USB Powered, Stereo Computer Speaker

This is the circuit diagram of USB powered computer speaker, or it widely known as multimedia speakers for PCs. The circuit has single-chipbased design, low-voltage electrical power supply, compatibility with USB power from computer, simple heat-sinking, inexpensive, large flexibility and wide temperature tolerance.


At the heart of the circuit is IC TDA2822M. This IC is, actually, monolithic type in 8-lead mini DIP (Dual Inline Package). It’s designed for use as a dual audio power amplifier in battery powered sound players. Features of TDA2822M are very low quiescent current, low crossover distortion, DC source voltage down to 1.8 volts and minimal output power of approximately 450 mW/channel with 4 ohm loudspeaker at 5V DC supply input.

An ideal power amplifier can be basically described as a circuit which can supply audio power into external loads without having producing substantial signal distortion and without having consuming extreme quiescent current.
This circuit is powered by 5V DC source obtainable from the USB port of the Computer. When electrical power switch S1 is turned to ‘on’ position, 5V power supply is extended towards the circuit and power indicator red LED1 illuminates immediately. Resistor R1 is actually a current surge limiter and capacitors C1 and C4 work as buffers.

How the circuit works..?
The operation of the circuit is very simple. Audio signals from the Computer audio port or headphone port are fed towards the amplifier circuit via R2 and C2 (for left channel), and R3 and C3 ( forright channel). Potensiometer VR1 used as the volume controller for left (L) channel, while potensiometer VR2 used to control the volume level of right (R) channel. Pin 7 of TDA2822M receives the left channel sound signals and pin 6 receives the right channel signals by way of VR1 and VR2, correspondingly. Amplified signals for driving the left and right loudspeakers can be obtained at pins 1 and pin 3 of IC1, correspondingly. Components R5 and C8, and R6 and C10 form the classic zobel network.
Construct the circuit on a medium size, general purpose PCB and enclose inside a appropriate case. It really is recommended to utilize a socket for IC TDA2822M. The external connections ought to be made working with suitably screened wires for improved result.
Source

Read More

Converter 9V to 13.5kV

This high voltage source is formed by an inverter, around the transistor, which provides pulses of 150V to the inverter formed by the thyristor and capacitor in series with the transformer 2. This pulse output of 4.5kV to be multiplied with the network so as to achieve the output voltage of 13.5kV.  Neon lamps (marked LN) form the thyristor triggering pulses.
The transformer T1 has a ratio 3000:500 Ω of the type used in audio output transistor. T2 is a transformer flash lamp trigger a secondary 6kV.
This converter circuit requires a 9VDC power supply with current 0.01A

Caution:
Apply this equipment on the human body can cause serious physical injury to death. Don’t use in humans.
Source

Read More

Laptop Protector

Here the notebook anti theft protector circuit to secure your important netbook / notebook from stealing. Basically, this is a mini security alarm generator. Fixed inside the notebook case, it will definitely sound a noisy alarm when a person attempts to grab the notebook. This very sensitive circuit utilizes a homemade tilt switch to turn on the alarm system through tilting of the laptop computer case.

The circuit utilizes readily available parts and also can easily be constructed on a little piece of general-purpose PCB or a Vero board. This circuit is operated by a 12V miniature battery applied in remote control devices.
IC TLO71 (IC1) is utilized as a voltage comparator with a potential divider composed of R2 and R3 delivering fifty percent power supply voltage at the non-inverting input (pin 3) of IC1. The inverting input gets a higher voltage through a water-activated tilt switch only when the probes in the tilt switch make contact with water. When the tilt switch is maintained in the horizontal position, the inverting input of IC1 receives a higher voltage than its noninverting input and the output continues to be low.
The CD4538 (IC2) is utilized as a monostable multivibrator with timing factors R5 and C1. Considering the shown values, the output of IC2 continues to be low for a duration of three minutes. CD4538 is an accuracy monostable multivibrator free from incorrect triggering and also is much more reliable compared to the well-known timer IC 555. Its output comes to be high when power is turned on and it gets low when the trigger input (pin 5) receives a low to high transition pulse.
The circuit device is fixed inside the notebook case in horizontal position. In this position, water inside the tilt switch properly shorts the contacts, so the output of IC1 continues to be low. The alarm system generator stays silent in the standby mode as trigger pin 5 of IC2 is low. When a person attempts to grab the notebook case, the unit takes the vertical position and the tilt switch breaks the electrical contact between the probes. Instantly the output of IC1 comes to be high and monostable IC2 is triggered. The low output from IC2 triggers the PNP transistor (T1) and then the buzzer starts beeping.
Construct the circuit as compactly as feasible so as to make the unit matchbox dimension. Make the tilt switch working with a small (2.5 centimeters long and 1cm wide) plastic bottle with two stainless pins as contacts. Fill two-third of the bottle with water such that the contacts never make electrical path when the tilt switch is in vertical position. Make sure the bottle is leakproof with adhesive or wax.
Fix the tilt switch inside the enclosure of the circuit in horizontal position. Fit the unit inside the notebook case in horizontal position working with adhesive. Work with a miniature buzzer and a micro switch (S1) for making the device small and lightweight. Maintain the notebook case in horizontal position and turn on the circuit. Your notebook is right now secured.
Source

Read More

220V AC Lamp Touch Dimmer

Here the 220V AC lamp touch dimmer circuit. By only touching this touch dimmer you are able to increase the light intensity of incandescent lamps in three stages. The touch dimmer is designed all around 8-pin CMOS IC TT8486A/TT6061A especially produced for touch dimmer applications.
In the beginning, when mains switch is “on”, the lamp is “off”. Now, when you touch the touch plate, the lamp glows dimly. On second touch, the lamp provides medium light. At the third touch, the lamp is powered fully. One more touch puts off the light.
Considering that the IC is very sensitive, utilize a long wire to connect the IC towards the touch sensor. The circuit utilizes minimal external parts. For touch plate, it is possible to utilize a simple copper plate of 1cm×1cm or simply the end of the lead wire. Touch plate is joined together towards the touch detector via 820pF, 2kV capacitors C1, C2, and C3 coupled in series. Internally IC TT6061A’s touch signal is connected to the counter/decoder via a resistor and clock input CK is connected to the counter/decoder via a frequency generator.
Line frequency signal is obtained via R4 at pin 2 of IC TT6061A. At zero crossing, the triac (BT136) triggers to drive a 200W lamp.
The 6.8V power supply is obtained straight from mains through resistors R1 and R3, diode D3, capacitor C4, and zener diode and given to power input pin 3 of the IC. Capacitors C1, C2, and C3 connected between touch input pin 4 and touch plate take out the shock potential from the touch plate, so don’t change these capacitors with a single capacitor or with a capacitor of a lower voltage rating. Mains potential is available in the circuit. Needless to say, it really is high risk to touch the circuit when mains is “on”.

Source

Read More

Simple Traffic Light Controller

Here the simple traffic light controller which is could be used to educate kids rudiments of traffic light guidelines. The circuit utilizes easily available electronic parts. It generally consists of rectifier diodes (1N4001), a 5V regulator 7805, two timers circuit using IC 555, two relays (5V, single-changeover), three 15W, 230V light bulbs and also several discrete parts.
Mains electrical power is stepped down by transformer X1 to provide a secondary output voltage of 9V, 300 mA – AC. Then the transformer output current is rectified by a full-wave bridge rectifier composed of diodes D1 through D4, filtered by capacitor C1 and also regulated by IC 7805 (IC1).

IC2 is wired as a multivibrator with ‘on’ and ‘off’ periods of about 30 seconds each with the part values determined. Once mains power switch is turned on, pin 3 of IC2 goes high for 30 seconds. This, in turn, energises relay RL1 via transistor T1 and the red bulb (B1) glows through its normally-open (N/O) contact. At the same time, mains power is turned off from the pole of relay RL2.
As the ‘on’ time of IC2 ends, a triggers IC3 through C5. IC3 is set up as a monostable with ‘on’ time of about 4 seconds, which indicates pin 3 of IC3 will stay high for this period of time and energise relay RL2 through driver transistor T2. The amber bulb (B2) thus lightings up for 4 seconds.
Immediately after 4-second time period of timer IC3 at pin 3 lapses, relay RL2 de-energises and also the green bulb (B3) lights up for the rest of ‘off’ period of IC2, which is about 26 seconds. The green bulb is turned on through the normally closed (N/C) contacts of relay RL2.
So when mains electrical switch is turned on, red light will light up for 30 seconds, amber for 4 seconds and green for 26 seconds.
You can easily build this circuit on a general purpose PCB and enclose in a protected box. The box needs to have sufficient area for installing transformer X1 and also two relays. It could be installed near 230V AC, 50Hz power supply or mounted on the PVC tube applied in assembly of the traffic light box.
Design of the traffic light container box is demonstrated in following image:

A stout cardboard box of 30x15x10cm3 is needed for housing the lights. To make certain durability, work with a 10x45cm2 plywood plate having 1.5 centimeters thickness and also secure onto it three light outlets and the box utilizing nuts and bolts or screws.
Make three tubes of thin aluminium sheet, which is easily offered in equipment stores. The inner diameter of aluminium tubes ought to be such that these can well match on the light outlets. Working with a sharp knife, make holes opposite the outlets carefully. Wire the outlets at the back and take the cables out through the PVC tube.
To begin with, fix three 15W light bulbs (B1 through B3) and then press on the tubes. Support the other ends of the tubes in the holes made on the front panel of cardboard box. Sandwich gelatine papers of the three colors in between two sheets of cardboard and fix over the tubes. The visibility of red, amber and also green lights enhances with their installation on the tubular shape.

Read More

Simple Symmetrical Power supply +25v -25v

This symmetrical unregulated power supply is used to feed the audio amplifier based on LM1875 amplifier module National Semiconductor. With symmetrical 30V DC source the amplifier capable of delivering up to 30W of power using 8 ohm load. The diagram above shows how the DC +25 V and-25V DC can be obtained. Ready to provide power to two stereo amplifiers, one 80VA transformer with 240V input and 36V output, with the center tap is used. The output of the transformer secondary repaired using four 1N5401 diodes and filtered through four electrolytic capacitors. A fuse and a varistor connected to the main circuit protection against voltage spikes.
Source

Read More

Touch switch electronic circuit based on a Schmitt trigger

This touch switch electronic circuit is based on a Schmitt trigger with latching, built IC1a, IC1b and R3. IC1b's output signal comes back to IC1a input through R3, resulting in maintaining stable condition of both gates. While the circuit is at rest, the anode of D1 is at "0" and the cathode of D2 is at level "1" retain their status.
When contact is shorted by finger touch, the voltage drop across R8 increases. This increase is translated into a short pulse of R1-C1. This pulse transmit through D1 a “ 1” at input of ICla. IC1b's output and output will also go to "1".
When C2 is charged circuit is ready to change the status of the next stimulus appeared on R1. This momentum will make it output IC1a become "0", in which the output of IC1b becomes “ 0 “ C2 voltage decreases. Output is again,, 0 "circuit again is at the point from which it started.

Source

Read More