Simple Triangle Square wave Oscillator Circuit Diagram

Simple triangle-square wave oscillator circuit diagram. In this circuit by making Rt variable it is possible to alter the operating frequency over a 100 to 1 range Versatile triangle/square wave oscillator has a possible frequency range of 0 Hz to 100 kHz.

Triangle Square wave Oscillator Circuit Diagram

Sourced By: circuitsdiagram-lab

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Dual Regulated Power Supply Circuit Diagram

In this Dual Regulated Power Supply Circuit Diagram, the 7815 regulates the positive supply, and the 7915 regulates the negative supply. The transformer should have a primary rating of 240/220 volts for europe, or 120 volts for North America. The centre tapped secondary coil should be rated about 18 volts at 1 amp or higher, allowing for losses in the regulator. An application for this type of circuit would be for a small regulated bench power supply. 

 Dual Regulated Power Supply Circuit Diagram

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Stabilized Capacitance Buffer Circuit Diagram

This is a simplest Stabilized Capacitance Buffer Circuit Diagram. In this simple circuit using Ql and Q2 constitute a simple, high-speed FET input buffer. Ql functions as a source follower, with the Q2 current source load setting the drain-source channel current. The LT1010 buffer provides output drive capability for cables or whatever load is required. Normally, this open-loop configuration would be quite drifty because there is no de feedback. 

Stabilized Capacitance Buffer Circuit Diagram

The LTC1052 contributes this function to stabilize the circuit. It does this by comparing the filtered circuit output to a similarly filtered version of the input signal. The amplified difference between these signals is used to set Q2`s bias, and hence Ql `s channel current. Ql `s source line ensures that the gate never forward biases, and the 2000 pF capacitor at Al provides stable loop compensation. 

The rc network in Al`s output prevents it from seeing high-speed edges coupled through Q2`s collector-base junction. A2`s output is also fed back to the shield around Ql`s gate lead, bootstrapping the circuit`s effective in_put capacitance down to less than 1 pF.  

Sourced By : Circuitsstream

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10 Watt Audio Power Amplifier Circuit Diagram

10 Watt Audio Power Amplifier Circuit Diagram

10W PA.The 10 watts power amplifier circuit by transistor describe here is an audio amplifier with output power of 10W.Used as a low frequency class AB Amplifier. Transistor has high output current and very low distortion.This 10W audio amplifier circuit diagram using Transistor is good for small room or car audio system.This circuit is a general-purpose 10W audio amplifier for moderate-power PA or modulator use in an AM transmitter.

With higher voltages and a change in bias resistors,up to 30 W can be obtained. 

Sourced by: Circuitsstream

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Build a Inexpensive Car Protection Unit Circuit Diagram

This is a simple Inexpensive car Protection Unit Circuit Diagram. This circuit to protect car stereo, etc from pilferage that costs less and requires no adjustments in the car but a good car cover. Place the circuit at your bedside and bring the two wires from the unit to the car (parked outside your home) and connect one wire-end to the cover and the other to the ground, with both wire-ends shorted by some weight such as a brick. So outwardly the mechanism is not visible.

Circuit of car protection unit with alarm

If someone tries to remove the cover, the alarm of the circuit starts sounding to alert you. The alarm can be switched off by resetting it using switch S1.

The car protection circuit comprises two timer ICs: one for the alarm circuit (see IC2 in Fig.1) and the other to indicate that the battery has taken over as the power source (see IC3 in Fig. 2). Normally, the protector operates off AC mains and the battery takes over only when mains fail. As the battery current is not high, the battery will last long.

As long as the two wires remain shorted, transistor T1 remains cut off. When shorting is removed, transistor T1 gets forward biased and its collector voltage drops to trigger IC2 and the piezobuzzer starts sounding.

 battery-takeover indicator

If mains fails, the battery-takeover indicator (shown in Fig. 2 and connected to points A, B and C in Fig. 1) immediately gets triggered at pin 2 of IC3. Its high output activates the battery-operation alarm for a couple of seconds. IC1 draws power from the battery to activate the protection unit.

After setting up the unit properly and shorting both the wires, press test switch S2. If there is no fault in the circuit, the alarm will sound. Now release test switch S2 and momentarily press reset switch S1 to switch off the alarm.

Sourced By:  EFY Author : M. Venkateswaran and T.E. Parthasarathy

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Build a Digital Electronic Lock Circuit Diagram

This Digital Electronic Lock Circuit Diagram shown below uses 4 common logic ICs to allow controlling a relay by entering a 4 digit number on a keypad. The first 4 outputs from the CD4017 decade counter (pins 3,2,4,7) are gated together with 4 digits from a keypad so that as the keys are depressed in the correct order, the counter will advance. As each correct key is pressed, a low level appears at the output of the dual NAND gate producing a high level at the output of the 8 input NAND at pin 13.

Read : Cheap Bicycle Alarm Schematics Circuit

Digital Electronic Lock Circuit Diagram

 

The momentary high level from pin 13 activates a one shot circuit which applies an approximate 80 millisecond positive going pulse to the clock line (pin 14) of the decade counter which advances it one count on the rising edge.

Read : Emergency Light and Alarm Circuit Diagram

A second monostable, one shot circuit is used to generate an approximate 40 millisecond positive going pulse which is applied to the common point of the keypad so that the appropriate NAND gate will see two logic high levels when the correct key is pressed (one from the counter and the other from the key). The inverted clock pulse (negative going) at pin 12 of the 74C14 and the positive going keypad pulse at pin 6 are gated together using two diodes as an AND gate (shown in lower right corner).

Read : Burglar Alarm With Timed Shutoff Circuit Diagram

The output at the junction of the diodes will be positive in the event a wrong key is pressed and will reset the counter. When a correct key is pressed, outputs will be present from both monostable circuits (clock and keypad) causing the reset line to remain low and allowing the counter to advance. However, since the keypad pulse begins slightly before the clock, a 0.1uF capacitor is connected to the reset line to delay the reset until the inverted clock arrives.

Read : 5 Zone alarm Circuit Diagram

The values are not critical and various other timing schemes could be used but the clock signal should be slightly longer than the keypad pulse so that the clock signal can mask out the keypad and avoid resetting the counter in the event the clock pulse ends before the keypad pulse. The fifth output of the counter is on pin 10, so that after four correct key entries have been made, pin 10 will move to a high level and can be used to activate a relay, illuminate an LED, ect. At this point, the lock can be reset simply by pressing any key. The circuit can be extended with additional gates (one more CD4011) to accept up to a 8 digit code.

Read :  Alarm Control Keypad Circuit Diagram

The 4017 counting order is 3 2 4 7 10 1 5 6 9 11 so that the first 8 outputs are connected to the NAND gates and pin 9 would be used to drive the relay or light. The 4 additional NAND gate outputs would connect to the 4 remaining inputs of the CD4068 (pins 9,10,11,12). The circuit will operate from 3 to 12 volts on 4000 series CMOS but only 6 volts or less if 74HC parts are used. The circuit draws very little current (about 165 microamps) so it could be powered for several months on 4 AA batteries assuming only intermittent use of the relay.

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High Voltage DC Generator Circuit Diagram

This circuit is fed from a 12-V de power supply. The input to the circuit is then amplified to provide a 10,000-Vdc output. The output of the up-converter is then fed into a 10 stage, high-voltage multiplier to produce an output of 10,000 Vdc.

High Voltage DC Generator Circuit Diagram

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7805 Voltage Regulator Circuit

A voltage regulator is used to produce a constant linear output voltage. It’s generally used with AC to DC power supply. And also it can be used as well as a DC to DC voltage converter . To regulating low voltage, most used device is one single IC. 7805, 7812, 7905 etc. 78xx series are design for positive and 79xx series are for Negative voltage regulator.

7805 is a three terminal +5v voltage regulator IC from 78XX chips family. See 7805 pinout below. LM78XX series are from National Semiconductor. They are linear positive voltage regulator IC; used to produce a fixed linear stable output voltage.  National Semiconductor has also negative voltage regulator chips family, they indicate with LM 79XX. 78xx is used more than 79xx because negative voltage has a few usability purposes as we see.
I was previously posted a 5v regulated power supply circuit using 7805 IC, that circuit and this 7805 voltage regulator circuit is almost the same.

Circuit diagram of 7805 Voltage Regulator

Fig: 7805 Voltage Regulator Circuit

7805 pinout

Fig: Pinout of 7805

Its output voltage is +5V DC that we need. You can supply any voltage in input; the output voltage will be always regulated +5V. But my recommendation is, don’t supply more than 18V or less than 8V in input. There used two capacitors in this voltage regulator circuit, they aren’t mandatory to use. But it will be best if you use them. They helped to produce a smooth regulated voltage at output. Use electrolyte capacitor instead of ceramic capacitor.

One limitation of 7805 I have found that is its output current 1A maximum. Otherwise it is a good voltage regulator if you are happy with 1A. But if   you need over 400mA current in output then you should use a Heat Sink with IC LM7805. Otherwise it may fall damage for overheating.

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Pre regulated High Voltage Power Supply Circuit Diagram

This Pre-regulated High Voltage Power Supply Circuit Diagram triacs selects the tap on main transformer Tl, which provides the proper, pre-regulated voltage to the secondary regulator. T2 and its associated components comprise the secondary regulator. The ADC 0804, IC1, digitizes a voltage-feedback signal from the secondary regulator`s output. 

 Pre-regulated High Voltage Power Supply Circuit Diagram

The MC1415 De-multiplexer, IC2, decodes the digitizer`s output. IC2, in turn, drives Tl`s opto-isolated triacs via the 74LS240 driver chip, IC3, and associated opto-isolators. Transformer T3 samples the circuit`s current output. The auxiliary, 12 V winding on Tl ensures noload starting. The combination of op amp IC5 and the inverting transistor, Ql, square this current signal. 

The output of Ql is the CLK signal, which triggers one-half of the one shot, IC4A, to begin the circuit`s AID conversion. The one shots` periods are set to time out within 1l2 cycle of the ac input. Upon completion of its AID conversion, ICl`s INTR output triggers the other half of the one shot, IC4B, which enables the converter`s data outputs. The rising edge of the CLK signal resets the one shot and latches the new conversion value into IC2. The latch, associated driver, and optoisolator trigger a selected triac according to the latest value of the voltage-feedback signal, V, . Keep enjoying dont forget click on share button .

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Build a 12 14 Volt 3A Anti RF Filtered Power supply Circuit Diagram

How to Build a 12-14 Volt 3A - Anti-RF Filtered Power supply Circuit Diagram. This is not easy but you can do it . This Anti-RF Filtered Power supply Circuit Diagram is dedicated for use with rf equipments like, linear amplifiers, transmitters, receivers, and in every application that clean an-noisy signal is required. 

The circuit is very simple and you can drive it with a 220V/18V/3A transformer at the pins 1and 2.The regulator used here is the LM350K and make sure you place a good heat-sink to it because it gets too hot if current gets near to 3A. 

 12-14 Volt 3A - Anti-RF Filtered Power supply Circuit Diagram

Parts list
R1 = 220 Ohm 1/4W
R2 = 1,8 KOhm 1/4W
R3 = 330 Ohm 1/4W
 P1 = 100 Ohm
C1,C2,C3 = 4.700uf/25V
C4 = 100pf ceramic
C6 = 100uf/25V electrolitic
D1..4 = 1N5400-4 or RAX GI 837U
F1 = 5A
IC1 = LM350K

For Data Sheet Contact with us here

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Simple 12 V Battery Charger Circuit Diagram

This 12 V Battery Charger Circuit Diagram is a high performance charger for gelled electrolyte lead-acid batteries. Charger quickly recharges battery and shuts off at full charge. Initially, charging current is limited to 2A. As the battery voltage rises, current to the battery decreases, and when the current has decreased to 150 mA, the charger switches to a lower float voltage preventing overcharge.

 12 V Battery Charger Circuit Diagram

When the start switch is pushed, the output of the charger goes to 14 V. As the battery approaches full charge, the charging current decreases and the output voltage is reduced from 14 V to about 12 5 V terminating the charging. Transistor Ql then lights the LED as a visual indication of full charge.

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Circuit Diagram of Photocell Power Supply MAX630

This Circuit Diagram of Photocell Power Supply (MAX630) delivers either 4.8 or 7.2 V regulated at 15 mA with a 3-V input from a bank of photocells. R1 should be 453 k? for a 7.2-V output and 274 k? for a 4.8-Vdc output. Regulator efficiency is around 70%. This should be considered when selecting suitable solar cells.

Circuit Diagram of Photocell Power Supply (MAX630)

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Mains Slave Switcher Circuit

There are many situations where two or more pieces of equipment are used together and to avoid having to switch each item on separately or risk the possibility of leaving one of them on when switching the rest off, a slave switch is often used. Applications which spring to mind are a computer/printer/scanner etc or audio amplifier/record deck/tuner combinations or perhaps closest to every electronics enthusiast’s heart, the work bench where a bench power supply/oscilloscope/soldering iron etc are often required simultaneously. The last is perhaps a particularly good example as the soldering iron, often having no power indicator, is invariably left on after all the other items have been switched off. Obviously the simplest solution is to plug all of the items into one extension socket and switch this on and off at the mains socket but this is not always very convenient as the switch may be difficult to reach often being behind or under the work bench. Slave switches normally sense the current drawn from the mains supply when the master unit is switched on by detecting the resulting voltage across a series resistor and switching on a relay to power the slave unit(s).

This means that the Live or Neutral feed must be broken to allow the resistor to be inserted. This circuit, which is intended for switching power to a work bench when the bench light is switched on, avoids resistors or any modifications to the lamp or slave appliances by sensing the electric field around the lamp cable when this is switched on. The lamp then also functions as a ‘power on’ indicator (albeit a very large one that cannot be ignored) that shows when all of the equipment on the bench is switched on. The field, which appears around the lamp cable when the mains is connected, can be sensed by a short piece of insulated wire simply wrapped around it and this is amplified by the three stage amplifier which can be regarded as a single super-transistor with a very high gain. The extremely small a.c. base current results in an appreciable collector current which after smoothing (by C3) is used to switch on a relay to power the other sockets. Power for the relay is obtained from a capacitor ‘mains dropper’ that generates no heat and provides a d.c. supply of around 15 volts when the relay is off.

Circuit diagram:
 

Mains Slave Switcher Circuit Diagram

The output current of this supply is limited so that the voltage drops substantially when the relay pulls in but since relays require more current to operate them than they do to remain energized, this is not a problem. Since the transistor emitter is referenced to mains Neutral, it is the field around the mains Live which will be detected. Consequently, for correct operation the Live wire to the lamp must be switched and this will no doubt be the case in all lamps where the switch is factory fitted. In case of uncertainty, a double-pole switch to interrupt both the Live and Neutral should be used. The sensitivity of the circuit can be increased or decreased as required by altering the value of the T2 emitter resistor. The sensing wire must of course be wrapped around a section of the lamp lead after the switch otherwise the relay will remain energized even when the lamp has been switched off. The drawing shows the general idea with the circuit built into the extension socket although, depending on the space available an auxiliary plastic box may need to be used.

Warning:

The circuit itself is not isolated from the mains supply so that great care should be taken in its construction and testing. The sensor wire must also be adequately insulated and the circuit enclosed in a box to make it inaccessible to fingers etc. when it is in use.

Source :  www.extremecircuits.net

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A Simple Tan Timer Circuit Diagram

Six timing positions suited to different skin types, Timing affected by sunlight intensity

This timer was designed for people wanting to get tanned but at the same time wishing to avoid an excessive exposure to sunlight. A Rotary Switch sets the timer according to six classified Photo-types (see table). A Photo resistor extends the preset time value according to sunlight brightness (see table). When preset time ends, the beeper emits an intermittent signal and, to stop it, a complete switch-off of the circuit via SW2 is necessary.

Circuit diagram:

A Simple Tan Timer Circuit Diagram

Parts:

R1 = 47K - 1/4W Resistor
R2 = 1M - 1/4W Resistor
R3 = 120K - 1/4W Resistors
R4 = Photo resistor (any type)
R5 = 120K - 1/4W Resistors
C1 = 10µF - 25V Electrolytic Capacitors
C2 = 220nF - 63V Polyester Capacitor
C3 = 10µF - 25V Electrolytic Capacitors
D1 = 1N4148 - 75V 150mA Diodes
D2 = 1N4148 - 75V 150mA Diodes
Q1 = BC337 - 45V 800mA NPN Transistor
B1 = 3V Battery (two 1.5V AA or AAA cells in series)
IC1 = 4060 - 14 stage ripple counter and oscillator IC
IC2 = 4017 - Decade counter with 10 decoded outputs IC
SW1 = 2 poles 6 ways Rotary Switch (see notes)
SW2 = SPST Slider Switch
BZ1 = Piezo sounder (incorporating 3KHz oscillator)

 

Photo-type	Features	Exposure time
I & children	Light-eyed, red-haired, light complexion, freckly	20 to 33 minutes
II	Light-eyed, fair-haired, light complexion	28 to 47 minutes
III	Light or brown-eyed, fair or brown-haired, light or slightly dark complexion	40 to 67 minutes
IV	Dark-eyed, brown-haired, dark complexion	52 to 87 minutes
V	Dark-eyed, dark-haired, olive complexion	88 to 147 minutes
VI	The darkest of all	136 to 227 minutes
Note that pregnant women belong to Photo-type I

Notes:

• Needing only one time set suitable for your own skin type, the rotary switch can be replaced by hard-wired links.
• A DIP-Switch can be used in place of the rotary type. Please pay attention to use only one switch at a time when the device is off, or the ICs could be damaged.

Source : www.redcircuits.com

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FM Transmitter Bug Circuit

Circuit Diagram 

Notes:

 This small transmitter uses a hartley type oscillator. Normally the capacitor in the tank circuit would connect at the base of the transistor, but at VHF the base emitter capacitance of the transistor acts as a short circuit, so in effect, it still is. The coil is four turns of 18swg wire wound around a quarter inch former. The aerial tap is about one and a half turns from the supply end. Audio sensitivity is very good when used with an ECM type microphone insert

  

Author: David, radio_david@yahoo.com
Source http://www.electronics-lab.com/

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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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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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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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Precision Full Wave Ac Dc Converter Circuit Diagram

A dc level is produced that corresponds to the ac input rms value (if sine wave), -i set the gain of IC2 to 1.11. This factor is the average-to-rms conversion factor. IC1 and IC2 act as a full-wave rectifier circuit, with Dl and D2. 

Precision Full-Wave Ac/Dc Converter Circuit Diagram

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