The -12 Volt Supply by TIP42

The -12 volt supply, like the +12 volt supply, uses discrete components rather than a 7912 voltage regulator IC. Here, we use a 1N4742A Zener diode, rated at 12 volts, 1 watt, as the main regulating element.
The power supply shown in the above schematic diagram uses a Zener diode as the main regulating device, to maintain a constant output voltage in spite of changes in input voltage. The type 1N4742A diode is rated at 12 volts, with a power dissipation limit of 1 watt. Since we want to be able to deal with load currents of at least 100 mA and possibly more, we cannot use the Zener diode by itself. (Under no-load conditions, the Zener diode would have to handle that 100 mA, which would result in a power dissipation of 1.2 watts. This would overheat and destroy the diode in short order.) Therefore, we add a power transistor as the main current-handling device for the power supply. The TIP42 PNP silicon transistor (available from Radio Shack) is rated to carry up to 10A collector current and a power dissipation of 65 watts.

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Posted in: power supply

21W Class AB amplifier by TIP41

This is an instrument amplifier for monitoring music when on stage. It provides 21W output power of this little design. Previously I had a decent 10W amplifier (RED Free Circuits), but we blew that one somehow. Now I will put this into the old box. I haven’t built it yet, but the simulations say it works as I designed. In this design, wiring is important due to no differential amplifier. I might need to add ripple rejection with a zener as in the above design.

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Posted in: Power Amplifier

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).
[...]
Author: Len Cox – Copyright: Silicon Chip Electronics

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Posted in: electronic circuit

Chamberlain Wireless Alert System

# International Electronics state-of-the-art wireless alert security system
# Detects and reports human or vehicle motion
# Only products with an effective transmission range from the sensor to the base for up to 1200 feet
# Register a move up to 30 meters away
# Works in temperatures from -40 º C (40 º F) to 100 º C (212 * F)
# Resistant UV damage from sun
# Special learning feature allows up to 4 sensor units to report to a single base station with unique sounds per sensor unit
# Waterproof, includes a rain / sun shield
# Conformal coated circuit is
# Includes 10-amp outputs so it can be linked directly to a monitored system, a horn, lights, dents, bells, or any alarm device
# Protects driveways, businesses, large fronts, entryways, boats, RV’s and outbuildings
# Battery backup receiver protects even during power
# Easy to install, no wiring required
# Sensor is waterproof and uses 4 AA batteries lasting up to 2 years
# Black Package Contents:
# 1 Base Station Receiver
# 1 Sensor Unit
# Power Adapter
# 1 Gimbal bracket
# Non-slip feet and hardware

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Posted in: Alarm home system , alarm systems

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