Mobile Charger using Bike Battery

The circuit uses a Positive Voltage regulator IC 7805 to give 5 volt regulated output. The components around IC1 are meant for protecting the IC so as to give smooth output power. Zener diode ZD act as the Input Surge protecting diode. It provides 7.2 volts to the input of the regulator IC from the 12 volt bike battery. Diode D1 is the Output Surge and Input Short protecting diode.

When a surge voltage exceeding maximum voltage rating of the regulator is applied to the input or when a voltage in excess of the input voltage is applied to the output, the regulator will be destroyed. If the input terminal shorts with the ground, the output voltage increases above the input voltage(ground potential)and the charge in the capacitor connected to the output flows into the input side which is also fatal to the regulator. Both these situations can be avoided by using the Zener at the input and the diode D1 across the regulator. Capacitor C1 and C2 provide stability to the regulator and these should be soldered close to the legs of the regulator. Capacitor C3 act as a buffer to give constant voltage in the output.

7805 IC can tolerate maximum 35 volts and its current rating is 1 Amps maximum. Resistor R1 restricts the charging current to around 330 mA as per the Ohms law. Even if the current is low, charging process will not be affected. Slow charging with 80 to 100 mA current is generally advised. But in case of an emergency, quick charging can be done with high current
Assemble the circuit on a Perf board and enclose in a small case that can be fitted near the Bike battery. Use suitable pins to connect with the Mobile phone. Charging current can be tapped from the battery using Alligator Clips. Before using the circuit, double check the connections especially the polarity of connectors and measure output voltage and current using a Digital Multi Meter. The same circuit can be used for charging Mobile battery from 12 volt Car battery or from a 12 volt Solar panel.

Solar Charger

 

The circuit uses a 12 volt solar panel and a variable voltage regulator IC LM 317. The solar panel consists of solar cells each rated at 1.2 volts. 12 volt DC is available from the panel to charge the battery. Charging current passes through D1 to the voltage regulator IC LM 317. By adjusting its Adjust pin, output voltage and current can be regulated.

VR is placed between the adjust pin and ground to provide an output voltage of 9 volts to the battery. Resistor R3 Restrict the charging current and diode D2 prevents discharge of current from the battery. Transistor T1 and Zener diode ZD act as a cut off switch when the battery is full. Normally T1 is off and battery gets charging current.
When the terminal voltage of the battery rises above 6.8 volts, Zener conducts and provides base current to T1. It then turns on grounding the output of LM 317 to stop charging.

Car Battery Charger

This charger will quickly and easily charge most any lead acid battery. The charger delivers full current until the current drawn by the battery falls to 150 mA. At this time, a lower voltage is applied to finish off and keep from over charging. When the battery is fully charged, the circuit switches off and lights a LED, telling you that the cycle has finished.

PARTS:-

R1    1    500 Ohm 1/4 W Resistor   
R2    1    3K 1/4 W Resistor   
R3    1    1K 1/4 W Resistor   
R4    1    15 Ohm 1/4 W Resistor   
R5    1    230 Ohm 1/4 W Resistor   
R6    1    15K 1/4 W Resistor   
R7    1    0.2 Ohm 10 W Resistor   
C1    1    0.1uF 25V Ceramic Capacitor   
C2    1    1uF 25V Electrolytic Capacitor   
C3    1    1000pF 25V Ceramic Capacitor   
D1    1    1N457 Diode   
Q1    1    2N2905 PNP Transistor   
U1    1    LM350 Regulator   
U2    1    LM301A Op Amp   
S1    1    Normally Open Push Button Switch   
MISC    1    Wire, Board, Heatsink For U1, Case, Binding Posts or Alligator Clips For Output   

Electronic Stethoscope

Stethoscopes are not only useful for doctors, but home mechanics, exterminators, spying and any number of other uses. Standard stethoscopes provide no amplification which limits their use. This circuit uses op-amps to greatly amplify a standard stethoscope, and includes a low pass filter to remove background noise.


PARTS:-


R1    1    10K 1/4W Resistor  
R2    1    2.2K 1/4W Resistor  
R4    1    47K 1/4W Resistor  
R5, R6, R7    3    33K 1/4W Resistor  
R8    1    56K 1/4W Resistor  
R10    1    4.7K 1/4W Resistor  
R11    1    2.2K to 10K Audio Taper Pot  
R12    1    330K 1/4W Resistor  
R13, R15, R16    3    1K 1/4W Resistor  
R14    1    3.9 Ohm 1/4W Resistor  
C1, C8    2    470uF 16V Electrolytic Capacitor  
C2    1    4.7uF 16V Electrolytic Capacitor  
C3, C4    2    0.047uF 50V Metalized Plastic Film Capacitor  
C5    1    0.1uF 50V Ceramic Disc Capacitor  
C6, C7    2    1000uF 16V Electrolytic Capacitor  
U1    1    TL072 Low Noise Dual Op-Amp  
U4    1    741 Op-Amp  
U5    1    LM386 Audio Power Amp  
MIC    1    Two Wire Electret Microphone  
J1    1    1/8" Stereo Headphone Jack  
Batt1, Batt2    2    9V Alkaline Battery  
LED    1    Red/Green Dual Colour Two Wire LED  
SW    1    DPST Switch  
MISC    1    Stethoscope head or jar lid, rubber sleeve for microphone, board, wire, battery clips, knob for R11    

12V Halogen Lamp Electronics Transformer Circuit Diagram

A halogen lamp is a source of electric light that works by heat-driven light emissions produce from the combination of the halogen gas and the tungsten filament. Below schematic shows the 12V Halogen Lamp Electronics Transformer Circuit Diagram.
The following file is an application note from ST.com containing description of the 12V Halogen Lamp Electronics Transformer Circuit Diagram. These lamps are available with voltage ratings of 6, 12 or 24 Volts, and so a transformer is needed in order to provide the lamp with a low voltage supply from either 110V a.c. or 220V a.c. mains. The topology of the circuit is the classic half-bridge. The line voltage is rectified by the full-bridge rectifier, generating a semi-sinusoidal voltage at double the line frequency.
Get more information regarding the 12V Halogen Lamp Electronics Transformer Circuit Diagram design here.

Electronics Cricket Match Game

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This electronic cricket is a present for Kids. This simple battery powered circuit can be used to play Cricket Match with your friends. Each LED in the circuit indicates various status of the cricket match like Sixer, Run out, Catch etc.

The Circuit uses two ICs ,one in the Astable mode and the second in the display driver mode. IC1 is wired as an Astable Multivibrator with the timing elements R1, R2 and C1. With the shown values of these components very fast output pulses are generated from the Astable. Output from IC1 passes into the input of IC2 which is the popular Johnson Decade counter CD4017. It has 10 outputs. Of these 8 outputs are used. Output 9 ( pin9) is tied to the reset pin 15 to repeat the cycle. When the input pin 14 of IC2 gets low to high pluses, its output turns high one by one. Resistor R3 keeps the input of IC2 low in stand by state to avoid false When the Push Switch S1 is pressed momentarily, the Astable operates and all the LEDs run very fast sequentially. When S1 is released, any one of the LED stands lit which indicates the status of the match. For example, if LED D7 remains lit, it indicates Sixer and if LED 8 remains lit, it indicates Catch out.
Label each LED for its status as shown in the diagram. Pressing of S1 simulates Bowling and Running LEDs indicates running of Batsman.

Electronics Dog Repellent

The electronic dog repellent circuit diagram below is a high output ultrasonic transmitter which is primarily intended to act as a dog and cat repeller, which can be used individuals to act as a deterrent against some animals. It should NOT be relied upon as a defence against aggressive dogs but it may help distract them or encourage them to go away and do not consider this as an electronic pest repeller.

The ultrasonic dog repellant uses a standard 555 timer IC1 set up as an oscillator using a single RC network to give a 40 kHz square wave with equal mark/space ratio. This frequency is above the hearing threshold for humans but is known to be irritating frequency for dog and cats.

Since the maximum current that a 555 timer can supply is 200mA an amplifier stage was required so a high-power H-bridge network was devised, formed by 4 transistors TR1 to TR4. A second timer IC2 forms a buffer amplifier that feeds one input of the H-bridge driver, with an inverted waveform to that of IC1 output being fed to the opposite input of the H-bridge.
For more electronic dog repeller circuits check the related links bellow.

This means that conduction occurs through the complementary pairs of TR1/TR4 and TR2/TR3 on alternate marks and spaces, effectively doubling the voltage across the ultrasonic transducer, LS1. This is optimised to generate a high output at ultrasonic frequencies.
This configuration was tested by decreasing the frequency of the oscillator to an audible level and replacing the ultrasonic transducer with a loudspeaker; the results were astounding. If the dog repellent circuit was fed by a bench power supply rather than a battery that restrict the available current, the output reached 110dB with 4A running through the speaker which is plenty loud enough!
The Dog and Cat repellant was activated using a normal open switch S1 to control the current consumption, but many forms of automatic switching could be used such as pressure sensitive mats, light beams or PIR sensors. Thus it could be utilise as part of a dog or cat deterrent system to help prevent unwanted damage to gardens or flowerbeds, or a battery powered version can be carried for portable use. Consider also using a lead-acid battery if desired, and a single chip version could be built using the 556 dual timer IC to save space and improve battery life.