Light sensitive Alarm

[varsha]

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.

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 continuously an alkaline PP3 9V battery should last about a month, but for longer life (about 6 months) you can use a pack of 6 AA alkaline batteries.
This project uses an edge-triggered 555 monostable circuit.

Parts Required

resistors: 10k, 47k, 1M 3
presets: 100k, 1M
capacitors: 0.01 F, 0.1 F, 10 F 25V radial
transistor: BC108 (or equivalent)
7555 low-power timer IC
8-pin DIL socket for IC
LDR (light-dependant resistor) type ORP12
bleeper 9-12V
on/off switch
battery clip for 9V PP3
stripboard 12 rows 25 holes

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read more
http://kpsec.freeukdocs/lalarm.pdf
http://rshelectronics.co.uk/electronicsclubkits.htm

[SHAJAHAN]

[attachment=5143]

Light-sensitive Alarm Project

Light-sensitive Alarm Project
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.
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
continuously an alkaline PP3 9V battery should last about a month, but for longer life (about 6 months)
you can use a pack of 6 AA alkaline batteries.

[jithu_m16]

what type of Light Sensitive Alarm you want?

one project about discussed in http://seminarsprojects.net/Thread-light...tive-alarm check it out ..i hope if your a good engineer you will catch it at first sight

[sujitstar]

Hi !!
Who are you ???,What you want ???,What you know about "light sensitive alarm".???If you know any thing about this send me a mail.