Sunday, October 30, 2011

Light Alarm Circuit Using LDR

This light alarm circuit is very simple and very easy to assemble even for beginners though it is not difficult. The well-known UM66 is used as the sound generator and Will give a pleasent wake up alarm.
UM66 Pinout
LDR is a light dependent resistor. Normally the resistance of an LDR is very high, Sometimes as high as 1MΩ, but Pls They are illuminated with light resistance drops dramatically. In the circuit adjust the presets to the Desired 220KΩ sensitivity, meaning adjusting the threshold point where the alarms start singing.

When there is light on the light dependent resistor the transistor T1 will from the start conducting and musical UM66 powers the integrated circuit.

for more details about LDR light  alarm circuit please visit
Detail download here

Water Switch Sensor Using S201S02 IC

The following circuit shows about Water Switch Sensor circuit based on the S201S02 IC. Features: two closely spaced metal rings are used as the water sensor mechanism.

water circuit switch sensor can be used as applications for: rain alarm, watertap leak detectors, water level sensors for bathroom water heaters, wetness checker for flower pots and more.
Working principle of this circuit is very simple. When the sensor rings are bridged by water, an isolated electric switch turns on to activate the load (an alarm, for instance) connected through its switching contacts. Here, the renowned S201S02 solid-state relay (IC1) is wired as the electronic switch.

for more details about water switch sensor circuit  please visit
Detail download here

1 Hz Pulse Frequency Generator using IC 555

This is a 1Hz pulse frequency generator circuit using timer IC 555 which is wired as an Astable Multivibrator. The output pulses can be indicated visually by the LED. An Astable Multivibrator, often called a free-running Multivibrator, is a rectangular-wave generating circuit. This circuit can be used in applications that require clock pulses
1 Hz Pulse  Frequency  Generator  circuit
 Pinout of LM383 chip

We can set the 555 to work at the desired frequency by selecting the right combination of resistances & capacitance.

Frequency = 1.44 / {(R1 + 2R2) * C1}

Also, 555 can produce waves with duty cycle else than the 50 % cycle.

Duty Cycle = (R1 + R2) * 100/ (R1 + 2R2)
where duty cycle= Ratio of time period when the output is 1
Detail download here