It uses a 555 timer wired as an astable oscillator and powered by the emitter current of the BC109C. Under dry conditions, the transistor will have no bias current and be fully off. As the probes get wet, a small current flows between base and emitter and....

The block diagram explaining the device and operation of the sonic depth finder, is shown on fig. 1. The clock G1 generator operates interaction of knots of the device and provides its work in an automatic mode. Generated by it short (0, 1 c) rectangular....

Once the mains power supply cuts off, the relay will only be able to turn ON after a period of 150 - 210 secs depending on the tolerance of the RC ....

Such jobs as jewel cutting and polishing require the workers to switch on/off two electrical appliances one after another repeatedly for two different services on the same workpiece. This is cumbersome as they need to fully concentrate on delicate handwork....

and C code for a frequency counter circuit operating up to about 50MHz using a multiplexed seven segment display and uses timer 1 to count edges of the input signal....

This device was designed on request and allows sequential operation of four Leds either to left or right direction, obtained by means of a 7555 CMos timer IC (IC1) wired as an astable multivibrator driving a Decade counter (IC2). This IC is set to count a....

Many of us who use GTX 900 MHz radios to work amateur repeaters are well aware of the erratic output power problem. You go through the complete board replacement procedure, adjusting the deviation and output power, and everything looks great on the test....

The circuit diagram of this programmable sequencer could be applied in a number of timing uses. Prior to the start of each interval, an audible tone is generated, and a seven-segment LED display shows the interval number. Prior to the end of that inerval,....

The second circuit simulates the siren of an American police car. It uses two 555 timers in the circuit. The 555 on the right is wired as an alarm tone generator and the second 555 timer on the left is wired as a low frequency astable timer which generates a....

The 555 will activate a relay. When pins 2 and 6 are connected as an input, the chip requires only about 1uA to activate the output. This is equivalent to a gain of about 200, 000, 000 (200 million) and represents about 4 stages of amplification via....

This is a very basic circuit for flashing one or more LEDS and also to alternately flash one or more LEDs. It uses a 555 timer setup as an astable multivibrator with a variable frequency. With the preset at its max. the flashing rate of the LED is about 1/2....

This circuit is simple. The first 555 timer prevents the second timer from being triggered while the first is running...

A simple F to V converter circuit with diagram and schematic using LM555 Timer IC.This circuit has lots of applications in digital frequency meters, tachometers etc....

This circuit shows an ICM7217 and an ICM7555 that are connected as a basic frequency counter. The connections between the ICM7217 and a common-cathode LED display are shown in Fig. 12-18. The frequency counter is calibrated (against a known standard) using....

The following circuit shows a timer circuit with independent mark and space periods. This circuit based on the 7555 IC. Features: output high is calculated by T(on) = 0. 7 Ra Ct, output low is calculated by T(off) = 0. 7 Rb Ct, astable timer, (on) and (off)....

Switch applies positive pulse to gate of scs, triggering it on and thereby supplying power to relay load and ujt timing circuit. At end of timing interval, determined by R-C, timer feeds negative pulse to anode to turn off scs. -"Transistor Manual, " Seventh....

Running Message Display Circuit Diagram. This circuit  Based On The CD401IC. Fetures: Light emitting diodes are advantageous, cos smaller size, ....

This Dummy Alarm project makes an LED flash briefly once every 5 seconds to imitate the indicator light of a real alarm. The circuit is designed to use very little current to prolong battery life so that it can be left on permanently. An on/off switch is not....

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The following circuit is a Basic 555 squarewave oscillator. Feature : 1 Khz tone, Simple circuitry, limit = 200 mA, inductive voltage reduced, 4.5-9 Supply voltage. Component : 555 timer IC, resistor, capacitor, Speaker, 2N3053 transistor, push button...

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It will allow your car headlights to flash on and off at the same time or it will cause them to flash alternately. The circuit is based on the 555 timer. It is used in the astable mode. The 555 timer output will go high for an adjustable period of time and....

This Adjustable Analog Timer circuit starts timing when switched on. A green LED lights to show that timing is in progress. When the time period is over the green LED turns off, a red LED turns on and a bleeper sounds. The time period is set by a variable....

This 555 timer based circuit is a kind of voltmeter, also an analog to digital converter, that converts the analog input voltage to digital output pulses ..

This is the circuit diagram of a ding dong sound generator based on two NE555 timer ICs. The circuit is designed to toggle between two adjustable frequencies to produce the ding dong sound. The first NE555 (IC1) is wires as an astable multivibrator operating....

Accurate 50Hz Oscillator Circuit Using 555 And 7490 This circuit is a getting a 50Hz pulse. It comprises a 555 timer and two 7490 divide-by-ten....

Most switch-mode power supplies rely on a PWM (pulse-width-modulated) output that is controlled via voltage feedback. A 555-timer IC can inexpensively perform PWM. The circuit in Figure 1 shows how to turn a 555 PWM circuit into an switch-mode power supply....

The circuit shown is a simple digital frequency meter, which indicates the frequency in hertz of an astable 555 timer. It could, perhaps, be adapted for other uses. An NPN transistor, TR2, is connected to the 555 astable to be measured, as shown in the....

Astable Multivibrator can be designed by using 555 timer IC, Op Amps and also using transistors. The 555 IC provide accurate time delay from mille seconds to hours. The frequency of oscillation can be controlled manually by simple modification. This is a....

My vintage (62 year old) pole light has always been controlled by a timer ”a source of continual frustration due the requirement of readjustment for the ever-changing seasons. However, after knocking it over (I backed my car into it ), I decided it was time....

This is a simple LED flasher project that uses a common 555 timer IC for its operation. It is configured as an astable mode which means that its output is a square wave oscillator. Two LEDs are connected to its output in such a way that when one LED is ON,....