltage of about 6V. Any more than that and the crystal will be over-driven, causing it to shatter. This circuit solves the problem by using LEDs 1 & 2 and a 470nF capacitor (C3) to limit the drive to the crystal to about 4V peak-to-peak. Note that it may be necessary to adjust C1 & C2 to ensure reliable start-up and stable oscillation with some crystals. However, the C1:C2 ratio should be maintained. As a bonus, the two LEDs both glow, giving a visual indication that the oscillator is working.

The relatively high values used here for capacitors C1 & C2 will load the crystal, which means that the oscillator will run at less than the nominal crystal frequency (32.768kHz).
Author: Duncan Graham – Copyright: Silicon Chip Electronics 

Essential Home Theater Design

Relations every time require to bring habitat particular luxurious home entertainment structure. This is for the reason that just very a small number of households can afford home drama system. Of tardy, only the rich and the famous can afford such luxury. This notion is right away a feature of the ancient history. Home plays systems may well now stay vacant to greater numeral of households since of the familiarity of principal home drama design. The basic home theater design may well just require three basic components and these three components might already take place within your means in lieu of the working course group.

However, formerly you could need to think of the vital home-made show business design for your home theater organism, you may perhaps need to know the size of the scope for the home the stage stubborn up. The size of the scope to someplace the home drama want transpire set up will depend on how straightforward the home show business design needs to be.

Home theater experts recommends with the purpose of if the scope is quite diminutive, all you need pro your home plays design is a television set, three speakers and a DVD player. The home show business design may perhaps be there dependent of the shpre of the opportunity; however, the put of the speakers remains to be the not here, the aptly and the meeting place of the space. central residence show business design may perhaps require a television set superior than 27 inches. Too diminutive screen in support of your home drama design can not exist sufficient for a picture acting-like experience.

This is for the reason that even for the home acting design, you might need to consider the sight and sound of a picture drama. It is the chief consideration why dwell in stab to a show drama, the immense screen and the surround sound. With respect to the surround sound of a picture plays, the major three speakers is barely applicable on behalf of lesser quarters, if the space is larger, the local the stage design needs to take place added than three, you may perhaps go up to six speakers and a complimenting subwoofer may be needed for the surround effect. leaving back to a trivial space, if you force lone locate three speakers, you may perhaps care for to consider export a tall quality brand loudspeaker; this will make happen you adequate surround sound on behalf of a less significant scope.

If you boast a slight finances, ensure with the aim of the stockpile someplace you preference believe your speakers will allow you to test the outcome modish your opportunity and if it will not give you a fine surround sound, they be supposed to allow you to return before return the constituent. This is as roughly speakers sound good in the store but what time you at the end of the day suite them up in a insignificant opportunity, the effect is not very good. observe a neat deal wherever they can allow you to return otherwise restore the speakers. However, if your resources is sufficient, you might consider hiring the services of a residential home the stage designer. Your home theater designer wish be alive able to design the home acting better and with complete accessories. He may possibly require read-through the power rating, and the need in support of amplifiers. He may well too put in a good word for using home plays projectors and he may recommend how the speakers need to befall. You yearn for dig up a profit home drama design if you will be able to hire home drama designers. The need in favor of home theater seats and television cabinet may possibly additionally be vital for the complete package of your home acting.

You may possibly take pleasure in the entertainment exclusive of having to tide traffic jam and enjoy hip your own place of origin show business scheme.

TB2922HQ bassed 40 70 watt power audio amplifier Diagram Circuit

Using the TB2922HQ audio power IC can be designed a very simple and high efficiency power audio amplifier electronic project . TB2922HQ is 2ch BTL audio amplifier for TV or home audio applications.

It includes and the pure complementary P-ch and N-ch DMOS output stage.
This TB2922HQ power audio amplifier project is very simple to be implemented and require few external electronic parts . The TB2922HQ power audio amplifier module can be used with 4 or 8 ohms load . Using a 4 ohms load this power audio circuit will provide a output power around 40 watts and using a 8 ohms load the circuit will provide a output power of 23 volts . If you’ll use a bridge mode connection this circuit will provide an output power around 70 watts . If is used a 4 ohms load this TB2922HQ power audio amplifier project must be powered from a good filtered DC power supply that will provide an output voltage between 9 and 18 volts , and if is used a 8 ohms load , a DC power supply that will provide a n output voltage between 9 and 26 volts will be required .
Some features provided by this audio power amplifier module are : built-in standby switch function ,built-in muting function , built-in various protection circuits: thermal shut down, overvoltage, out to GND, out to VCC, out to out short speaker burned .

Low impedance microphone amplifier Circuit diagram

The circuit is a microphone amplifier used for handle with low impedance (~200 ohm) microphones. It hope against hope job with stabilized voltages sandwiched between 6-30VDC. If you dont build the impedance adapter part with T1, you obtain a micamp for upper impedance microphones. within this indictment, you ought to honestly bond the suggest to C7.

Add captionLow impedance microphone amplifier

R1=15k
R2= 150k
R3= 2k2
R4= 820
R6= 10k
R7= 10k
P1= 1M
C1= 3k9
C2= 100u
C3= 22u
C4= 4u7
C5= 470u
C6= 10u
C7= 100n
C8= 47u UNIPOLAR
D1= 1N4148
U1= TL081
CN1= SIL6

Expandable Multi Zone Modular Burglar Alarm

The Basic Alarm Circuit has an automatic Exit/Entry Zone - an Instant Alarm Zone that will accept both normally-closed and normally-open triggering devices - and an "Always On" 24-hour Personal Attack/Tamper Zone. By using the Expansion Modules - you can add as many extra alarm zones as you require.

Schematic Diagram

The Alarm is armed and disarmed by SW1. Before you move the switch to the "set" position - all the green LEDs should be lighting. You then have up to about a minute to leave the building. As you do so - the Buzzer will sound. It should stop sounding when you close the door behind you. This indicates that the Exit/Entry loop has been successfully restored within the time allowed. 

When you re-enter the building - you have up to about a minute to move SW1 to the "off" position. If SW1 is not switched off in time - the relay will energize - and the main bell will ring. It will continue ringing for up to about 40 minutes. But it can be turned off at any time by SW1. 

The "Instant" zone has no Entry Delay. The moment one of its normally-open switches is closed - the main bell will ring. Similarly - the moment one of its normally-closed switches is opened - the main bell will ring. If you dont want to use normally-open switches - leave out R8, C8 and Q2 - and fit a link between Led 3 and C7.

The 24 Hour Personal Attack and Tamper protection is provided by the SCR/Thyristor. If one of the switches in the normally-closed loop is opened - current through R11 will trigger the SCR - and the main bell will ring. In this case the bell has no time limit. To reset the PA/Tamper zone - first restore the normally-closed loop - then press SW2 momentarily. This will interrupt the current and reset the SCR.

Two-Zone Expansion Module

The basic circuit will be satisfactory in many situations. However, if you have a large building to protect - its much easier to find a fault - when the system is divided into zones - and the control panel can "remember" which zone has caused the activation. 

The expansion modules are designed to do this. Although they will work with the existing instant zone - they are intended to replace it. When a zone is triggered - its red LED will light and remain lit - to indicate that the zone has been activated. 

The idea is that - once youve noted the zone in question - you then press the reset button and turn off the LED. The reset button simply turns off the LED. It doesnt reset the zone. The zone resets automatically when the trigger circuit is restored. If youre using more than one expansion module - they can all share a single reset button.

Inertia-Sensor Module

What is an Autotransformer

WHAT IS AN AUTOTRANSFORMER? HOW IS IT IMPLEMENTED?
An autotransformer is a type of transformer in which a single inductor coil is used. It has a single continuous winding of coil, with a connection point between the primary and secondary sides. This connection point is called tap. The tap has its own characteristics: an adjustable joint that is used vary the number of turns and  influence the turn ratio, to either step up and step down the voltage across the device. This feature can be used to provide a variable voltage to a load connected to the transformer.

Construction:
The main difference in the construction of autotransformers for a step down or step up voltages lies in the connection between the voltage source and the connected load with the single inductor coil. Variable voltage is produced in this way.

Some key mathematical expressions for step down and step up transformers are given below:
•    For a step down transformer circuit, the voltage ratio is given by:
            V1/V2 = (N1+N2) / N2
•    And the current ratio is given as:
            I1/I2 = N2 / (N1+N2)
•    For a step up transformer circuit, the voltage ratio is given by:
            V1/V2 = N1 / (N1+N2)
•    And the current ratio is given as:
            I1/I2 = (N1+N2) / N1

Where    V1 = Voltage across the inductor coil of an autotransformer
        V2 = voltage across the load connected to the autotransformer
        I1 = Electric current passing through the inductor coil
        I2 = Electric current passing through the load
        N1 = Number of turns of coil on the primary side
        N2 = Number of turns of coil on the secondary side

Comparing an autotransformer with a conventional transformer:
 An autotransformer is a type of power transformer. It can transfer a larger apparent power than a two-inductor coil-wound transformer. When compared to standard transformers, autotransformers tend to be smaller in size and lighter in weight. However, a major disadvantage of an autotransformer is its lack of electrical isolation between primary and secondary windings due to the presence of a single winding inductor coil. This property of lacking electrical isolation does not make an autotransformer a useless device - application where electrical isolation is not required do exist.
A full range of transformers and autotransformers are supplied by element 14, through their business partner Panduit.

Amplifier Classes Circuit

In these pages, we discuss three amplifier configurations, the amplifier class A, class B and class AB. Class of amplifier is distinguished by the location of the work load point of the transistor. Load point is located in the load line as shown in Figure 2, assuming the transistor circuit is the common emitter configuration (as in Figure 1).

Transistor in the circuit in Figure 1, will have a working point between points A and B, along the load line. Point A is the working area when the transistor is experiencing saturation, while point B is when the transistor cut-off.

Class A Amplifier 
The point of the load transistors in class A amplifier is placed between points A and B, usually to produce a good performance then the point load is placed right in the middle of the load line. This has meant that the output signal will have a form of signal symmetry between positive and negative cycles. In order to obtain the exact middle point of the load, then VCE is designed to be equal to VCC / 2. To produce this, the IB is designed to produce the ICRC together with VCC / 2. Class A amplifier can be realized with the circuit as Figure 3 below.

Figure 3. Amplifier class A.

Class A amplifier is designed to strengthen the small signals. While the shortcomings of the amplifier of this type is when there is no input signal, the transistor will still consume electricity.


Class B Amplifier
The amplifier is realized by assembling a pair of complementary transistors as shown in Figure 4. Unlike the class A amplifier, the load point of the class B amplifier transistor pad placed point B (the cut-off). With these conditions, then when there is no input signal, the transistor does not consume electricity. The amplifier of this type is also known as push-pull amplifier as the work of the transistor pair is alternately. This amplifier is applied as the final amplifier, or a large signal amplifier.

Figure 4. Class B amplifier (push-pull).

When Vin is in the positive phase only NPN transistor is ON, while when the signal Vin is in the negative phase only the PNP transistor is ON. However, because the bias voltage of the transistor from the signal Vin, the signal will be clipped by the VBE voltage, so that the output signal will experience a disability (distortion).

Class AB amplifiers
To overcome the distortion of the amplifier permaslahan class B, then made a class AB amplifier. This amplifier has a load point is located slightly above the point B (Figure 2), the transistor in the tegnagn dibias threshold condition of VBE. In this condition, then in a state with no signal Vin, the transistor does not consume electricity. Meanwhile, when Vin comes up then this signal is not interrupted by the signal output voltage VBE that is not distorted. Example of a class AB amplifier is as

Figure 5. Class AB amplifiers

STK404 130S bassed 100w power amplifier Diagram Circuit

A very high power and efficiency 100w power amplifier electronic project can be designed using the STK404 audio power amplifier hybrid ICs that consist of optimally-designed discrete component power amplifier circuits that have been miniaturized using SANYO’s unique insulated metal substrate technology (IMST).

STK404 power audio IC is pin to pin compatible with some other STK series power amplifiers ranging from 45W to 180W (10%/1kHz) .
This audio power amplifier use the STK404-130S audio IC that will provide a maximum of 100 watt output power on a 6 ohms load with 0.4% THD . Using the same IC , can be obtained an output power of 150 watts with 10% THD.
The STK404-130S power audio IC supports a maximum input DC voltage of 64 volts , but typically is recommended a 45 volt dual ( +/-) power supply.
Like other audio amplifiers electronic projects , this high power 100w power amplifier circuit require a very well filtered DC power supply .
Because of the power dissipation , the STK404-130S hybrid audio power IC must be mounted on a heatsink . Therefore, the thermal resistance that satisfies all requirements of these power audio amplifier (for a guaranteed ambient temperature of 50°C) is 1.48°C/W.

BTL Stereo Amplifier TDA7052 3

This is BTL stereo power amplifier with basic amplifier on IC TDA7052 / TDA7053

Cranial Electrotherapy Stimulator

Current generated flows through clips placed on the earlobes Output current adjustable from 80 to 600 microAmperes. Owing to the recent launching in Europe of Cranial Electrotherapy Stimulation (CES) portable sets, we have been "Electronically Stimulated" in designing a similar circuit for the sake of hobbyists. CES is the most popular technique for electrically boosting brain power, and has long been prescribed by doctors, mainly in the USA, for therapeutic reasons, including the treatment of anxiety, depression, insomnia, and chemical dependency. CES units generate an adjustable current (80 to 600 microAmperes) that flows through clips placed on the earlobes. 

The waveform of this device is a 400 milliseconds positive pulse followed by a negative one of the same duration, then a pause of 1.2 seconds. The main frequency is 0.5 Hz, i.e. a double pulse every 2 seconds. Some people report that this kind of minute specialized electrical impulses contributes to achieve a relaxed state that leaves the mind alert. Obviously we cant claim or prove any therapeutic effectiveness for this device, but if you are interested in trying it, the circuit is so cheap and so simple to build that an attempt can be made with quite no harm.

Cranial Electrotherapy Stimulator  Circuit diagram:

 

 

Parts:
R1___________1M5 1/4W Resistor
R2___________15K 1/4W Resistor
R3___________100K Linear Potentiometer
R4___________2K2 1/4W Resistor
C1___________330nF 63V Polyester Capacitor
C2___________100µF 25V Electrolytic Capacitor
D1___________3mm. Red LED
IC1___________7555 or TS555CN CMos Timer IC
IC2___________4017 Decade counter with 10 decoded outputs IC
SW1__________SPST Slider Switch
B1____________9V PP3 Battery Clip for PP3 Battery
Two Earclips with wires (see notes)

Circuit operation:

IC1 forms a narrow pulse, 2.5Hz oscillator feeding IC2. This chip generates the various timings for the output pulses. Output is taken at pins 2 & 3 to easily obtain negative going pulses also. Current output is limited to 600µA by R2 and can be regulated from 80 to 600µA by means of R3. The LED flashes every 2 seconds signaling proper operation and can also be used for setting purposes. It can be omitted together with R4, greatly increasing battery life.

Notes:

• In order to obtain a more precise frequency setting take R1=1M2 and add a 500K trimmer in series with it.
• In this case use a frequency meter to read 2.5Hz at pin 3 of IC1, or an oscilloscope to read 400msec pulses at pins 2, 3 or 10, adjusting the added trimmer.
• A simpler setting can be made adjusting the trimmer to count exactly a LED flash every 2 seconds.
• Earclips can be made with little plastic clips and cementing the end of the wire in a position suited to make good contact with earlobes.
• Ultra-simple earclips can be made using a thin copper foil with rounded corners 4 cm. long and 1.5 cm. wide, soldering the wire end in the center, and then folding the foil in two parts holding the earlobes.
• To ensure a better current transfer, this kind of devices usually has felt pads moistened with a conducting solution interposed between clips and skin.
• Commercial sets have frequently a built-in timer. Timing sessions last usually 20 minutes to 1 hour. For this purpose you can use the Timed Beeper the Bedside Lamp Timer or the Jogging Timer circuits available on this website, adjusting the timing components in order to suit your needs.
  

Wiring diagram 1957 Pontiac

This wiring diagram is for all models of 1957 Pontiac. Click the picture to download.

LED light Organ Circuit Diagram

This is a fun circuit that can be at parties, for example. The four LEDs flash to the beat of the music. The light organ responds using a microphone to sound.T1 amplifies the signal from MIC. The sensitivity can be adjusted by P1. T4 controls the LEDs. 

These are preferably LEDs with a high light intensity.MIC is a condenser microphone. The circuit can be powered by a 9 V battery.

 LED light Organ Circuit Diagram

The 4 Budget

This circuit costs about € 6.15.


Parts List

•      R1 = 10 k
•      R2 = 330 K?
•      R3, R6, R13 = 100 k
•      R4, R8, R11, R14 = 47 Ω
•      R5, R9, R12 = 1.5 MΩ
•      R7, R10 = 47 k
•      P1 = 220 K?
•      C1, C2, C3 = 100 nF
•      C4 = 100 uF
•      D1-D4 = LED
•      T1, T2, T3 = BC547B
•      T4 = BC557B
•      MIC = microphone capsule

10 Watts Stereo Power Amplifier TDA2009A

Here are a power amplifier with TDA2009A integrated circuits produced by 10 +10 W stereo amplifier (see figure). As a result of ASIC, making her the production becomes very simple, the performance is not bad.

Her main performance characteristics in the table below.

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Power Supply Voltage: DC 8-24V/1-2A
Power Output:

1. 10W RMS / channel, 4 ohm load, 24V/DC power;
2. 6W RMS / channel, 8 ohm load, 24V/DC power;
3. 4W RMS / channel, 4 ohm load, 12V/DC power.

S/N: >75dB/10W output
Frequency response: 10Hz-50kHz,-3dB
Gain: 36dB
Input Level: 100mV Full output power

Schematic and Prototype:

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Principle and production elements:

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C1, C2 as the input capacitor, C10, C11 for the output capacitor. C6, C7 for the feedback capacitance. R1/R2, or (R3/R4) control the amount of feedback. Amplifier gain is equal to 1 + (R1/R2) = 68, or 37dB. C4, C5 for the power supply filter capacitor. The device maximum supply voltage of 28V. Hours of work required to add TDA2009A heat sink, and should pay attention to the power lines and then the choice of speaker wiring. Input should use shielded lines and as short as possible. Welding TDA200A not take too long when you pay attention, action to be fast, but if you want their full integration with the circuit board.

2N3055 Variable DC Power Supply circuit Diagram

Voltage range: 0.7 – 24V Current limiting range: 50mA – 2A

A Variable DC Power Supply is one of the most useful tools on the electronics hobbyist’s workbench. This circuit is not an absolute novelty, but it is simple, reliable, “rugged” and short-proof, featuring variable voltage up to 24V and variable current limiting up to 2A. Well suited to supply the circuits shown in this website. You can adapt it to your own requirements as explained in the notes below.
Notes:

* P1 sets the maximum output current you want to be delivered by the power supply at a given output voltage.
* P2 sets the output voltage and must be a logarithmic taper type, in order to obtain a more linear scale voltage indication.
* You can choose the Transformer on the grounds of maximum voltage and current output needed. Best choices are: 36, 40 or 48V center-tapped and 50, 75, 80 or 100VA.
* Capacitor C1 can be 2200 to 6800µF, 35 to 50V.
* Q4 must be mounted on a good heatsink in order to withstand sustained output short-circuit. In some cases the rear panel of the metal box in which you will enclose the circuit can do the job.
* The 2N3055 transistor (Q4) can be replaced with the slightly less powerful TIP3055 type.

Parts:
P1____________500R Linear Potentiometer
P2_____________10K Log. Potentiometer
R1,R2___________2K2 1/2W Resistors
R3____________330R 1/4W Resistor
R4____________150R 1/4W Resistor
R5______________1R 5W Resistor
C1___________3300µF 35V Electrolytic Capacitor (see Notes)
C2______________1µF 63V Polyester Capacitor
D1,D2________1N5402 200V 3A Diodes
D3_____________5mm. Red LED
Q1____________BC182 50V 100mA NPN Transistor
Q2____________BD139 80V 1.5A NPN Transistor
Q3____________BC212 50V 100mA PNP Transistor
Q4 __________2N3055 60V 15A NPN Transistor
T1_____________220V Primary, 36V Center-tapped Secondary
50VA Mains transformer (see Notes)
PL1____________Male Mains plug
SW1____________SPST Mains switch

NCP2824 Class D amplifier electronic project circuit and explanation

Using the NCP2824 filterless Class D amplifier can be designed a very simple low power audio amplifier electronic project, capable of delivering up to 2.4 W to a 4 ohms load with a 5 V supply voltage.
With the same battery voltage, it can deliver 1.2 W to an 8 ohms load with less than 1% THD+N. The non−clipping function automatically adjusts the output voltage in order to control the distortion when an excessive input is applied to the amplifier.

This adjustment is done thanks to an Automatic Gain Control circuitry (AGC) built into the chip. A simple single wire interface allows to the non Clipping function to be enabled and disabled.
A programmable power limit function is also embedded in order to protect speakers from damage caused by an excessive sound level.

latest Light Detector by IC CD4001 circuit and explanation

Variable resistor R1 adjusts 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 resets the circuit. The output device may be a low power piezo buzzer.

Kindly submitted by Mick Devine from the UK 

Charge Balance converter circuit

AD7711 IC for Charge Balance converter circuit

AD7711 IC for Charge Balance converter circuit

Phone Alarm Dialer using MT8880 and PIC 16F84A

Phone Alarm Dialer using MT8880 and PIC 16F84A

Just angle this Anxiety Buzz Dialer up to article you would like to monitor, for example, a aerial baptize alarm, low temperature alarm, aback window, barn door, etc. Back the arrangement is activated it will anxiety a cardinal of programmed numbers to let you apperceive the anxiety has been activated. This would be abundant to get alerts of anxiety altitude from your home back you are at work.

The ambit uses a MT8880 DTMF dialer dent and a PIC 16F84A microcontroller. After putting calm this little device, you charge access programming-mode to apprentice some buzz numbers which this bore will anxiety afterwards audition an ascribe on it’s sensor pin.

After programming aloof accumulation ability to the device. Afterwards acute the button “Pokreni dojavu alarma” it will alpha to punch (tone or pulse, depending on the jumper setup). Back the buzz anxiety is auspiciously established, the alleged affair should columnist batter key “#” to stop the accessory from calling addition cardinal or again.

Car Anti Theft Burglar Alarm Security Circuit

A car thief will avoid a car that causes him trouble and attracts attention. A good anti theft alarm in your car will soon convince a would be thief that there are easier pickings elsewhere.

The present circuit (figure 63), when set, reacts to the opening of a door (via the door switch for the interior courtesy lights). Such switches can also guard the engine compartment and boot. Fitting switches to the rear doors, boot lid, and bonnet makes sense, because thieves aren’t so sporting as to always try to break in via the driver’s or front passenger’s door. The alarm is set by a well hidden switch, S. Once it is set, you have about one minute to leave the car and lock the doors. A lamp La, goes out just before the minute has lapsed. After that, whenever one of the doors is opened  even for a short time  the alarm goes off unless switch S has been disabled (hopefully by the owner) within 6 seconds from the door opening. The normal car horn is used as alarm and you should therefore check that this is not in easy reach of the thief. lf the horn, for instance, is fitted under the wings of the car, it is fairly easy to cut through the connecting wires. As may be seen from figure 63, the circuit consists of a control stage, the alarm section, and a switching stage which operates the horn via a relay.

Construction hints  When the hidden switch S has been closed, the anti—theft alarm is powered, and the following actions take place: a) gates  form a NAND gate latch (also called R-S flip—flop) which acts as a (set) (reset)g1ange;Jver switch that can be set to the required state by logic levels via inputs S and R . The convention with these circuits is that they are sg when the O output is high, or reset (= cleared) when the O output is low; the O output is complementary to the O output. The set input (pin 13) is logic high via R2 and R3, while the R input is low. To begin with, capacitor C6 is not charged. The low level at the O output (pg 11) inhibits the clock of IC3 via NAND gates N5 and N6, while the high level at O resets binary counter (C3 to zero. . b) To begin with, the inputs of N4 are logic low, so that its output is ‘l’ and this causes transistor T3 to conduct via D3 and R11: lamp La then lights. At the sang time, T1 is switched on via R9 and short—circuits R2 and R3 which holds the S input logic high. This means that when a door is opened, nothing happens!  c) As long as counter IC3 is set to zero, its outputs O and Q7 are logic low, which makes the output of N3 high. As diode D2 is reverse biased, capacitor C6 charges via R5. After about 1 minute (determined by the values of C6 and R5) the trigger level of N4 has been reached, the output of the gate goes low, and La extinguishes. At the same time, C5 charges via R9 so that after six seconds T1 is cut off. The alarm is then set.


Alarm stage

When the alarm is set, and a door—switch is opened, the driver stages, as you have already ascertained, cause a high logic level at pin 11 of IC1 and a low logic level at pin 10. The high level clears the clock generator formed by N5 and N6: the clock pulses are applied to the CLOCK input of IC3. The low level at the CLR (clear) input of the counter releases the handbrake so to speak: IC3 now starts counting the clock pulses. Since outputs O3 and O4 of IC3 are taken through an OR circuit (diodes D7, D8, and resistor R12), the parallel-connected NAND gates N7 and N8 are cleared for a total of four periods after the first four clock pulses: during each of these periods twelve clock pulses are applied to T3. The horn therefore gives twelves short sounds fol- lowed by a pause, then twelve short sounds again, and so on until sixty—four pulses have passed. After the sixty—fourth pulse, both inputs of N3 go high (from O7, O1). The inverted output level of N3 causes the partial discharge of C6 and the reset of flip-flop N1/N2: the counter and clock are then inhibited again. At the same time, N4 causes the base of T1 to go logic high for a brief moment: this allows C5 to discharge. After that, it takes six seconds again for the alarm to become ’live afresh.

Installation  

Well, the most difficult part is now behind you: the alarm unit is ready for installation. The best place to fit the alarm is under or behind the instrument panel. Connections of the mating sockets for PLT and PL5 should not present too much of a difficulty, but remember that PLl must be permanently connected to the positive battery line, irrespective of the ignition switch! The positive line is identified in most cars by the code number 30, while earth (chassis = battery negative line) is coded 31. Control lamp La should be fitted in good view of the driver: its terminals should be connected to a socket mating with PL3 and to earth.

The horn relay should be fitted in the engine compartment: the pin—out of a typical horn relay is shown in figure 65. Remember what we said about the location of the horn at the beginning of this chapter: make sure it is not within easy reach of a prospective thief. If it is, a second horn may be the answer, and this should then, of course, be located in a secure position. The door switches in most cars (normally only fitted to the front doos) close when the door is opened and so connect the interior lights to chassis (see lLa in figure 63). lf the socket mating with PL2 is connected to the take—off point of this switch con- tact, the alarm is operational. However, as remarked before, a// doors (if not already factory—fitted), bonnet, and boot lid should be provided with a switch. Microswitches or reed switches which you may already have in stock are perfectly suitable.

As a matter of fact, they are probably better than switches fitted by the car manufacturer: those are invariably of a cheap, ,unprotected type which rusts easily. Obviously, such switches are not very reliable. lt’s therefore better to spend a little more and get g0od·quality switches on which you can depend for reliable operation of your alarm! The real problem is bound to be the location of the alarm switch: thieves seem to have second sight when it comes to spotting non-standard knobs and switches in cars they are interested in. Here you’|l have to use your imagination: on the one hand you dont want to do acrobatics to turn the alarm on, and on the other the switch should be in easy reach known only to yourself. We cannot give you any hints on this, if only because car thieves also read hobby books and will be very grateful for our tips! The terminals of all switches, as well as soldering joints, should be given a good layer of spray—on protective lacquer: this will prevent rattles and corrosion, while connecetions will remain easily undone or unsoldered.