Mutchus

Today I am going to present you a Simple Transistorized one Minute Delay Timer Circuit . It doesn’t include any complex or critical parts. You can use this circuit to generate a time delay of about one minute. That is, When you press the switch (Push button type is preferred) the LED turns ON and it prolongs for a 1 minute time. Read More.....

Finkbuilt has very detailed instructions on building a one-shot 555 timer. The article is full of diagrams and pictures of the circuit building process. This is a great read for anyone interested in the famous 555 timer. [ ]

In this circuit, the alarm will be switched on under the following four different conditions: 1. When light falls on LDR1 (at the entry to the premises). 2. When light falling on LDR2 is obstructed. 3. When door switches are opened or a wire is broken. 4. When a handle is touched. The light dependent resistor LDR1 should be placed in darkness near the door lock or handle etc. If an intruder flashes his torch, its light will fall on LDR1, reducing the voltage drop across it and so also the voltage applied to trigger 1 (pin 6) of IC1. Thus transistor T2 will get forward biased and relay RL1 energise and operate the alarm. Sensitivity of LDR1 can be adjusted by varying preset VR1. LDR2 may be placed on one side of a corridor such that the beam of light from a light source always falls on it. When an intruder passes through the corridor, his shadow falls on LDR2. As a result voltage drop across LDR2 increases and pin 8 of IC1 goes low while output pin 9 of IC1 goes high. Transistor T2 gets...

ALL IN ONE REPELLENT CIRCUIT INTRODUCTION Now i am going to introduce you an All in one Repellent circuit. Ya i mean it, by using this circuit you can keep nasty insects, Mosquitoes, lizards, and dogs away. Lets look the PRINCIPLE of this circuit:- This circuit works under the Principle of Ultrasonics. As you may know, we can't hear Ultrasonic sounds but animals or insects like Mosquitoes, bees, lizards and even dog can hear Ultrasonic sounds well. How this repellent circuit keeps Insects, lizards, Mosquitos and Dogs away? As i mentioned above, they can hear Ultrasonic sonic sound well at a particular Frequency range. Above that, they may get IRRITATED continuously. That's how this repellent circuit works. CIRCUIT DIAGRAM FOR ALL IN ONE REPELLENT CIRCUIT. CIRCUIT EXPLANATION FOR ALL IN ONE REPELLENT. The ALL in one REPELLENT CIRCUIT mainly consisting of a 555 timer, Frequency determining network, and a buzzer. The 555(NE555) timer is wired here as an ASTABLE MULTIVIBRATOR, whi...