USB Powered Mobile Phone Battery Charger Circuit

Description 

 This simple circuit can give regulated 4.7 volts for charging a mobile phone. USB outlet can give 5 volts DC at 100mA current which is sufficient for the slow charging of mobile phones. Most of the Mobile Phone batteries are rated 3.6 volts at 1000 to 1300 mAh. These battery packs have 3 NiMh or Lithium cells having 1.2 volt rating. Usually the battery pack requires 4.5 volts at 300-500 mA current for fast charging.

But low current charging is better to increase the efficiency of the battery. The circuit described here provides 4.7 regulated voltage and sufficient current for the slow charging of the mobile phone. Transistor Q1 is used to give the regulated output. Any medium power NPN transistor like CL100, BD139, TIP122 can be used. Zener diode D2 controls the output voltage and D1 protects the polarity of the output supply. Front end of the circuit should be connected to a A type USB plug.

Connect a red wire to pin1 and black wire to pin 4 of the plug for easy polarity identification. Connect the output to a suitable charger pin to connect it with the mobile phone. After assembling the circuit, insert the USB plug into the socket and measure the output from the circuit. If the output is OK and polarity is correct, connect it with the mobile phone.

Circuit Diagram:

Parts

• Q1 = BD139
• D1 = 1N4001
• D2 = 4.7V - 1/2W
• R1 = 560R - 1/2W
• C1 = 16V - 100uF 

 Note:
 If the polarity is incorrect, it will destroy the mobile battery. So take extreme care.

Source - http://www.extremecircuits.net/2010/02/usb-powered-mobile-phone-battery.html

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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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170W power amplifier LM4651 and LM4652

170 Watt power amplifier is a power amplifier that is built by IC LM4651 and LM4652.


Part of this power amplifier driver using the LM4651 IC designed specifically for the purpose of the class AB amplifier driver with short circuit protection feature, containing under voltage, thermal shutdown protection and standby functions. Section 170 Watt power amplifier using LM4651 IC with a MOSFET power amplifier is equipped with temperature sensors that will be used by IC LM4651 as controlnya thermal signal. IC IC LM4651 and LM4652 are designed specifically to each other in pairs to create a class AB power amplifier with protection features are detailed. Detailed series of 170 Watt power amplifier can be seen in thethe following figure .

Power amplifier circuit requires supply voltages +22 V DC symmetrical 0-22V. Power Amplifier with IC LM4651 and LM4652 are often used in portable HiFi systems such as powered speakers, power subwoofer and car audio power Booter. D1, D2, D3 and D4 in series 170 watt power amplifier with LM4651 and LM4652 is a 22V zener diode.

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Simple Light Sensor Alarm circuit with NE555

Occurring this circuit sent out an alarm when its LDR sensor is exposed to light by sun or lamp. A 555 stable multivariate was used here which sent signal a tone of about 1kHz upon detecting light.The sensor when exposed by light completes the circuit and makes the 555 oscillate at about 1kHz with transistor to drive current.

The sensor is also shown in the circuit diagram. It has to placed making an angle of about 30 – 45 degrees to the ground.

 Sensitivity can be adjust with P1.
 This makes the sun light to flow through it to the ground and prevents the alarm from going on due to the stored light on the sensor

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Solar Relay

With extended periods of bright sunshine and warm weather, even relatively large storage batteries in solar-power systems can become rather warm. Consequently, a circuit is usually connected in parallel with the storage battery to either connect a high-power shunt (in order to dissipate the excess solar power in the form of heat) or switch on a ventilation fan via a power FET, whenever the voltage rises above approximately 14.4 V. However, the latter option tends to oscillate, since switching on a powerful 12-V fan motor causes the voltage to drop below 14.4 V, causing the fan to be switched off.

In the absence of an external load, the battery voltage recovers quickly, the terminal voltage rises above 14.4 V again and the switching process starts once again, despite the built-in hysteresis. A solution to this problem is provided by the circuit shown here, which switches on the fan in response to the sweltering heat produced by the solar irradiation instead of an excessively high voltage at the battery terminals. Based on experience, the risk of battery overheating is only present in the summer between 2 and 6 pm. The intensity of the sunlight falling within the viewing angle of a suitably configured ‘sun probe’ is especially high precisely during this interval.

This is the operating principle of the solar relay. The trick to this apparently rather simple circuit consists of using a suitable combination of components. Instead of a power FET, it employs a special 12-V relay that can handle a large load in spite of its small size. This relay must have a coil resistance of at least 600 Ω, rather than the usual value of 100-200 Ω. This requirement can be met by several Schrack Components relays (available from, among others, Conrad Electronics). Here we have used the least expensive model, a type RYII 8-A printed circuit board relay. The light probe is connected in series with the relay. It consists of two BPW40 photo-transistors wired in parallel.

The type number refers to the 40-degree acceptance angle for incident light. In bright sunlight, the combined current generated by the two photo-transistors is sufficient to cause the relay to engage, in this case without twitching. Every relay has a large hysteresis, so the fan connected via the a/b contacts will run for many minutes, or even until the probe no longer receives sufficient light. The NTC thermistor connected in series performs two functions. First, it compensates for changes in the resistance of the copper wire in the coil, which increases by approximately 4 percent for every 10 ºC increase in temperature, and second, it causes the relay to drop out earlier than it otherwise would (the relay only drops out at a coil voltage of 4 V).

Depending on the intended use, the 220-Ω resistance of the thermistor can be modified by connecting a 100-Ω resistor in series or a 470-Ω resistor in parallel. If the photo-transistors are fastened with the axes of their incident-angle cones in parallel, the 40-degree incident angle corresponds to 2 pm with suitable solar orientation. If they are bent at a slight angle to each other, their incident angles overlap to cover a wider angle, such as 70 degrees. With the tested prototype circuit, the axes were oriented nearly parallel, and this fully met our demands. The automatic switch-off occurs quite abruptly, just like the switch-on, with no contact jitter.

This behavior is also promoted by the NTC thermistor, since its temperature coefficient is opposite to that of the ‘PTC’ relay coil and approximately five times as large. This yields exactly the desired effect for energizing and de-energizing the relay: a large relay current for engagement and a small relay current for disengagement. Building the circuit is actually straightforward, but you must pay attention to one thing. The photo-transistors resemble colorless LEDs, so there is a tendency to think that their ‘pinning’ is the same as that of LEDs, with the long lead being positive and the short lead negative. However, with the BPW40 the situation is exactly the opposite; the short lead is the collector lead. Naturally, the back-emf diode for the relay must also be connected with the right polarity. The residual current on cloudy days and at night is negligibly small.

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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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