3x3x3 LED Cube Circuit Diagram

This circuit drives a 3x3x3 cube consisting of 27 white LEDs. The 4020 IC is a 14 stage binary counter and we have used 9 outputs. Each output drives 3 white LEDs in series and we have omitted a dropper resistor as the chip can only deliver a maximum of 15mA per output. The 4020 produces 512 different patterns before the sequence repeats and you have to build the project to see the effects it produces on the 3D cube.

Circuit diagram

 3x3x3 LED Cube Circuit diagram

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IR Remote Control Tester

Here’s a simple, low cost, and easy to construct infrared remote control tester. The tester is built around an easily available infrared receiver module (TSOP 1238).
Circuit Diagram:

 IR Remote Control Tester Circuit Diagram

Normally, data output pin 3 of the IR receiver module is at a high level (5 volts)and as such driver transistor T1 is in cut-off state. Whenever the IR receiver module receives a valid (modulated) infrared signal, its data output pin goes low in synchronism with the received infrared bursts. As a result, transistor T1 conducts during negative pulse period and the.LED blinks to indicate reception of signals from the remote such as TV remote control. A miniature active buzzer is connected at the collector of transistor T1 for audio indication.


The 5V DC for energizing the circuit is directly derived from the 230V AC mains supply. Unlike the conventional resistive voltage divider, a capacitive potential divider is used here, which does not radiate any heat and makes the tester quite compact. Another advantage of this tester is no false triggering due to the ambient light or electronic ballast-operated tubelights. A suggested enclosure for the circuit is shown in Fig. 2.

Author : T.K. Hareendran : Copyright :Electronics For You September 2002

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Condenser Mic Audio Amplifier

The compact, low-cost condenser mic audio amplifier described here provides good-quality audio of 0.5 watts at 4.5 volts. It can be used as part of intercoms, walkie-talkies, low-power transmitters, and packet radio receivers. Transistors T1 and T2 form the mic preamplifier. Resistor R1 provides the necessary bias for the condenser mic while preset VR1 functions as gain control for varying its gain. In order to increase the audio power, the low-level audio output from the preamplifier stage is coupled via coupling capacitor C7 to the audio power amplifier built around BEL1895 IC.

Circuit diagram:

Condenser Mic Audio Amplifier Circuit Diagram

BEL1895 is a monolithic audio power amplifier IC designed specifically for sensitive AM radio applications that delivers 1 watt into 4 ohms at 6V power supply voltage. It exhibits low distortion and noise and operates over 3V-9V supply voltage, which makes it ideal for battery operation. A turn-on pop reduction circuit prevents thud when the power supply is switched on. Coupling capacitor C7 determines low-frequency response of the amplifier. Capacitor C9 acts as the ripple-rejection filter.

Capacitor C13 couples the output available at pin 1 to the loudspeaker. R15-C13 combination acts as the damping circuit for output oscillations. Capacitor C12 provides the boot strapping function. This circuit is suitable for low-power HAM radio transmitters to supply the necessary audio power for modulation. With simple modifications it can also be used in intercom circuits.

Author: D. Prabakaran - Copyright: Electronics For You Mag

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Playback Amplifier For Cassette Deck

For some time now, there have been a number of tape cassette decks available at low prices from mail order businesses and electronics retailers. Such decks do not contain any electronics, of course. It is not easy to build a recording amplifier and the fairly complex magnetic biasing circuits, but a playback amplifier is not too difficult as the present one shows. The stereo circuits in the diagram, in conjunction with a suitable deck, form a good-quality cassette player. The distortion and frequency range (up to 23 kHz) are up to good standards. Moreover, the circuit can be built on a small board for incorporation with the deck in a suitable enclosure. Both terminals of coupling capacitor C1 are at ground potential when the amplifier is switched on.

Circuit diagram:

Cassette Deck Playback Amplifier Circuit Diagram

Because of the symmetrical ±12 V supply lines, the capacitor will not be charged. If a single supply is used, the initial surge when the capacitor is being charged causes a loud click in the loudspeaker and, worse, magnetizes the tape. The playback head provides an audio signal at a level of 200–500 mV. The two amplifiers raise this to line level, not linearly, but in accordance with the RIAA equalization characteristic for tape recorders. Broadly speaking, this characteristic divides the frequency range into three bands:

• Up to 50 Hz, corresponding to a time constant of 3.18 ms, the signal is highly and linearly amplified.
• Between 50 Hz and 1.326 kHz, corresponding to a time constant of 120 µs, for normal tape, or 2.274 kHz, corresponding to a time constant of 70 µs, for chromium dioxide tape, the signal is amplified at a steadily decreasing rate.
• Above 1.326 kHz or 2.274 kHz, as the case may be, the signal is slightly and linearly amplified. This characteristic is determined entirely by A1 (A1’). To make the amplifier suitable for use with chromium dioxide tape, add a double-pole switch (for stereo) to connect a 2.2 kΩ resistor in parallel with R3 (R3’). The output of A1 (A1’) is applied to a passive high-pass rumble filter, C3-R5 (C3’-R5’) with a very low cut-off frequency of 7 Hz. The components of this filter have exactly the same value as the input filter, C1-R1 (C1’-R1’). The second stage, A2 (A2’) amplifies the signal ´100, that is, to line level (1V r.m.s.).

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Mini Portable Guitar Amplifier

Can be fitted into a packet of cigarettes, Also suitable as Fuzz-box

This small amplifier was intended to be used in conjunction with an electric guitar to do some low power monitoring, mainly for practice, either via an incorporated small loudspeaker or headphones. The complete circuit, loudspeaker, batteries, input and output jacks can be encased in a small box having the dimensions of a packet of cigarettes, or it could be fitted also into a real packet of cigarettes like some ready-made units available on the market.
This design can be used in three different ways:

1. Loudspeaker amplifier: when powered by a 9V alkaline battery it can deliver about 1.5W peak output power to the incorporated loudspeaker.
2. Headphone amplifier or low power loudspeaker amplifier: when powered by a 3V battery (2x1.5V cells) it can drive any headphone set type at a satisfactory output power level or deliver to the incorporated loudspeaker about 60mW of output power. This configuration is useful for saving battery costs.
3. Fuzz-box: when powered by a 3V battery (2x1.5V cells) and having its output connected to a guitar amplifier input the circuit will behave as a good Fuzz-box, showing an output square wave with marked rounded corners, typical of valve-circuits output when driven into saturation.

Circuit diagram:

Mini Guitar Amplifier Circuit Diagram

Parts:

R1______________22K 1/4W Resistor
C1______________10µF 25V Electrolytic Capacitor
C2_____________100nF 63V Polyester or Ceramic Capacitor
C3_____________220µF 25V Electrolytic Capacitor
IC1__________TDA7052 Audio power amplifier IC
J1,J2__________6.3mm Stereo Jack sockets (switched)
SPKR___________8 Ohm Loudspeaker (See Notes)
B1________________9V PP3 Battery or 3V Battery (2 x 1.5V AA, AAA Cells in series etc.)
Clip for PP3 Battery or socket for 2 x 1.5V AA or AAA Cells

Notes:

• For the sake of simplicity and compactness, this unit employs a dual bridge IC amplifier and a few other parts. For the same reason no volume or tone controls are provided as it is supposed that the controls already existing on the electric guitar will serve satisfactorily to the purpose.
• No power switch is used: the battery voltage will be applied to the circuit when the input plug will be inserted in the input jack socket J1. For this purpose be sure that the input plug is a common 1/4 inch guitar mono jack plug and J1 is a 1/4 inch stereo jack socket.
• The output jack socket J2 must be a switched stereo type. The changeover switching is arranged in such a way that, when a common headphones stereo jack plug is inserted into the socket, the loudspeaker will be disabled and the mono output signal will drive both the headsets in series, allowing full headphone reproduction. When used as a Fuzz-box output, a mono jack plug must be inserted into J2.
• If the amplifier is intended to be encased in a packet of cigarettes, standard loudspeaker diameter should be 57 or 50mm.

Technical data:

Max output power: 1.5W @ 9V supply - 8 Ohm load; 60mW @ 3V supply - 8 Ohm load
Frequency response: Flat from 20Hz to 20kHz
Total harmonic distortion @ 100mW output: 0.2%
Max input voltage @ 3V supply: 8mV RMS
Minimum input voltage for Fuzz-box operation: 18mV RMS @ 3V supply
Current consumption @ 400mW and 9V supply: 200mA
Current consumption @ 250mW and 9V supply: 150mA
Current consumption @ 60mW and 3V supply: 80mA
Quiescent current consumption: 6mA @ 9V, 4mA @ 3V supply
Fuzz-box current consumption: 3mA @ 3V supply
Copyright: www.redcircuits.com

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