Rongge

Generated millions of times every day by our telephone keypads, the eight DTMF frequencies were chosen so that the harmonics and intermodulation do not generate significant in-band signal levels. The signal is encoded as a pair of sine waves, ensuring that no frequency is a multiple of the other and the sum and difference between two frequencies does not match any single tone and that’s why DTMF sounds so ugly!T he DTMF encoder circuit show n here is based on the HT9200B tone generator device produced by Holtek and distributed by Futurlec  among others. The encoder is complemented by a decoder elsew her e in this publication. 8-Channel DTMF : Encoder Schematic The HT2900B is supplied as a nice old fashioned 14-pin device. It can be instructed by a microcontroller to generate 16 dual tones and (in serial mode only) 8 single tones from the DTMF pin output . It s 8 - pin ‘ younger brother’ the HT9200A provides a serial mode only whereas the HT9200B contains a select-able serial/parall...

TDA 7482   g eneral description: The TDA7482 is an audio class-D amplifier assembled in Multiwatt15 package specially designed for high efficiency applications mainly for TV and HomeStereo sets.  TDA7482 Audio Amplifier 1 x 25W TDA 7482  features : 25W OUTPUT POWER: RL =8Ω/4Ω; THD = 10% HIGHEFFICIENCY WIDE SUPPLY VOLTAGE RANGE (UP TO±25V) SPLITSUPPLY OVERVOLTAGEPROTECTION ST-BY AND MUTEFEATURES SHORTCIRCUIT PROTECTION THERMALOVERLOADPROTECTION TDA 7482  circuit diagram : TDA7482 Audio Amplifier 1 x 25W circuit diagram TDA 7482  sterio circuit layout : TDA7482 Audio Amplifier 1 x 25W pcb layout

The circuit of the running light comprises two integrated circuits (ICs), a resistor, a capacitor and seven light-emitting diodes (LEDs), Decade scaler IC2 ensures that the LEDs light sequentially. The rate at which this happens is determined by the clock at pin 14. The clock is generated by IC1, which is arranged as an astable multivibrator. Its frequency is determined by R1-C1. 6-Channel Running Light Circuit Diagram The touch switch, consisting of two small metal disks is optional. When switch S1 is in position ‘off’, the circuit may be actuated by the touch switch. By the way, this enables the circuit to be used as an electronic die (in which case the LEDs have to be numbered from 1 to 6). The running light is powered by a 9 V battery or mains adapter. It draws a current not exceeding 20 mA. Author: L. v/d Heeden Copyright: Elektor Electronics 1998

General Description: Above schematic is for a three channel audio mixer. That will provide an overall gain of one between the output and each input channel. Each input channel includes a single 0.1uf capacitor and 100-Kilohms resistor to provide an output impedance of 100K. The number of input channels to this audio mixer can be increased by adding more capacitors and resistors with same value as capacitor(0.1uf) and resistor(100K). The mixer should be located between the output of tone control circuitry and the input to the power amplifier. One input should be taken from the output of the tone control circuit, and the other inputs should either be grounded or taken from desired source. Circuit diagram: Three Channel Audio Mixer circuit diagram

Features 1 watt per channel with 8-ohm load Max. efficiency » 80% with 8-ohm load at 5 volts Filterless Digital gain control Build-in depop circuitry Error protection for short circuit and over-temperature Mute (shutdown) current < 1µA typical Low operating current (4mA at 5 volts without load) TSSOP 24L package available  General Description The AP130 is an oversampling class-D power amplifier for  stereo audio applications. It provides high power-efficiency for filterless 8-ohm load. Build-in depop, mute and gain control features simplify the applications. BTL (Bridge-Tied-Load) configuration delivers up to 1 watt into 8-ohm load per channel at 5-V supply voltage. It allows direct coupling of the power signal. Reliability is improved through over-temperature and short circuit protections. The class-D power amplifier enables high efficiency applications for portable devices. Circuit Diagram 1W Per Channel Stereo Class-D Audio Power Amplifier

A very simple 6 channel low cost led driver electronic circuit project can be designed using the MCP34845 LED drivers manufactured by Free scale Semiconductor.The MCP34845 LED drivers operates from 5 to 21 volts and is specially designed for use in back lighting LCD displays from 10" to 17"+ for devices like : PC Notebooks , Net books , Picture Frames , Portable DVD Players , Small Screen Televisions , Industrial Displays , Medical Displays , etc. 6 Channel LED Driver Circuit Diagram The MCP34845 LED drivers is capable of driving up to 16 LEDs in series in 6 separate strings.PWM dimming is performed by applying a PWM input signal to the PWM pin which modulates the LED channels directly.Main features of this driver circuit project are : input voltage of 5.0 to 21 V , boost output voltage up to 60 V, 2.0 A integrated boost FET , fixed boost frequency - 600 kHz or 1.2 MHz , OTP, OCP, UVLO fault detection , LED short/open protection , programmable LED current between 3.0 mA and 3...