Bulb Burnt Detector

[ysgoay]

I am making a circuit which will make an indication when a sudden shadow(Not gradually rate) falling on the LDR.

I start with a circuit named as dark detector which can give indication when bulb is burnt.

Thanks to ericgibbs's suggestion in an old thread,I already make several changes again to my circuit.

Please refer my attachment for any comment.

I add another LED and 680Ω resisitor parrallel with my buzzer since that buzzer minimum voltage consumption is 5V, I wonder it will continue buzz after some time due to 555 timer.

I replace BC108 NPN transistor with 2N3904, because it is cheaper.

For the LDR, is it all the same? I meant operating ways.Because I heard that some LDR operate in different way, resistance will increase when light intensity is increase. Is it exist?

For the 3 pin of variable resistor, I still no idea how to connect it. Cannot get the idea from ericgibbs.Let says the 3 pin named as pin 1,pin 2, and pin 3,where pin 2 is the middle pin.I should connect pin 1 and pin 2 in series, then connect the circuit with 1 end at pin 1 and pin 2 which are connected by a wire,the another end at pin 3, is it correct?

 

[audioguru]

when it gets dark then the LDR resistance increases and the transistor turns on which triggers the monostable 555.
The RC at pin 4 resets the 555 when power is applied.

 

[Boncuk]

connect the variable resistor (potentiometer) to the 47K resistor, meaning in the schematic, connect the center tap to the upper end tap.

That way monostable time increases when you turn the pot clockwise.

Boncuk

 

[ysgoay]

Thanks for reply.
I got further more idea how to visualise my circuit board already.

I still have another question.

How should I connect the pin 5 to ground?
Just leave it without any connection on stripboard
or need connect it through a crocodile clip,
and clip it to something that will ground the current?
e.g:Water pipe.

 

[audioguru]

Do not connect pin 5 of the 555 to anything.
The circuit's "ground" is just a common connection for its parts. It has nothing to do with "earth". Some old AM radios needed to have their circuit's ground connected to a water pipe earth.

 

[ysgoay]

Okay,seems like everything is in control now.

This is my first pratical circuit during my degree study.
Hope everything is all right at next week soldering work.

Thanks everyone those help me in comment with this circuit.

 

[ericgibbs]

Okay,seems like everything is in control now.

This is my first pratical circuit during my degree study.
Hope everything is all right at next week soldering work.

Thanks everyone those help me in comment with this circuit.

hi,
Look at this diagram for the 1M0 pot connection.