VHF UHF HF active antenna electronic circuit project with explanation

A very simple and efficiency active antenna electronic project can be designed using this electronic schematic circuit that is based on transistors. This active antenna electronic project is useful for a wide range of RF frequencies covering three RF bands HF , VHF and UHF . This simple active antenna is designed to amplify signals from 3 to 3000 MegaHertz, including three recognized ranges: 3-30Mhz high-frequency (HF) signals; 3-300Mhz veryhigh frequency (VHF) signals; 300-3000MHz ultra-high (UHF) frequency signals.

This HF VHF UHF active antenna contains only two active elements : Q1 (which is

 MFE201 N-Channel dual-gate MOSFET) and Q2 (which is an 2SC2570 NPN VHF silicon transistor). Those transistors provide the basis of two independent, switchable RF pre-amplifiers. Two DPDT switches play a major role in this circuit , switch S1 used to select one of the two pre-amplifier circuits (either HF or VHF/UHF) and switch 2 is used to turn off the power to the circuit, while coupling the incoming RF directly to the input of the receiver.This circuit must be powered from a simple 9 volt DC power circuit ( or a 9 volts battery) and is very useful for use as an indoor antenna
S2 is useful to give to receiver nonamplified signal access to the auxiliary antenna jack, at J1, as well as the on-board telescoping whip antenna.

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Posted in: electronic circuit , Radio

DC to AC Inverter by IC 555 and TIP41 TIP42

This be basic AC inverter Circuit. Convenient for the initiator who have to is extremely fond of something experience. Because of use IC 555 highly popular, perform produce the frequency ,then enlarge with transistor NPN and PNP number TIP41 and TIP42 drive the coil transformer. Get by can pay Voltage output about 120V to 230V at frequency 50Hz. By have R4 perform control the frequency and should use. Voltage supply about 5V to 15V the detail sees in circuit picture sir.

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Posted in: electronic circuit , inverter

Free drawing circuit diagram License LGPL

Today younger brother generation that study same college comes to see at a house and beg to seek design good circuit and free. I advises a program TindyCAD because it drawing circuit diagrams commonly known as schematic drawings. It supports model the equipment is a lot of and still apply to PCB layout programs change the system netlist formats. Besides still be usable cooperate SPICE simulation netlists get as well. About the copyright be model freedom License LGPL be usable get freely model open

source. Link : http://sourceforge.net/projects/tinycad/

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Posted in: electronic circuit

Simple Combination Lock by IC 4017 74C14

This simple combination lock accommodates codes from 1-9 digits long, with the only restriction being that the same digit cannot be used twice. The circuit shows strapping for a 4-digit code, in this case “2057″. Any unused switches are strapped to ground. When power is applied, the 330nF capacitor connected to pin 1 of inverter IC1a is discharged, holding it at a logic low level. The high output is inverted by a second gate (IC1b), with the result being a logic low on pin 4. This pulls Q1’s emitter low via D1, causing the transistor to conduct. The falling voltage on the collector then pulls the input of IC1c low, which in turn resets counter IC2.
On reset, output O0 (pin 3) of IC2 goes high, charging the 330nF capacitor via D2 and the 33k? resistor. If switch S2 is now pressed, Q2′s emitter will be pulled high and so Q2 conducts, applying a rising positive voltage to one end of the 1M? resistor. This resistor and the 33nF capacitor act as a switch “debounce” circuit, delaying the pulse through IC1e by about 33ms. After the delay, the output of IC1e goes low. However, counter IC2 does not increment at this stage, since it needs a positive-going edge at the clock input (pin 14). When the switch is released, Q2 turns off, IC1e’s output goes high after the debounce period and the counter advances to the next state (ie. O0 goes low and O1 goes high).
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Author: Len Cox – Copyright: Silicon Chip Electronics

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Super Sensitive Intruder Alarm

Here is the circuit diagram of an ultra sensitive intruder alarm.The shadow of an intruder passing few meters nearby the circuit is enough to trigger the alarm.
Here IC2 uA 741 is wired as a sensitive comparator ,whose set point is set by R6 &R7.The voltage divide by LDR and R9 is given at non inverting pin of IC2.At standby mode these two voltages are set equal by adjusting R9.Now the out put (pin6) of comparator will be high.Transistor Q1 will be off.The voltage at trigger pin of IC1 will be positive and there will be no alarm.When there is an intruder near the LDR the shadow causes its resistance to increase. [...]

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Posted in: Alarm home system , alarm systems , electronic circuit

Window foil burglar alarm with scr

Here is a simple but effective burglar alarm circuit that can be fixed on windows to detect break throughs. The circuit uses a fine wire element fixed as a network through the window glass for sensing the break through . Normally the base of Q1 is held to ground potential by the wire element.So Q1 will be off and SCR H1 will not be conducting,and horn will be off.When the wire element is broken the base of Q1 will be raised to positive potential, Q1 will be on and so SCR H1 (TYN 612) will be ON making the horn to blow and this condition will be latched by the SCR.The circuit remains ON until the normal condition is restored or the power supply is switched OFF.

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Posted in: Alarm home system , alarm systems , electronic circuit

Night security light

Here is a simple circuit switches on a light around 2 hours after midnight, the time at which most of the robberies taking place.
This simple circuit is build around a CMOS IC 4060 to obtain the required timing. During day time the LDR has low resistance and keeps the pin 12 of the IC1 high, preventing the IC1 from oscillating. When it is dark the LDR resistance becomes high and the pin 12 of IC1 becomes low and the IC starts oscillating, which indicated by the flashing of LED D3.The values of the timing components R1, R2, C4 are so selected that the out put pin3 of IC1 goes high after 8 hours. That means the high output drives the triac to switch on the lamp around 2’O clock. At morning, the LDR resistance drops and the pin 12 of IC1 goes high and stops the oscillation, making the lamp OFF. The switch S1 can be used to manually ON the lamp. The capacitor C2 prevents false triggering.

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Posted in: Alarm home system , alarm systems , electronic circuit , Lighting

Petrol Gas Switch For A Pajero

My current vehicle, a Pajero, was modified for dual fuel – ie, petrol and gas. However, it’s necessary to run the vehicle on petrol at regular intervals to stop the injectors from clogging up. This simple circuit allows the vehicle to be started using petrol and then automatically switches it to gas when the speed exceeds 45km/h and the brake pedal is pressed. Alternatively, the vehicle may be run on petrol simply by switching the existing petrol/gas switch to petrol. You can also start the vehicle on gas by pressing the brake pedal while starting the vehicle. The circuit is based on an LM324 dual op amp, with both op amps wired as comparators. It works like this: IC1a buffers the signal from the vehicle’s speed sensor and drives an output filter network (D1, a 560kO resistor and a 10µF capacitor) to produce a DC voltage that’s proportional to the vehicle’s speed.
This voltage is then applied to pin 5 of IC1b and compared with the voltage set by trimpot VR1. When pin 7 of IC1b goes high, transistor Q1 turns on. This also turns on transistor Q2 when the brake pedal is pressed (pressing the brake pedal applies +12V from the brake light circuit to Q2′s emitter). And when Q2 turns on, relay 1 turns on and its contacts switch to the gas position. Trimpot VR1 must be adjusted so that IC1b’s pin 7 output switches high when the desired trigger speed is reached (ie, 45km/h). In effect, the speed signal is AND’ed with the brake light signal to turn on the relay. The vehicle has been running this circuit for several years now and is still running well, with no further injector cleans required.
Author: J. Malnar – Copyright: Silicon Chip Electronics

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Posted in: Alarm home system , electronic circuit , Lighting

Wireless Protable Intercom Voice Activated

Chamberlain wireless portable inte- Provides convenient and expandablemunication for your home- Advanced features include voice activation and monitor mode- Crystal clear secure 900 MHz digitalmunication- 1000 Foot rangeCHNLS2
Technical Details
* This wireless intercom system has an amazing 1000 ft.
* This portable wireless intercom system is fully expandable to an unlimited number of intercom stations that share 4 Channels.
* The Monitor Mode features the most advanced Voice Operated Switch (VOX) allowing you to customize sensitivity settings
* Secure 900 MHZ radio link. Compact size- each intercom unit measures less than 4″x5.5″x2″.

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Posted in: Alarm home system , electronic circuit

Low Cost Burglar Alarm For Boats

This low-cost burglar alarm employs a 12V strobe light and a truck reversing horn as the visible and audible alarm outputs while the alarm itself is a 12V horn relay and some pressure mat switches. This simple approach has the benefit that the alarm continues to operate even if the entry point is immediately closed and it draws no current while in the armed condition. To make it independent of the boat supply it runs from a single 12V or two 6V alkaline lantern batteries connected in series. These should last well in excess of two years. An advantage of a lantern battery is that it will last less than an hour while powering the alarm in its active role.
This means the alarm system will not seriously contravene noise pollution laws. If there are very strict noise regulations in your area, you can fit an alarm timer, available from some electronic shops, in the circuit between the battery positive and the key switch. The key switch can be installed in the cockpit bulkhead and connects to two normally open (NO) switches wired in parallel. One switch is a pressure mat placed on the cockpit floor near the entry, underneath a suitable piece of carpet or pliable cover. If a pressure mat is unsuitable, the main entry can be protected by a mechanical switch such as an automobile boot lid or door courtesy light switch.
The second switch can be used to protect against entry through a forward hatch or second wheelhouse door. Any number of normally open (NO) switches can be installed in this system, all wired in parallel. If the alarm is tripped, the relay closes and latches on due to the wiring of its contacts and the horn and strobe light are powered. The suggested truck reversing horn is the Hella 6023 intermittent reversing buzzer which has an 85dB sound level and a current drain of 0.9A at 12V. The suggested strobe is a Hella 1657 which has an amber lens in a weatherproof housing. This strobe flashes about once per second and the current drain at 12V is 0.25A. The strobe can be installed outside on deck or in the main cabin where its flash will be seen through most ports and windows. Wiring to both the warning horn and strobe light should be concealed.
Author: Dave Jeanes – Copyright: Silicon Chip Electronics

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Posted in: Alarm home system , electronic circuit

Fridge door Alarm

Beeps if you leave open the door over 20 seconds
3V battery operation, simple circuitry
This circuit, enclosed into a small box, is placed in the fridge near the lamp (if any) or the opening. With the door closed the interior of the fridge is in the dark, the photo resistor R2 presents a high resistance (>200K) thus clamping IC1 by holding pin 12 high. When a beam of light enters from the opening, or the fridge lamp illuminates, the photo resistor lowers its resistance (<2K), pin 12 goes low, IC1 starts counting and, after a preset delay (20 seconds in this case) the piezo sounder beeps for 20 sec. then stops for the same lapse of time and the cycle repeats until the fridge door closes. D2 connected to pin 6 of IC1 allows the piezo sounder beeping 3 times per second.
Parts:
R1____________10K 1/4W Resistor
R2___________Photo resistor (any type)
R3,R4________100K 1/4W Resistors
C1____________10nF 63V Polyester Capacitor
C2___________100µF 25V Electrolytic Capacitor
D1,D2_______1N4148 75V 150mA Diodes
IC1___________4060 14 stage ripple counter and oscillator IC
Q1___________BC337 45V 800mA NPN Transistor
BZ1__________Piezo sounder (incorporating 3KHz oscillator)
SW1__________Miniature SPST slide Switch
B1___________3V Battery (2 AA 1.5V Cells in series)

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12V Battery Charger

Solid state two color LED indicates stage of charger; a quick connect harness for use in hard to reach areas
Perfect for all lead-acid, flooded or sealed maintenance free batteries (AGM and gel cell)
Complete 4-step charging program (initialization, bulk charge, absorption mode and float mode) that maintains batteries at full charge without overcharging via its 4-step charging system
Automatically switches to float/maintenance mode voltage after fully charging the battery
Temperature compensated to ensure optimum charge voltage according to ambient temperature, and spark proof and reverse polarity protected; 10-year limited warranty

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Posted in: electronic circuit

Simple Battery Isolator

This circuit is even simpler and employs a 6V feed from one of the stator connections on the vehicle’s alternator. This is connected to a 6V automotive relay (RLY1) which controls a Continuous Duty Solenoid (RLY2). This solenoid electrically connects or isolates the batteries. When the engine is started and the alternator stator voltage rises, the 6V relay turns on. This turns on the Continuous Duty Solenoid to connect the two batteries in parallel. As long as the engine is running, the vehicle’s alternator will maintain charge in both batteries.
When the engine is shut down, the alternator stator voltage drops and the Continuous Duty Solenoid switches off, thus isolating the second battery from the vehicle’s electrical system. Provided that camping accessories are only connected to the second battery, the main battery should never discharge. Because the concept is entirely dependent upon the alternator’s stator output voltage, you cannot forget to turn the system on or off as it happens automatically.
Copyright: Silicon Chip Electronic

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Posted in: electronic circuit

Easy dry cell charger with CMOS IC 4011

The dry cell charger circuit can be fully charged about 12 hours.When used with a 9 volt supply,the equipments in the circuit for the AA type cell.When using the C and D type cell, should reduce the value of the resistance Rx to be 68 ohms.In charge of the cell, you should not be charged to the same series, may cause cell damage is fully charged.
If the cell voltage is below 1.6 volt,The compared circuit to leave the square wave oscillator by the CMOS gate,then the transistor made a charge until the cell voltage is 1.6 volt.The comparison circuit will cut the charging LED blinks, notice prevents over-charging.

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Posted in: electronic circuit

alarm with countdown timer

This circuit is IC implementation schedule. No. 555 applied with IC number LM3905.By the IC to the number 555 are the circuits Stable multi-vibrator. How often do produce it.This frequency is then forwarded to the scheduling with the integrated circuit number LM3905.
When entering the power supply circuit IC1 No. 555. To be atable multivibrator circuit. Produce about 0.5 hertz frequency out.The R1, VR1, R2 and C1 determine the frequency.The output pin 3 will be out of a square wave LED1 will be lit.The signal is a negative split.and LED2 will be lit during a split positive signal.This will flash alternately throughout the duration of scheduled. IC2 is a timer IC.Includes VR2, R6 and C3.The setup time will be how long it can adjust the VR2.And while time is the output pin 7 of IC2 pin voltage will be 0 volt.And when it’s time to set the output pin 7 will have a positive voltage to Buzzer beeps out the rhythmic flashing of the LED.

Source : Countdown timer with alarm

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Posted in: electronic circuit

Simple Wireless Security Alarm For Car

Alarm circuit is functioning as a car wireless security alarm. Yes, this is an FM radio-controlled anti-theft alarm. This alarm can be used on any vehicle that has a DC power supply 6-12V.
Alarm circuit system is divided into two parts, the transmitter unit and receiver unit. Transmitter unit is working on the range of VHF Band II, exactly at a frequency of 88-108 MHz. This transmitter is a miniature FM transmitter that is installed in vehicles at night while parked in the car porch or car park.

Simple Car Wireless Security Alarm Schematic

The receiver is a single IC-based FM radio module, CXA1019, kept inside. Receiver tuned frequency matches the transmitter. CXA1019 IC is widely available in the market with an affordable price, or you can find replacement parts CXA1191.
How This Car Wireless Secuity Alarm Works
When the transmitter is on and the signals are being received by the FM radio receiver, no hissing noise is available at the output of the receiver. Thus transistor T2 (BC548) does not conduct. This result in the relay driver transistor T3 getting its forward base bias via 10k resistor R5 and the relay gets energized.
When an intruder tries to drive the car and takes it a few metres away from the car porch, the radio link between the car (transmitter) and alarm (receiver) is broken. As a result FM radio module generates hissing noise.
Hissing AC signals are coupled to relay switching circuit via an audio transformer. These AC signals are rectified and filtered by diode D1 and capacitor C8, and the resulting positive DC voltage provides a forward bias to transistor T2. Thus transistor T2 conducts, and it pulls the base of relay driver transistor T3 to ground level. The relay thus gets de-activated and the alarm connected via N/C contacts of relay is switched on.
If, by chance, the intruder finds out about the wireless security alarm and disconnects the transmitter from battery, still remote alarm remains activated because in the absence of signal, the receiver continues to produce hissing noise at its output. So the burglar alarm is fool-proof and highly reliable.

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Posted in: electronic circuit