Mutchus

This is also known as Sun up alarm, in this circuit you can set the LDR’s sensitivity by 100k potentiometer, you can set it with any lamp around your room (tube light, bulb, LED etc) by varrying the 100k potentiometer. We can also control the buzzer time by 1M potentiometer    You can Enhance this project and set the sensitivity of the LDR with a lazer light and keep it on the way of any door circuit at one side and lazer at other side of the door and a then you can make this project to buzz as soon as some one enters in a room  I personally set this project in my room with sensitivity of tube light and whenever i came in and turn my room’s tube light on rookieelectronics Parts Required: 100k & 1M potentiometers  10k, 1Mx(3), 47k 0.1mF, 0.01mF & 10mF LDR BC337 transistor Beeper/Buzzer 9v Battery Supply     Circuit Diagram:

The circuit detects a sudden shadow falling on the light-sensor and sounds the bleeper when this happens. The circuit will not respond to gradual changes in brightness to avoid false alarms. The bleeper sounds for only a short time to prevent the battery running flat. Normal lighting can be used, but the circuit will work best if a beam of light is arranged to fall on the light-sensor. Breaking this beam will then cause the bleeper to sound. The light sensor is an LDR (light-dependant resistor), this has a low resistance in bright light and a high resistance in dim light. Simple Light Sensitive Alarm Circuit Diagram The light-sensitivity of the circuit can be adjusted by varying the 100k preset. The length of bleep can be varied from 0.5 to 10 seconds using the 1M preset. Using the 7555 low-power timer ensures that the circuit draws very little current (about 0.5mA) except for the short times when the bleeper is sounding (this uses about 7mA). If the circuit is switched on contin...

This circuit automatically turns on a night lamp when bedroom light is switched off. The lamp remains ‘on’ until the light sensor senses daylight in the morning. A super-bright white LED is used as the night lamp. It gives bright and cool light in the room. When the sensor detects the daylight in the morning, a melodious morning alarm sounds. The circuit is powered from a standard 0-9V transformer. Diodes D1 through D4 rectify the AC voltage and the resulting DC voltage is smoothed by C1. Regulator IC 7806 gives regulated 6V DC to the circuit. A battery backup is provided to power the circuit when mains fails. When mains supply is available, the 9V rechargeable battery charges via diode D5 and resistor R1 with a reasonably constant current. In the event of mains failure, the battery automatically takes up the load without any delay. Diode D5 prevents the battery from discharging backwards following the mains failure and diode D6 provides current path from the battery. Circuit diagram ...

This is the simple Electronic Low-volts Alarm Circuit Diagram. This inexpensive dc supply-voltage monitor sounds a warning when the voltage falls below a preset value. It is ideal for monitoring rechargeable batteries since it draws only a few microamperes when not sounding.   Electronic Low-volts Alarm Circuit Diagram The voltage at which the alarm sounds is determined by the zener diode. When the voltage falls below the zener voltage, the alarm sounds. The alarm tone is determined by the RC time constant of the 39 k resistor and 0.01 mf capacitor.

Are you having a hard time waking your hubby from sleeping? And when you leave the house for work, are you in doubt that he has not gotten out of bed? One thing that will stop your worries is to use this clock that does not just tell time but also “swears”. This is an All-in-one alarm clock. It shows an alphanumeric character, it has a calendar, temperature, and a light sensor to control its brightness. You can plug it on to your power source or use a battery. Although this is cool, It’s not ok being around kids. We don’t want young kids to learn to swear or say bad things, right? 

Circuit Diagram Description This is a circuit which sounds on the momentary breaking up of a guard circuit comprising a magnet and a reed switch a small permanent magnet is fitted at the edge of the door to be guarded, a normally open reed switch is fitted on the door frame or a wall facing the magnet. In the normally closed condition of the door, the reed switch is very close to the magnet and hence the reed contact is kept closed. When the door is opened the reed switch contact opens. This triggers a scr, the gate of the scr is connected to its cathode through the reed switch. As long as the switch is closed, the scr dose not fire, but when the door is opened the switch also opens and the scr fires, supplying voltage to the alarm. Engineers note: This alarm looks so simple but it is more effective and fool proof the audio signals can further be amplified according to the area or the place it is fixed and the major plus point is that even if the door is closed after opening or in ca...

Even the best car alarm is useless if you forget to set it upon leaving your car, whence this circuit. The relay has a make and a break contact: the  former is necessary to delay the switching in of the  alarm after you have got out of your car, and the  latter serves to switch on the car alarm proper. Immediately on re-entering your car, you must press the hidden switch, Si. This causes silicon-controlled rectifier Thi to conduct so that the relay is energized. At the same time, the green LED lights to indicate that the alarm is switched off.   Circuit diagram :  Best Automatic Car Alarm Circuit Diagram As soon as the ignition is switched off, T, is off, T2  is on, and the buzzer sounds. At the same time,  monostable IC1 is triggered, which causes T3 to  conduct and the red LED to light. The silicon- controlled rectifier is then off, and D4 is reverse  biased, but the relay remains energized via its make  contact for a short time,...

The receiver circuit in Figure 1 sounds an audio alarm when the transmitter (Figure 2) moves beyond a designated perimeter. The transmitter, a voltage-controlled oscillator, operates at approximately 915 MHz in the unlicensed ISM (industrial/scientific/medical) band. It has a tuning voltage of 1.5V=3×R2/(R1+R2), which lets you easily adjust the frequency by varying the values of resistors R1 and R2. Alarm Circuit Keeps Wandering Children   The receiver comprises low-noise amplifier IC1, power detector IC2, comparator IC3, and a buzzer. When the transmitter is within range—for example, when a child or a pet is carrying it—the receiver detects the RF signal and provides a voltage greater than 400 mV at the inverting terminal of the comparator. Resistors R9 and R10 preset the reference voltage at the comparator’s noninverting terminal. The reference voltage is 3×R10/(R9+R10), and the comparator’s output remains low. Circuit keeps wandering children and pets nearby figure 2When the tra...

This is the simple Electronic Low-volts Alarm Circuit Diagram. This inexpensive dc supply-voltage monitor sounds a warning when the voltage falls below a preset value. It is ideal for monitoring rechargeable batteries since it draws only a few microamperes when not sounding.   Electronic Low-volts Alarm Circuit Diagram The voltage at which the alarm sounds is determined by the zener diode. When the voltage falls below the zener voltage, the alarm sounds. The alarm tone is determined by the RC time constant of the 39 k resistor and 0.01 mf capacitor.

This Auto Anti-Hijack Alarm Circuit Diagram was designed primarily for the situation where a hijacker forces the driver from the vehicle. If a door is opened while the ignition is switched on - the circuit will trip. After a few minutes delay - when the thief is at a safe distance - the Siren will sound. Where it differs from the first two alarms - is in what happens next. I'm obliged to Victor Montanez from the USA who suggested that the engine cut-out should not operate - until the vehicle comes to a stop. That way - the engine will not fail suddenly or unexpectedly. And the hijacker will retain control. I haven't been able to implement Victor's excellent suggestion completely - because I couldn't think of a simple, reliable and universally applicable way of sensing when the vehicle has come to a stop. Instead - I have postponed engine failure until the ignition is switched off. Once the thief turns off the ignition - the engine will not re-start. Clearly - there is ...