Build a Inexpensive Car Protection Unit Circuit Diagram

This is a simple Inexpensive car Protection Unit Circuit Diagram. This circuit to protect car stereo, etc from pilferage that costs less and requires no adjustments in the car but a good car cover. Place the circuit at your bedside and bring the two wires from the unit to the car (parked outside your home) and connect one wire-end to the cover and the other to the ground, with both wire-ends shorted by some weight such as a brick. So outwardly the mechanism is not visible.

Circuit of car protection unit with alarm

If someone tries to remove the cover, the alarm of the circuit starts sounding to alert you. The alarm can be switched off by resetting it using switch S1.

The car protection circuit comprises two timer ICs: one for the alarm circuit (see IC2 in Fig.1) and the other to indicate that the battery has taken over as the power source (see IC3 in Fig. 2). Normally, the protector operates off AC mains and the battery takes over only when mains fail. As the battery current is not high, the battery will last long.

As long as the two wires remain shorted, transistor T1 remains cut off. When shorting is removed, transistor T1 gets forward biased and its collector voltage drops to trigger IC2 and the piezobuzzer starts sounding.

 battery-takeover indicator

If mains fails, the battery-takeover indicator (shown in Fig. 2 and connected to points A, B and C in Fig. 1) immediately gets triggered at pin 2 of IC3. Its high output activates the battery-operation alarm for a couple of seconds. IC1 draws power from the battery to activate the protection unit.

After setting up the unit properly and shorting both the wires, press test switch S2. If there is no fault in the circuit, the alarm will sound. Now release test switch S2 and momentarily press reset switch S1 to switch off the alarm.

Sourced By:  EFY Author : M. Venkateswaran and T.E. Parthasarathy

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Build a Digital Electronic Lock Circuit Diagram

This Digital Electronic Lock Circuit Diagram shown below uses 4 common logic ICs to allow controlling a relay by entering a 4 digit number on a keypad. The first 4 outputs from the CD4017 decade counter (pins 3,2,4,7) are gated together with 4 digits from a keypad so that as the keys are depressed in the correct order, the counter will advance. As each correct key is pressed, a low level appears at the output of the dual NAND gate producing a high level at the output of the 8 input NAND at pin 13.

Read : Cheap Bicycle Alarm Schematics Circuit

Digital Electronic Lock Circuit Diagram

 

The momentary high level from pin 13 activates a one shot circuit which applies an approximate 80 millisecond positive going pulse to the clock line (pin 14) of the decade counter which advances it one count on the rising edge.

Read : Emergency Light and Alarm Circuit Diagram

A second monostable, one shot circuit is used to generate an approximate 40 millisecond positive going pulse which is applied to the common point of the keypad so that the appropriate NAND gate will see two logic high levels when the correct key is pressed (one from the counter and the other from the key). The inverted clock pulse (negative going) at pin 12 of the 74C14 and the positive going keypad pulse at pin 6 are gated together using two diodes as an AND gate (shown in lower right corner).

Read : Burglar Alarm With Timed Shutoff Circuit Diagram

The output at the junction of the diodes will be positive in the event a wrong key is pressed and will reset the counter. When a correct key is pressed, outputs will be present from both monostable circuits (clock and keypad) causing the reset line to remain low and allowing the counter to advance. However, since the keypad pulse begins slightly before the clock, a 0.1uF capacitor is connected to the reset line to delay the reset until the inverted clock arrives.

Read : 5 Zone alarm Circuit Diagram

The values are not critical and various other timing schemes could be used but the clock signal should be slightly longer than the keypad pulse so that the clock signal can mask out the keypad and avoid resetting the counter in the event the clock pulse ends before the keypad pulse. The fifth output of the counter is on pin 10, so that after four correct key entries have been made, pin 10 will move to a high level and can be used to activate a relay, illuminate an LED, ect. At this point, the lock can be reset simply by pressing any key. The circuit can be extended with additional gates (one more CD4011) to accept up to a 8 digit code.

Read :  Alarm Control Keypad Circuit Diagram

The 4017 counting order is 3 2 4 7 10 1 5 6 9 11 so that the first 8 outputs are connected to the NAND gates and pin 9 would be used to drive the relay or light. The 4 additional NAND gate outputs would connect to the 4 remaining inputs of the CD4068 (pins 9,10,11,12). The circuit will operate from 3 to 12 volts on 4000 series CMOS but only 6 volts or less if 74HC parts are used. The circuit draws very little current (about 165 microamps) so it could be powered for several months on 4 AA batteries assuming only intermittent use of the relay.

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Build a 12 14 Volt 3A Anti RF Filtered Power supply Circuit Diagram

How to Build a 12-14 Volt 3A - Anti-RF Filtered Power supply Circuit Diagram. This is not easy but you can do it . This Anti-RF Filtered Power supply Circuit Diagram is dedicated for use with rf equipments like, linear amplifiers, transmitters, receivers, and in every application that clean an-noisy signal is required. 

The circuit is very simple and you can drive it with a 220V/18V/3A transformer at the pins 1and 2.The regulator used here is the LM350K and make sure you place a good heat-sink to it because it gets too hot if current gets near to 3A. 

 12-14 Volt 3A - Anti-RF Filtered Power supply Circuit Diagram

Parts list
R1 = 220 Ohm 1/4W
R2 = 1,8 KOhm 1/4W
R3 = 330 Ohm 1/4W
 P1 = 100 Ohm
C1,C2,C3 = 4.700uf/25V
C4 = 100pf ceramic
C6 = 100uf/25V electrolitic
D1..4 = 1N5400-4 or RAX GI 837U
F1 = 5A
IC1 = LM350K

For Data Sheet Contact with us here

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Power Flip Flop Using A Triac

Modern electronics is indispensable for every large model railroad system, and it provides a solution to almost every problem. Although ready-made products are exorbitantly expensive, clever electronics hobbyists try to use a minimum number of components to achieve optimum results together with low costs. This approach can be demonstrated using the rather unusual semiconductor power flip-flop described here. A flip-flop is a toggling circuit with two stable switching states (bistable multivibrator). It maintains its output state even in the absence of an input pulse.

Flip-flops can easily be implemented using triacs if no DC voltage is available. Triacs are also so inexpensive that they are often used by model railway builders as semiconductor power switches. The decisive advantage of triacs is that they are bi-directional, which means they can be triggered during both the positive and the negative half-cycle by applying an AC voltage to the gate electrode (G). The polarity of the trigger voltage is thus irrelevant. Triggering with a DC current is also possible. Figure 1 shows the circuit diagram of such a power flop-flop. A permanent magnet is fitted to the model train, and when it travels from left to right, the magnet switches the flip-flop on and off via reed switches S1 and S2.

In order for this to work in both directions of travel, another pair of reed switches (S3 and S4) is connected in parallel with S1 and S2. Briefly closing S1 or S3 triggers the triac. The RC network C1/R2, which acts as a phase shifter, maintains the trigger current. The current through R2, C1 and the gate electrode (G) reaches its maximum value when the voltage across the load passes through zero. This causes the triac to be triggered anew for each half-cycle, even though no pulse is present at the gate. It remains triggered until S2 or S4 is closed, which causes it to return to the blocking state.The load can be incandescent lamps in the station area (platform lighting) or a

solenoid-operated device, such as a crossing gate. The LED connected across the output (with a rectifier diode) indicates the state of the flip-flop. The circuit shown here is designed for use in a model railway system, but there is no reason why it could not be used for other applications. The reed switches can also be replaced by normal push-button switches. For the commonly used TIC206D triac, which has a maximum current rating of 4 A, no heat sink is necessary in this application unless a load current exceeding 1 A must be supplied continuously or for an extended period of time. If the switch-on or switch-off pulse proves to be inadequate, the value of electrolytic capacitor C1 must be increased slightly.

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A Simple Tan Timer Circuit Diagram

Six timing positions suited to different skin types, Timing affected by sunlight intensity

This timer was designed for people wanting to get tanned but at the same time wishing to avoid an excessive exposure to sunlight. A Rotary Switch sets the timer according to six classified Photo-types (see table). A Photo resistor extends the preset time value according to sunlight brightness (see table). When preset time ends, the beeper emits an intermittent signal and, to stop it, a complete switch-off of the circuit via SW2 is necessary.

Circuit diagram:

A Simple Tan Timer Circuit Diagram

Parts:

R1 = 47K - 1/4W Resistor
R2 = 1M - 1/4W Resistor
R3 = 120K - 1/4W Resistors
R4 = Photo resistor (any type)
R5 = 120K - 1/4W Resistors
C1 = 10µF - 25V Electrolytic Capacitors
C2 = 220nF - 63V Polyester Capacitor
C3 = 10µF - 25V Electrolytic Capacitors
D1 = 1N4148 - 75V 150mA Diodes
D2 = 1N4148 - 75V 150mA Diodes
Q1 = BC337 - 45V 800mA NPN Transistor
B1 = 3V Battery (two 1.5V AA or AAA cells in series)
IC1 = 4060 - 14 stage ripple counter and oscillator IC
IC2 = 4017 - Decade counter with 10 decoded outputs IC
SW1 = 2 poles 6 ways Rotary Switch (see notes)
SW2 = SPST Slider Switch
BZ1 = Piezo sounder (incorporating 3KHz oscillator)

 

Photo-type	Features	Exposure time
I & children	Light-eyed, red-haired, light complexion, freckly	20 to 33 minutes
II	Light-eyed, fair-haired, light complexion	28 to 47 minutes
III	Light or brown-eyed, fair or brown-haired, light or slightly dark complexion	40 to 67 minutes
IV	Dark-eyed, brown-haired, dark complexion	52 to 87 minutes
V	Dark-eyed, dark-haired, olive complexion	88 to 147 minutes
VI	The darkest of all	136 to 227 minutes
Note that pregnant women belong to Photo-type I

Notes:

• Needing only one time set suitable for your own skin type, the rotary switch can be replaced by hard-wired links.
• A DIP-Switch can be used in place of the rotary type. Please pay attention to use only one switch at a time when the device is off, or the ICs could be damaged.

Source : www.redcircuits.com

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A Low Cost Hearing Aid Circuit

Small and transportable unit, Useful for previous men and previous women

This most economical, general-purpose electronic hearing help works off 3V DC (2x1.5V battery). The circuit will additionally be simply assembled on a veroboard. For easy assembling and repairs, use an 8-pin DIP IC socket for TDA2822M.

Circuit Diagrams:

 A Low Cost hearing Aid Circuit

Parts:
P1 = 10K
R1 = 2.2K
R2 = 330K
R3 = 680R
R4 = 33R
R5 = 100R
R6 = four.7R
R7 = 4.7R
R8 = 220R
C1 = zero.01uF-10V
C2 = 100nF-63V
C3 = four7uF-10V
C4 = 10uF-10V
C5 = 0.01uF-10V
C6 = 100uF-10V
C7 = 100nF-63V
C8 = 100nF-63V
D1 = Red LED
Q1 = BC547
IC1 = TDA2822M
EP1 = Mono Earphone 32R
SW1 = On-Off Switch

Circuit Operation:

In this circuit, transistor Q1 and related elements kind the audio signal preamplifier for the acoustic signals picked up via the condenser microphone and transformed into corresponding electrical signals. Resistor R5 and capacitor C3 decouple the facility supply of the preamplifier stage. Resistor R1 biases the interior circuit of the low-voltage condenser microphone for correct working. The audio output from the preamplifier stage is fed to the input of the medium-power amplifier circuit by method of capacitor C2 and quantity keep watch over P1.

The medium-power amplifier section is wired round in style audio amplifier IC TDA2822M (not TDA2822). This IC, specially designed for moveable low-power utilitys, is readily available in 8-pin mini DIP bundle. Here the IC is wired in bridge configuration to pressure the 32-ohm general-purpose monophonic earphone. Red LED (D1) point outs the facility status. Resistor R8 restricts the running present of D1. The audio output of this circuit is 10 to 15mW and the quiescent present drain is below 1 mA.

Source : www.electronsforu.com

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Build a Voice Scrambler or Descrambler Circuit Diagram

This Voice Scrambler or De-scrambler Circuit Diagram uses an NE602 as an inversion mixer. U2 is set to run at about 2.5 to 3.5 kHz. U3 drives a loudspeaker. Because speech inversion scrambling is its own inverse, the circuit will also descramble . 

Voice Scrambler or Descrambler Circuit Diagram

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Build A Relay Toggle Switch

Half of RL1 and RL2 manipulate the switching and the other is connected to an application. Relays are 200 ohms above ground and at one point are referenced to positive that turns them off.

Description:

RL1 (which is off) applies plus voltage from its armature and latches RL2 “on”. The application terminals are set to [A]. The condition changes when S1 is activated, voltage is applied to RL2 latching RL1 “on” releasing S1 turns RL2 “off”. RL2’s armature is then directed to R1. Terminals are set to [B].

When S1 is pressed again, the relays negative side are referenced to positive, RL1 turns “off” (there’s no current flow). RL2 turns “on” when S1 is released, terminals are set to [A]. There is slight lag between relays depending on how long S1 is held.

Relay Toggle Switch Circuit Diagram

Note: 

If different relays are used, adjustment of R1’s value may be required. For example, OEG relays (12vdc, 270 ohm coil) need R1 at 60 - 70 ohms. The prime motivation for this design was to avoid using toggle switches for my audio control panel. Another plus, it can be controlled from a remote transmitted pulse.

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14W CLASS A AMPLIFIER CIRCUIT USING 2N3055 SCHEMATIC DIAGRAM

14W CLASS A AMPLIFIER CIRCUIT USING 2N3055 SCHEMATIC DIAGRAM

Many early amplifiers operated in Class A, but as output powers rose above 10W the problems of heat dissipation and power supply design caused most manufacturers to turn to the simpler, more efficient Class B arrangements and to put up with the resulting drop in perceived output quality. Why Class A ? Because , when biased to class A, the transistors are always turned on, always ready to respond instantaneously to an input signal. Class B and Class AB output stages require a microsecond or more to turn on. The Class A operation permits cleaner operation under the high-current slewing conditions that occur when transient audio signal are fed difficult loads. His amplifier is basically simple, as can be seen from the block diagram.

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How to Make a 200 Watt Transformerless Inverter Circuit

    A 12 V car battery can be used as the 12V source.
    Use the POT R1 to set the output frequency to50Hz.
    For the transformer get a 9-0-9 V , 10A step down transformer.But here the 9-0-9 V winding will be the primary and 220V winding will be the secondary.
    If you could not get a 10A rated transformer , don’t worry a 5A one will be just enough. But the allowed out put power will be reduced to 60W.
    Use a 10 A fuse in series with the battery as shown in circuit.
    Mount the IC on an IC holder.
    Remember,this circuit is nothing when compared to advanced PWM inverters.This is a low cost circuit meant for low scale applications.

Inverter Design Tips.

The maximum allowed output power of an inverter depends on two factors.The maximum current rating of the transformer primary and the current rating of the driving transistors.

For example ,to get a 100 Watt output using 12 V car battery the primary current will be ~8A ,(100/12) because P=VxI.So the primary of transformer must be rated above 8A.

Also here ,each final driver transistors must be rated above 4A. Here two will be conducting parallel in each half cycle, so I=8/2 = 4A .

source: circuitstoday.com

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How to Make a Simplest Compact 1 Watt LED Driver Circuit at 220V 110V Mains Voltage

Circuit diagram.

Seetharaman’s words about the circuit: I am sending you a table lamp made from defunct energy saver lamp with broken tubes. CFL converted into LED lamp. Most of the components will be available in ones scrap box. Few components available in the CFL PCB also can be used.

Procedure
1. Carefully remove the broken glasses
2. Open the assembly carefully
3. Remove electronics and discard
4. Assemble the circuit in dot matrix PC or on a 1mm laminate sheet.
5. Cut a round laminate sheet with (scissor)
6. Mark the position of the 6 round holes on the sheet
7. Drill the holes to suit the LEDs to flush fit in the six holes
8. Use a dab of adhesive to keep the LED assembly in position
9. Close the assembly
10. Ensure the internal wiring does not touch each other
11. Now test on 230Volt AC
Your nice compact table lamp / puja room lamp / passage lamp is ready for use.

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