555 Timer Circuits

The circuit presented here wakes you up with a loud alarm at the break of the daylight. Once again the 555 timer is used here. It is working as an astable multivibrator at a frequency of about 1kHz. When no light falls on the LDR, the transistor is pulled high by the variable resistor. Hence the transistor is OFF and the reset pin of the 555 is pulled low. Due the this the 555 is reset. When light falls on the LDR, its resistance decreases and pulls the base of the.....

The 555 timer IC is connected for Astable Operation, the clock pulses are fed to the 4017 IC via the 10K resistor. The 4017 is a 10 stage counter, each of the outputs is connected to the appropriate LED, as some LEDs need to be on for more than one count, we use diodes to avoid a short circuit situation between outputs. The capacitor and resistor on pin 15 of the 4017 are used to reset the counter to zero at initial power up. The ULN2001N used on the bulb version is a.....

This is basically a flasher circuit modified to turn on and off a bulb instead of a LED. It uses a 555 timer IC working as an astable multivibrator. The flashing rate can be varied from very fast to a maximum of once in 1.5 sec by varying the preset VR1...

Described timer to participate in the current circuit switch - bulb without any modification of existing pipelines. Connect the timer is in Figure 1 The time switch has only two outlets, which is connected in parallel to the button (Fig. 1a) or switch (Fig. 1b). If you use the button works as a classical staircase circuit switch. Connect a timer switch in parallel to the original, we will extend bulb shines as the time required to leave the room. Dimensions of the timer.....

A 555 timer can be used to generate a squarewave to produce a negative voltage relative to the negative battery terminal. When the timer output at pin 3 goes positive, the series 22 uF capacitor charges through the diode (D1) to about 8 volts. When the output switches to ground, the 22 uF cap discharges through the second diode (D2) and charges the 100 uF capacitor to a negative voltage. The negative voltage can rise over several cycles to about -7 volts but is limited by.....

The Control System uses an East and a West Cadmium Sulfide photoresistor (Sensors)to vary resistance to pin 2 of the corresponding 555 timer chip (East/West. The timer chips are wired for monostable "one shot" operation equal to approximately 1/10 of a second total output from pin 3 to the appropriate relay. The relays default to a positive voltage on either side of the motor (motor stopped). Light activates the appropriate timer/relay pair to momentarily ground one motor.....

The 555 timer IC is connected for Astable Operation, the clock pulses are fed to the 4017 IC via the 10K resistor. The 4017 is a 10 stage counter, output 6 (pin 5) is connected to RESET (pin 15), thus giving us a 6 stage counter , outputs 0 to 5. 6 of the LEDs are connected as 3 pairs, thus requiring 4 different signals, these signals come from the 4 transistors, which in turn are connected to the nescessary outputs of the 4017. Where a transistor is operated from more.....

The LED traffic Light circuit controls 6 LEDs (red, yellow and green) for both north/south directions and east/west directions. The timing sequence is generated using a CMOS 4017 decade counter and a 555 timer. Counter outputs 1 through 4 are wire ORed using 4 diodes so that the (Red - North/South) and (Green - East/West) LEDs will be on during the first four counts. The fifth count (pin 10) illuminates (Yellow - East/West) and (Red - North/South). ..

This circuit demonstrates how to use bootstrapping to seriously boost the output power of the timer. The LC555 can only put out about 50mA as it is. This circuit can put out at least 200mA and goes to the rail as well...

This is a basic 555 squarewave oscillator used to produce a 1 Khz tone from an 8 ohm speaker. In the circuit on the left, the speaker is isolated from the oscillator by the NPN medium power transistor which also provides more current than can be obtained directly from the 555 (limit = 200 mA). A small capacitor is used at the transistor base to slow the switching times which reduces the inductive voltage produced by the speaker. Frequency is about 1.44/(R1 + 2*R2)C where.....

This circuit confuses the infra-red receiver in a TV. It produces a constant signal that interferes with the signal from a remote control and prevents the TV detecting a channel-change or any other command. This allows you to watch your own program without anyone changing the channel !! The circuit is adjusted to produce a 38kHz signal. The IR diode is called an Infra-red transmitting Diode or IR emitter diode to distinguish it from a receiving diode, called an IR.....

IR appliances use pulses (control signals) sent over a modulated IR carrier wave. The carrier wave may be modulated at various frequencies, 36-38KHz being the most popular.Some Satellite receivers use even higher frequencies than this. The IR1 remote module receives an infra red signal and separates control pulses from the modulation. To re-transmit, a 555 timer is configured as an astable oscillator...

The 555 timer "light dimmer" schematic circuit is shown in figure 1 below. For the light dimmer to work the 555 timer is configured as a "variable cycle", astable oscillator running some where around 300 Hz. The power mosfet used here would be a TO-220 type such as MTP3055E or similar. Note the need for a TO-220 type heat sink for full rated loads...

This is a convenient design for a transistor tester. The advantage of this circuit is that transistors can be tested without actually doing the circuit soldering. The tortester uses two ICs: an NE 555 timer and a CMOS IC 4027. In 4027 there are two flip-flops. The timer generates a square wave of about 12 Hz. IC2 through the square wave then used to test the transistor. ..

This circuit produces a sound similar to a factory siren. It makes use of a 555 timer Ic used as an astable multivibrator of a center frequency of about 300Hz. The frequency is controlled by the pin 5 of the IC. When the supply is switched ON, the capacitor charges slowly and this alters the voltage at pin 5 of the IC hence the frequenct gradually increases. After the capacitor is fully charged, the frequency no longer increases. Now when the push button siren control.....

This circuit takes standard 0-10V control voltage (for example from analogue light controlling desk) and outputs a standard 1-2 ms RC servo motors control pulse. Power supply: 4-5V DC (same as for RC servo), consumes 15 mA of current. Control voltage range: 0-10V. Control input impedance: > 30 kohm. Output control signal suitable for RC servo motors: 1-2 ms pulse with and pulse repeat rate is around 80 Hz. Estimated component cost: less than 10 US dollars. Circuit.....

I don`t know why, but people like blinking lights. You see LED chasers everywhere, in TV shows (Knight Rider), movies, and store windows. This schematic is my version of a simple 10 LED chaser. There is no 555 timer used because at my local electronics store they are over $4 Cdn. Instead, an oscillator made up of two sections of a 4011 NAND gate is employed. This chip is very inexpensive and extremely common...

This circuit detects metal and also magnets. When a magnet is brought close to the 10mH choke, the output frequency changes. ..

This is a very simple circuit utilising a 555 timer IC to generate square wave of frequency that can be adjusted by a potentiometer. With values given the frequency can be adjusted from a few Hz to several Khz. To get very low frequencies replace the 0.01uF capacitor with a higher value. The formula to calculate the frequency is given by: 1/f = 0.69 * C * ( R1 + 2*R2) ..

The LED Torch is based on a 7555 timer running in astable mode (do not use an ordinary 555). A white LED (Maplin order code NR73) produces 400 mcd light output, which, when focussed, can illuminate objects at 30 metres. Try Conrad Electronic for what appears to be a stronger white LED (order code 15 37 45-11). A convex lens with short focal length is placed in front of the LED to focus the beam. If banding occurs at the beams perimeter, use another very short focal.....