Portable power pack using LM1086 for mobile phonesThis project is backup energy when need portable mobile phone that no electrical outlet. we use LM1086 is main on a low dropout voltage, making it has high-efficiency.When we need to take the mobile phone to location-based applications. No electrical outlet to plug in to recharge the battery. and In event that use often mobile phones. Which moderate power consumption.If the batteries run out still not certainly, Many people chose to carry a backed up battery. and another alternative is buying the Portable power pack In order to solve this problem.But the price is high reasonable, when sit think we as an electronics amateur.You can build it yourself is not difficult by use simple principal of dc regulator circuit, which Many people are already familiar. If interested, you can see that it is really simple.

Automatic ni-mh battery chargerA nickel-metal hydride battery, also known as NiMH, is a secondary cell.They are used in cameras and other electronic devices. They are widely used Because its cheap and has a flow rate capacity of the cells to be used as required. Can replace the generic battery immediately.Important. Can bring to new charging hundreds to thousands of times. Make savings in the long run. and also help maintain the the environment.Though we will generally choose to buy battery charger. Which is both fast and slow charging. Based on the budget, there, which is most expensive. We should build it up by yourself, because its cheap and good quality.The project is the Ni-MH battery charger on automatically shut off when fully charged. Can charge the batteries from 1-10 pcs. Depending on the input voltage.In circuit has LED indicator are 2 LEDs. By showing the charging status and will be off when the battery is fully charged.And the LED function indicator that the battery is connected correctly.For input voltage is supplied to the charger circuit can be used for the power supply ranging from 12-16 volts and use current to charge to 800 milliamperes.

The Component layout for the PCB.The Detail ComponentsIC1_____TL072___LOW NOISE J-FET DUAL OPERATIONAL AMPLIFIERS = 1 pcs.Q1______BC327__ 50V 800mA PNP Transistor ___________= 1 pcs.Q2__________MJE2955___50V 3A PNP Transistor_________= 1 pcsD1,D4______1N4148_____75V 150mA Diodes____________ = 2 pcs.D2,D3______1N4001_____50V 1A Diodes_______________ = 2 pcs.Electrolytic capacitorsC1,C4______1000uF 25V Electrolytic capacitors___________ = 2 pcs.C5_____1uF 50V Electrolytic capacitors__________________= 1 pcs.C2,C3______0.1uF 100uF polyester capacitors_____________ = 2 pcs.1/4 watts 1% ResistorsR1_________10K_______________= 1 pcs.R2_________1M_______________= 1 pcs.R3,R9_______1K_______________= 1 pcs.R4_________ 470 ohms__________= 1 pcs.R5_________ 150 ohms 2 watts____= 1 pcs.R6, R8______100K______________ = 2 pcs.R7___________1 ohms 2 watts_____= 1 pcs.

Simple Battery Level IndicatorDescriptionHere is a easy to build low battery level indicator circuit that produces a visible indication by flashing a LED when the battery voltage drops below a predetermined voltage.The circuit is based on Panasonics IC MN13811G and a efficient flasher based on transistors Q1&Q2.Here when the battery voltage drops below 2.4 V the output of the IC is activated and the flasher starts flashing.This circuit here is an ideal one for monitoring the level of all types of 3V batteries.The circuit is power efficient with a idle current drawing as less as 1 uA , and a current drawing while flashing as less as 20uA.Circuit Diagram with Parts list .

Notes.Assemble the circuit on a good quality PCB or common board.Do not keep the soldering iron tip on the ICs pins for long time.IC MN13811 series are available with different trip point voltages( from 2.4V t0 4.8V) ie MN13811G to MN13811U .If you need a trip point other than 2.4 shown here, you can choose the corresponding IC from the data sheet and use it in the circuit here.

Simple audio mixer circuit with fet 2N3819

This circuit is a simple mixer circuit. It can mix two signal channels and one channel is output. Using a codec circuit,Convert stereo audio to mono audio time.-In circuit a FET number 2N3819 is main, it is better than a common transistors that a high impedane input and high gain too. so cause low noise and.. It can increase the number of channels too, By adding a VR1, R1 and C1 to the amount needed. Then connected to Buffett a new one. Most importantly is eating circuit current is very low.Can use with 9-volt batteries immediately.When entering voice signal, one of input 1 and input 2. Audio is via C1 and C2 of each channel,served coupling signals to VR1 and VR2. To adjust the audio to the Fet Q1.Which it serves, including audio. Then expand signal the output pin S through C3 For coupling signal again, before leaving to the output.

This is the idea of the simple audio mixer circuit. Perhaps you might need to take advantage of it.

Some time you want high gain than FET, I think an OP-AMP IC is good way for you. The LF353 has JFET within it so very well same common FET but it has many components inside it, makes high gain and better than 2N3819 but in normal using we may need it because too cost in some places.

Basic Timer using FETThis circuit be Basic Timer Circuit by use important equipment is FET2N3819. By this circuit can can delay long ago arrive at 1.5 minute. Stand S1 at a position Reset an electric bell will loud. Totter S1 come back at time an electric bell will silent until time drag will stop electric bell talk at one time again.If friends enhance the value C1 or R1 for delay long ago go up. devalue R2 while stay in a position Reset for Reset fast go up. Request friends have fun Basic Timer Circuit , please sir.

Simple Delay turn on the monitor

This is Simple Delay turn on the monitor, by use contact of relay acts as a switch. When entering an AC main to this circuit. The circuit will delay while Reduce the surge current protection with fuse. Same as current will gradually flow into the first period.Currently we use the same computer. Most are connected to an outlet with a switch to turn off with the easier to use. But when we turn off the switch, plug it in short strokes will be.Surge current flows into. This may result in damage and lost a hard drive. Therefore require a delay for a while. It is time to turn on itself, which will help prevent hard disk the damage.This circuit can be used with 220 volt house power. by contact of the relay switch to acting. When 220-volt power input to circuit, the lower the voltage to 220 volts to 15 Volts, with R1, R2, C1 and C2 current limiting it to about 41 milliamps. and C Partners diodes ZD1 limited pressure it to 15 volt and Direct Optical Fire through D1,. D2 and C3 to the party circuit.

Figure 1 The simple delay turn on the monitor circuitThere will be current through R3 to charge C4, which takes time to charge and when the C4 charge fully to make a current flowing into pin B of Q1. the Q1 runs and drive currents to RY1 switch contacts touch. Each per 220-volt power to the monitor acts C4 delay. If you want a long delay, it added the C4, but if you want to delay it a little to reduce the C4.The Diode-D3 prevent reverse voltage from coil of relay. Which may be damaged to the circuit.How to build this projectsThis project is not used many components so can assemble on the universal PCB board as Figure 2 the wiring and various components to look out carefully for the polarity of the electrolytic capacitors,Diodes,Transistor and relay are correct.

Figure 2 the components layout and wiring of this project.

The components ListResistors +5%R1____________470 ohm 1WR2____________150K 0.5WR3____________3.3K WCapacitorsC1___________0.01uF 250V_____PolyesterC2___________0.33uF 250V_____PolyesterC3, C4________470uF 16V____ElectrolyticSemiconductorsD1-D3________1N4007___1000V 1A DiodesZD1__________Zener diode 15V 1WOthersRY____________Relay 12V see textThe universal PCB board.

Street light circuit.

The circuit diagram present here is that of a street light that automatically switches ON when the night falls and turns OFF when the sun rises. In fact you can this circuit for implementing any type of automatic night light.The circuit uses aLight Dependent Resistor (LDR)to sense the light .When there is light the resistance of LDR will be low. So the voltage drop across POT R2 will be high.This keeps the transistor Q1 ON. The collector of Q1(BC107) is coupled to base of Q2(SL100). So Q2 will be OFF and so do the relay. The bulb will remain OFF.When night falls the resistance of LDR increases to make the voltage across the POT R2 to decrease below 0.6V. This makes transistor Q1 OFF which in turn makes Q2 ON. The relay will be energized and the bulb will glow.Circuit diagram with Parts list.

FET based audio preamplifier.

Description.This is the circuit of a based audio preamplifier which has very low noise. One FET and one BJT are used in this circuit. The audio signal to be amplified is coupled to the base of FET Q1 using capacitor C1 and resistor R3.Base of transistor Q2 is coupled to the drain terminal of FET Q1. Transistor Q2 provides additional current gain. The final signal will be available at the collector of Q2.Capacitor C3 provides necessary negative feedback, which improves stability. Capacitor C2 is an output DC decoupling capacitor. Since an FET is used in the input stage this particular amplifier circuit has very high band width (10 KHz- 450 KHz) and input impedance (around 1M).Circuit diagram.

Notes. The circuit can be assembled on a vero board. Use 12V DC for powering the circuit. For optimum performance, input and output grounds must be properly decoupled.

DoorbellThe electronic doorbell in this article is the most simplest among the advance projects in this website. There are many other benefits of the project doorbell. The circuit for the electronic doorbell here will help realise whether the visitor is in front door or in back door. More about there is two LED indicatorwith different colours which provide visual indication to check if anyone had come nor not in your absence.Capacitors

C1,C2,C30.01 F

PART LISTDiodes

D1,D2,D3,D41N4001

D5GREEN LED

D6RED LED

Transistors

T1,T2,T5BC148B

T3,T4BC158B

T6AC128

Resistors

R1,R7,R8.R9,R102.2 K

R247

R3,R4100K

R5,R610K

R11,R12330

Miscellaneous

S1ON/OFF toggle switch for memory

S2,S3Switch for doorbell

BATT9-Volt Battery

LSLoud Speaker 8

OTHERSPCB , Connecting Wires,Hardware,enclosure etc