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Yes this simple transistor circuit can be used as a home door bell and it’s ON time can be set as preferred by the user, meaning if you wanted that the sound of the bell to remain switched ON for a particular period of time, you could easily do it just by adjusting the given pot. The actual tune is derived from the IC UM66 and the associated components, while all the included transistors along with the relay are configured for producing the time delay for keeping the music switched ON.             Parts List R1, R2, R4, R5 = 1K VR1 = 100K, D1, D2 = 1N4007, C1, C2 = 100uF/25 T1 = BC547, T2 = BC557 T3 = 2N2222 Z1 = 3V/400mW Transformer = 0-12V/500mA, S1 = Bell Push IC = UM66

The electronic circuit provides a visual time 9 second delay using ten LED before control by closing a 12 Vdc relay. That the reset switch has closed, IC 4017 decade counter will be reset to zero count which illuminates the LED driven from pin 3. IC 555 timer output at pin 3 will be high and the voltage at pins 6 and 2 of the timer will be a little less than the lower trigger point, or about 3 Vdc. 9 Sec Timer with LED Indication and Control Relay Circuit Schematic   That time the switch is opened, the transistor in parallel with the timing capacitor (22uF) is shut off allowing the capacitor to begin charging and the IC 555 timer circuit to produce an approximate one second clock signal to the decade counter. The counter advances on each positive going change at pin 14 and is enabled with pin 13 terminated low. When the 9th count is reached, pin 11 and 13 will be high, stopping the counter and energizing the relay. Longer delay times can be obtained with most capacitor or most resi...

Applications of 555 timer IC is very diverse, one series of 10 Minute Timer with IC 555. 10 Minute Timer This circuit uses IC NE555 is set as a monostable multivibrator. The timing of the timer circuit 10 minutes with the IC 555 is governed by the configuration of C2, R4 and R5. The greater the value of C2 at 10-minute timer circuit with IC 555 timer is active then the time will stay longer.  Total resistance value between R4 and R5 also determine the active circuit 10 minute timer with IC 555, where the greater the value the longer time was also active. The core active setting the timer on the set of C2 charging time for 10 minutes on the timer circuit with IC 555. So, with the value of C2 remain so with time on the circuit timing Timer 10 minutes by IC 555 can be set by changing the resistance value R 4 + R 5. Indicators of active timer at 10 minute timer circuit with IC 555 uses the LED D2 and D3 will light up only one course to identify the active timer and the timer has not be...

For a lower parts count than the 2 transistor multivibrators, 2 LED s can be alternately flashed with a 555 integrated circuit configured as shown in Schematic 2.  I chose the combination of a 2K2 and a 47K resistor to determine the oscillation frequency along with the 10 uF capacitor connected to pins 2 and 6. You can practically change the (R Speed) 47K value to between 10K and 100K or more. Greater resistance = lower speed. You may also wish to connect up a 100K or so potentiometer instead of the 47K resistor for a variable speed version. Additionally, the 10 uF capacitor value can be changed. Feel free to experiment. Although, alternately flashing LED s  is great for the beginner to electronics, the basic one ON, one OFF circuit gets boring quickly. In the next section, we will try to improve the look and try to approximate a flash like a police car (within limits).

Description  This circuit turns-off an amplifier or any other device when a low level audio signal fed to its input is absent for 15 minutes at least. Pushing P1 the device is switched-on feeding any appliance connected to SK1. Input audio signal is boosted and squared by IC2A & IC2B and monitored by LED D4. When D4 illuminates, albeit for a very short peak, IC3 is reset and restarts its counting. Pin 2 of IC3 remains in the low state, the two transistors are on and the relay operates. When, after a 15 minutes delay, no signal appeared at the input, IC3 ends its counting and pin 2 goes high. Q1 & Q2 stop conducting and the relay switches-off. The device is thus completely off as also are the appliances connected to SK1. C5 & R9 reset IC3 at power-on. P2 allows switch-off at any moment.  Circuit Diagram  Parts: R1,R8___________1K 1/4W Resistors R2,R3___________4K7 1/4W Resistors R4_____________22K 1/4W Resistor R5______________4M7 1/4W Resistor R6,R9__________1...

This circuit is used to drives relays of 24 and 18 VDC from a 12 Volt power supply. The basic circuit on the IC NE 555 timer and use this circuit with almost any NPN or PNP power transistor. Parts: Resistor R1 = 47K R2 = 10K R3 = 56R Capacitor C1 = 0.01uF C2 = 0.01uF C3 = 0.001uF C4 = 0.1uF C5 = 50uF Transistor Q1 = TIP29 , TIP120, 2N4922, TIP61, TIP110, or 2N4921 Q2 = TIP30 , TIP125, 2N4919, TIP62, TIP115, or 2N4918 IC U1 = NE555

BURGLAR ALARM USING IC TIMER 555/556 ELECTRONIC DIAGRAM circuit diagram of burglar alarm using IC timer 555/556 is functioned as an alarm to prevent thief entering your house. The alarm would produce loud sound when a thin wire connecting resistor R1 with IC pin no 4 is broken. Thin fiber is used as the wire. The thinner the wire, the more responsive the alarm. This circuit needs 5-15V power supply, buzzer is used as a speaker. Here is the circuit schematic : Parts list :     Resistor R1 : 10k     Resistor R2 : 68k     Resistor R3 : 1k     Polar capacitor C1 : 1uF/15 B     Capacitor C2-C3 : 0.01uF     IC Timer : NE555

This is my first post and and this is the first circuit i made. There are many types of circuits for controlling home appliances using TV Remote. In fact I had confused a lot when I am a beginner searching for this type of circuits. The circuit here 555 timer IC to avoid fast switching. you can only switch the circuit after 3 seconds. IR remote sensor IC TSOP 1738 is used for recieving the signal. Normally when no signal is falling on IC3 the output of it will be high.This makes Q1 OFF.When a signal of 38 KHz from the TV remote falls on the IC3 its output goes low.This makes Q1 conduct and a negative pulse is obtained at pin 2 of IC 1 NE 555.Due to this IC1 wired as a monostable multivibrator produces a 4 Sec long high signal at its out put. This high out put is the clock for IC 2 which is wired as a Flipflop and of , its two outputs pin 3 goes low and pin 2 goes high.The high output at pin 2 is amplified to drive the relay .For the next signal the outputs of IC2 toggles state. Result...

This circuit is based on a passive infrared (PIR) sensor, which automatically switches on a device when someone comes close to it. It can be used for detection of theft or an unauthorised person entering a restricted area or building. It can also turn on lights when someone approaches the area where it is installed. Applications of this circuit include security systems, corridor lights and bathroom lights, among others. Fig. 1: Circuit diagram of the motion detector Circuit and working The circuit diagram of the motion detector using NE555 timer is shown in Fig. 1. It is built around 230V AC primary to 9V, 300mA secondary transformer X1, bridge rectifier DB107 (BR1), 6V voltage regulator 7806 (IC1), timer NE555 (IC2) and a few other components. The 230V AC mains is stepped down to 9V, 300mA through step-down transformer X1. Secondary output of X1 goes to bridge rectifier BR1. Capacitor C1 filters the ripples and the rectified output is given to regulator 7806 (IC1). IC1 provides 6V reg...

A monostable multivibrator (MMV) often called a one-shot multivibrator, is a pulse generator circuit in which the duration of the pulse is determined by the R-C network,connected externally to the 555 timer . In such a vibrator, one state of output is stable while the other is quasi-stable (unstable). For auto-triggering of output from quasi-stable state to stable state energy is stored by an externally connected capaci­tor C to a reference level. The time taken in storage determines the pulse width. The transition of output from stable state to quasi-stable state is accom­plished by external triggering. The schematic of a 555 timer in monostable mode of operation is shown in figure. Monostable Multivibrator Circuit details Pin 1 is grounded. Trigger input is applied to pin 2. In quiescent condition of output this input is kept at + V CC . To obtain transition of output from stable state to quasi-stable state, a negative-going pulse of narrow width (a width smaller than expected ...

In this circuit the 555 timer is used in a novel way, as a voltage controlled switch.The old and omnipresent NE555 can be very good at something it was not meant for: driving relays or other loads up to 200 mA. The picture shows an example circuit: if the input level rises over 2/3 of the supply voltage - it will turn on the relay, and the relay will stay on until the level at the input drops below one third of the supply voltage. If the relay and D1 were connected between pin 3 and ground, the relay would be activated when the input voltage drops below one third, and deactivated when the input voltage goes over two thirds of the supply voltage. It is also a nice advantage that the input requires only about 1 uA, which is something bipolar transistors can't compete with. (This high impedance input must not be left open.) A large hysteresis makes the circuit immune to noise. The output (pin 3) can only be either high or low (voltage-wise), and it changes its state almost instantenou...

This doorbell control porch light using timer ic (ne555),can be used in doorbell in order to get indication of porch light with door alarm if any one rings the door bell. Doorbell Control Porch Light Circuit Diagram: The circuit of doorbell control porch light is build around timer IC NE555 (IC2) and is here used as astable multivibrator. The output at pin 3 goes high of IC1 when trigger is given to pin 2 from power supply. Here transistor T1 is used as relay driver transistor which energized relay when output from pin 3 of IC1 is high. After relay energized AC current flow via N/O terminal and switch on the porch light. Triac1 with Diac1 hear is used for switch in order to glow porch light during night and switch it off at day with the help of preset VR1 and LDR1. Note:- Here the power source of 230V AC is replaced by 110V with replacing transformer having primary 110V and secondary 12V. Rest of the circuit  of door bell controll porch light is same. PARTS LIST : Resistors (all ¼...

The circuit is sometimes called a voltage-to-frequency converter because the output frequency can be changed by changing the input voltage. As discussed in previous blog posts, pin 5 terminal is voltage control terminal and its function is  to control the threshold and trigger levels. Normally, the control voltage is ++2/3V CC because of the internal voltage divider. However, an external voltage can be applied to this terminal directly or through a pot, as illustrated in figure, and by adjusting the pot, control voltage can be varied. Voltage across the timing capacitor is depicted in figure, which varies between +V control and ½ V control . If control voltage is increased, the capacitor takes a longer to charge and discharge; the frequency, therefore, decreases. Thus the fre­quency can be changed by changing the control volt­age. Incidentally, the control voltage may be made available through a pot, or it may be output of a transistor circuit, op-amp, or some other de...