Thursday, December 26, 2013

V Charger Circuit Diagram

The charger is based on a charging voltage of 2.4 V per cell, in accordance with most manufacturers recommendations. The circuit pulses the battery under charge with 14.4 V (6 cells ? 2.4 V per cell) at a rate of 120 Hz. The design provides current limiting to protect the chargers internal components while limiting the charging rate to prevent damaging severely discharged lead-acid batteries. 

The maximum recommended charging current is normally about one-fourth the ampere-hour rating of the battery. For example, the maximum charging current for an average 44 ampere-hour battery is 11 A. If the impedance of the load requires a charging current greater than the 11 A current limit, the circuit will go into current limiting. The amplitude of the charging pulses is controlled to maintain a maximum peak charging current of 11 A (8 A average).

V Charger Circuit Diagram

V Charger Circuit Diagram

V Charger Circuit Diagram
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Tuesday, December 24, 2013

LM4990 2 Watt Audio Power Amplifier with Selectable Shutdown Logic Level

The LM4990 is an audio power amplifier primarily designed for demanding applications in mobile phones and other portable communication device applications. It is capable of delivering 1.25 watts of continuous average power to an 8Ω BTL load and 2 watts of continuous average power (LD and MH only) to a 4Ω BTL load with less than 1% distortion (THD+N+N) from a 5VDC power supply. Boomer audio power amplifiers were designed specifically to provide high quality output power with a minimal amount of external components. The LM4990 does not require output coupling capacitors or bootstrap capacitors, and therefore is ideally suited for mobile phone and other low voltage applications where minimal power consumption is a primary requirement.



2 Watt Audio Power Amplifier with Selectable Shutdown Logic Level  2 Watt Audio Power Amplifier with Selectable Shutdown Logic Level

The LM4990 features a low-power consumption shutdown mode. To facilitate this, Shutdown may be enabled by either logic high or low depending on mode selection. Driving the shutdown mode pin either high or low enables the shutdown pin to be driven in a likewise manner to enable shutdown. The LM4990 contains advanced pop & click circuitry which eliminates noise which would otherwise occur during turn-on and turn-off transitions. The LM4990 is unity-gain stable and can be configured by external gain-setting resistors.
 Features

  • Available in space-saving packages: LLP, Exposed-DAP TSSOP, MSOP, and ITL
  • Ultra low current shutdown mode
  • Improved pop & click circuitry eliminates noise during turn-on and turn-off transitions
  • 2.2 - 5.5V operation
  • No output coupling capacitors, snubber networks or bootstrap capacitors required
  • Unity-gain stable
  • External gain configuration capability

  • User selectable shutdown High or Low logic Level
    Key Specification
    Improved PSRR at 217Hz & 1KHz  62dB
    Power Output at 5.0V, 1% THD+N, 4Ω (LD and MH only) 2W (typ)
    Power Output at 5.0V, 1% THD+N, 8Ω 1.25W (typ)
    Power Output at 3.0V, 1% THD+N, 4Ω 600mW (typ)
    Power Output at 3.0V, 1% THD+N, 8Ω 425mW (typ)
    Shutdown Current 0.1µA (typ)

    Applications

    • Mobile Phones
    • PDAs
    • Portable electronic devices
    Datasheets

    Source: http://www.ecircuitslab.com/2011/07/lm4990-2-watt-audio-power-amplifier.html

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    Sunday, December 22, 2013

    Simple Digital Switching System

    This circuit can control any one out of 16 devices with the help of two push-to-on switches. An up/down counter acts as a master-controller for the system. A visual indication in the form of LEDs is also available.  IC1 (74LS193) is a presettable up/ down counter. IC2 and IC3 (74LS154) (1of 16 decoder/demultiplexer) perform different functions, i.e. IC2 is used to indicate the channel number while IC3 switches on the selected channel.

    Digital Switching System Circuit Diagram :
    Digital Switching System-Circuit Diagram

    Before using the circuit, press switch S1 to reset the circuit. Now the circuit is ready to receive the input clock. By pressing pressing switch S2 once, the counter advances by one count. Thus, each pressing of switch S2 enables the counter to advance by one count. Likewise, by pressing switch S3 the counter counts downwards.

    The counter provides BCD output. This BCD output is used as address input for IC2 and IC3 to switch one (desired channel) out of sixteen channels by turning on the appropriate triac and the corresponding LED to indicate the selected channel.  The outputs of IC3 are passed through inverter gates (IC4 through IC6) because IC3 provides negative going pulses while for driving the triacs we need positive-going pulses. The high output of inverter gates turn on the npn transistors to drive the triacs. Diodes connected in series with triac gates serve to provide unidirectional current for the gate-drive.

    Sorce : www.ecircuitslab.com/2012/08/digital-switching-system.html
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    Friday, December 20, 2013

    Fox Hunt Transmitter

    This 2 meter 144 MHz fox hunt transmitter is used in amateur competitions where a hidden transmitter is to be “hunted” using mostly home brewed receivers and antennas. The foxhunt electronic circuit is the transmitter. It radiates a high quality signal without unwanted harmonics. Transistor T1 and the crystal together make the oscillator that generates a 36MHz signal.

    The unwanted 12MHz basic frequency of the oscillator is suppressed by the filter circuit made of L1, C3, C2. The L2/C4 circuit is set to the fourth harmonic or 144 MHz. The signal goes to the dual-gate-FET driver stage before finally radiating through the transmitting antenna. The output power is from 10…40mW. The radiated signal is also modulated by the gate circuit made of U1, U2, U3, U4. Gate U1 is a low frequency oscillator which generates a signal from 0.1 to 0.5Hz. This signal modulates the transmitter through the transistor T3.

    Fox Hunt Transmitter Circuit diagram

    If the U1 output is “0″, transistor T3 is off and the transmitter is also off. On the other hand, if the U1 output is “1″, transistor T3 is on and the transmitter is on. During the “1″ period, gate U2 generates a square wave signal with a frequency form 0.1 to 1Hz. Gate U3 works as an inverter only. It determines whether gate U4 generates a 1KHz signal or not. A periodic burst signal is now present at the gate FET T2 to modulate the transmitter used at foxhunt.

    Calibration of the foxhunt transmitter: Adjust the three trimmer capacitors to produse a maximum signal amplitude at the output.
    Coil data:
    L1 = 470 nH
    L2 is made of 5 windings of 0.8mm copper wire, 8 mm winding diameter. It is tapped at the first winding from the ground.
    L3 is made of 0.8mm copper wire, 8mm winding diameter, 3 windings at the FET side and 2 windings at the antenna side. Adjust the coupling between the two windings sides to get a maximum signal output amplitude.
    The circuit can be powered with a 9 volt battery. It consumes around 20mA only.

    Fox Hunt Transmitter Active Components.

    T1 = 2SA256
    T2 = 3N205
    U1, U2, U3, U4 = IC1 = 4093
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    Wednesday, December 18, 2013

    the layout of the electricity line around cell phone jammers should be done

    And some revise of the layout of the electricity line around  cell phone jammers should be done.
    And mobile, China Unicom, not limited to the scope of telecommunications triple-play cell phone number to send, according to the specific needs of custom personalized service. Students as a distinct group, have higher education, higher information needs with the progress, contact television and other media opportunities, the phone reports that the new target audience. Campus mobile newspaper reading population is more focused and precise, and naturally become a new choice in the promotion of business products. Campus phone reported. Campus mobile newspaper "News" is the fundamental content. Planning Students mobile newspaper content loved by readers, of course, we must first understand the interest of the target audience of university students, according to their characteristics, needs.  Industrial environment: As the sponsor reasonable ease the demand for advertising, legal and mobile advertising services, so in fact played a large role in governance spam messages, thereby purifying the industrial environment, the industrial chain win. Status and Prospects of the development of mobile media. As information technology continues to progress, the original mobile phone as an interpersonal exchange of information intermediaries.
    Rather to ensure that each piece of information, "Jane and deep." To do Jane and deep "will be a higher demand for editing, you need enough news sensitivity. Such as to make the correct interpretation of the country, the government introduced the policy of involving university students to study or work, and make predictable judgments, and even make incisive reviews, make the appropriate adjustments to help and facilitate college students to use the relevant policies give practical advice. Recommendations for mobile newspaper audience attention of contention. According to the spread scientist Melvin De Fule theory, when major changes occur, the audience will generate an exception to the media rely on. Which media can be timely and adequate to provide information to who he would rely on.  However, todays mobile newspaper is considered to be a subsidiary of the print media, the contents of the value of the performance of the force and the media not been fully recognized and mining. Information personalization. First of all must be aware, mobile newspaper should not just newspapers optional supplement. The mobile newspapers content to get out of the shadow of the newspaper, to form their own style and play their own unique advantages, mining the content of expression, and expansion of channel function.
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