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motion or light sensor

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New Member
HI i have some suggestion

see you can do one thing, make a voltage divider by PHOTO RESISTOR and one common resistor. Give supply to one terminal of photo resistor and connect other terminal to another simple resistor, now take this junction to drive one npn transitor. You shoul put current limit resistor betweent BASE and the junction of npn transitor. Connect buzzer between supply and collector of npn transistor. Ground emitter of same transistor.
Here as light falls on photo resistor the voltage at junction of this photo resistor and simple resistor will increase and it will ON the npn transitor.
Here the critical thing you have to take care of is selection of voltage divider.
This circuit will sound only when the intesity of light is increased. you must put variable resistor in seriese with photo resistor so that you can adjust level of intensity. and so on. there are so many practicles on this you have to do


Well-Known Member
andy_jr_2001 said:
i want either motion or light to activate a circuit that has a speaker and will sound off a voice, any ideas?
How big is the speaker? (What are its specs?) How loud should it be?

Which is preferable: motion, or light? If light, should it trigger when it detects more light, or less?

How is the voice recorded? (SD Card, tape, .WAV file, what?) What kind of device is it on?

What exactly is the application? Burglar alarm? Haunted house FX?

What sorts of things have you Googled for so far?

It's hard to guess what you're after, so it's hard to guess what to suggest.



New Member
its a little speaker , its a 20sec recording module from radio shack, and instead of a button to turn on the speaker i want either light or motion to set it off, it for a pumpkin.
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Well-Known Member
Most Helpful Member
When somebody steals the pumpkin and rolls it down the street then the recorded voice will say, "Help, I am being stolen!"
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