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An LED is usually a series resistor needed to ensure that the LED does not get too much power. The disadvantage of such a resistor is that the current thus also changes by the LED and the brightness as the voltage changes.  This circuit prevents that, by independent of the voltage, a constant current through the LED.The circuit uses two transistors and two resistors. The circuit can be connected to voltages of from 5 to 24 V.   Constant LED Power Supply Circuit Diagram

The debate still goes on as to which are better, valves or transistors. We don’t intend to get involved in that argument here. But if you can’t make your mind up, you should try out this simple amplifier. This amplifier uses a valve as a pre-amplifier and a MOSFET in the output stage. The strong negative feedback makes the frequency response as flat as a pancake. In the prototype of the amplifier we’ve also tried a few alternative components. For example, the BUZ11 can be replaced by an IRFZ34N and an ECC83 can be used instead of the ECC88. In that case the anode voltage should be reduced slightly to 155 V. The ECC83 (or its US equivalent the 12AX7) requires 2 x 6.3 V for the filament supply and there is no screen between the two triodes, normally connected to pin 9. This pin is now connected to the common of the two filaments. The filaments are connected to ground via R5. If you’re keeping an eye on the quality, you should at least use MKT types for coupling capacitors C1, C4 and C7. ...

A very simple PIR motion detector circuit can be designed using this diagram. This project PIR sensor PIR motion detector circuit, operational amplifier, a sound generator circuit and use some other common electronic components. The op-amp IC1D shapes the frequency response to amplify those frequencies produced when motion is detected and rejects all others, such as those due to noise or slow temperature changes. As motion is detected, the voltage at the output will change and trigger either IC1C or IC1B.The op-amps IC1A, IC1B and IC1C are configured as voltage comparators. PIR Motion Detector Circuit Diagram: When IC1D outputs a voltage lower than 1.41V, it will force pin 2 of IC1 high. When IC1D outputs a voltage higher than 1.67V, it forces pin 8 and pin 2 of IC1 to go high. A high in with one of these cases causes the output to go low and allows C9 to discharge through IC1A. The discharging of C9 will pull pin 6 of IC2 low and trigger the sound generator. The Passive Infrared Senso...

How to Build a 1W Long Range FM Transmitter Circuit Diagram. This is a simple1W Long Range FM Transmitter Circuit Diagram. This is a long range, very stable, harmonic free, FM transmitter circuit which can be used for FM frequencies between 88 and 108 MHz. With good antenna transmitter can cover 5km range.   1W Long Range FM Transmitter Circuit Diagram It has a very stable oscillator because it uses LM7809 voltage regulator which is a 9V stabilized power supply for T1 transistor. Frequency adjustment is achieved by using the 10K linear potentiometer. The output power of this long range RF transmitter is around 1W but can be higher if you use transistors like KT920A, BLX65, BLY81, 2N3553, 2SC1970 or 2SC1971.

Have you ever needed to power a 12-volt relay in a circuit but only had 6 or 9 volts available? This simple circuit will solve that problem. It allows 12-volt relays to be operated from 6 or 9 volts, or 24-volt relays from 12 volts. While most normal relays require the manufacturer-specified coil voltage to reliably pull the contacts together, once the contacts are together you only need about half that rated voltage to hold them in. This circuit works by using that principle to provide a short burst of twice the supply voltage to move the contacts and then applies the available 6 or 9 volts to the relay to lock the contacts in place. With reference to Figure A., when the main supply is applied to the circuit the 220-µF capacitor, C1, charges quickly to +6 volts through resistor R3. The circuit is now awaiting voltage on the control input. When a control voltage (can be as little as 3 volts) is applied to the control input, transistor T1 switches on. The other transistor, a BC558, is a...

This easy to construct “Handy pen torch” electronic circuit and low component count, uses two power white LEDs for lighting. Low volt (4.8V dc) supply available from the built in rechargeable Ni-Cd battery pack is first converted into two channel (independent) constant current sources by two pieces of the renowned precision adjustable shunt regulator chip LM334 (IC1 and IC2). Around 25mA at 3.6 volt dc is available at the output of these ICs. This regulated dc supply is used to drive two power white LEDs D4 and D6. Resistors R3 and R5 limits the output current (and hence the light output) of IC1 and IC2 circuits respectively. Besides these components, one red color LED (D2) is included in the main circuit which works as a battery charging supply input indicator. Resistor R1 limits the operating current of this LED. Pen Torch Electronic Circuit Schematic Diode D1 works as an input polarity guard cum reverse current flow preventer. Capacitor C1 is a simple buffer for circuit stabilizatio...

LM380, Build 2 Watts Audio Amplifier Circuit Diagram . Small audio amplifier is useful for audio troubleshooting or simple audio projects. It should be a low cost and easy to build. Using integrated circuit for this purpose is the right choice. With LM380  audio amplifier integrated circuit, 2 Watts power can be delivered. For better thermal endurance, a large copper track can be printed in the board to provide heat sinking, this copper track should be soldered to pins 4, 3, 10, 5, 12 and 11. Here is the schematic diagram of the circuit. LM380, Build 2 Watts Audio Amplifier Circuit Diagram

A very simple universal battery charger electronic project can be designed using the LM317 voltage regulator and some other electronic components . As you can see in this schematic circuit this charger has extreme few components , but is doing a very good job . When power is applied to the circuit the SCR1 is off, so there is no bias-current path to ground. Universal Battery Charger Circuit Diagram: The LM317 is connected to the battery through diode D1, limiting resistor R1, and bias resistor R2. The D1 diode is used to prevent the battery from discharging through the LED and the SCR when power is removed from the circuit. When LED1 is on, the circuit is in the voltage-regulating mode and when LED1 is off, the circuit is in the current-regulating mode.

This inverter circuit can provide up to 800mA of 12V power from a 6V supply. For example, you could run 12V car accessories in a 6V (British?) car. The circuit is simple, about 75% efficient and quite useful. By changing just a few components, you can also modify it for different voltages. 6 V to 12 V Power Supply Inverter Circuit Diagram Part List: R1, R4 2.2K 1/4W Resistor R2, R3 4.7K 1/4W Resistor R5 1K 1/4W Resistor R6 1.5K 1/4W Resistor R7 33K 1/4W Resistor R8 10K 1/4W Resistor C1,C2 0.1uF Ceramic Disc Capacitor C3 470uF 25V Electrolytic Capcitor D1 1N914 Diode D2 1N4004 Diode D3 12V 400mW Zener Diode Q1, Q2, Q4 BC547 NPN Transistor Q3 BD679 NPN Transistor L1 See Notes MISC Heatsink For Q3, Binding Posts (For Input/Output), Wire, Board

A reactor connected in series with other equipment to limit the flow of fault current, harmonic currents, or for reactive power compensation.  Shunt Reactors are used for long EHV transmission lines to control voltage during low – load period. Shunt reactors is also used to compensate shunt capacitance of transmission line during low load periods.  Usually Shunt reactors are unswitched. eactors  and  Series Reactors  are used widely in AC networks to limit the overvoltage or to limit the shortcut current. With more high-voltage overhead lines for long transmission distance and increasing network capacity,  Reactors  and Series Reactors  play an important role in the modern network system. Application: Fault current reduction. Impedance matching of parallel feeder.

AMZ Mini Booster - PCB Transfer and Layout

Tiny Audio Amplifier Using LM386 Specifications The Tiny Audio Amplifier kit is a good choice for battery operation. It is based on LM386 IC. Power supply - 6 - 12 VDC Output power - 1 W, 8 Ohm The quiescent power drain is only 24 mW when operating from 6 VDC Self-centering output quiescent voltage Onboard PRESET to adjust volume Terminal pins for connecting power supply, audio signal and speaker Power-On LED indicator ON/OFF PCB mounted slide switch for power supply Four mounting holes of 3.2 mm each PCB dimensions 44 mm x 44 mm Schematic Inputs - Outputs configuration  Parts List  PCB

Understanding the parameters of "diode recovery time" .For prospective technicians are still learning and inexperienced, they generally recognize only two kinds of parameters of a diode, namely: The maximum working voltage (bias voltage when he gets back - or when not deliver - or when "off") The maximum operating current (when he gets a forward bias voltage of - or as leads - or when "on") Fast  Recovery diodes A similar experience we had some twenty years ago when a new SMPS first introduced on the television. When there is a diode voltage B + is broken. And then we replace the diode from the outside (our point of diode being sold in stores, rather than the official service) diode turns hot and soon broken. We think that the replacement diode voltage or current is less bulky. Then after replacement with a larger, but the result remains the same damage. Finally we order the diode with the same part number, and when the part arrived and was installed wrong...

This simple and flexible timer is more accurate than the real-time clock of the computer used for the purpose. It can be used in laboratories, dark rooms, kitchens, and for competitions in educational institutes. The program written in Q-Basic is self-explanatory. Generally, a universal timer provides the facility for switching on an electrical/electronic device after elapse of a certain time period, say, 5 minutes. The software does the same job here.   Circuit diagram : Computerised Universal Timer Circuit Diagram   When the program is executed, it displays 0:0:0 on the monitor, indicating 0 hour, 0 minute, and 0 second. The display time 0:0:0 is increased by 10 seconds each time function key F1 of the computer keyboard is depressed. So by depressing function key F1 the required time is set for which the electrical or electronic device is to be switched on. However, in debate competitions the time allowed for a candidate to speak is filled the way it is discussed above. The pr...

The circuit above above makes use of the CMOS 4017 decade counter IC. Each depression of a switch steps the output through 0– 9. By coupling the output via an AND gate to the next IC, apredefined code has to be input to create the output. Each PBSswitch is debounced by tw1o gates of a CMOS4001 quad 2-input NORgate. This ensures a clean pulse to the input of each CMOS4017 counter. Only when the correct number of presses at PBS Awill allow PBS B to become active. This is similar for PBS C andPBS D. At IC4, PBS D must be pressed 7 times. Then PBS C is againpressed 7 times, stepping from output 1 to output 8. The ANDgate formed around CMOS4081 then goes high, lighting the LED. TheReset switch can be pressed at any time. Power on resetis provided by the 100n capacitor near the reset switch. Below isa picture of one that I made about 15 years ago:   Unfortunately, this board was part of a much larger project containing multiple power supplies. One day whilst working on another circu...

Basically siren on a police patrol car and an ambulance use electronic circuit connected to the DC current. When the switch is pressed, the siren sounds immediately come out. For those of you who own a car, or any motor you can also create a similar horn. Placement was also very practical. And if you want the flashing lights can add your own. In a series of above do not use flashing lights as the sirens sound. Part List : R1 = 47K R2 = 200R C1 = 0,02uF C2 = 50uF 16V C3 = 0,005uF T1 = 2SB178 PNP transistor S1 = Push button switch G1 = 6-12V battery  TR1 , IT transformer is reversed. used a two-legged. TR2 , OT output transformer OT240 How to use it is to put the above series into a box. Adjust the size to be more practical. Then insert the cable of a car or motorcycle battery voltage as described above that is 6-12 V battery into the plug. In accordance with their respective poles. Three feet of IT transformer wrapped so as not to stick to the body of the car or motorcycle. Cover wi...

The adjustment control for the contrast of an LC-Display is typically a 10-k potentiometer. This works fine, provided that the power supply voltage is constant. If this is not the case (for example, with a battery power supply) then the potentiometer has to be repeatedly adjusted. Very awkward, in other words. The circuit described here offers a solution for this problem. The aforementioned potentiometer is intended to maintain a constant current from the contrast connection (usually pin 3 or Vo) to ground. A popular green display with 2x16 characters ‘supplies’ about 200 µA. At a power supply voltage of 5 V there is also an additional current of 500 µA in the potentiometer itself. Not very energy efficient either. Now there is an IC, the LM334, which, with the aid of one resistor, can be made into a constant current source. The circuit presented here ensures that there is a current of 200 µA to ground, independent of the power supply voltage. By substituting a 2.2-k? potentiometer for...

The hobby circuit below uses an unusual method to generate about 12,000 volts with about 5uA of current. Two SCRs form two pulse generator circuits. The two SCRs discharge a 0.047uF a 400v capacitor through a xenon lamp trigger coil at 120 times a second. 12KV High Voltage Generator Circuit Diagram The high voltage pulses produced at the secondary of the trigger coil are rectified using two 6KV damper diodes. The voltage doubler circuit at the secondary of the trigger coil charges up two high voltage disc capacitors up to about 12KV. Although this circuit can’t produce a lot of current be very careful with it. A 12KV spark can jump about 0.75 of an inch so the electronic circuit needs to be carefully wired with lots of space between components.

Build a 18w FM Transmitter. Here's a transmitter for commercial FM band provides up to 18 watts of power. Entering an audio signal 1 Vpp standard , which may come from a mixer or stereo coding stage , this system can cover an entire medium of low houses people or an entire neighborhood in a city. If required you can build more power and interconnect output stages to increase the coverage area of the station.  Since the electronic diagram is too wide for placement on screen we decided segregated into two , in order to be seen without the need to move from side to side of the screen. The point where we cut only two drivers ( represented by A and B ) which are marked with arrows.    See the Complete Circuit Diagram     The Coils and Shocks Should Be Made According to the Following Table: L1 ------- 3 Turns on ferrite of 5x10mm L2 ------- 3 Turns on air 9mm ( 10mm long ) L3 ------- 1 Return on 12mm air L4 ------- 4 turns on air 9mm ( 12mm long ) L5 ------- 2.5 laps ...

The LED bicycle light that we described in the July/August 2009 edition of Elektor has proved very  popular. The author was particularly struck by the basic design, but as always, there is room for a little improvement! Below we describe two enhanced variations on the original theme. Both circuits are, like the 2009 original, powered from a 6 V (rechargeable) battery, shown here as Vl. The simpler of the two circuits, which consists of four transistors, is in function essentially the same as the original version. lt takes the form of a boost converter with feedback provided by the voltage drop across a current sensing resistor, in this case R2. A value of 6.2 O for R2 is suitable for use with four white LEDs at D4 to D7, and gives an LED current of approximately 20 mA. The 250 mW Zener diode D10 is provided to limit the output voltage in the case that the LED chain should go open-circuit, pulling  the gate of the  MOSFET to ground via T3, T1 and T2 if the output voltage exceeds the br...

This is a very interesting Protection speakers Stereo Circuit Diagram , it makes the protection of speakers in case of a short or overload in the output. This scheme now includes two audio channels (stereo), it uses relays to cut the speakers circuit sound output. In equipment sound power, is common to burn transistors or output modules, this can cause damage to the speakers home voltage equipment is sent to the output, this circuit just protects the speakers of this tension.  Protection speakers Stereo Circuit Diagram

Battery level indicator circuit is a circuit that is used to measure the battery voltage / battery. The main components of the battery level indicator circuit is an LM3914 IC. LM 3914 on Circuit battery level indicator is a monolithic IC that detects an analog voltage. And drive the 10 LEDs that produce a linear analog display on a given input voltage. IC LM3914 is easy to get in the market and not expensive. IC LM3914 battery level indicator on the circuit is often encountered in a series of peak indicator audio signals in analog audio equipment. Battery level indicator circuit consists of IC LM3914, 10 pieces of LED, and a few resistors. The scheme of  battery level indicator can be seen below. LM3914 battery level indicator In the circuit of the battery level indicator on the supply circuit voltage taken from the battery / batteries through a switch. Didesaimn this circuit will only display the battery level when the switch is pressed. This is intended to save the battery v...

LIGHT ALARM - 1 This circuit operates when lightweight|the sunshine} Dependent Resistor receives light. When no lightweight falls on the LDR, its resistance is high and also the transistor driving the speaker isn't turned on. When lightweight falls on the LDR its resistance decreases and also the collector of the second transistor falls. This turns off the primary transistor slightly via the second 100n and also the initial 100n puts a further spike into the bottom of the second transistor. This continues till the second transistor is turned on as onerous because it will go. the primary 100n is currently nearly charged and it cannot keep the second transistor turned on. The second transistor starts to turn off and each transistors swap conditions to provide the second half of the cycle. LIGHT ALARM - 2 This circuit is comparable to lightweight Alarm -1 however produces a louder output as a result of the speaker being connected directly to the circuit. The circuit is essentially a h...