Friday, August 3, 2012

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.
Light  Alarm Circuit Using LDR
Light  Alarm Circuit Using LDR
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

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